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corrosion resistance of titanium

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In most power plant surface condenser tubing, tubesheet and service water pipe applications, TIMET CODEWELD®
Tubing and CODEROLL® Sheet, Strip and Plate can be covered by written warranties against failure by corrosion for
a period of 40 years.

For additional information and copies of these warranties, please contact any of the TIMET locations shown on the
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The data and other information contained herein are derived from a variety of sources which TIMET believes are reliable.
Because it is not possible to anticipate specific uses and operating conditions, TIMET urges you to consult with our
technical service personnel on your particular applications. A copy of TIMET’s warranty is available on request.

TIMET ®, TIMETAL®, CODEROLL® and CODEWELD® are registered trademarks of Titanium Metals Corporation.

FORWARD

Since titanium metal first became a This brochure summarizes the
commercial reality in 1950, corrosion corrosion resistance data accumulated
resistance has been an important in over forty years of laboratory
consideration in its selection as an testing and application experience.
engineering structural material. The corrosion data were obtained
Titanium has gained acceptance using generally acceptable testing
in many media where its corrosion methods; however, since service
resistance and engineering properties conditions may be dissimilar, TIMET
have provided the corrosion and recommends testing under the actual
design engineer with a reliable and anticipated operating conditions.
economic material.

i

CONTENTS

Forward ........................................................................... i
Introduction ...................................................................... 1
Chlorine, Chlorine Chemicals, and Chlorides ............................ 2

Chlorine Gas
Chlorine Chemicals
Chlorides

Bromine, Iodine, and Fluorine ............................................... 4
Resistance to Waters ........................................................... 5

Fresh Water – Steam
Seawater

General Corrosion
Erosion
Stress Corrosion Cracking
Corrosion Fatigue
Biofouling/MIC
Crevice Corrosion
Galvanic Corrosion

Acids ............................................................................... 8

Oxidizing Acids
Nitric Acid
Red Fuming Nitric Acid
Chromic Acid

Reducing Acids
Hydrochloric Acid
Sulfuric Acid
Phosphoric Acid
Hydrofluoric Acid
Sulfurous Acid

Other Inorganic Acids
Mixed Acids

A l k a l i n e M e d i a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
I n o r g a n i c S a l t S o l u t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
O r g a n i c C h e m i c a l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
O r g a n i c A c i d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
O x y g e n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
H y d r o g e n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
S u l f u r D i o x i d e a n d H y d r o g e n S u l f i d e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
N i t r o g e n a n d A m m o n i a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
L i q u i d M e t a l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
A n o d i z i n g a n d O x i d a t i o n T r e a t m e n t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
T y p e s o f C o r r o s i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

General Corrosion
Crevice Corrosion
Stress Corrosion Cracking
Anodic Breakdown Pitting
Hydrogen Embrittlement
Galvanic Corrosion

R e f e r e n c e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
A p p e n d i x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

INTRODUCTION

Many titanium alloys have been Titanium offers outstanding resistance Titanium and its alloys provide excellent
developed for aerospace applications to a wide variety of environments. resistance to general localized attack
where mechanical properties are the In general, TIMETAL Code 12 and under most oxidizing, neutral and
primary consideration. In industrial TIMETAL 50A .15Pd extend the inhibited reducing conditions. They also
applications, however, corrosion usefulness of unalloyed titanium to remain passive under mildly reducing
resistance is the most important property. more severe conditions. TIMETAL 6-4, conditions, although they may be
on the other hand, has somewhat less attacked by strongly reducing or
The commercially pure (c.p.) and alloy resistance than unalloyed titanium, but complexing media.
grades typically used in industrial service is still outstanding in many environments
are listed in Table 1. Discussion of compared to other structural metals. Titanium metal’s corrosion resistance is
corrosion resistance in this brochure will due to a stable, protective, strongly
be limited to these alloys. Recently, ASTM incorporated a series of adherent oxide film. This film forms
new titanium grades containing 0.05% instantly when a fresh surface is
In the following sections, the resistance Pd. (See Table 1 below.) These new exposed to air or moisture. According to
of titanium to specific environments is grades exhibit nearly identical corrosion Andreeva(1) the oxide film formed on
discussed followed by an explanation of resistance to the old 0.15% Pd grades, titanium at room temperature
the types of corrosion that can affect yet offer considerable cost savings. TIMET immediately after a clean surface is
titanium. The principles outlined and the is pleased to offer these new titanium exposed to air is 12-16 Angstroms thick.
data given should be used with caution grades: 16 (TIMETAL 50A .05Pd), After 70 days it is about 50 Angstroms.
as a guide for the application of titanium. 17 (TIMETAL 35A .05Pd), and It continues to grow slowly reaching a
In many cases, data were obtained in the 18 (TIMETAL 3-2.5 .05Pd). thickness of 80-90 Angstroms in 545
laboratory. Actual in-plant environments Throughout this brochure, wherever days and 250 Angstroms in four years.
often contain impurities which can exert information is given regarding Grade 7 The film growth is accelerated under
their own effects. Heat transfer (TIMETAL 50A .15Pd), these new strongly oxidizing conditions, such as
conditions or unanticipated deposited grades may be substituted. As always, heating in air, anodic polarization in an
residues can also alter results. Such this information should only be used as electrolyte or exposure to oxidizing
factors may require in-plant corrosion a guideline. TIMET technical agents such as HNO3, CrO3 etc.
tests. Corrosion coupons are available representatives should be consulted to
from TIMET for laboratory or in-plant assure proper titanium material The composition of this film varies from
testing programs. A tabulation of selection. Additional information TiO2 at the surface to Ti2O3, to TiO at
available general corrosion data is given concerning these new grades may be the metal interface.(2) Oxidizing
in the Appendix. obtained from TIMET. conditions promote the formation of
TiO2 so that in such environments the
Table 1 film is primarily TiO2. This film is
transparent in its normal thin
Titanium alloys commonly used in industry configuration and not detectable by
visual means.
TIMET ASTM UNS Ultimate Tensile Yield Strength (min.) Nominal
Designation Grade A study of the corrosion resistance of
Designation Strength (min.) 0.2% Offset Composition titanium is basically a study of the
TIMETAL 1 properties of the oxide film. The oxide
2 R50250 35,000 psi 25,000 psi C.P. Titanium* film on titanium is very stable and is
35A 3 R50400 50,000 psi 40,000 psi C.P. Titanium* only attacked by a few substances, most
50A 4 R50550 65,000 psi 55,000 psi C.P. Titanium* notably, hydrofluoric acid. Titanium is
65A 5 R50700 80,000 psi 70,000 psi C.P. Titanium* capable of healing this film almost
75A 7 R56400 130,000 psi 120,000 psi 6% AI, 4% V instantly in any environment where a
6-4 9 R52400 50,000 psi 40,000 psi Grade 2+0.15% Pd trace of moisture or oxygen is present
50A .15Pd 11 R56320 90,000 psi 70,000 psi 3.0% AI, 2.5% V because of its strong affinity for oxygen.
3-2.5 12 R52250 35,000 psi 25,000 psi Grade 1+0.15% Pd
35A .15Pd 16 R53400 70,000 psi 50,000 psi 0.3% Mo, 0.8% Ni Anhydrous conditions in the absence of
Code 12 17 R52402 50,000 psi 40,000 psi Grade 2+0.05% Pd a source of oxygen should be avoided
50A .05Pd 18 R52252 35,000 psi 25,000 psi Grade 1+0.05% Pd since the protective film may not be
35A .05Pd R56322 90,000 psi 70,000 psi Grade 9+0.05% Pd regenerated if damaged.
3-2.5 .05Pd

*Commercially Pure (Unalloyed) Titanium

1

CHLORINE, CHLORINE
CHEMICALS AND CHLORIDES

Chlorine and chlorine compounds in mechanical damage to titanium in Chlorides

aqueous solution are not corrosive chlorine gas under static conditions at Titanium has excellent resistance to
toward titanium because of their room temperature (Figure 1).(4) Factors corrosion by neutral chloride solutions
strongly oxidizing natures. Titanium is such as gas pressure, gas flow, and even at relatively high temperatures
unique among metals in handling temperature as well as mechanical (Table 3). Titanium generally exhibits
these environments. damage to the oxide film on the very low corrosion rates in chloride
titanium, influence the actual amount of environments.
The corrosion resistance of titanium moisture required. Approximately 1.5
to moist chlorine gas and chloride- percent moisture is apparently required The limiting factor for application of
containing solutions is the basis for the for passivation at 390°F (199°C).(3) titanium and its alloys to aqueous
largest number of titanium applications. Caution should be exercised when chloride environments appears to be
Titanium is widely used in chlor-alkali employing titanium in chlorine gas crevice corrosion. When crevices are
cells; dimensionally stable anodes; where moisture content is low. present, unalloyed titanium will
bleaching equipment for pulp and sometimes corrode under conditions not
paper; heat exchangers, pumps, piping Chlorine Chemicals predicted by general corrosion rates
and vessels used in the production of (See Crevice Corrosion). TIMET studies
organic intermediates; pollution control Titanium is fully resistant to solutions of have shown that pH and temperature
devices; and even for human body chlorites, hypochlorites, chlorates, are important variables with regard to
prosthetic devices. perchlorates and chlorine dioxide. crevice corrosion in brines.
Titanium equipment has been used to

The equipment manufacturer or user handle these chemicals in the pulp and

faced with a chlorine or chloride paper industry for many years with no

corrosion problem will find titanium’s evidence of corrosion.(5) Titanium is used

resistance over a wide range of today in nearly every piece of

temperatures and concentrations equipment handling wet chlorine or

particularly useful. chlorine chemicals in a modern bleach

Chlorine Gas plant, such as chlorine dioxide mixers,
piping, and washers. In the future it is
Titanium is widely used to handle expected that these applications will
moist chlorine gas and has earned a expand including use of titanium in
reputation for outstanding performance equipment for ClO2 generators and
in this service. The strongly oxidizing waste water recovery.
nature of moist chlorine passivates
FIGURE 1

titanium resulting in low corrosion rates PRELIMINARY DATA REFLECTING|yz,y,180
in moist chlorine. PERCENT WATER CONTENT
NECESSARY TO PASSIVATE(82)
Dry chlorine can cause rapid attack on UNALLOYED TITANIUM IN
titanium and may even cause ignition if CHLORINE GAS 160
moisture content is sufficiently low (71)
(Table 2).(3) However, one percent of 220
water is generally sufficient for (104) POSITIVE
passivation or repassivation after REACTION
200
z|,y,y140(93)

TEMPERATURE °F (°C) (60) AREA OF
U N C E R TA I N T Y
120
(49) NO
Table 2 |yz,,y80 REACTION

RESISTANCE OF TITANIUM TO CHLORINE (27)

Environment Temperature Corrosion Rate – mpy (mm/y) 10060
°F (°C) TIMETAL 50A TIMETAL Code 12 (38)(16)
Wet Chlorine
Water Saturated, 50-190 (10-88) Nil-0.02 (0.001) — y|,z,y0

Chlorine Cell Gas 190 (88) 0.065* (0.002) 0.035* (0.001) 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Dry Chlorine 86 (30) Rapid Attack, —

Ignition PERCENT OF WATER BY WEIGHT IN CHLORINE GAS

*Welded Samples
2

The temperature-pH relationship defines Table 3
crevice corrosion susceptibility for
TIMETAL 50A, TIMETAL Code 12, and resistance of unalloyed titanium to
TIMETAL 50A .15Pd in saturated corrosion by aerated Chloride solutions
sodium chloride brines (Figures 2, 3,
and 4). Corrosion in sharp crevices in (R EF. 17) Concentration Temperature Corrosion Rate
near neutral brine is possible with Chloride % °F (°C) mpy (mm/y)
unalloyed titanium at about 200°F
(93°C) and above (Figure 2). Lowering Aluminum chloride 5-10 140 (60) 0.12 (0.003)
the pH of the brine lowers the 10 212 (100) 0.09 (0.002)
temperature at which crevice corrosion Ammonium chloride 10 302 (150) 1.3 (0.033)
is likely, whereas raising the pH reduces Barium chloride 20 300 (149) 630 (16.0)
crevice corrosion susceptibility. However, Calcium chloride 25 0.04 (0.001)
crevice corrosion on titanium is not 25 68 (20) 258 (6.55)
likely to occur below 158°F (70°C). The Cupric chloride 40 212 (100) 4300 (109.2)
presence of high concentrations of Cuprous chloride All 250 (121) <0.5 (<0.013)
cations other than sodium such as Ca+2 Ferric chloride 5-25 68-212 (20-100) <0.01 (<0.000)
or Mg+2, can also alter this relationship 5 212 (100) 0.02 (0.001)
and cause localized corrosion at lower Lithium chloride 10 212 (100) 0.3 (0.008)
temperatures than those indicated in Magnesium chloride 20 212 (100) 0.6 (0.015)
the diagrams. Manganous chloride 55 212 (100) 0.02 (0.001)
Mercuric chloride 60 220 (104) <0.01 (<0.000)
TIMETAL Code 12 and TIMETAL 50A 62 300 (149) 2-16 (0.051-0.406)
.15Pd offer considerably improved Nickel chloride 73 310 (154) 84 (2.13)
resistance to crevice corrosion compared Potassium chloride 1-20 350 (177) <0.5 (<0.013)
to unalloyed titanium (Figures 3 and 4). Stannic chloride 40 212 (100) 0.2 (0.005)
These alloys have not shown any Stannous chloride 50 <0.1 (<0.003)
indication of any kind of corrosion in Sodium chloride 1-20 Boiling
laboratory tests in neutral saturated 1-40 194 (90) Nil
brines to temperatures in excess of 600°F Zinc chloride 50 <0.5 (<0.013)
(316°C). TIMETAL Code 12 maintains 50 70 (21)
excellent resistance to crevice corrosion 50 Boiling 0.16 (0.004)
down to pH values of about 3. Below pH 5 Boiling <0.7 (<0.018)
3, TIMETAL 50A .15Pd offers distinctly 20 302 (150)
better resistance than TIMETAL Code 12. 50 300 (149) Nil
TIMETAL Code 12 or TIMETAL 50A .15Pd 5-20 212 (100) 0.03 (0.001)
will resist crevice corrosion in boiling, 1 212 (100) 0.4 (0.010)
low pH salt solutions which corrode 5 390 (199) 0.2 (0.005)
TIMETAL 50A (Table 4). 10 212 (100)
55 212 (100) Nil
5-20 212 (100) 0.01 (0.000)
Saturated 212 (100) 0.42 (0.011)
Saturated 215 (102) 0.04 (0.001)
5 212 (100)
Saturated 70 (21) Nil
3 140 (60) 0.14 (0.004)
20 212 (100)
29 70 (21) Nil
Saturated Boiling <0.01 (<0.000)
Saturated 165 (74)
20 230 (110) 0.12 (0.003)
50 70 (21) Nil
75 Boiling
80 220 (104) 0.01 (0.000)
302 (150) 0.01 (0.000)
392 (200) 0.01 (0.0003)
392 (200)
Nil
Nil
Nil
Nil
24 (0.610)
8000 (203.2)

3

BROMINE IODINE FIGURE 2
AND FLUORINE
The resistance of titanium to bromine EFFECT OF TEMPERATURE and PH
and iodines is similar to its resistance to on Crevice Corrosion of
chlorine. It is attacked by the dry gas unalloyed Titanium (TIMETAL 50A)
but is passivated by the presence of in Saturated NaCL Brine
moisture. Titanium is reported to be
resistant to bromine water.(4) 14
Titanium is not recommended for use in
contact with fluorine gas. The possibility 12
of formation of hydrofluoric acid
even in minute quantities can lead to IMMUNE
very high corrosion rates. Similarly, 10
the presence of free fluorides in acid y,,y,yy,,yy,y,,y6
aqueous environments can lead to 8
formation of hydrofluoric acid and, 4 CREVICE CORROSION
consequently, rapid attack on titanium. pH pH pH ,y,yy,,yy,,y,y,y2
On the other hand, fluorides chemically 0
bound or fully complexed by metal ions,
or highly stable fluorine containing ,y,y,y,yy,y,y,,y100 200 300 400
compounds (e.g., fluorocarbons), are 500 600
generally noncorrosive to titanium. (38) (93) (149) (204) (260) (316)

4 TEMPERATURE °F(°C)

FIGURE 3

EFFECT OF TEMPERATURE and PH
on Crevice Corrosion of
TIMETAL Code 12
in Saturated NaCL Brine

14

12

IMMUNE

10,y,y,yy,4

8

62

,yy,,y,y0
100
,y,y,yy,(38)
CREVICE CORROSION

200 300 400 500 600
(93) (149) (204) (260) (316)

TEMPERATURE °F(°C)

FIGURE 4

EFFECT OF TEMPERATURE and PH
on Crevice Corrosion of
TIMETAL 50A .15PD
in Saturated NaCL Brine

14

12

IMMUNE

10,yy,,yy,4

CREVICE CORROSION8
2
6y,,y,yy,0

100200 300 400 500 600
(93) (149) (204) (260) (316)
y,y,y,,y(38)
TEMPERATURE °F(°C)

RESISTANCE TO WATERS

Fresh Water – Steam Table 4

Titanium resists all forms of corrosive resistance of titanium to
attack by fresh water and steam to crevice corrosIOn in boiling solutions
temperatures in excess of 600°F
(316°C).(7) The corrosion rate is very low 500 hour test results
or a slight weight gain is experienced.
Titanium surfaces are likely to acquire a TIMETAL TIMETAL TIMETAL
tarnished appearance in hot water steam
but will be free of corrosion. Environment pH 50A Code 12 50A .15Pd

Some natural river waters contain ZnCl2 (saturated) 3.0 F R R
manganese which deposits as 10% AlCl3 —F R R
manganese dioxide on heat exchanger 42% MgCl2 4.2 F R R
surfaces. Chlorination treatments used 10% NH4Cl 4.1 F R R
to control sliming results in severe NaCl (saturated) 3.0 F R R
pitting and crevice corrosion on stainless NaCl (saturated) + Cl2 2.0 F F R
steel surfaces. Titanium is immune to 10% Na2SO4 2.0 F R R
this form of corrosion and is an ideal 10% FeCl3 0.6 F F R
material for handling all natural waters.
Metal-to-Teflon crevice samples used.
Seawater F = Failed (samples showed corrosion in metal-to-Teflon crevices).
General Corrosion R = Resisted (samples showed no evidence of corrosion).

Titanium resists corrosion by seawater to Table 5
temperatures as high as 500°F (260°C).
Titanium tubing, exposed for 16 years to CORROSION OF TITANIUM IN AMBIENT SEAWATER
polluted seawater in a surface condenser,
was slightly discolored but showed no Alloy Ocean Depth Corrosion Rate Reference
evidence of corrosion.(8) Titanium has Unalloyed titanium ft (m) mpy (mm/y)
provided over thirty years of trouble-free (10)
seawater service for the chemical, oil TIMETAL 6-4 Shallow 3.15 x 10-5 (0.8 x 10-6) (9)
refining and desalination industries. 2,362-6,790 (720-2070) <0.010 (<0.00025) (9)
4,264-4,494 (1300-1370) <0.010 (<0.00025) (9)
Exposure of titanium for many years to (0.0)
depths of over a mile below the ocean 5-6,790 (1.5-2070) 0.002 (0.00004) (12)
surface has not produced any 5,642 (1720) <0.010 (<0.00025) (9)
measurable corrosion(9) (Table 5). Pitting
and crevice corrosion are totally absent, 5-6,790 (1.5-2070) 3.15 x 10-5 (8 x 10-6) (12)
even if marine deposits form. The 5,642 (1720) ≤0.039 (≤0.001) (13)
presence of sulfides in seawater does 5,642 (1720)
not affect the resistance of titanium to
corrosion. Exposure of titanium to Table 6
marine atmospheres or splash or tide
zone does not cause corrosion.(10,11,12,13) effect of seawater velocity on erosion of
unalloyed titanium and timetal 6-4

Erosion Rate – mpy (mm/y)

Seawater Velocity Unalloyed
ft/sec (m/sec)
Titanium TIMETAL 6-4
0-2 (0-0.61)
25 (7.6) Nil —
120 (36.6) Nil —
0.3 (0.008) 0.4 (0.010)

5

Erosion

Titanium has the ability to resist erosion
by high velocity seawater (Table 6).
Velocities as high as 120 ft./sec. cause
only a minimal rise in erosion rate.(14) The
presence of abrasive particles, such as
sand, has only a small effect on the
corrosion resistance of titanium under
conditions that are extremely detrimental
to copper and aluminum base alloys
(Table 7). Titanium is considered
one of the best cavitation-resistant
materials available for seawater
service (15) (Table 8).

Table 7

erosion of unalloyed titanium in seawater
containing suspended solids

( RE F. 1 5 ) Corrosion/Erosion – mpy (mm/y)

Flow Rate Suspended Matter Duration TIMETAL 50A 70 Cu-30 Ni* Aluminum
ft/sec (m/sec) in Seawater Hrs. Brass

23.6 (7.2) None 10,000 Nil Pitted Pitted
6.6 (2) 40 g/l 60 Mesh Sand 2,000 0.1 (0.0025) 3.9 (0.10) 2.0 (0.05)
6.6 (2) 40 g/l 10 Mesh Emery 2,000 0.5 (0.0125) Severe Erosion Severe Erosion
1% 80 Mesh Emery 17.5 0.15 (0.0037) 1.1 (.028)
11.5 (3.5) 4% 80 Mesh Emery 17.5 3.3 (0.083) 2.6 (.065) —
13.5 (4.1) 40% 80 Mesh Emery 59.1 (1.5) 78.7 (2.0) —
23.6 (7.2) 1 —

*High iron, high manganese 70-30 cupro-nickel.

Table 8

erosion of unalloyed titanium in seawater Locations

( RE F. 1 5 ) Corrosion Rate – mpy (mm/y)

Location Flow Rate Duration TIMETAL 50A 70 Cu-30 Ni* Aluminum
Brixham Sea ft/sec (m/sec) Months
Kure Beach <0.098 (<0.0025) 11.8 (0.3) 39.4 (1.0**)
32.2 (9.8) 12 3x10-5 (0.75 x 10-6) — —
Wrightsville Beach 3.3 (1) 54 4.9x10-3 (0.000125) —
Mediterranean Sea 2 1.1x10-2 (0.000275) 1.9 (0.048) —
Dead Sea 27.9 (8.5) 2 0.020 (0.0005) 81.1 (2.06) —
29.5 (9) 1 0.004 (0.0001) 4.7 (0.12) —
23.6 (7.2 [Plus Air]) 6 0.007 (0.000175) 0.9 (0.022) —
2.0-4.3(0.6-1.3) 2 19.3
29.5 (9) 0.5 0.5 —
23.6 (7.2 [Plus Air]) mg/day 8.9 mg/day
0.5 mg/day 6.7
23.6 (7.2 [Plus Air]) 0.2 9
mg/day mg/day mg/day

*High iron, high manganese 70-30 cupro-nickel. **Sample perforated.
6

Stress Corrosion Microbiologically
Cracking Influenced Corrosion

TIMETAL 35A and TIMETAL 50A are Titanium, uniquely among the common
essentially immune to stress-corrosion engineering metals, appears to be
cracking (SCC) in seawater. This has immune to MIC. Laboratory studies
been confirmed many times as reviewed confirm that titanium is resistant to the
by Blackburn et al. (1973).(16) Other most aggressive aerobic and anaerobic
unalloyed titanium grades with oxygen organisms.(55) Also, there has never
levels greater than 0.2% may be been a reported case of MIC attack
susceptible to SCC under some on titanium.
conditions. Some titanium alloys may be
susceptible to SCC in seawater if Crevice Corrosion
highly-stressed, pre-existing cracks are
present. TIMETAL 6-4 ELI (low oxygen Localized pitting or crevice corrosion is
content) is considered one of the best of a possibility on unalloyed titanium in
the high strength titanium-base alloys seawater at temperatures above 180°F
for seawater service.(17) (82°C). TIMETAL Code 12 and
TIMETAL 50A .15Pd offer resistance to
Corrosion Fatigue crevice corrosion in seawater at
temperatures as high as 500°F (260°C)
Titanium, unlike many other materials, and are discussed more thoroughly in
does not suffer a significant loss of the section on chlorides.
fatigue properties in seawater.(11,18,19) This
is illustrated by the data in Table 9. Galvanic Corrosion

Biofouling Titanium is not subject to galvanic
corrosion in seawater, however, it may
Titanium does not display any toxicity accelerate the corrosion of the other
toward marine organisms. Biofouling can member of the galvanic couple
occur on surfaces immersed in seawater. (see Galvanic Corrosion).
Cotton et al. (1957) reported extensive
biofouling on titanium after 800 hours Table 9
immersion in shallow seawater.(11) The
integrity of the corrosion resistant oxide EFFECT OF SEAWATER ON
film, however, is fully maintained under FATIGUE PROPERTIES OF TITANIUM
marine deposits and no pitting or crevice
corrosion has been observed.

It has been pointed out that marine
fouling of titanium heat exchanger
surfaces can be minimized by
maintaining water velocities in excess of
2 m/sec.(20) Chlorination is recommended
for protection of titanium heat
exchanger surfaces from biofouling
where seawater velocities less than
2 m/sec are anticipated.

(R E F. 11, 19) Stress to Cause Failure
in 10 7 Cycles,* ksi (MPa)
Alloy Air Seawater
Unalloyed
TIMETAL 6-4 52 (359) 54 (372)
70 (480) 60 (410)

*Rotating beam fatigue tests on smooth, round bar specimens.

7

Table 10 ACIDS

CORROSION OF TITANIUM AND STAINLESS STEEL Oxidizing Acids
HEATING SURFACES EXPOSED TO BOILING
90% NITRIC ACID (215°F) Titanium is highly resistant to oxidizing
acids over a wide range of
( RE F. 2 3 ) concentrations and temperatures.
Common acids in this category include
Corrosion Rate – mpy (mm/y) nitric, chromic, perchloric, and
hypochlorous (wet Cl2) acids. These
Metal Type 304L oxidizing compounds assure oxide film
Temperature °F (°C) stability. Low, but finite, corrosion rates
TIMETAL 50A Stainless Steel from continued surface oxidation may
be observed under high temperature,
240 (116) 1.1-6.6 (0.03-0.17) 150-518 (3.8-13.2) highly oxidizing conditions.
275 (135) 1.6-6.1 (0.04-0.15) 676-2900 (17.2-73.7)
310 (154) 1.0-2.3 (0.03-0.06) 722-2900 (18.3-73.7) Titanium has been extensively utilized
for handling and producing nitric acid (4,21)
Table 11 in applications where stainless steels
have exhibited significant uniform or
effect of chromium on corrosion of intergranular attack (Table 10). Titanium
stainless steel and titanium in boiling offers excellent resistance over the full
hno3 (68%*) concentration range at sub-boiling
temperatures. At higher temperatures,
( RE F. 2 3 ) however, titanium’s corrosion resistance
is highly dependent on nitric acid purity.
Corrosion Rate – mpy (mm/y) In hot, very pure solutions or vapor
condensates of nitric acid, significant
Percent Type 304L general corrosion (and trickling acid
Chromium condensate attack) may occur in the 20
(Annealed) TIMETAL 50A to 70 wt.% range as seen in Figure 5.
Under marginal high temperature
0.0 12-18 (0.30-0.46) 3.5-3.8 (0.09-0.10) conditions, higher purity unalloyed
0.0005 12-20 (0.30-0.51) — grades of titanium (i.e., TIMETAL 35A)
0.005 60-90 (1.5-2.3) are preferred for curtailing accelerated
0.05 980-1600 (24.9-40.6) 0.9-1.6 (0.022-0.041) corrosion of weldments.
0.01 —
— On the other hand, various metallic
0.1-1.4 (0.003-0.036) species such as Si, Cr, Fe, Ti or various
precious metal ions (i.e., Pt, Ru) in very
*Exposed for three 48-hr. periods, acid changed each period. minute amounts tend to inhibit high
temperature corrosion of titanium in nitric
Table 12 acid solutions (Table 11). Titanium often
exhibits superior performance to stainless
effect of dissolved titanium on the steel alloys in high temperature metal-
corrosion rate of unalloyed titanium in contaminated nitric acid media, such as
boiling nitric acid solutions those associated with the Purex Process
for U3O8 recovery. Titanium’s own
( RE F. 2 2 ) Corrosion Rate – mpy (mm/y) corrosion product Ti+4, is a very potent
inhibitor as shown in Table 12. This is
Titanium Ion 40% HNO3 68% HNO3 particularly useful in recirculating nitric
Added (mg/l) acid process streams, such as stripper
29.5 (0.75) 31.8 (0.81) reboiler loops (Table 10), where effective
0 — 0.8 (0.02) inhibition results from achievement of
10 2.4 (0.06) steady-state levels of dissolved Ti +4.
20 8.6 (0.22) 0.4 (0.01)
40 1.9 (0.05) 0.4 (0.01)
80 0.8 (0.02)

Duration of Test: 24 hours

8

FIGURE 5 TIMETAL CODE 12
Resistance of Titanium to Pure Nitric acid TIMETAL 50A
TIMETAL 50A .15Pd
40
(1.02)

32
(0.81)

CORROSION RATE – MPY(MM/Y) 24
(0.61)

16
(0.41)

8
(0.20)

0

10 20 30 40 50 60 70 80

B O I L I N G W T. % H N O 3

The data in Table 13 shows that Table 13
titanium also offers good resistance to
nitric acid vapors. RESISTANCE OF TITANIUM TO CORROSION
BY HNO3 VAPORS
CAUTION: Titanium is not
recommended for use in red fuming Alloy Corrosion Rate – mpy (mm/y)*
nitric acid because of the danger of
pyrophoric reactions. TIMETAL 50A 2.0 (0.051)
TIMETAL Code 12 0.8 (0.020)
TIMETAL 50A .15Pd 0.08 (0.002)

* Samples suspended in vapors above boiling 70% HNO3 Azeotrope. 144 hour exposure.

9

FIGURE 6NO2 % Red Fuming Nitric Acid

EFFECT OF Acid composition on the Pyrophoric Although titanium in general has
Reaction with Unalloyed Titanium in Red Fuming excellent resistance to nitric acid over
Nitric Acid a wide range of concentrations and
temperatures, it should not be used with
,,yy,y,y,yyyy,yy,,,,12340000 yyyy,,yy,,,,yy,y,,y,,y,yy,,,y,y,,yyy,yy,POSITIVE,yy,y,,y,y,y,yy,y,,yREACNTIOONRy,yy,yy,yyy,,,,y,,,yEACTIONyyy,yy,yy,,,y,y,,,,yAREAOFy,,,,y,yyyyy,,y,,yy,UNCERTAyy,,y,yy,y,y,,y,,yy,INTY red fuming nitric acid. A pyrophoric
reaction product can be produced
1 2 resulting in serious accidents. An
H2O % investigation of these accidents has
shown that the pyrophoric reaction is
always preceded by a rapid corrosive
attack on the titanium.(24,25) This attack
is intergranular and results in a surface
residue of finely divided particles of
metallic titanium. These are highly
pyrophoric and are capable of detonating
in the presence of a strong oxidizing
agent such as fuming nitric acid.

It has been established that the water
content of the solution must be less
than 1.34% and the NO2 content
greater than 6% for the pyrophoric
reaction to develop. This relationship is
shown in Figure 6.(24)

Chromic Acid

The data on chromic acid is not as
extensive as that on nitric acid. However,
the corrosion resistance of titanium to
chromic acid appears to be very similar
to that observed in nitric acid. This is
shown by the data in Table 14 and by
service experience.

Reducing Acids

Titanium offers moderate resistance to
reducing acids such as hydrochloric,
sulfuric, and phosphoric. Corrosion
rates increase with increasing acid
concentration and temperature. The
TIMETAL 50A .15Pd alloy offers best
resistance to these environments,
followed by TIMETAL Code 12,
unalloyed titanium, and TIMETAL 6-4.

Table 14

CORROSION OF UNALLOYED TITANIUM IN
CHROMIC ACID

Acid Concentration Temperature Corrosion Rate Reference
% °F (°C) mpy (mm/y)
(26)
20 70 (21°) 4.0 Max (0.102 Max) (27)
10 Boiling Nil (28)
10 Boiling (29)
20 Room <5.0 (<0.127)
Nil

10

Hydrochloric Acid Severe corrosion damage on titanium clean titanium surfaces, it is
equipment has resulted from cleaning recommended that sufficient ferric
Iso-corrosion data illustrate that procedures utilizing pure hydrochloric chloride be added to effectively inhibit
TIMETAL 50A offers useful corrosion acid or acid inhibited with amines. If corrosion of the titanium.
resistance to about 7% hydrochloric acid hydrochloric or sulfuric acid is used to
at room temperature; TIMETAL Code 12
to about 9% HCl; and TIMETAL 50A FIGURE 7
.15Pd to about 27% (See Figure 7). This
resistance is significantly lowered at near Corrosion of Titanium Alloys in Naturally
boiling temperatures.
Aerated HCL Solutions
Typical corrosion rate data for
TIMETAL 50A, TIMETAL 6-4, TIMETAL 275
Code 12 and TIMETAL 50A .15Pd in
pure HCl solutions are given in Table 15. (135)

Small amounts of certain multi-valent 200250 TIMETAL 50A .15Pd
metal ions in solution, such as ferric ion, (121) TIMETAL CODE 12
can effectively inhibit the corrosion of |z,yz|yz|,,y(93) TIMETAL 50A
titanium in hydrochloric acid (Figures 8, 9, 225
10). When sufficient ferric ion is present, (107) 5 mpy (0.127 mm/y) ISO-CORROSION LINES
TIMETAL 50A, TIMETAL Code 12 and BOILING POINT
TIMETAL 50A .15Pd show similar
corrosion resistance. Other metal ions 175TEMPERATURE °F (°C)
such as Cu+2, Ni+2, Mo+6, and Ti+4, also (79)
passivate titanium against attack by
hydrochloric acid. Oxidizing agents such |z,yz|yz|,y,150
as nitric acid, chlorine, sodium (66)
hypochlorite, or chromate ions, also have |zy,z|zy|,y,100125
been shown to be effective inhibitors. (38)(52)
These have allowed titanium to be
successfully utilized in many hydrochloric 75
acid applications. (24) 0 5 10 15 20 25 30 35

|z,z|yzy|,,yWEIGHT%HCl
Table 15

CORROSION OF TITANIUM IN DILUTE PURE HYDROCHLORIC ACID

Corrosion Rate – mpy (mm/y)

Wt. FeCl3 Temp. TIMETAL TIMETAL TIMETAL TIMETAL
% HCL added 50A 6-4 Code 12 50A .15Pd
Room
1 — Room Nil — 0.2 (0.005) 0.1 (0.003)
2 — Room Nil — 0.1 (0.003) 0.2 (0.006)
3 — Room 0.5 (0.013) — 0.5 (0.013) 0.4 (0.010)
5 — Room 0.2 (0.005) — 0.5 (0.013) 0.6 (0.015)
8 — Boiling 0.2 (0.005) — 0.2 (0.005) 0.1 (0.025)
1 — Boiling 85 (2.16) — 1.4 (0.036) 0.8 (0.020)
2 — Boiling 280 (7.11) 260 (6.60) 10.0 (0.254) 1.8 (0.046)
3 — Boiling 550 (14.0) 520 (13.2) 400 (10.2) 2.7 (0.069)
5 — Boiling 840 (21.3) 1030 (26.2) 1500 (38.1) 10.0 (0.254)
8 — 200°F (93°C) >2000 (>50.8) 1900 (48.3) 3000 (76.2) 24.0 (0.610)
3 2g/l 200°F (93°C) 0.2 (0.005) — 1.0 (0.025) 0.1 (0.003)
4 2g/l 0.4 (0.010) — 2.0 (0.050) 0.3 (0.008)

11

TEMPERATURE (°C)FIGURE 8
Effect of Ferric Ions on the Corrosion of TIMETAL 50A,
5mpy (0.127 mm/y) Iso-Corrosion Line

125

0 ppm Fe+3
30 ppm Fe+3 = .0087% FeCl3
60 ppm Fe+3 = .0174% FeCl3

121

75 ppm Fe+3 = .0218% FeCl3
125 ppm Fe+3 = .0362% FeCl3

BOILING POINT

107

93

79

66

52

38

24
0 5 10 15 20 25 30 35
WEIGHT % HCl

12

TEMPERATURE (°C)FIGURE 9
Effect of Ferric Ions on the Corrosion of TIMETAL Code 12,
5mpy (0.127 mm/y) Iso-Corrosion Line

125

0 ppm Fe+3
30 ppm Fe+3 = .0087% FeCl3
60 ppm Fe+3 = .0174% FeCl3

121

75 ppm Fe+3 = .0218% FeCl3
125 ppm Fe+3 = .0362% FeCl3

BOILING POINT

107

93

79

66

52

38

24
0 5 10 15 20 25 30 35
WEIGHT % HCl

13

FIGURE 10
Effect of Ferric Ions on the Corrosion of TIMETAL 50A .15pd,
5mpy (0.127 mm/y) Iso-Corrosion Line

125

0 ppm Fe+3
30 ppm Fe+3 = .0087% FeCl3
60 ppm Fe+3 = .0174% FeCl3

121

75 ppm Fe+3 = .0218% FeCl3
125 ppm Fe+3 = .0362% FeCl3

BOILING POINT

107

93

TEMPERATURE (°C) 79

66

52

38

24

05 10 15 20 25 30 35

WEIGHT % HCL

14

Sulfuric Acid FIGURE 11

Titanium is resistant to corrosive attack Iso-Corrosion Chart for Titanium Alloys in
by dilute solutions of pure sulfuric acid H2SO4 Solutions
at low temperatures. At 32°F (0°C),
unalloyed titanium is resistant to 250
concentrations of about 20 percent (121)
sulfuric acid. This decreases to about 5
percent acid at room temperature 225 5 mpy (0.127 mm/y) ISO-CORROSION LINES
(Figure 11). TIMETAL 50A .15Pd is (107)
resistant to about 45 percent acid at TIMETAL 50A .15Pd
room temperature. In boiling sulfuric TIMETAL CODE 12
acid, unalloyed titanium will show high TIMETAL 50A
corrosion rates in solutions with as
little as 0.5 percent sulfuric acid. 200
TIMETAL Code 12 has useful resistance (93)
up to about 1 percent boiling acid.
TIMETAL 50A .15Pd is useful in boiling TEMPERATURE °F (°C) 175
sulfuric acid to about 7 percent (79)
concentration. The TIMETAL 6-4 alloy
has somewhat less resistance than 150
unalloyed titanium. (66)

The presence of certain multi-valent 125
metal ions or oxidizing agents in sulfuric (52)
acid inhibit the corrosion of titanium in
a manner similar to hydrochloric acid. 100
For instance, cupric and ferric ions (38)
inhibit the corrosion of unalloyed
titanium in 20 percent sulfuric acid
(Table 16). Oxidizing agents, such as
nitric acid, chromic acid, and chlorine
are also effective inhibitors.

75 10 20 30 40 50 60
(24) 0

W E I G H T % H 2S O 4 ( N AT U R A L LY A E R AT E D )

Table 16

EFFECTS OF INHIBITORS ON THE CORROSION OF
UNALLOYED TITANIUM IN 20% SULFURIC ACID

% H2SO4 Addition Temperature °F (°C) Corrosion Rate
20 210 (99) mpy (mm/y)
20 None 210 (99)
2.5 Grams Per Liter >2400 (>61.8)
20 Boiling <2 (<0.051)
Copper Sulfate
16 Grams Per Liter 5 (0.127)

Ferric Ion

15

Phosphoric Acid TIMETAL 50A .15Pd offers significantly Hydrofluoric Acid
improved resistance. At room
Unalloyed titanium is resistant to temperature, 140°F (60°C), and boiling Titanium is rapidly attacked by
naturally aerated pure solutions of TIMETAL 50A .15Pd will resist hydrofluoric acid of even very dilute
phosphoric acid up to 30 percent concentrations of about 80, 15 and 6 concentrations and is therefore not
concentration at room temperature percent, respectively, of the pure recommended for use with hydrofluoric
(Figure 12). This resistance extends to phosphoric acid. TIMETAL Code 12 offers acid solutions or in fluoride containing
about 10 percent pure acid at 140°F somewhat better resistance to phosphoric solutions below pH 7. Certain
(60°C) and 2 percent acid at 212°F acid than unalloyed titanium, but not as complexing metal ions (i.e., Al +3, Cr +6)
(100°C). Boiling solutions significantly good as TIMETAL 50A .15Pd. may effectively inhibit corrosion in
accelerate attack. dilute fluoride solutions.
The presence of multi-valent metal ions,
such as ferric or cupric, or oxidizing Sulfurous Acid
species can be used to inhibit titanium
corrosion in phosphoric acid. Corrosion of unalloyed titanium in
sulfurous acid is low: 0.02 mpy
FIGURE 12 (0.0005 mm/y) in 6 percent
concentration at room temperature.
Corrosion of Titanium Alloys in naturally aerated Samples exposed to sulfurous acid (6
H3pO4 Solutions percent sulfur dioxide content) 212°F
(100°C) showed a corrosion rate of
250 0.04 mpy (0.001 mm/y).
(121)
Other Inorganic Acids
225 5 mpy (0.127 mm/y) ISO-CORROSION LINES
(107) Titanium offers excellent resistance to
TIMETAL 50A .15Pd corrosion by several other inorganic
TIMETAL CODE 12 acids. It is not significantly attacked by
TIMETAL 50A boiling 10 percent solutions of boric or
hydriodic acids. At room temperature,
200 low corrosion rates are obtained on
(93) exposure to 50 percent hydriodic and
40 percent hydrobromic acid solutions.(30)
TEMPERATURE °F (°C) 175
(79) Mixed Acids

150 The addition of nitric acid to hydrochloric
(66) or sulfuric acids significantly reduces
corrosion rates. Titanium is essentially
immune to corrosion by aqua regia
(3 parts HCl: 1 part HNO3) at room
temperature. TIMETAL 50A, TIMETAL
Code 12 and TIMETAL 50A .15Pd show
respectable corrosion rates in boiling
aqua regia (Table 17). Corrosion rates
in mixed acids will generally rise with
increases in the reducing acid component
concentration or temperature.

125
(52)

100
(38)

75 10 20 30 40 50 60 70 80
(24) 0 WEIGHT % H3PO4

16

ALKALINE I N O R G A N I C S A LT
MEDIA SOLUTIONS

Titanium is very resistant to alkaline Titanium is highly resistant to corrosion
media including solutions of sodium by inorganic salt solutions. Corrosion
hydroxide, potassium hydroxide, calcium rates are generally very low at all
hydroxide and ammonium hydroxide. temperatures to the boiling point.
Regardless of concentration, titanium The resistance of titanium to chloride
generally exhibits corrosion rates of less solutions is excellent (Table 3). However,
than or equal to 5 mpy (0.127 mm/yr) crevice corrosion is a concern as
[Table 18]. Near nil corrosion rates are illustrated in Figures 2, 3 and 4. Other
exhibited in boiling calcium hydroxide, acidic salt solutions, particularly those
magnesium hydroxide, and ammonium formed from reducing acids, may also
hydroxide solutions up to saturation. cause crevice corrosion of unalloyed
titanium at elevated temperatures.
Despite low corrosion rates in alkaline For instance, a boiling solution of 10
solutions, hydrogen pickup and possible percent sodium sulfate, pH 2.0, causes
embrittlement of titanium can occur at crevice corrosion on TIMETAL 50A
temperatures above 170°F (77°C) when (Table 4). The TIMETAL Code 12 and
solution pH is greater than or equal to TIMETAL 50A .15Pd alloys, on the other
12. Successful application can be hand, are resistant to this environment.
achieved where this guideline is observed.

Table 17

RESISTANCE OF TITANIUM TO CORROSION
BY BOILING AQUA REGIA*

Alloy Corrosion Rate – mpy (mm/y)

TIMETAL 50A 44 (1.12)
TIMETAL Code 12 24 (0.61)
TIMETAL 50A .15Pd 44 (1.12)

*(1 part HNO3: 3 parts HCl, 96 hour tests)

Table 18

CORROSION RATES OF UNALLOYED TITANIUM
IN NaOH and KOH Solutions

Wt % Temperature Corrosion Rate
°F (°C) mpy (mm/y)
5-10 NaOH
40 NaOH 70 (21) 0.04 (0.001)
40 NaOH 150 (66) 1.5 (0.038)
40 NaOH 200 (93) 2.5 (0.064)
50 NaOH 250 (121) 5.0 (0.127)
50 NaOH 100 (38) 0.06 (0.002)
50 NaOH 150 (66) 0.7 (0.018)
50-73 NaOH 250 (121) 1.3 (0.033)
73 NaOH 370 (188) >43 (>1.09)
73 NaOH 230 (110) 2.0 (0.051)
73 NaOH 240 (116) 5.0 (0.127)
75 NaOH 265 (129) 7.0 (0.178)
10 KOH 250 (121) 1.3 (0.033)
25 KOH 217 (103) 5.1 (0.13)
226 (108) 11.8 (0.30)

17

ORGANIC CHEMICALS

Titanium generally shows good stress corrosion cracking in unalloyed
corrosion resistance to organic media titanium (see Stress Corrosion Cracking)
(Table 19) and is steadily finding when the water content is below
increasing application in equipment for 1.5%.(31,32) At high temperatures in
handling organic compounds. Kane (4) anhydrous environments where
points out that titanium is a standard dissociation of the organic compound
construction material in the Wacker can occur, hydrogen embrittlement of
Process for the production of the titanium may be possible. Since
acetaldehyde by oxidation of ethylene many organic processes contain either
in an aqueous solution of metal trace amounts of water and/or oxygen,
chlorides. Successful application has also titanium has found successful
been established in critical areas of application in organic process streams.
terephthalic and adipic acid production.

Generally, the presence of moisture
(even trace amounts) and oxygen is
very beneficial to the passivity of
titanium in organic media. In certain
anhydrous organic media, titanium
passivity can be difficult to maintain.
For example, methyl alcohol can cause

Table 19

RESISTANCE OF UNALLOYED TITANIUM TO ORGANIC COMPOUNDS

( RE F. 4 ) Concentration % Temperature °F (°C) Corrosion Rate mpy (mm/y)

Medium 99-99.5 68-Boiling (20-Boiling) <5 (<0.127)
25 380-392 (193-200) Nil
Acetic anhydride 700 (371)
Adipic acid + 15-20% glutaric + acetic Vapor — 0.3 (<0.008)
Adiponitrile solution — 95-212 (35-100) 0.1 (0.003)
Adipyl-chloride + chlorobenzene 600 (316) <0.03 (<0.001)
Aniline hydrochloride 5-20 176 (80) 804 (20.4)
Aniline + 2% aluminum chloride 98 Boiling 0.2 (0.005)
Benzene + HCl, NaCl Boiling <5 (<0.127)
Carbon tetrachloride Vapor and Liquid Boiling 0.01 (0.000)
Chloroform 99 302 (150)
Chloroform + water Boiling 5 (0.127)
Cyclohexane + traces formic acid 100 Boiling 0.1 (0.003)
Ethylene dichloride — Boiling <5 (<0.127)
Formaldehyde — Boiling <5 (<0.127)
Tetrachloroethylene 100 Boiling <5 (<0.127)
Tetrachloroethane 37 <5 (<0.127)
Trichlorethylene 100 <0.1 (<0.003)
100
99

18

ORGANIC ACIDS

Titanium is generally quite resistant to Table 20
organic acids.(33) Its behavior is
dependent on whether the environment RESISTANCE OF UNALLOYED TITANIUM TO
is reducing or oxidizing. Only a few ORGANIC ACIDS
organic acids are known to attack
titanium. Among these are hot (R EF. 33) Concentration Temperature Corrosion Rate
non-aerated formic acid, hot oxalic acid, % °F (°C) mpy (mm/y)
concentrated trichloroacetic acid and Acid
solutions of sulfamic acid. Aeration 5 212 (100) Nil
improves the resistance of titanium in Acetic 25 212 (100) Nil
most of these nonoxidizing acid Acetic 50 212 (100) Nil
solutions. In the case of formic acid, it Acetic 75 212 (100) Nil
reduces the corrosion rates to very low Acetic 99.5 212 (100) Nil
values (Table 20). Acetic 50 212 (100) <.01 (<0.0003)
Citric 50 212 (100) <5 ( <0.127)
Unalloyed titanium corrodes at a very Citric (aerated) 50 14 (0.356)
low rate in boiling 0.3 percent sulfamic Citric (nonaerated) 10 Boil <5 (<0.127)
acid and at a rate of over 100 mpy Formic (aerated) 25 212 (100) <5 (<0.127)
(2.54 mm/y) in 0.7 percent boiling Formic (aerated) 50 212 (100) <5 (<0.127)
sulfamic acid. Addition of ferric chloride Formic (aerated) 90 212 (100) <5 (<0.127)
(0.375 g/l) to the 0.7 percent solution Formic (aerated) 10 212 (100) >50 (>01.27)
reduces the corrosion rate to 1.2 mpy Formic (nonaerated) 25 >50 (>01.27)
(0.031 mm/y). Formic (nonaerated) 50 Boil >50 (>01.27)
Formic (nonaerated) 90 Boil >50 (>01.27)
Boiling solutions containing more than Formic (nonaerated) 10 Boil 0.12 (0.003)
3.5 g/l of sulfamic acid can rapidly attack Lactic 10 Boil 1.88 (0.048)
unalloyed titanium. For this reason, Lactic 85 140 (60) 0.33 (0.008)
extreme care should be exercised when Lactic 10 212 (100) 0.55 (0.014)
titanium heat exchangers are descaled Lactic (nonaerated) 25 212 (100) 1.09 (0.028)
with sulfamic acid. The pH of the acid Lactic (nonaerated) 85 Boil 0.40 (0.010)
should not be allowed to go below 1.0 Lactic (nonaerated) Boil 5.96 (0.151)
to avoid corrosion of titanium. Oxalic 1 Boil 177 (4.50)
Consideration should also be given to Oxalic 1 95 (35) 1945 (49.4)
inhibiting the acid with ferric chloride. Oxalic 25 140 (60) <5 (<0.127)
Stearic 100 212 (100) 0.2 (0.005)
Titanium is resistant to acetic acid(4) over Tartaric 50 360 (182) Nil
a wide range of concentrations and Tannic 25 212 (100)
temperatures well beyond the boiling 212 (100)
point. It is being used in terephthalic acid
and adipic acid up to 400°F (204°C) and Table 21
at 67% concentration. Good resistance is
observed in citric, tartaric, stearic, lactic resistance of titanium to boiling
and tannic acids (see Table 20). NONAERATED ORGANIC ACIDS

TIMETAL Code 12 and TIMETAL 50A Corrosion Rate – mpy (mm/y)
.15Pd may offer considerably improved
corrosion resistance to organic acids TIMETAL TIMETAL TIMETAL
which attack unalloyed titanium (Table
21). Similarly, the presence of multi-valent Acid Solution 50A Code 12 50A .15Pd
metal ions in solution may result in
substantially reduced corrosion rates. 50% Citric 14 (0.356) 0.5 (0.01) 0.6 (0.015)
10% Sulfamic 538 (13.7) 455 (11.6) 14.6 (0.371)
45% Formic 433 (11.0)
88-90% Formic 83-141 (2.1-3.6) Nil Nil
90% Formic 0-22 (0-0.56) 0-2.2 (0-0.056)
90 (2.29)
(Anodized Specimens) 2.2 (0.056) Nil
10% Oxalic
3,700 (94.0) 4,100 (104) 1,270 (32.3)

19

OXYGEN

FIGURE 13 Titanium has excellent resistance to
gaseous oxygen and air at temperatures
Ignition and Propagation Limits of Unalloyed up to about 700°F (371°C). At 700°F it
Titanium in Helium-Oxygen and Steam-Oxygen Mixtures acquires a light straw color. Further
heating to 800°F (426°C) in air may
( R E F. 3 6 ) result in a heavy oxide layer because of
increased diffusion of oxygen through
2200 the titanium lattice. Above 1,200°F
(649°C), titanium lacks oxidation
1800 STATIC TESTS resistance and will become brittle. Scale
forms rapidly at 1,700°F (927°C).
TOTAL PRESSURE PSI 1400 IGNITION
1000 REGION Titanium resists atmospheric corrosion.
Twenty year ambient temperature tests
DYNAMIC produced a maximum corrosion rate of
TESTS 0.0010 mpy (2.54 x 10-5 mm/y) in a
marine atmosphere and a similar rate in
600 P R O PA G AT I O N industrial and rural atmospheres.(34)
(HELIUM-OXYGEN)
200 Caution should be exercised in using
0 P R O PA G AT I O N titanium in high oxygen atmospheres.
0 (STEAM-OXYGEN) Under some conditions, it may ignite
and burn. J.D. Jackson and Associates
P R O PA G AT I O N reported that ignition cannot be induced
REGION even at very high pressure when the
oxygen content of the environment was
20 40 60 80 100 less than 35%.(35) However, once the
VOLUME PERCENT OXYGEN reaction has started, it will propagate in
atmospheres with much lower oxygen
FIGURE 14 levels than are needed to start it. Steam
Effect of Temperature on Spontaneous ignition of as a diluent allowed the reaction to
Ruptured unalloyed titanium in Oxygen proceed at even lower O2 levels. The
temperature, oxygen pressure, and
( R E F. 3 6 ) concentration limits under which ignition
2192 and propagation occur are shown in
Figures 13 and 14. When a fresh
(1200) titanium surface is exposed to an oxygen
atmosphere, it oxidizes rapidly and
1832 exothermically. Rate of oxidation
(1000) depends on O2 pressure and
concentration. When the rate is high
TEMPERATURE °F (°C) 1472 IGNITION enough so that heat is given off faster
(800) than it can be conducted away, the
1112 surface may begin to melt. The reaction
(600) becomes self-sustaining because, above
the melting point, the oxides diffuse
rapidly into the titanium interior,
allowing highly reactive fresh molten
titanium to react at the surface.

752 NO IGNITION
(400)

392
(200)

0

0 50 100 150 200 250 300 350
OXYGEN PRESSURE PSI

20

HYDROGEN

The surface oxide film on titanium acts 1. The pH of the solution is less than 3. There must be some mechanism for
as an effective barrier to penetration by 3 or greater than 12; the metal generating hydrogen. This may be a
hydrogen. Disruption of the oxide film surface must be damaged by galvanic couple, cathodic protection
allows easy penetration by hydrogen. abrasion; or impressed potentials are by impressed current, corrosion of
When the solubility limit of hydrogen in more negative than -0.70V.(39) titanium, or dynamic abrasion of the
titanium (about 100-150 ppm for surface with sufficient intensity to
TIMETAL 50A) is exceeded, hydrides 2. The temperature is above 170°F depress the metal potential below
begin to precipitate. Absorption of (77°C) or only surface hydride films that required for spontaneous
several hundred ppm of hydrogen results will form which, experience indicates, evolution of hydrogen.
in embrittlement and the possibility of do not seriously affect the properties
cracking under conditions of stress. of the metal. Failures due to
hydriding are rarely encountered
Titanium can absorb hydrogen from below this temperature. (There is
environments containing hydrogen gas. some evidence that severe tensile
At temperatures below 170°F (77°C) stresses may promote hydriding at
hydrogen pickup occurs so slowly that it low temperatures.)(39)
has no practical significance, except in
cases where severe tensile stresses are Table 22
present.(37) In the presence of pure
hydrogen gas under anhydrous effect of VARIOUS SURFACE TREATMENTS ON
conditions, severe hydriding can be ABSORPTION OF DRY AND OXYGEN-FREE HYDROGEN
expected at elevated temperatures and BY UNALLOYED TITANIUM*
pressures. This is shown by the data in
Table 22. These data also demonstrate Temperature Hydrogen Freshly Hydrogen Pickup ppm
that surface condition is important to °F (°C) Pressure Picked
hydrogen penetration. Iron
300 (149) psi 0 Contaminated Anodized
Titanium is not recommended for use in 300 (149) 58
pure hydrogen because of the 300 (149) Atmospheric 28 0 0
possibility of hydriding if the oxide film 600 (316) 400 174 0
is broken. Laboratory tests (Table 23) 600 (316) 800 0 117 0
have shown that the presence of as 600 (316) 2,586 0
little as 2% moisture in hydrogen gas Atmospheric 4,480 0 516
effectively passivates titanium so that 400 5,951 10,000
hydrogen absorption does not occur. 800 13,500
This probably accounts for the fact that
titanium is being used successfully in *96 hour exposures. Oxygen was removed by passing hydrogen over an incandescent platinum filament
many process streams containing and then through silica gel to remove moisture.
hydrogen with very few instances of
hydriding being reported. Table 23

A more serious situation exists when effect of MOISTURE ON ABSORPTION OF HYDROGEN
cathodically impressed or galvanically BY UNALLOYED TITANIUM AT 600°F (316°C)
induced currents generate nascent AND 800 PSI PRESSURE*
hydrogen directly on the surface of
titanium. The presence of moisture % H2O Hydrogen Pickup ppm
does not inhibit hydrogen absorption
of this type. 0 4,480
0.5 51,000
Laboratory experiments have shown 1.0
that three conditions usually exist 2.0 700
simultaneously for hydriding to occur:(38) 3.3 7
5.3
10.2 10
22.5 17
37.5 11
56.2
0
0
0

*96 hour exposures.

21

SULFUR DIOXIDE
AND HYDROGEN SULFIDE

Most of the hydriding failures of Titanium is resistant to corrosion by TIMETAL 50A, TIMETAL 75A, TIMETAL
titanium that have occurred in service gaseous sulfur dioxide and water 50A .15Pd and TIMETAL Code 12
can be explained on this basis.(38) saturated with sulfur dioxide (Table 24). stressed to 98 percent of yield strength in
Sulfurous acid solutions also have little this environment survived a 30-day room
In seawater, hydrogen can be produced effect on titanium. Titanium has temperature exposure.
on titanium as the cathode by galvanic demonstrated superior performance in
coupling to a dissimilar metal such as wet SO2 scrubber environments of In addition, C-ring specimens of these
zinc or aluminum which are very active power plant FGD systems. same grades of titanium were subjected
(low) in the galvanic series. Coupling to to a stress corrosion cracking test as
carbon steel or other metals higher in Titanium is not corroded by moist or dry specified in ASTM G38-73 Standard
the galvanic series generally does not hydrogen sulfide gas. It is also highly Recommended Practice. Two series of
generate hydrogen in neutral solutions, resistant to aqueous solutions containing tests were run: one with the specimens
even though corrosion is progressing on hydrogen sulfide. The only known stressed to 75% of yield, and the other
the dissimilar metal. The presence of detrimental effect is the hydriding stressed to 100% of yield. The specimens
hydrogen sulfide, which dissociates problem discussed in the previous were exposed in an ASTM synthetic
readily and lowers pH, apparently allows section. In galvanic couples with certain seawater solution saturated with H2S and
generation of hydrogen on titanium if it metals such as iron, the presence of CO2 at 400°F (204°C). Solution pH was
is coupled to actively corroding carbon H2S will promote hydriding. Hydriding, 3.5 and specimens were exposed for 30
steel or stainless steel. however, does not occur in aqueous days. There were no failures and no
solutions containing H2S if unfavorable evidence of any corrosion.
Within the range pH 3 to 12, the oxide galvanic couples are avoided. For
film on titanium is stable and presents a example, titanium is fully resistant to Titanium is highly resistant to general
barrier to penetration by hydrogen. corrosion and stress cracking in the corrosion and pitting in the sulfide
Efforts at cathodically charging NACE* test solution which consists of environment to temperatures as high as
hydrogen into titanium in this pH range oxygen-free water containing about 500°F (260°C). Sulfide scales do not
have been unsuccessful in short-term 3,000 ppm dissolved H2S, 5 percent form on titanium, thereby maintaining
tests.(38) If pH is below 3 or above 12, NaCl, and 0.5 percent acetic acid good heat transfer.
the oxide film is believed to be unstable (pH 3.5). Tensile specimens of
and less protective. Breakdown of the
oxide film facilitates access of available *National Association of Corrosion Engineers
hydrogen to the underlying titanium
metal. Mechanical disruption of the film Table 24
(i.e. iron is smeared into the surface)
permits entry of hydrogen at any pH Corrosion of Unalloyed Titanium by
level. Impressed currents involving Sulfur-Containing Gases
cathodic potentials more negative than
-0.7V in near neutral brines can result in (R EF. 33) Temperature Corrosion Rate
hydrogen pickup in long-term °F (°C) mpy (mm/y)
exposures.(39) Furthermore, very high Gas
cathodic current densities (more Sulfur dioxide (dry) 70 (21) Nil
negative than -1.0V SCE) may Sulfur dioxide (water saturated) 70 (21) <0.1 (<0.003)
accelerate hydrogen absorption and Hydrogen sulfide (water saturated) 70 (21) <5.0 (<0.127)
eventual embrittlement of titanium in
seawater even at ambient temperatures.

Hydriding can be avoided if proper
consideration is given to equipment
design and service conditions in order
to eliminate detrimental galvanic
couples or other conditions that will
promote hydriding.

22

NITROGEN AND AMMONIA LIQUID METALS

Titanium reacts with pure nitrogen to The formation of ammonium chloride Titanium has good resistance to many
form surface films having a gold color scale could result in crevice corrosion of liquid metals at moderate temperatures.
above 1,000°F (538°C). Above 1,500°F TIMETAL 50A at boiling temperatures as In some cases at higher temperatures it
(816°C), diffusion of the nitride into shown in Table 25. TIMETAL Code 12 dissolves rapidly. It is used successfully in
titanium may cause embrittlement. and TIMETAL 50A .15Pd are totally some applications up to 1,650°F (899°C).
resistant under these conditions. This Kane cites the use of titanium in molten
Jones et al. (1977) have shown that crevice corrosion behavior is similar to aluminum for pouring nozzles, skimmer
titanium is not corroded by liquid that shown in Figures 2 and 4 for rakes and casting ladles.(4) However,
anhydrous ammonia at room sodium chloride. rapidly flowing molten aluminum can
temperature.(40) Low corrosion rates are erode titanium and some metals such as
obtained at 104°F (40°C).(41) Titanium cadmium can cause stress corrosion
also resists gaseous ammonia. cracking. Some data for titanium in liquid
However, at temperatures above 302°F metals is reported in Table 26.
(150°C), ammonia will decompose and
form hydrogen and nitrogen. Under
these circumstances, titanium could
absorb hydrogen and become
embrittled. The high corrosion rate
experienced by titanium in the
ammonia-steam environment at 428°F
(220°C) in Table 25 is believed to be
associated with hydriding.

Table 25 also contains data which
illustrate the resistance of titanium to
ammonium hydroxide. Excellent
resistance is offered by titanium to
concentrated solutions (up to 70%
NH4OH) to the boiling point.(41)

Table 25

Corrosion of Unalloyed Titanium in Ammonia
and Ammonium Compounds

Environment Temperature Duration Corrosion Rate References
°F (°C) Days mpy (mm/y)
Liquid Anhydrous Ammonia (40)
Anhydrous Ammonia 75 (24) 30-240 0 to wt. Gain (41)
NH3, Steam Water 104 (40) — 5.1 (0.13) (41)
28% NH4OH 431 (221) — (42)
70% NH4OH, Boiling — 440.0 (11.2) (41)
NH4OH, (NH4)2CO3, NH4Cl, NaCl 75 (24) 21 0.10 (0.0025) (43)
NH4OH, (NH4)2CO3, NH4Cl, NaCl, (NH4)2S 210 (99) 220 Nil* (43)
10% NH4Cl (pH 4.1) 150 (66) 220 (41)
150 (66) 21 0.003 (0.00008)
Boiling 0.20 (0.005)
Nil**

**No corrosion experienced on TIMETAL 50A, TIMETAL Code 12 or TIMETAL 50A .15Pd.
**No corrosion on TIMETAL Code 12 or TIMETAL 50A .15Pd; crevice corrosion on TIMETAL 50A.

23

ANODIZING AND
O X I D AT I O N
T R E AT M E N T S

Table 26 Anodizing has been recommended for
many years as a method of improving
CORROSION OF Unalloyed Titanium the corrosion resistance of titanium and
in Liquid Metal removing surface impurities such as
embedded iron particles.(44) It was
( RE F. 4 ) Temperature °F (°C) Resistance reasoned that since titanium’s corrosion
resistance is due to the oxide film that
Liquid Metal 1380 (749) Good forms on its surface, any treatment,
300 (149) Good such as anodizing, which thickens this
Magnesium 600 (316) Poor film will serve to increase the corrosion
Mercury* Good resistance of titanium.
Mercury* 1000 (538) Good
NaK 930 (499) Good Careful laboratory tests have shown this
Tin 750 (399) Poor may not be true. The films formed on
Gallium 840 (449) Poor titanium at elevated temperatures in air
Gallium 930 (499) Poor have been found to have a rutile
Cadmium* 140 (60) Poor structure which is quite resistant to acids
Lithium and can, therefore, improve the corrosion
Lead 1500 (816) resistance. Anodizing, on the other hand,
forms a hydrated structure which is much
*May cause stress corrosion. Silver and gold have also been reported to cause stress corrosion. less resistant to acids.(45,46) Tests in boiling
HCl solution (Table 27) have shown no
Table 27 significant difference in corrosion
resistance between anodized and freshly
Corrosion Rate vs. Weight Percent HCL pickled specimens. Anodizing has been
for Pickled, Anodized and Thermally shown to give a marginal improvement
Oxidized TIMETAL 50A in resistance to hydrogen absorption
(Table 28) but not nearly as much
Corrosion Rate – mpy (mm/y) as thermal oxidation.(45)

Boiling Pickled Anodized Thermally Oxidized It is true that anodizing helps to remove
wt. % HCl (+25 volts) (677°C, 1 min.) surface impurities such as embedded
0.08 (0.002) iron particles. However, excessively long
0.05 3.0 (0.076) 0.09 (0.002) 0.11 (0.003) anodizing times may be required to
0.10 7.6 (0.193) 3.5 (0.089) Nil completely remove these particles.
0.20 8.3 (0.211) Examination with a scanning electron
0.50 30.0 (0.762) 0.07 (0.002) microscope has proven that surface iron
0.70 47.0 (1.19) 30.0 (0.762) 0.07 (0.002) contamination still persists, although
0.80 57.9 (1.47) 48.3 (1.23) 0.07 (0.002) diminished, even after 20 minutes
0.90 56.0 (1.42) 0.11 (0.003) anodizing. A more effective method is
1.00 — 73.0 (1.85) to pickle in 12% HNO3/1% HF at
75.0 (1.91) — 85.8 (2.18) ambient temperature for 5 minutes
80.0 (2.03) followed by a water rinse. Specimens
known to have embedded iron particles
Table 28 were found to be completely free of any
surface iron contamination by the
Effect of Surface Condition oF TIMETAL 50A on scanning electron microscope following
Hydrogen Uptake from Cathodic Charging this procedure.

Surface Condition Average Hydrogen
Pickup (ppm)
Pickled
Anodized 164
Thermally Oxidized (677°C) (1 min.) 140
Thermally Oxidized (677°C) (5 min.) 94
Thermally Oxidized (760°C) (1 min.) 92
Thermally Oxidized (760°C) (5 min.) 82
42

24

TYPES OF CORROSION

Titanium, like any other metal, is subject Table 29
to corrosion in some environments.
The types of corrosion that have been POTENTIALs FOR ANODIC PASSIVATION OF
observed on titanium may be classified UNALLOYED TITANIUM
under the general headings: general
corrosion, crevice corrosion, stress Acid Applied Corrosion Rate Reduction
corrosion cracking, anodic breakdown Potential mpy (mm/y) of
pitting, hydriding and galvanic corrosion. 40% Sulfuric (1)
37% Hydrochloric (1) Volts 0.2 (0.005) Corrosion
In any contemplated application of 60% Phosphoric (1) (H2) 2.7 (0.068) Rate
titanium, its susceptibility to corrosion 50% Formic (2) 0.7 (0.018)
by any of these modes should be 25% Oxalic (2) 2.1 3.3 (0.083) 11,000X
considered. In order to understand the 20% Sulfamic (3) 1.7 9.8 (0.250) 2,080X
advantages and limitations of titanium, 2.7 0.2 (0.005) 307X
each of these types of corrosion will 1.4 70X
be explained. 1.6 350X
0.7 2,710X
General Corrosion
(1)60°C (2)B.P. (3)90°C
General corrosion is characterized by a
uniform attack over the entire exposed Figure 15. - Crevice Corrosion Under Deposit
surface of the metal. The severity of this 25
type of attack can be expressed by a
corrosion rate. This type of corrosion is
most frequently encountered in hot
reducing acid solutions.

Oxidizing agents and certain
multi-valent metal ions have the ability
to passivate titanium in environments
where the metal may be subject to
general corrosion. Many process
streams, particularly H2SO4 and HCl
solutions, contain enough impurities in
the form of ferric, cupric ions, etc., to
passivate titanium and give trouble-free
service. In some cases, it may be
possible to inhibit corrosion by the
addition of suitable passivating agents.

Anodic protection has proven to be
quite effective in suppressing corrosion
of titanium in many acid solutions.
Almost complete passivity can be
maintained at almost any acid
concentration by the proper application
of a small anodic potential. Table 29 (47)
gives data showing the passivation
achieved in some typical environments.

This procedure is most often employed
in acid solutions having a high
breakdown potential such as sulfates
and phosphates. In halides and some
other media, there is a danger of
exceeding the breakdown potential
which can result in severe pitting. The
method is only effective in the area
immersed in the solution. It will not
prevent attack in the vapor phase.

If the use of passivating agents or metal outside the crevice acting as the these metals have proven to be quite
anodic protection is not feasible, cathode as shown in Figure 16.(48) Metal effective in suppressing crevice corrosion.
TIMETAL Code 12 or TIMETAL 50A .15Pd dissolves at the anode under the
may solve the problem since these alloys influence of the resulting current. Alloying with elements such as nickel,
are much more corrosion resistant than Titanium chlorides formed in the crevice molybdenum, or palladium is also an
the commercially pure grades. are unstable and tend to hydrolize, effective means of overcoming crevice
forming small amounts of HCl. This corrosion problems. This is demonstrated
Crevice Corrosion reaction is very slow at first, but in the by the performance of TIMETAL Code 12
very restricted volume of the crevice, it and TIMETAL 50A .15Pd alloys which are
This is a localized type of attack that can reduce the pH of the solution to much more resistant to crevice corrosion
occurs only in tight crevices. The values as low as 1. This reduces the than commercially pure grades.
crevice may be the result of a potential still further until corrosion
structural feature such as a flange or becomes quite severe. Stress Corrosion
gasket, or it may be caused by the Cracking (SCC)
buildup of scales or deposits. Figure 15 Although crevice corrosion of titanium
shows a typical example of crevice is most often observed in hot chloride This mode of corrosion is characterized
corrosion under a deposit. solutions, it has also been observed in by cracking under stress in certain
iodide, bromide, fluoride and sulfate environments. Titanium is subject to
Dissolved oxygen or other oxidizing solutions.(44) this form of corrosion in only a few
species present in the solution are environments such as red fuming nitric
depleted in restricted volume of solution The presence of small amounts of multi- acid, nitrogen tetraoxide and absolute
in the crevice. These species are valent ions in the crevice of such metals methanol.(50) In most cases, the
consumed faster than they can be as nickel, copper or molybdenum, which addition of a small amount of water
replenished by diffusion from the bulk act as cathodic depolarizers, tends to will serve to passivate the titanium.(51)
solution.(44) As a result, the potential of drive the corrosion potential of the Titanium is not recommended for use
the metal in the crevice becomes more titanium in the crevice in the positive in these environments under
negative than the potential of the metal direction. This counteracts the effect of anhydrous conditions.
exposed to the bulk solution. This sets oxygen depletion and low pH and
up an electrolytic cell with the metal in effectively prevents crevice corrosion. The TIMETAL 6-4 alloy is subject to SCC
the crevice acting as the anode and the Gaskets impregnated with oxides of in chloride environments under some
circumstances. TIMETAL 35A and
FIGURE 16 TIMETAL 50A appear to be immune
Schematic Diagram of a crevice corrosion cell to chloride SCC.

( R E F. 4 8 ) Anodic Breakdown
Pitting
Na+ O2 OH e
This type of corrosion is highly localized
O2 CI O2 OH e and can cause extensive damage to
Na+ equipment in a very short time. Pitting
occurs when the potential of the metal
M+ M+ exceeds the breakdown potential of the
protective oxide film on the titanium
O2 CI CI M+ M+ CI surface.(52) Fortunately, the breakdown
CI M+ M+ M+ potential of titanium is very high in most
CI environments so that this mode of failure
CI H+ is not common. The breakdown potential
in sulfate and phosphate environments is
O2 O2 O2 C I CI in the 100 volt range. In chlorides it is
about 8 to 10 volts, but in bromides and
CI M+ H+ iodides it may be as low as 1 volt.
CI
Increasing temperature and acidity tend
OH OH OH M+ M+ to lower the breakdown potential so that
under some extreme conditions the
M+ potential of the metal may equal or
M+ exceed the breakdown potential and
spontaneous pitting will occur. This
e type of corrosion is most frequently
encountered in applications where an
anodic potential exceeding the

26

breakdown potential is impressed on the Figure 17. - Anodic Breakdown Pitting of Titanium
metal. An example is shown in Figure 17.
This is a close-up view of the side plate Figure 18. - Unalloyed Titanium Tube which has been perforated by
of a titanium anode basket used in a zinc Pitting in Hot Brine
plating cell. It was a chloride electrolyte
and the cell was operated at 10 volts
which is about 1-2 volts above the
breakdown potential for titanium in this
environment. Extensive pitting
completely destroyed the basket.

This type of pitting is sometimes caused
inadvertently by improper grounding of
equipment during welding or other
operations that can produce an anodic
potential on the titanium.

This type of corrosion can be avoided in
most instances by making certain that no
impressed anodic currents approaching
the breakdown potential are applied to
the equipment.

Another type of pitting failure that is
sometimes encountered in commercially
pure titanium is shown in Figure 18. The
specimen in Figure 18 showed scratch
marks which gave indications of iron
when examined with an electronprobe.
It is believed the pit initiated at a point
where iron had been smeared into the
titanium surface until it penetrated the
TiO2 protective film.

Potential measurements on mild steel
and unalloyed titanium immersed in a
saturated brine solution at temperatures
near the boiling point gave a potential
difference of nearly 0.5 volt. This is
sufficient to establish an electrochemical
cell in which the iron would be
consumed as the anode. By the time the
iron is consumed, a pit has started to
grow in which acid conditions develop
preventing the formation of a passive
film and the reaction continues until the
tube is perforated.(53)

This type of pitting appears to be a
high temperature phenomenon. It has
not been known to occur below 170°F
(77°C). It has not been induced on
TIMETAL Code 12 or TIMETAL 50A .15Pd
in laboratory tests. These two alloys are
believed to be highly resistant to this type
of attack. However precautions should be
taken with all titanium alloys to remove
or avoid surface iron contamination, if the
application involves temperatures in
excess of 170°F (77°C).

27

The most effective means of removing The oxide film which covers the surface Titanium is being used extensively with
surface iron contamination is to clean of titanium is a very effective barrier to very few problems in oil refineries in
the titanium surface by immersion in hydrogen penetration, however, many applications where the process
35% HNO3 – 5% HF solution for two to titanium can absorb hydrogen from streams contain hydrogen.
five minutes followed by a water rinse. hydrogen containing environments
under some circumstances. A more serious problem occurs when
Hydrogen Embrittlement cathodically impressed or galvanically
At temperatures below 170°F (77°C) induced currents generate atomic
Titanium is being widely used in hydriding occurs so slowly that it has no (nascent) hydrogen directly on the
hydrogen-containing environments and practical significance, except in cases surface of titanium. The presence of
under conditions where galvanic couples where severe tensile stresses are present. moisture does not inhibit hydrogen
or cathodic protection systems cause In the presence of pure anhydrous absorption of this type.(38)
hydrogen to be evolved on the surface hydrogen gas at elevated temperatures
of titanium. In most instances, no and pressures, severe hydriding of Laboratory investigations and experience
problems have been reported. However, titanium can be expected. Titanium is have demonstrated that three conditions
there have been some equipment not recommended for use in pure usually exist simultaneously for hydriding
failures in which embrittlement by hydrogen because of the possibility of of unalloyed titanium to occur:
hydride formation was implicated. hydriding if the oxide film is broken.
Laboratory tests, however, have shown 1. The pH of the solution is less than
An example of a hydrided titanium tube that the presence of as little as 2% 3 or greater than 12; the metal
is shown in Figure 19. This is a moisture in hydrogen gas effectively surface must be damaged by
photomicrograph of a cross section of passivates titanium so that hydrogen abrasion; or impressed potentials are
the tube wall. The brown-black absorption does not occur even at more negative than -0.70V.(39)
needle-like formations are hydrides. pressures as high as 800 psi and
Note the heavy concentration at the temperatures to 315°F (157°C). It is 2. The temperature is above 170°F
bottom which indicates the hydrogen believed that the moisture serves as a (77°C) or only surface hydride films
entered from this surface. source of oxygen to keep the protective will form, which experience indicates
oxide film in a good state of repair. do not seriously affect the properties
of the metal. Failures due to
hydriding are rarely encountered
below this temperature.(37) (There is
some evidence that severe tensile
stresses may promote diffusion at
low temperatures.)

3. There must be some mechanism for
generating hydrogen. This may be a
galvanic couple, cathodic protection
by impressed current, corrosion of
titanium, or dynamic abrasion of the
surface with sufficient intensity to
depress the metal potential below
that required for spontaneous
evolution of hydrogen.

Most of the hydriding failures of
titanium that have occurred in service
can be explained on this basis.(38)
Hydriding can usually be avoided by
altering at least one of the three
conditions listed above. Note that
accelerated hydrogen absorption of
titanium at very high cathodic current
densities (more negative than -1.0V
SCE) in ambient temperature seawater
represents an exception to this rule.

Magnification 75X

Figure 19. - Hydrided Titanium
28

Galvanic Corrosion FIGURE 20

The coupling of titanium with dissimilar Galvanic Series of Various Metals in Flowing Water
metals usually does not accelerate the at 2.4 to 4.0 m/s for 5 to 15 days at 5° to 30°C
corrosion of the titanium. The exception
is in reducing environments where ( R E F. 5 6 )
titanium does not passivate. Under
these conditions, it has a potential (ACTIVE) V O LT S V E R S U S S AT U R AT E D C A L O M E L R E F E R E N C E E L E C T R O D E (NOBLE)
similar to aluminum and will undergo -1.6 +0.2
accelerated corrosion when coupled to -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0
other more noble metals.
GRAPHITE
Figure 20 gives the galvanic series in P L AT I N U M
seawater. In this environment, titanium is
passive and exhibits a potential of about Ni-Cr-Mo ALLOY C
0.0V versus a saturated calomel T I TA N I U M
reference cell(56) which places it high on
the passive or noble end of the series. Ni-Cr-Mo-Cu-Si ALLOY B
NICKEL-IRON CHROMIUM ALLOY 825
For most environments, titanium will be
the cathodic member of any galvanic ALLOY “20” STAINLESS STEELS, CAST AND WROUGHT
couple. It may accelerate the corrosion of STAINLESS STEEL - TYPES 316, 317
the other member of the couple, but in
most cases, the titanium will be NICKEL-COPPER ALLOYS 400, K-500
unaffected. Figure 21 shows the
accelerating effect that titanium has on STAINLESS STEEL - TYPES 302, 304, 321, 347
the corrosion rate of various metals when
they are galvanically connected in S I LV E R
seawater. If the area of the titanium NICKEL 200
exposed is small in relation to the area of
the other metal, the effect on the S I LV E R B R A Z E A L L O Y S
corrosion rate is negligible. However, if NICKEL-CHROMIUM ALLOY 600
the area of the titanium (cathode) greatly
exceeds the area of the other metal NICKEL-ALUMINUM BRONZE
(anode) severe corrosion may result.
70-30 COPPER NICKEL
Because titanium is usually the cathodic
member of any galvanic couple, LEAD
hydrogen will be evolved on its surface STAINLESS STEEL TYPE 430
proportional to the galvanic current
flow. This may result in the formation 80-20 COPPER NICKEL
of surface hydride films that are 90-10 COPPER NICKEL
generally stable and cause no
problems. If the temperature is above N I C K E L S I LV E R
170°F (77°C), however, hydriding can
cause embrittlement. STAINLESS STEEL - TYPES 410, 416

In order to avoid problems with galvanic TIN BRONZES (G&M)
corrosion, it is best to construct SILICON BRONZE
equipment of a single metal. If this is
not practical, use two metals that are MANGANESE BRONZE
close together in the galvanic series, A D M I R A LT Y B R A S S , A L U M I N U M B R A S S
insulate the joint or cathodically protect
the less noble metal. If dissimilar metals Pb-Sn SOLDER (50/50)
are necessary, construct the critical parts COPPER
out of titanium, since it is usually not TIN
attacked, and use large areas of the less
noble metal and heavy sections to allow NAVAL BRASS, YELLOW BRASS, RED BRASS
for increased corrosion.
ALUMINUM BRONZE
AUSTENITIC NICKEL CAST IRON

LOW ALLOY STEEL

MILD STEEL, CAST IRON
CADMIUM

ALUMINUM ALLOYS
BERYLIUM

ZINC

MAGNESIUM

NOTE: GREEN BOXES INDICATE ACTIVE BEHAVIOR OF ACTIVE-PASSIVE ALLOYS

29

FIGURE 21 1
The dissimilar Metals Problem

(REF 11)

1 - LOW CARBON STEEL
2 - GUNMETAL (88/10/2)
3 - ALUMINUM
4 - 70 Cu-30Ni
5 - 80 Cu-20 Ni
6 - MONEL 967/31/1/1)
7 - ALUMINUM BRONZE 614
8 - 60/40 BRASS (MUNTZ METAL)
9 - ALUMINUM BRASS (ALLOY 687)
10 - 18/8 STAINLESS (304)

2500 HOUR IN SEAWATER

10/1 1/10

Ti ANODE/CATHODE Ti
AREA RATIO

G A LVA N I C mpy (mm/y) 2
AT TA C K 10 (.254) 3
ADDITION
8 (.203)
NORMAL
UNCOUPLED
CORROSION

1

6 (.152)

4 (.102) 4

9 65

2 2 (.051) 87

345 7 10
8 00
6

9 10

30

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1. V.V. Andreeva, Corrosion, 20, 11. J.B. Cotton and B.P. Downing, 20. W.L. Adamson, “Marine Fouling of
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Series, John Wiley & Sons, Inc., ASTM STP 576, (1967). Nitric Acid,” The Science,
New York (1967). Technology and Applications of
14. G.J. Danek, Jr., “The Effect of Titanium, Ed. by R.I. Jaffee and N.E.
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Kane, “The Use of Titanium in the Behavior of Metals,” Naval (1970), p. 209.
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presented at the fall meeting of the p. 763, (1966). 23. T.F. Degnan, “Materials for
Technical Association of the Pulp Handling Hydrofluoric, Nitric and
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Colorado, 1970. Service in Seawater, Brine and Other Corrosion, NACE, Houston, Texas,
Natural Aqueous Environments: The p. 229, (1975).
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Imperial Metal Industries (Kynoch) Corrosion Characteristics of Titanium 24. L.L. Gilbert and C.W. Funk,
Ltd., Birmingham, England, (1969). in Seawater, Polluted Inland “Explosions of Titanium and Fuming
Waters and in Brines,” Titanium Nitric Acid Mixtures,” Metal
7. P.C. Hughes, and I.R. Lamborn, Information Bulletin, Imperial Progress, Nov. 1956, pp. 93-96.
“Contamination of Titanium by Metal Industries (Kynoch) Limited,
Water Vapor,” Jr. of the Institute May (1970). 25. H.B. Bomberger, “Titanium
of Metals, 1960-61 Vol. 89, Corrosion and Inhibition in Fuming
pp. 165-168. 16. M.J. Blackburn, J.A. Feeney and Nitric Acid,” Corrosion, Vol.13,
T.R. Beck, “Stress-Corrosion Cracking No. 5, May 1957, pp. 287-291.
8. L.C. Covington, W.M. Parris, and of Titanium Alloys”, pp. 67-292 in
D.M. McCue, “The Resistance of Advances in Corrosion Science and 26. Handbook on Titanium Metal,
Titanium Tubes to Hydrogen Technology, Vol. 3, Plenum Press, 7th Edition, Titanium Metals Corp.
Embrittlement in Surface New York (1973). of America.
Condensers,” paper No. 79
Corrosion/79, March 22-26, 1976, 17. F.W. Fink and W.K. Boyd, “The 27. F.L. LaQue, “Corrosion Resistance
Houston, Texas. Corrosion of Metals in Marine of Titanium,” Report on Corrosion
Environments,” DMIC Report 245, Tests, Oct. 1951, Development and
9. F.M. Reinhart, “Corrosion of May, (1970). Research Division, The International
Materials in Hydrospace, Part III, Nickel Co., Inc., 67 Wall St., New
Titanium and Titanium Alloys,” 18. D.R. Mitchell, “Fatigue Properties York, New York.
U.S. Naval Civil Engineering Lab., of Ti-50A Welds in 1-inch Plate,”
Tech. Note N-921, Port Hueneme, TMCA Case Study W-20, 28. “Design Away Corrosion with
California, (Sept. 1967). March (1969). Titanium,” Mallory-Sharon Titanium
Corp., April 1956.
10. H.B. Bomberger, P.J. Cambourelis, 19. A.G.S. Morton, “Mechanical
and G.E. Hutchinson, “Corrosion Properties of Thick Plate 29. Summary of Green Sheet Data
Properties of Titanium in Marine Ti-6A1-4V,” MEL Report 266/66, (Ti-75A), Allegheny Ludlum Steel
Environments,” J. Electrochem. (January 1967). Corp., Jan. 1, 1957.
Soc., Vol. 101, p. 442, (1954).
30. Corrosion Data Survey (Metals
Section), 5th Edition; National
Assn. of Corrosion Engineers,
Houston, Texas.

31

31. E.G. Haney, G. Goldberg, 39. H. Satoh, T. Fukuzuka, 49. L.C. Covington, “The Role of Multi-
R.E. Emsberger, and W.T. Brehm, K. Shimogori, and H. Tanabe, Valent Metal Ions in Suppressing
“Investigation of Stress Corrosion “Hydrogen Pickup by Titanium Held Crevice Corrosion of Titanium,”
Cracking of Titanium Alloys,” Cathodic in Seawater.” Paper Titanium Science and Technology,
Second Progress Report, Mellon presented at 2nd International Vol. 4, Ed. by R.I. Jaffee and
Institute, under NASA Grant Congress on Hydrogen in Metals, H.M. Burte, Plenum Press,
N6R- 39-008-014 (May, 1967). June 6-11, 1977, Paris, France. New York, (1973).

32. C.M. Chen, H.B. Kirkpatrick and 40. D.A. Jones and B.E. Wilde, 50. W.K. Boyd, “Stress Corrosion
H.L. Gegel, “Cracking of Titanium Corrosion Performance of Some Cracking of Titanium Alloys—An
Alloys in Methanolic and Other Metals and Alloys in Liquid Overview.” Paper presented at
Media.” Paper presented at the Ammonia, Corrosion, Vol. 33, the International Symposium on
International Symposium on Stress p. 46 (1977). Stress Corrosion Mechanisms in
Corrosion Mechanisms in Titanium Titanium Alloys, Jan. 27-29, 1971,
Alloys, Jan. 27, 28, and 19, 1971, 41. Unpublished TIMET data. Georgia Institute of Technology,
Georgia Institute of Technology, Atlanta, Georgia.
Atlanta, Georgia. 42. D. Schlain, “Corrosion Properties of
Titanium and its Alloys,” p. 131, 51. E.G. Haney, G. Goldberg,
33. D.W. Stough, F.W. Fink and R.S. Bulletin 619, Bureau of Mines, R.E. Emsberger, and W.T. Brehm,
Peoples, “The Corrosion of U.S. Department of Interior, “Investigation of Stress Corrosion
Titanium”, Battelle Memorial (1964), p. 32 Cracking of Titanium Alloys,”
Institute, Titanium Metallurgical Second Progress Report, Mellon
Laboratory, Report No. 57, (1956). 43. R.S. Sheppard, D.R. Hise, P.J. Institute, under NASA Grant
Gegner and W.L. Wilson, N6R- 39-008-014 (May, 1967).
34. L.C. Covington, and R.W. Schutz, “Performance of Titanium vs.
“Resistance of Titanium to Other Materials in Chemical Plan 52. F.A. Posey and E.G. Bohlmann,
Atmospheric Corrosion,” Paper Exposures,” Corrosion, Vol. 18, “Pitting of Titanium Alloys in Saline
No. 113, Corrosion/81, Toronto, p. 211t (1962). Waters.” Paper presented at the
Ontario, Canada, April 6-10, 1981. Second European Symposium on
44. John C. Griess, Jr., “Crevice Fresh Water from the Sea, Athens,
35. J.D. Jackson, W.K. Boyd, and P.D. Corrosion of Titanium in Aqueous Greece, May 9-12, 1967.
Miller, “Reactivity of Metals with Salt Solutions,” Corrosion, Vol. 24,
liquid and Gaseous Oxygen,” DMIC No. 4, April 1968, pp. 96-109. 53. L.C. Covington and R.W. Schultz,
Memorandum 163, Jan. 15, 1963, “The Effects of Iron on the Corrosion
Battelle Memorial Institute. 45. R.W. Shultz and L.C. Covington,“ Resistance of Titanium,” ASTM STP
Effect of Oxide Films on the 728, ASTM, 1981, pp. 163-180.
36. Fred E. Littman and Frank M. Corrosion Resistance of Titanium,”
Church, “Reactions of Metals with Corrosion, Vol. 37, No. 10, 54. Data supplied by Robert Smallwood,
Oxygen and Steam,” Stanford October, 1981. E.I. DuPont de Nemours and Co.
Research Institute to Union Carbide (Inc.), Wilmington, Delaware.
Nuclear Co., Final Report AECU- 46. T. Fukuzuka, K. Shimogori,
4092 (Feb. 15, 1959). H. Satoh, F. Kanikubo and H. Hirose, 55. P. Wagner and B. Little, “Impact of
“Application of Surface Air- Alloying on Microbiologically
37. I.I. Phillips, P. Pool and L.L. Shreir, Oxidizing for Preventing Titanium Influenced Corrosion—A Review,”
“Hydride Formation During Cathodic for Hydrogen Embrittlement in the Materials Performance, Volume 32,
Polarization of Ti.-II. Effect of Chemical Plant.” Paper presented at No. 9, Sept. 1993, pp. 65-68.
Temperature and pH of Solution on the ASTM Symposium on Industrial
Hydride Growth,” Corrosion Science, Applications of Zirconium and 56. F.L. LaQue, Marine Corrosion, Causes
Vol. 14, pp. 533-542 (1974). Titanium, Oct. 15-17, 1979, New and Prevention, John Wiley and Sons,
Orleans, LA. New York, NY, 1975, p. 179.
38. L.C. Covington, “The influence of
Surface Condition and Environment 47. J.B. Cotton, “Using Titanium in FOR FURTHER READING
on the Hydriding of Titanium,” the Chemical Plant,” Chemical
Corrosion, Vol. 35, No. 8, pp. 378- Engineering Progress, Vol. 66, ASM Metals Handbook Ninth Edition,
382 (1979) August. No. 10, p. 57, (1970). Vol. 13, “Corrosion of Titanium and
Titanium Alloys,” pp. 669-706.
32 48. M.G. Fontana and N.D. Greene,
Corrosion Engineering, McGraw-Hill J.S. Grauman, “Titanium-Properties and
Book Co., (1967). Application for the Chemical Process
Industry”, Encyclopedia of Chemical
Processing and Design, Vol. 58, Marcel
Dekker, Inc., NY, NY, 1997, pp. 123-
146. (Reprints available from TIMET)

APPENDIX

Titanium Corrosion Rate Data – Timetal Commercially Pure Grades

These data were determined in laboratory tests and are intended only as a guide. Since service conditions may be dissimilar, TIMET recommends testing under the

anticipated operating conditions. C = Concentration % T = Temperature °F (°C) R = Corrosion rate, mpy (mm/y)

Media CTR Media CTR

Acetaldehyde 75 300 (149) 0.02 (0.001) Arsenous oxide Saturated Room Nil
100 300 (149) Nil Barium carbonate Saturated Room Nil
Acetate, n-propyl Barium chloride 5 212 (100) Nil
Acetic acid — 188 (87) Nil 20 212 (100) 0.01 (0.000)
Barium hydroxide 25 212 (100) Nil
Acetic acid 5 to 99.7 255 (124) Nil Barium hydroxide Saturated Room Nil
Acetic acid + 109 ppm Cl 33-vapor Boiling Nil 27 Boiling Some
Acetic acid + 106 ppm Cl 65 250 (121) 0.1 (0.003) Barium nitrate small pits
Acetic anhydride 58 266 (130) 15.0 (0.381) Barium fluoride 10 Room Nil
Acidic gases containing CO2, Benzaldehyde Saturated Room Nil
99.7 255 (124) 0.1 (0.003) Benzene (traces of HCl) 100 Room Nil
H2O, Cl2, SO2, SO3, H2S, Vapor 176 (80) 0.2 (0.005)
O2, NH3 31.2 Boiling 10.2 (0.259) Benzene (traces of HCl) & liquid
Adipic acid + 15-20% glutaric Benzene Liquid
+ 2% acetic acid 62.0 Boiling 10.7 (0.272) Benzene + trace HCl, Liquid
Adipic acid —
Adipyl chloride (acid 99.5 Boiling 0.5 (0.013) NaCl and CS2
chlorobenzene solution) Benzoic acid
Adiponitrile — 100-500 <1.0 (<0.025) Bismuth
Aluminum chloride, aerated (38-260) Bismuth/lead
Aluminum chloride, aerated
Aluminum chloride, non-aerated 25 390 (199) Nil Boric acid 122 (50) 1.0 (0.025)
Boric acid Room Nil
Aluminum 67 450 (232) Nil Bromine 176 (80) 0.2 (0.005)
Aluminum fluoride — — Nil Bromine, moist
Aluminum nitrate Bromine, gas dry Saturated Room Nil
Aluminum sulfate Vapor 700 (371) 0.3 (0.008) Molten 1500 (816)
Aluminum sulfate + 1% H2SO4 10 Bromine-water solution Molten 572 (300) High
Amines, synthesis of organic 25 212 (100) 0.09 (0.002)* Bromine-methyl alcohol solution
10 Saturated Room Good
Ammonium acid phosphate 25 212 (100) 124 (3.15)* Bromine in methyl alcohol 10 Boiling resistance
Ammonium aluminum chloride Molten N-butyric acid Liquid 86 (30)
Saturated 302 (150) 1.3 (0.033)* Calcium bisulfite Vapor 86 (30) Nil
Ammonia anhydrous Saturated 212 (100) 258 (6.55)* — 70 (21)
Ammonia, steam, water Saturated Calcium carbonate Nil
Ammonium acetate Saturated 1250 (677) 6480 (164.6) Calcium chloride — Room
Ammonium bicarbonate — 500 ppm 140 (60) Rapid
Ammonium bisulfite, pH 2.05 Room Nil Calcium hydroxide
10 Calcium hydroxide 5 — <0.1 (<0.003)
Ammonium carbamate Molten Room Nil Calcium hypochlorite Undiluted Room
Ammonium chloride Cooking 79 (26) Dissolves
Ammonium chlorate 100 Room Nil Carbon dioxide liquor rapidly
— Carbon tetrachloride Saturated Boiling
(+ 215-250 g/l NaCl) 10 Room Nil 5 212 (100) Nil
(+ 36 g/l NaClO4) 50 Chlorine gas, wet 10 212 (100)
Ammonium fluoride Spent 300-400 15 (0.381) 20 212 (100) 1.2 (0.030)
Ammonium hydroxide pulping (149-204) 55 220 (104) some
Ammonium nitrate liquor 60 300 (149) cracking
Ammonium nitrate 50 Room Nil 62 310 (154)
+ 1% nitric acid Saturated 757 (19.2)
Ammonium oxalate 300 g/l 662-716 Very rapid 73 350 (177)
Ammonium perchlorate (350-380) Saturated Room Nil
Ammonium sulfate Saturated Boiling
Ammonium sulfate 104 (40) <5.0 (<0.127) 2 212 (100) 0.02 (0.001)
+ 1% H2SO4 6 212 (100)
Aniline 431 (222) 440 (11.2) 18 70 (21) Nil
Aniline + 2% AlCl3 Saturated —
Aniline + 2% AlCl3 Room Nil slurry 0.02 (0.005)*
Aniline hydrochloride 100 — 0.29 (0.007)*
Aniline hydrochloride 212 (100) Nil 99 Boiling 0.61 (0.015)*
Antimony trichloride Liquid Boiling 0.02 (0.001)*
Aqua regia 159 (71) 0.6 (0.015) Vapor Boiling <0.1 (<0.003)*
Aqua regia >0.7 H2O Room 2.0 and 16
212 (100) Nil >0.95 H2O 284 (140) (0.051 and
212 (100) <0.5 (<0.013) <1.5 H2O 392 (200) 0.406)*
122 (50) 0.1 (0.003) Liquid Room 84 (2.13)*
water on
10 Room 4.0 (0.102) surface Nil

28 Room 0.1 (0.003) Nil

28 Boiling Nil 0.05 (0.001)
0.05 (0.001)
28 Boiling Nil Nil
Nil
Saturated Room Nil
20 190 (88) Nil Excellent
10 212 (100) Nil
Saturated Room 0.4 (0.010) 0.18 (0.005)
Nil
100 Room Nil Nil

98 316 (158) >50 (>1.27) Nil
Nil
Nil
Nil

98 600 (316) 840 (21.3)

5 212 (100) Nil

20 212 (100) Nil

27 Room Nil *May corrode in crevices
**TIMETAL Code 12 and TIMETAL 50A .15Pd immune
3:1 Room Nil

3:1 175 (79) 34.8 (0.884)

33

Titanium Corrosion Rate Data – Timetal Commercially Pure Grades

These data were determined in laboratory tests and are intended only as a guide. Since service conditions may be dissimilar, TIMET recommends testing under the

anticipated operating conditions. C = Concentration % T = Temperature °F (°C) R = Corrosion rate, mpy (mm/y)

Media CTR Media CTR

Chlorine saturated water Saturated 207 (97) Nil Ferrous chloride + 0.5% HCl 30 175 (79) 0.2 (0.006)
Chlorine header sludge and — 207 (97) 0.03 (0.001) + 3% resorcinal pH 1

wet chlorine Ferrous sulfate Saturated Room Nil
Chlorine gas, dry Fluoroboric acid 5-20
Chlorine dioxide <0.5 H2O Room May react Fluorine, commercial Gas-liquid Elevated Rapid
+ H2O and air 180 (82) <0.1 (<0.003) alternated
Chlorine dioxide 5 in steam Fluorine, HF free Gas 109(43) 18-34
+ some HOCl and wet Cl2 gas 110 (43) Nil 12 Liquid
Chlorine dioxide in steam Fluorine, HF free 12 Gas Liquid (0.457-0.864)
Chlorine monoxide 15 Fluorine, HF free Liquid
+ some HOCl, Cl2 & H2O Fluorosilicic acid Gas -320 (-196)
Chlorine trifluoride Food products 10
Formaldehyde — -320 (-196) 0.08 (0.002)
Chloracetic acid Formamide vapor 37
Chloracetic acid 5 210 (99) Nil Formic acid, aerated — -320 (-196) <0.43 (0.011)
Chlorosulfonic acid Up to 15 110 (43) Nil 10
Formic acid, non-aerated
Chloroform 25 -320 (-196) 0.42 (0.011)
Formic acid
Chloropicrin 100 <86 (30) Vigorous Furfural 50 Room 1870 (47.5)
Chromic acid reaction Gluconic acid
<5.0 (<0.127) Glycerin 90 Ambient No attack
Chromium plating bath <5.0 (<0.127) Hydrogen chloride, gas
containing fluoride 30 180 (82) 7.5-12.3 Hydrochloric acid, aerated 10 Boiling Nil
100 Boiling (0.191-0.312) 25
Chromic acid + 5% nitric acid 100 Room 0.01 (0.000) Hydrochloric acid 50 572 (300) Nil
Citric acid 90
Vapor & Boiling 0.1 (0.003) Hydrochloric acid, 9 212 (100) 0.18
Copper nitrate liquid 0.1 (0.003) nitrogen saturated 100 212 (100) (0.005)**
Copper sulfate 203 (95) 0.2 (0.006) 50 212 (100) 0.04
Copper sulfate + 2% H2SO4 100 Boiling 0.6 (0.015) Hydrochloric acid, — 212 (100) (0.001)**
Cupric carbonate 75 (24) 0.5 (0.013) nitrogen saturated Air mixture 0.04
10 180 (82) 1.1 (0.028) 5 (0.001)**
+ cupric hydroxide 15 75 (24) 58.3 (1.48) Hydrochloric acid, 10 0.05
Cupric chloride 15 180 (82) nitrogen saturated 20 (0.001)**
50 171 (77) <0.1 (<0.003) 37.5
Cupric cyanide 50 0.36 (0.009) Hydrochloric acid, 1 212 (100) >50 (>1.27)**
Cuprous chloride 70 (21) 0.03 (0.001) oxygen saturated 3 212 (100) 96 (2.44)**
Cyclohexylamine 240 g/l 212 (100) 0.01 (0.000) 5 Boiling 126 (3.20)**
Cyclohexane (plus traces of plating salt 212 (100) <5.0 (<0.127) chlorine saturated 3 212 (100) 118 (3.00)**
140 (60) 5-50
formic acid) 5 212 (100) (0.127-1.27) Hydrochloric acid, 200 ppm Cl2 122 (50) <5 (<0.127)
Dichloroacetic acid Boiling Corroded Hydrochloric acid,
Dichloroacetic acid 10 Nil Room Nil
Dichlorobenzene + 4-5% HCl 25 Nil + 1% HNO3
Diethylene triamine 50 0.7 (0.018) + 1% HNO3 Room Nil
Ethyl alcohol 50 aerated Nil + 5% HNO3
Ethyl alcohol 50 + 5% HNO3 Room Nil
Ethylene dichloride + 10% HNO3
+ 10% HNO3 Ambient Nil
Ethylene diamine + 3% HNO3
Ferric chloride 62 300 (149) + 5% HNO3 95 (35) 1.5 (0.038)
Saturated Room + 5% HNO3 + 1.7 g/l TiCl4 95 (35) 40 (1.02)
Ferric sulfate • 9 H2O 50 Boiling Hydrochloric acid 95 (35) 175 (4.45)
Saturated Room + 2.5% NaClO3 95 (35) 1990 (50.6)
Saturated Ambient + 5.0% NaClO3
Boiling >100 (>2.54)
Boiling 550 (14.0)
Boiling 400 (10.2)

374 (190) >1120 (>28.5)

20 Boiling Nil 5 374 (190) >1120 (>28.5)
40 Boiling 0.2 (0.005)
55 246 (119) 0.1 (0.003) 10 374 (190) >1120 (>28.5)
(Boiling)
Saturated Nil 3 374 (190) >1120 (>28.5)
50 Room <0.1 (<0.003) 5 374 (190) >1120 (>28.5)
100 Nil 10 374 (190) >1120 (>28.5)
— 194 (90) 0.1 (0.003) 5 374 (190) <1 (<0.025)
10 374 (190) >1120 (>28.5)
Room
36 Room 17.0 (0.432)
302 (150)
5
100 212 (100) <0.5 (<0.013) 5 100 (38) Nil
100 Boiling 0.29 (0.007) 5 200 (93) 3.6 (0.091)
— 355 (179) 4 (0.102) 5 100 (38) 0.84 (0.025)
100 Room Nil 5 200 (93) 1.2 (0.030)
95 Boiling 0.5 (0.013) 5 100 (38) Nil
100 Room Nil 8.5 200 (93) 7.2 (0.183)
100 Boiling 0.2-5.0 1 176 (80) 2.0 (0.051)
(0.005-0.127) 1 Boiling 2.9 (0.074)
100 Room Nil Boiling Nil
10-20 Room Nil 10.2
10-30 212 (100) <0.5 (<0.127) 10.2 176 (80) 0.37 (0.009)
10-40 Boiling Nil 175 (79) 0.25 (0.006)
50 236 (113) Nil
(Boiling) *May corrode in crevices
50 302 (150) 0.1 (0.003) **TIMETAL Code 12 and TIMETAL 50A .15Pd immune
10 Room Nil

34

Titanium Corrosion Rate Data – Timetal Commercially Pure Grades

These data were determined in laboratory tests and are intended only as a guide. Since service conditions may be dissimilar, TIMET recommends testing under the

anticipated operating conditions. C = Concentration % T = Temperature °F (°C) R = Corrosion rate, mpy (mm/y)

Media CTR Media CTR

Hydrochloric acid, 5 100 (38) Nil Mercuric cyanide Saturated Room Nil
+ 0.5% CrO3 5 200 (93) 1.2 (0.031) Mercury 100 Up to
+ 0.5% CrO3 5 100 (38) 0.72 (0.018) 100 (38) Satisfactory
+ 1% CrO3 5 200 (93) 1.2 (0.031) Mercury + Fe 100 Room
+ 1% CrO3 Mercury + Cu — 700 (371) Nil
5 100 (38) 1.56 (0.040) Mercury + Zr — 700 (371) 119.4 (3.03)
Hydrochloric acid, 5 200 (93) 3.6 (0.091) Mercury + Mg — 700 (371)
+ 0.05% CuSO4 5 100 (38) 3.6 (0.091) Methyl alcohol — 700 (371) 3.12 (0.079)
+ 0.05% CuSO4 5 200 (93) 2.4 (0.061) Nickel chloride — 700 (371)
+ 0.5% CuSO4 5 100 (38) 1.2 (0.031) Nickel chloride 91 95 (35) 2.48 (0.063)
+ 0.5% CuSO4 5 200 (93) 3.6 (0.091) Nickel nitrate • 6 H20 5 212 (100)
+ 1% CuSO4 5 100 (38) 0.8 (0.020) Nitric acid, aerated 20 212 (100) 1.28 (0.033)
+ 1% CuSO4 5 200 (93) 2.4 (0.061) 50 Room
+ 5% CuSO4 5 Boiling 2.5 (0.064) Nitric acid, non-aerated 10 Room 3.26 (0.083)
+ 5% CuSO4 5 Boiling 3.3 (0.084) 20 Room
+ 0.05% CuSO4 Nitric acid 30 Room Nil
+ 0.5% CuSO4 10 150 (66) 0.68-1.32 40 Room
(0.017-0.025) Nitric acid, white fuming 50 Room 0.17 (0.004)
Hydrochloric acid, 10 150 (66) Nil 60 Room
+ 0.05% CuSO4 10 150 (66) Nil-0.68 Nitric acid, red fuming 70 Room 0.11 (0.003)
(0.023) Nitric acid, red fuming 10 104 (40)
+ 0.20% CuSO4 10 150 (66) 0.68 (0.023) Nitric acid + 0.1% CrO3 20 104 (40) Nil
+ 0.5% CuSO4 10 Boiling 11.6 (0.295) Nitric acid + 10% FeCl3 30 122 (50)
10 Boiling 11.4 (0.290) Nitric acid + 0.1% K2Cr2O3 40 122 (50) 0.19 (0.005)
+ 1% CuSO4 10 Boiling 9.0 (0.229) Nitric acid + 10% NaClO3 50 140 (60) 9.69 (0.246)
+ 0.05% CuSO4 60 140 (60) 0.17 (0.004)
+ 0.5% CuSO4 1.48 Room Rapid 70 158 (70) 0.08 (0.002)
+ 0.2% CuSO4 100 Room 40 392 (200) 0.08 (0.002)
+ 0.2% organic amine 5.0-50 70 518 (270) 0.02 (0.001)
Room (0.127-1.27) 20 554 (290) 0.18 (0.005)
Hydrofluoric acid 35 176 (80) 0.10 (0.003)
Rapid 0.21 (0.005)
Hydrofluoric acid, anhydrous 70 176 (80) 0.61 (0.015)
0.64 (0.016)
Hydrofluoric-nitric acid 1-HF Room <5 (<0.127) 17 Boiling 1.46 (0.037)
-15 HNO3 Room <5 (<0.127) 1.56 (0.040)
Hydrogen peroxide 3 Room <12 (<0.305) 35 Boiling 1.56 (0.040)
6 Nil 24 (0.610)
Hydrogen sulfide, steam and 30 200-230 70 Boiling 48 (1.22)
0.077% mercaptans 7.65 (93-110) 1.2 (0.031) 12 (0.305)
0.001 (0.000) — Room
Hydroxy-acetic acid — 104 (40) Liquid Room 2-4
Hypochlorous acid + ClO2 and 17 or vapor (0.051-0.102)
100 (38) — 1-3
Cl2 gases — — (0.025-0.076)
Iodine, dry gas — 70 (21) <4 (<0.102) —
Iodine in water + potassium iodide Saturated <about 3-4
Iodine in alcohol 10-85 Room Nil 2% H2O (0.076-0.102)
Lactic acid 10 >about 5-20
Lactic acid — Room Pitted 2% H2O (0.127-0.508)
Lead — 40 2.5-37
Lead (0.064-0.940)
40
0.1 (0.003)
40 Nil

212 (100) <5.0 (<0.127) 40 180 (82) 6.0 (0.152)
252 (122) <5.0 (<.127)
Boiling <5.0 (<0.127) 320 (160) <5.0 (<.127)
Room
1500 (816) Attacked Ignition
Room sensitive
615-1100 Good
(324-593) Boiling Not ignition
sensitive
Lead acetate Saturated Room Nil Boiling
Linseed oil, boiled — 0.12-0.99
Lithium, molten — Room Nil Boiling (0.003-0.025)

600-900 Nil Boiling 4.8-7.4
(316-482) (0.122-0.188)

Lithium chloride 50 300 (149) Nil Nil-0.62
Magnesium Molten (Nil-0.016)
1400 (760) Limited
& 1750 resistance 0.12-1.40
(954) (0.003-0.036)

Magnesium chloride 5-20 212 (100) <0.4
(<0.010)*
Magnesium chloride 5-40
Magnesium hydroxide Saturated Boiling Nil
Magnesium sulfate Saturated
Manganous chloride 5-20 Room Nil
Maleic acid 18-20
Mercuric chloride 1 Room Nil
5
10 212 (100) Nil
Saturated
95 (35) .06 (0.002)

212 (100) 0.01 (0.000)

212 (100) 0.42 (0.011)

212 (100) 0.04 (0.001) *May corrode in crevices
**TIMETAL Code 12 and TIMETAL 50A .15Pd immune
212 (100) <5 (<0.127)

35

Titanium Corrosion Rate Data – Timetal Commercially Pure Grades

These data were determined in laboratory tests and are intended only as a guide. Since service conditions may be dissimilar, TIMET recommends testing under the

anticipated operating conditions. C = Concentration % T = Temperature °F (°C) R = Corrosion rate, mpy (mm/y)

Media CTR Media CTR

Nitric acid, saturated with 33-45 245 (118) Nil Silver nitrate 50 Room Nil
zirconyl nitrate Sodium 100 to 1100 Good
65 260 (127) Nil (593)
Nitric acid Sodium acetate Saturated Room Nil
+ 15% zirconyl nitrate 20.8 Boiling 5-11.6 Sodium aluminate 25 Boiling 3.6 (0.091)
(0.127-0.295) Sodium bifluoride Saturated Room Rapid
Nitric acid + 179 g/l NaNO3 27.4 Boiling Sodium bisulfate Saturated Room Nil
and 32 g/l NaCl 19-115 Sodium bisulfate 10 150 (66) 72 (1.83)
— Ambient (0.483-2.92) Sodium bisulfite 10 Boiling Nil
Nitric acid + 170 g/l NaNO3 Sodium bisulfite 25 Boiling Nil
and 2.9 g/l NaCl 1 98.6 (37) 0.26-23.2 Sodium carbonate 25 Boiling Nil
1 Boiling (0.007-0.589) Sodium chlorate Saturated Room Nil
Oil well crudes, 25 140 (60) Sodium chlorate 0-721 g/l 104 (40) 0.1 (0.003)
varying amounts of abrasion Saturated Room 12 (0.025)
100 86 (30) 4247 (107.9) + NaCl 80-250 g/l Saturated
Oxalic acid 470 (11.9) + Na2Cr2O3 14 g/l 23
20 (0.508) carbon 0.3-0.9 g/l 23
Perchloryl fluoride Sodium chloride 23
+ liquid ClO3 0.07 (0.002) Sodium chloride pH 1.5
Sodium chloride pH 1.2 23
Perchloryl fluoride 99 86 (30) Liquid Sodium chloride, titanium in
+ 1% H2O 11.4 (0.290) contact with teflon Saturated
Saturated 70 (21) Vapor Sodium chloride, pH 1.2 Saturated Room Nil
Phenol solution Room 0.1 (0.003) some dissolved chlorine Saturated Boiling Nil*
Sodium citrate Saturated Boiling 28 (0.711)*
Phosphoric acid 10-30 4.0 (0.102) Sodium cyanide 5-12 Boiling Corrosion
Sodium dichromate in crevice
Phosphoric acid + 3% nitric 0.8-2 Sodium fluoride 5-10 Boiling Nil*
acid and 16% water (0.020-0.051) Sodium hydrosulfide + unknown 10
30-80 Room 2-30 amounts of sodium sulfide 28
Phosphorous oxychloride (0.051-0.762) and polysulfides 40
Phosphorous trichloride 1 Boiling 10 (0.254) Sodium hydroxide 50 Room Nil
Photographic emulsions 10 Boiling 400 (10.2) 73 Room Nil
Pthalic acid 30 Boiling 1030 (26.2) Sodium hypochlorite 50-73 Room Nil
Potassium bromide 10 176 (80) 72 (1.83) Sodium hypochlorite 6 Room 0.3 (0.008)
Potassium chloride 1.5-4 230 (110) <0.1 (<0.003)
Potassium chloride 81 190 (88) 15 (0.381) + 12-15% NaCl + 1% NaOH
Potassium dichromate + 1-2% sodium carbonate Saturated
Potassium ethyl zanthate 100 Room 0.14 (0.004) Sodium nitrate Saturated 70 (21) 0.04 (0.001)
Potassium ferricyanide Saturated Room Nil Sodium nitrite 900 g/l Boiling 0.84 (0.021)
Potassium hydroxide — — <5.0 (<0.127) Sodium perchlorate Saturated Room 0.1 (0.003)
Saturated Room Nil Sodium phosphate 25 176 (80) 5.0 (0.127)
+ 13% potassium chloride Saturated Room Nil Sodium silicate 10-20 135 (57) 0.5 (0.0127)
Potassium hydroxide Saturated Room Nil Sodium sulfate Saturated 265 (129) 7.0 (0.178)
Saturated 140 (60) <.01 (0.000) Sodium sulfate 10 370 (188) >43 (>1.09)
Potassium iodide — — Nil Sodium sulfide Saturated
Potassium permanganate 10 Room Nil Sodium sulfide Saturated Room Nil
Potassium perchlorate Saturated Room Nil Sodium sulfite 25
13 85 (29) Nil Sodium thiosulfate 20 150-200 1.2 (0.030)
(Ti specimen cathodic) Sodium thiosulfate (66-93)
Potassium perchlorate + 20% acetic acid —
50 80 (29) 0.4 (0.010) Soils, corrosive 5 Room Nil
+ NaClO4, 600-900 g/l 10 Boiling <5.0 (<0.127) Stannic chloride 24 Room Nil
KCl, 0-500 g/l, NaCl, 25 Boiling 12 (0.305) Stannic chloride 100 122 (50) 0.1 (0.003)
0-250 g/l, NaClO3, 6-24 g/l 50 Boiling 108 (2.74) Stannic chloride, molten Saturated Room Nil
Potassium sulfate 50 to 465-710 40-60 Stannic chloride — Boiling Nil
Potassium thiosulfate anhydrous (241-377) (1.02-1.52) Steam + air Boiling Nil
Propionic acid Room Nil
Pyrogaltic acid Saturated Room Nil Boiling 1.08 (0.027)
Salicylic acid sodium salt Room Nil
Seawater Saturated Room Nil Boiling Nil
Seawater, 4 1⁄ 2-year test Boiling Nil
Sebacic acid 20 Room 0.12 (0.003) Room Nil

0-30 122 (50) 0.1 (0.003)

10 Room Nil Ambient Nil
1 — Nil 212 (100) 0.12 (0.003)
Vapor 374 (190) Rapid Boiling 1.76 (0.045)
355 g/l Room Nil 150 (66) Nil
Saturated Room Nil Room Nil
— 76 (24) Nil 180 (82) 0.01 (0.000)
— — Nil
— 464 (240) 0.3 (0.008) *May corrode in crevices
**TIMETAL Code 12 and TIMETAL 50A .15Pd immune

36

Titanium Corrosion Rate Data – Timetal Commercially Pure Grades

These data were determined in laboratory tests and are intended only as a guide. Since service conditions may be dissimilar, TIMET recommends testing under the

anticipated operating conditions. C = Concentration % T = Temperature °F (°C) R = Corrosion rate, mpy (mm/y)

Media CTR Media CTR

Steam + 7.65% hydrogen sulfide — 200-230 Nil Tartaric acid 10-50 212 (100) <5 (<0.127)
+ 0.17% mercaptans (93-110) 10 140 (60) 0.10 (0.003)
100 356 (180) 0.1 (0.003) Terepthalic acid 25 140 (60) 0.10 (0.003)
Stearic acid, molten 365 (185) Nil Tetrachloroethane, 50 140 (60) 0.02 (0.001)
Succinic acid 100 Room Nil 10 212 (100) 0.13 (0.003)
Succinic acid Room Nil liquid and vapor 25 212 (100) Nil
Sulfanilic acid Saturated Boiling Nil Tetrachloroethylene + H2O 50 212 (100) 0.2-0.49
Sulfamic acid Boiling 108 (2.74) Tetrachloroethylene (0.005-
Sulfamic acid Saturated Boiling 1.2 (0.030) Tetrachloroethylene, 77 425 (218) 0.0121)
Sulfamic acid + .375 g/l FeCl3 464 (240) Nil 100 Boiling Nil
Sulfur, molten 3.75 g/l 395 (202) >43 (>1.09) liquid and vapor 0.02 (0.001)
Sulfur monochloride Room 0.1 (0.003) stabilized with ethyl alcohol — Boiling
Sulfur dioxide, water saturated 7.5 g/l 600 (316) 0.2 (0.006) Tin, molten 100 Boiling 5 (0.127)
Sulfur dioxide gas + small amount Titanium tetrachloride 100 Boiling Nil
7.5 g/l 140 (60) 0.3 (0.008) Titanium tetrachloride 0.02 (0.001)
SO3 and approx. 3% O2 140 (60) 0.5 (0.013) 100 930 (499)
Sulfuric acid, aerated with air 100 140 (60) 190 (4.83) Trichloroacetic acid 99.8 572 (300) Resistant
95 (35) 50 (1.27) Trichloroethylene Concen- Room 62 (1.57)
Sulfuric acid, aerated with nitrogen Major 95 (35) 340 (8.64) trated Nil
95 (35) 42 (1.07) Uranium chloride 100 Boiling
Sulfuric acid Near 100 Room 427 (10.8) 99 Boiling 573 (14.6)
Boiling 6082 (154.5) Uranyl ammonium 0.1-5
Sulfuric acid 18 212 (100) 0.2 (0.005) phosphate filtrate + 25% Saturated 70-194 (0.003-0.127)
+ 0.25% CuSO4 212 (100) 920 (23.4) chloride + 0.5% fluoride, (21-90) Nil
+ 0.25% CuSO4 1 212 (100) 810 (20.6) 1.4% ammonia 20.9 165
+ 0.25% CuSO4 3 Room 316 (8.03) + 2.4% uranium <0.1 (<0.003)
+ 0.5% CuSO4 5 Boiling 7460 (189.5) 120 g/l U Boiling
+ 0.5% CuSO4 10 Room 62 (1.57) Uranyl nitrate 0.012 (0.000)
+ 1.0% CuSO4 40 containing 25.3 g/l Fe3+, 3.1 molar 482 (250)
+ 1.0% CuSO4 75 Boiling 212 (5.38) 6.9 g/l Cr3+, 2.8 g/l Ni2+, <0.078
+ 1.0% CuSO4 75 5.9 molar NO3, 4.0 molar H+, 3.8 molar 662 (350) (<0.020)
+ 0.5% CrO3 75 212 (100) 282 (7.16) 1.0 molar Cl- 0.22-17
+ 0.5% CrO3 1 212 (100) 830 (21.1) — Elevated (0.006-0.432)
3 212 (100) 1060 (26.9) Uranyl sulfate + 3.1 molar Li2SO4 temp. and No attack
Sulfuric acid vapors 5 + 100-200 ppm O2 28 pressure
80 Boiling 700 (17.8) 360 (182) 3.1 (0.079)
80 Boiling 1000 (25.4) Uranyl sulfate + 3.6 molar Li2SO4, —
Concen- 50 psi O2 — 600 (316) Nil
trated 200 (93) Nil 200 (93) Nil
Concen- 100 (38) 2.4 (0.061) Urea-ammonia reaction mass —
trated 200 (93) 3.48 (0.088) — 95 (35) Nil
100 (38) 2.64 (0.067) Urea + 32% ammonia, 100 Room Nil
1 200 (93) 32.4 (0.823) + 20.5% H2O, 19% CO2 Molten Withstood
3 100 (38) 0.78 (0.020) 20 several
5 200 (93) 34.8 (0.884) Water, degassed 50 220 (104) thousand
Boiling 65 (1.65) Water, river, saturated 75 302 (150) contact cycles
1 200 (93) Nil 80 392 (200) Nil*
5 200 (93) Nil with Cl2 Saturated 392 (200) Nil*
Water, synthetic sea Room 24 (0.610)*
5 100 (38) Nil X-ray developer solution 8000 (203.2)*
30 150 (66) Nil Zinc, subjected to zinc Nil
30 200-300 0.4-0.5
30 (93-149) (0.010-0.013) ammonium chloride preflux
30
30 Zinc chloride
30
30 Zinc sulfate
5
30

96
96
96

Sulfuric acid, 90 Room 18 (0.457)
+ 10% HNO3 70 Room 25 (0.635)
+ 30% HNO3 50 Room 25 (0.635)
+ 50% HNO3 30 Room 4.0 (0.102)
+ 70% HNO3 10 Room Nil
+ 90% HNO3 10 140 (60) 0.45 (0.011)
+ 90% HNO3 50 140 (60) 15.7 (0.399)
+ 50% HNO3 80 140 (60) 62.5 (1.59)
+ 20% HNO3
45 75 (24) 0.13 (0.003)
Sulfuric acid saturated
with chlorine 62 60 (16) 0.07 (0.002) *May corrode in crevices
5 374 (190) <1 (<0.025) **TIMETAL Code 12 and TIMETAL 50A .15Pd immune
Sulfuric acid + 4.79 g/l Ti +4 82 122 (50) >47 (>1.19)
Sulfurous acid
Tannic acid 40 212 (100) Passive

6 Room Nil

25 212 (100) Nil

37

Corrosion Rate Data for Timetal 50A .15Pd

These data were determined in laboratory tests and are intended only as a guide. Since service conditions may be dissimilar, TIMET recommends testing under the

anticipated operating conditions. C = Concentration % T = Temperature °F (°C) R = Corrosion rate, mpy (mm/y)

Media CTR Media CTR

Aluminum chloride 10 212 (100) <1 (<0.25) Sodium chloride brine — 200 (93) 0.0005
Calcium chloride 25 212 (100) 1 (0.25) (0.000)
Chlorine, wet Sodium chloride 10 374 (190)
Chlorine, H2O saturated. 62 310 (154) Nil Sulfuric acid, <1 (<0.025)
Chromic acid 73 350 (177) Nil 5 Room
Ferric chloride N2 saturated 10 Room <1 (<0.025)
Formic acid — Room Slight gain 40 Room 1 (0.025)
Hydrochloric acid, Sulfuric acid, 60 Room 9 (0.229)
— Room <1 (<0.025) O2 saturated 80 Room 34 (0.864)
H2 saturated 95 Room 645 (16.4)
10 Boiling Slight gain Sulfuric acid, 5 158 (70) 68 (1.73)
Hydrochloric acid, Cl2 saturated 10 158 (70) 6 (0.152)
air saturated 30 Boiling Slight gain 40 158 (70) 10 (0.254)
Sulfuric acid, 60 158 (70) 87 (2.21)
Hydrochloric acid, 50 Boiling 3 (0.076) air saturated 80 158 (70) 184 (4.67)
O2 saturated 96 158 (70) 226 (5.74)
1-15 Room <1 (<0.025) Sulfuric acid 1 374 (190) 62 (1.57)
Hydrochloric acid, 20 Room 4 (0.102) 5 374 (190) 5 (0.127)
Cl2 saturated 25 Room 11 (0.279) Sulfuric acid 10 374 (190) 5 (0.127)
1 158 (70) 3 (0.076) + 0.5 g/l Fe2 (SO4)3 20 374 (190) 59 (1.50)
Hydrochloric acid 5 158 (70) 3 (0.076) + 16 g/l Fe2 (SO4)3 355 (9.02)
10 158 (70) 7 (0.178) + 16 g/l Fe2 (SO4)3 1 374 (190)
Hydrochloric acid 15 158 (70) 13 (0.330) + 40 g/l Fe2 (SO4)3 5 374 (190) 5 (0.127)
+ 5 g/l FeCl3 20 158 (70) 61 (1.55) 10 374 (190) 3 (0.076)
+ 16 g/l FeCl3 25 158 (70) 169 (4.29) Sulfuric acid 20 374 (190) 5 (0.127)
+ 16 g/l FeCl3 3 374 (190) 1 (0.025) + 15% CuSO4 30 374 (190) 59 (1.50)
+ 16 g/l CuCl2 5 374 (190) 4 (0.102) 2440 (62.0)
+ 16 g/l CuCl2 10 374 (190) 350 (8.89) Sulfuric acid + 10% FeSO4 1 and 5 374 (190)
15 374 (190) 1620 (41.1) 11% solids, and 170 g/l TiO2 10 374 (190) <1 (<0.025)
Nitric acid 20 374 (190) 2 (0.05)
1 and 5 158 (70) <1 (<0.025) Sulfuric acid + 0.01% CuSO4 30 374 (190) 15 (0.38)
Nitric acid, unbleached 10 158 (70) 2 (0.050) + 0.05% CuSO4 3060 (77.7)
Phosphoric acid 15 158 (70) 6 (0.152) + 0.50% CuSO4 5 158 (70)
20 158 (70) 26 (0.660) + 1.0% CuSO4 10 158 (70) 3 (0.08)
25 158 (70) 78 (1.98) 40 158 (70) 4 (0.10)
60 158 (70) 37 (0.94)
3 374 (190) 5 (0.127) 80 158 (70) 392 (10.0)
5 374 (190) 5 (0.127) 96 158 (70) 447 (11.4)
10 374 (190) 368 (9.34) 83 (2.1)
5 Boiling
3 and 5 374 (190) <1 (<0.025) 10 Boiling 20 (0.05)
10 374 (190) 1140 (29.0) 20 Boiling 59 (1.5)
207 (5.3)
5 Boiling 7 (0.178) 10
10 Boiling 32 (0.813) 10
15 Boiling 267 (6.78) 20
20 Boiling 770 (19.6) 40

10 Boiling 11 (0.279) 15 Boiling 7 (0.18)
10 Boiling 3 (0.076) Boiling <1 (<0.025)
20 Boiling 113 (2.87) 23 Boiling 6 (0.15)
10 Boiling 5 (0.127) Boiling 87 (2.2)
20 Boiling 146 (3.71) 30
30 Boiling 25 (0.64)
30 374 (190) 94 (2.39) 30
30 482 (250) Slight gain 30 to 212 84 (2.13)
65 Boiling 26 (0.66) (100)
65 374 (190) Slight gain 1090 (27.7)
65 482 (250) Slight gain Boiling 1310 (33.3)
Boiling 79 (2.01)
60 Boiling 15.5 (0.394) Boiling 69 (1.75)
Boiling
10 Boiling 5.8 (0.147)

38

Corrosion Rate Data for Timetal Code 12

These data were determined in laboratory tests and are intended only as a guide. Since service conditions may be dissimilar, TIMET recommends testing under the

anticipated operating conditions. C = Concentration % T = Temperature °F (°C) R = Corrosion rate, mpy (mm/y)

Media C TR Remarks

Ammonium hydro-oxide 30 Boiling Nil No hydrogen pick-up
Aluminum chloride 10 Boiling Nil 500 hours
Aqua regia (1 part HNO3 Boiling 24 (0.610)
-3 parts HCl) 500 hours
Ammonium chloride 10 Boiling Nil 3700 hours
Chlorine cell off-gas — 190 (88) .035 (0.001) Natural aeration
Citric acid 50 Boiling 0.5 (0.013) Natural aeration
Formic acid 45 Boiling Nil Natural aeration
Formic acid 88 Boiling Nil
Formic acid 90 Boiling 20.5 (0.521) 500 hours
Hydrochloric acid 5 120 (49) 0.1 (0.003) Acidified to pH 1
Hydrochloric acid 5 150 (66) 0.2 (0.005) 500 hours
Hydrochloric acid 5 200 (93) 1176 (29.9) 500 hours
Hydrochloric acid 2 200 (93) 1.2 (0.031)
HCl + 2 g/l FeCl3 3.32 196 (91) 1.0 (0.025)
HCl + 2 g/l FeCl3 4.15 196 (91) 2.3 (0.058)
Sulfuric acid 0.54 Boiling 0.6 (0.015)
Sulfuric acid 1.08 Boiling 35.4 (0.899)
Sulfuric acid 1.62 Boiling 578 (14.7)
Vapor above boiling HNO3 — — 0.8 (0.020)
Saturated Boiling Nil
MgCl2 10 Boiling Nil
Sodium Sulfate — Boiling 2.4 (0.061)
5% NaOCl + 2% NaCl + 4% NaOH Saturated 600 (316) Nil

NaCl

39

First in Titanium Worldwide

W o r l d H e a d q u a rt e r s
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Phone: (303) 296-5600
Fax: (303) 296-5640
W ebsite: www. timet. com

D i v i s i o n a l H e a d q u a rt e r s
TIM ET Castings
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P. O . Box 9 0 8
A lbany, O regon 9 7 3 2 1 U SA
Phone: (541) 926-7711
Fax: (541) 967-7786
Titanium H earth Technologies, Inc.
900 Hemlock Road
M organtown Business Park
M organtown, Pennsylvania 19543 USA
Phone: (610) 286-6100
Fax: (610) 286-3831
TIM ET EURO PE
P. O . Box 7 0 4 , W itton
Birmingham B6 7UR England
Phone: 44-121-356-1155
Fax: 44-121-356-5413

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