ASTM G157-98
(Guide)Standard Guide for Evaluating the Corrosion Properties of Wrought Iron- and Nickel-Based Corrosion Resistant Alloys for the Chemical Process Industries
Standard Guide for Evaluating the Corrosion Properties of Wrought Iron- and Nickel-Based Corrosion Resistant Alloys for the Chemical Process Industries
SCOPE
1.1 This guide covers an evaluation approach that is designed to provide information on the corrosion properties of wrought iron- and nickel-based alloys for the chemical process industries. This guide incorporates test conditions for general corrosion measurements in a variety of environments, crevice corrosion resistance in chloride environments, and stress corrosion cracking resistance in chloride environments.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:G157–98
Standard Guide for
Evaluating the Corrosion Properties of Wrought Iron- and
Nickel-Based Corrosion Resistant Alloys for the Chemical
Process Industries
This standard is issued under the fixed designation G 157; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope G 123 Test Method of Evaluating Stress-Corrosion Crack-
ing of Stainless Alloys with Different Nickel Content in
1.1 This guide covers an evaluation approach that is de-
Boiling Acidified Sodium Chloride Solution
signed to provide information on the corrosion properties of
wrought iron- and nickel-based alloys for the chemical process
3. Terminology
industries. This guide incorporates test conditions for general
3.1 Terms such as crevice corrosion, stress corrosion crack-
corrosion measurements in a variety of environments, crevice
ing, and corrosion rate are defined in Terminology G 15.
corrosion resistance in chloride environments, and stress cor-
rosion cracking resistance in chloride environments.
4. Significance and Use
1.2 This standard does not purport to address all of the
4.1 This guide is intended to provide a series of evaluations
safety concerns, if any, associated with its use. It is the
that will assist engineers dealing with chemical environments
responsibility of the user of this standard to establish appro-
inselectingappropriatealloys(1-3).Inchemicalenvironments,
priate safety and health practices and to determine the
an important issue for determining general corrosion resistance
applicability of regulatory limitations prior to use.
is the temperature at which an alloy transitions from corrosion
2. Referenced Documents at a low rate to corrosion at a much higher rate. Other
important concerns include the tendency towards crevice
2.1 ASTM Standards:
corrosionandstresscorrosioncrackingresistance,especiallyin
D 1193 Specification for Reagent Water
hot chloride-containing aqueous environments.
G 1 Practice for Preparing, Cleaning, and Evaluating Cor-
3 4.2 This guide is also intended for alloy developers to assist
rosion Test Specimens
them in choosing environments and test methods that are of
G 15 Terminology Relating to Corrosion and Corrosion
3 particular interest to the chemical process industries.
Testing
4.3 The use of this approach will allow direct comparisons
G 30 Practice for Making and Using U-Bend Stress-
3 to be made among alloys from various suppliers and, thereby,
Corrosion Test Specimens
to assist engineers in selecting the most appropriate materials
G 36 Practice for Evaluating Stress-Corrosion-Cracking
for further testing to determine suitability in their application.
Resistance of Metals and Alloys in a Boiling Magnesium
Chloride Solution
5. General Corrosion Resistance
G 46 Guide for Examination and Evaluation of Pitting
5.1 The general corrosion resistance of nickel- and iron-
Corrosion
based alloys is determined in 14 test solutions at various
G 48 Test Methods for Pitting and Crevice Corrosion Re-
temperatures to determine the lowest temperature at which the
sistance of Stainless Steels and Related Alloys by Use of
3 corrosion rate exceeds 0.13 mm/y (5 mpy). The test solutions
Ferric Chloride Solution
are listed in Table 1. A suggested procedure is provided in
Appendix X1. The test is run on three coupons of metal for
each environment. The tests are run for two 48-h exposures
with one specimen exposed for the total 96 h. Welded speci-
This guide is under the jurisdiction of ASTM Committee G-1 on Corrosion of
Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory
mens may be used if results are required on weldments.
Corrosion Tests.
5.2 The corrosion rates are based on mass loss measure-
Current edition approved Apr. 10, 1998. Published August 1998.
2 ments with appropriate conversion to thickness loss as shown
Annual Book of ASTM Standards, Vol 11.01.
Annual Book of ASTM Standards, Vol 03.02. in Appendix X1.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G157
TABLE 1 Fourteen Environments for Evaluating General
Corrosion Resistance
A
Corrodent Formula Concentration, %
Hydrochloric Acid HCl 0.2, 1.0, 5.0
B
Sulfuric Acid H SO 10, 60, 96
2 4
B
Nitric Acid HNO 10, 70
B
Phosphoric Acid H PO 85
3 4
Formic Acid HCOOH 50
Acetic Acid CH COOH 80
Sodium Hydroxide NaOH 50
C
Hydrochloric Acid + HCl + FeCl 1.0 HCl + 0.3 FeCl
3 3
Ferric Chloride
Acetic Acid + CH COOH + (CH CO) O 50/50
3 3 2
Acetic Anhydride
A
All chemicals are ACS reagent grade mixed with Specification D 1193 Type 4
reagent water.
B
Undiluted reagent grade acid may be used.
C
Ferric chloride concentration calculated on anhydrous basis.
5.3 The results of the tests in each solution should be
FIG. 2 Summary Results Form - General Corrosion Resistance
reported on a summary results sheet.Atypical format is shown
in Fig. 1 and Fig. 2.
6. Six Percent Ferric Chloride Solution Critical Crevice
Corrosion Temperature
6.1 The crevice corrosion resistance of each alloy is to be
evaluated as described in Test Methods G 48, Method D. The
standard exposure period of 72 h is to be used. Mass loss
resultsarealsotobeobtainedandreportedinthisenvironment.
6.2 The results of this test are to be reported as discussed in
Test Methods G 48. The results should also be entered on the
summary results sheet shown in Fig. 3.
7. Chloride Stress Corrosion Resistance
7.1 Theresistancetochloridestresscorrosioncrackingisan
important characteristic of alloys used in the chemical process
industries. Two environments are provided to evaluate and
report chloride stress corrosion cracking behavior–acidified
sodium chloride and magnesium chloride. The magnesium
chloride environment is highly acidic and, as a consequence,
tends to cause many suitably resistant alloys to fail. The
acidified sodium chloride environment gives results closer to
experience in cooling water and process water environments.
7.2 Acidified Sodium Chloride Test—Test Method G 123
should be used to evaluate all alloys for resistance to chloride
FIG. 3 Summary Results Form - Localized Corrosion
stress corrosion cracking. The specimen design suggested in
Performance
Test Method G 123 should be used, if possible. This design is
based on the Practice G 30 U-bend and the tests should be
carried out with at least triplicate specimens for a period of
1000 h. The results are to be reported as described in Test
Method G 123 and entered on the summary results sheet. See
Fig. 3.
7.3 Magnesium Chloride Test, Optional—Alloys that do not
crack in the acidified sodium chloride environment may be
tested in a magnesium chloride test. The test environment is
described in Practice G 36. U-bend specimens similar to those
suggested in Test Method G 123 should be used with triplicate
replication.The test should be run for 30 days or until cracking
FIG. 1 Summary Results Form - Alloy Description is observed. The specimens should be removed at convenient
G157
intervals not to exceed three days during exposure and exam- shown in Figs. 1-3 provide a convenient form to present the
ined for cracking. The time to first crack is reported. Metallo- results in a consistent format.
graphic sectioning is to be carried out on at least one of each
set of replicates at the end of the exposure to document the
9. Keywords
crack morphology or, in the case of surviving specimens, that
9.1 chemical process industry; crevice corrosion; general
no microcracks are present. The result of this test is to be
corrosion; iron-base corrosion resistant alloys; nickel-base
reported on the summary results sheet (Fig. 3).
corrosion resistant alloys; stress corrosion cracking
8. Report
8.1 The results of these tests are to be reported as specified
in the test method referenced. The summary results sheets
APPENDIX
(Nonmandatory Information)
X1. SUGGESTED LABORATORY TESTING OF IRON- AND NICKEL-BASED ALLOYS FOR CORROSION RESISTANCE IN
SELECTED MEDIA FOR GENERAL CORROSION PERFORMANCE
X1.1 Scope non-oxidizing solutions, should be capable of sparging nitro-
gen at the rate of 100 mL/min.Adevice to prevent backflow of
X1.1.1 Thistestmethoddescribesasuggestedprocedurefor
test solution into the gas supply system should be included.
corrosion tests to determine the relative resistance of wrought
iron- and nickel-based alloys to corrosion in selected media.
X1.3 Test Specimens
These tests are intended to provide corrosion data suitable for
preliminary evaluation prior to testing for specific chemical
X1.3.1 The specimens should be made from sheet, plate, or
applications.
strip produced by commercial methods.
X1.1.2 Each alloy is tested in the as-manufactured condi-
X1.3.2 Material from which the specimens are made should
tion;as-weldedspecimensmaybeincluded.(SeeX1.3.10.2for
be in the annealed condition, the final heat treatment being
when only the as-welded condition need be tested.)
done after any cold rolling. Temperature of the final heat
X1.1.3 Specimen evaluation procedures provide for mass
treatment and method of cooling should be reported.
loss measurements for evaluation of general corrosion and low
X1.3.3 Thickness of the sheet materials used for specimens
power surface microscopic examination for presence of local-
should be between 1.5 and 4.8 mm (0.06 and 0.188 in.). Width
ized corrosion, such as pitting, stress corrosion, intergranular
of the specimens should be 20 mm (0.8 in.) and the length 50
attack, end-grain corrosion, and preferential weld attack.
mm (2.0 in.).
X1.3.4 Specimens are to be cut to size by a machining
X1.2 Apparatus
operation. If sheared specimens are used, the sheared edges are
X1.2.1 A1000 mL Erlenmeyer flask equipped with a reflux
to be removed by grinding or machining; the amount of metal
condenser, a sparger with a fitted glass disc for deaerating
removed by machining should equal the thickness of the
certain solutions, a specimen support system, and a means for
specimen.
controlling the temperature of the contents of the flask are
X1.3.5 All specimens should be abraded to provide a
recommended for all tests.
uniform surface finish free of scale and dirt, and to remove any
X1.2.2 All components of the apparatus described in X1.2.1
sharp edges or burrs due to machining or drilling operations.
which are in contact with the test environment (liquid and gas
The final step in this abrading operation should be done with
phases) are to be made of glass or polytetrafluoroethylene
wet No. 80 or dry No. 120 grit abrasive paper. Exercise care to
(PTFE) or other inert nonconductive material.
avoid overheating the surface. This step should be omitted
X1.2.3 The temperature-regulating device used for tests at
when the intent of the test is to evaluate mill finish or other
temperatures other than the boiling temperature should be
surface conditions.
capable of controlling the temperature of the contents of the
X1.3.6 Specimens should be stamped with identifying let-
flask to within 61°C of the selected test temperature.
ters and numbers, using clean, hardened steel stamps.
X1.2.4 The specimen support system should be designed so
X1.3.7 Specimens should be measured prior to test and the
that the specimen is separated from the flask and its internal
total exposed area, including edges, calculated and reported to
components. The specimen is to be maintained in a vertical
2 2
the closest 65 mm (0.1 in. ).
position, totally immersed in the test solution. One desirable
support system is to use an individual glass cradle for each X1.3.8 Following the abrasive treatment, the specimens
specimen. should be cleaned with a magnesium oxide paste or detergent
X1.2.5 Anitrogen sparging system, which is used for initial solution to remove any residual dirt or grease, rinsed in water,
deaeration in tests at temperatures below boiling and in and dipped in acetone and air dried.
G157
X1.3.9 The dried specimens should be weighed to an
Desired % mL Concentrated Acid mL Reagent H O
10 72 1148
accuracy of at least 60.2 mg. Weighed specimens should be
60 608 680
stored in a desiccator for at least 24 h before use.
Add water to a 1.5 L beaker, then carefully and slowly add
X1.3.10 Two kinds of specimens may be used – (a)as
manufactured specimens and (b) as-welded specimens. concentrated acid to flask with constant stirring. In the case of
the 60 % solution, it is desirable to cool the mixture to 30°C
X1.3.10.1 As-Manufactured Specimens—These specimens
should be prepared according to the procedure described in after about half of the acid has been added to avoid boiling.
Then complete the acid addition. When cool, measure 600 mL
X1.3.1-X1.3.9.
X1.3.10.2 As-Welded Specimens—The principal reason for into each flask for the test.
X1.4.4.3 Ten Percent Nitric Acid Solution—Use nitric acid
using these specimens is to evaluate the corrosion resistance of
69 to 70 %, specific gravity 1.416 to 1.424. Prepare 1200 mL
the weld deposit. However, where the corrosion resistance of
of the 10 % solution as follows. Measure 1083 mL of water to
the weld deposit is equal to, or better than, that of the parent
the flask. Then carefully and slowly add 128 mL of the
metal, a welded specimen can be used in lieu of the as-
concentrated acid to the water with constant stirring. When
manufactured specimen and thus avoid running an additional
cool, measure 600 mL into each flask for the test.
test. The welded specimens should be prepared from material
described in X1.3.1 and X1.3.2. The minimum thickness of X1.4.4.4 Fifty Percent Formic Acid Solution—Use formic
acid88 %minimum(specificgravity1.201min).Prepare1200
material for these specimens should be 3.0 mm (0.12 in.). The
weld should be made so that it will be in the center of the mLof 50 % solution as follows. Measure 597 mLof water into
the flask. Then carefully and slowly, add 729 mL of the
specimen and be parallel to the long direction of the specimen.
The weld should be a gas-tungsten arc (GTAW) with filler concentrated acid to the water with constant stirring. Measure
600 mL into each flask for the test.
metal. The filler metal and welding procedure should corre-
spondtothatrecommendedbythemanufacturerforfabrication X1.4.4.5 Eighty Percent Acetic Acid Solution—Use glacial
acetic acid 99.7 min. Prepare 1200 mL of the 80 % solution as
of process equipment. The weld bead should be ground or
machinedflushwiththebasemetal.Thefinalpreparationofthe follows. Measure 256 mL of water into a 1.5 L
...
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