ASTM G157-98(2005)
(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
SIGNIFICANCE AND USE
This guide is intended to provide a series of evaluations that will assist engineers dealing with chemical environments in selecting appropriate alloys (1-3). In chemical environments, an important issue for determining general corrosion resistance is the temperature at which an alloy transitions from corrosion at a low rate to corrosion at a much higher rate. Other important concerns include the tendency towards crevice corrosion and stress corrosion cracking resistance, especially in hot chloride-containing aqueous environments.
This guide is also intended for alloy developers to assist them in choosing environments and test methods that are of particular interest to the chemical process industries.
The use of this approach will allow direct comparisons to be made among alloys from various suppliers and, thereby, to assist engineers in selecting the most appropriate materials for further testing to determine suitability in their application.
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 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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 to determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: G157 − 98(Reapproved 2005)
Standard Guide for
Evaluating Corrosion Properties of Wrought Iron- and
Nickel-Based Corrosion Resistant Alloys for Chemical
Process Industries
This standard is issued under the fixed designation G157; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope G46Guide for Examination and Evaluation of Pitting Cor-
rosion
1.1 This guide covers an evaluation approach that is de-
G48Test Methods for Pitting and Crevice Corrosion Resis-
signed to provide information on the corrosion properties of
tance of Stainless Steels and Related Alloys by Use of
wroughtiron-andnickel-basedalloysforthechemicalprocess
Ferric Chloride Solution
industries. This guide incorporates test conditions for general
G123TestMethodforEvaluatingStress-CorrosionCracking
corrosion measurements in a variety of environments, crevice
of Stainless Alloys with Different Nickel Content in
corrosion resistance in chloride environments, and stress cor-
Boiling Acidified Sodium Chloride Solution
rosion cracking resistance in chloride environments.
3. Terminology
1.2 The values stated in SI units are to be regarded as
standard. The values given in parentheses are for information
3.1 Terms such as crevice corrosion, stress corrosion
only.
cracking, and corrosion rate are defined in Terminology G15.
1.3 This standard does not purport to address all of the
4. Significance and Use
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 4.1 This guide is intended to provide a series of evaluations
that will assist engineers dealing with chemical environments
priate safety and health practices and to determine the
inselectingappropriatealloys(1-3).Inchemicalenvironments,
applicability of regulatory limitations prior to use.
animportantissuefordetermininggeneralcorrosionresistance
2. Referenced Documents
is the temperature at which an alloy transitions from corrosion
at a low rate to corrosion at a much higher rate. Other
2.1 ASTM Standards:
important concerns include the tendency towards crevice
D1193Specification for Reagent Water
corrosionandstresscorrosioncrackingresistance,especiallyin
G1Practice for Preparing, Cleaning, and Evaluating Corro-
hot chloride-containing aqueous environments.
sion Test Specimens
G15TerminologyRelatingtoCorrosionandCorrosionTest-
4.2 Thisguideisalsointendedforalloydeveloperstoassist
ing (Withdrawn 2010)
them in choosing environments and test methods that are of
G30 Practice for Making and Using U-Bend Stress-
particular interest to the chemical process industries.
Corrosion Test Specimens
4.3 The use of this approach will allow direct comparisons
G36Practice for Evaluating Stress-Corrosion-Cracking Re-
to be made among alloys from various suppliers and, thereby,
sistance of Metals and Alloys in a Boiling Magnesium
to assist engineers in selecting the most appropriate materials
Chloride Solution
for further testing to determine suitability in their application.
5. General Corrosion Resistance
This guide is under the jurisdiction ofASTM Committee G01 on Corrosion of
5.1 The general corrosion resistance of nickel- and iron-
Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory
Corrosion Tests.
based alloys is determined in 14 test solutions at various
Current edition approved Oct. 1, 2005. Published October 2005. Originally
temperatures to determine the lowest temperature at which the
approved in 1998. Last previous edition approved in 1998 as G157–98. DOI:
corrosion rate exceeds 0.13 mm/y (5 mpy). The test solutions
10.1520/G0157-98R05.
are listed in Table 1. A suggested procedure is provided in
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Appendix X1. The test is run on three coupons of metal for
Standards volume information, refer to the standard’s Document Summary page on
each environment. The tests are run for two 48-h exposures
the ASTM website.
with one specimen exposed for the total 96 h. Welded speci-
The last approved version of this historical standard is referenced on
www.astm.org. mens may be used if results are required on weldments.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G157 − 98 (2005)
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 D1193 Type 4
reagent water.
B
Undiluted reagent grade acid may be used.
C
Ferric chloride concentration calculated on anhydrous basis.
FIG. 2 Summary Results Form - General Corrosion Resistance
5.2 The corrosion rates are based on mass loss measure-
ments with appropriate conversion to thickness loss as shown
in Appendix X1.
5.3 The results of the tests in each solution should be
reportedonasummaryresultssheet.Atypicalformatisshown
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 G48, 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 G48. 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,
FIG. 3 Summary Results Form - Localized Corrosion Perfor-
tends to cause many suitably resistant alloys to fail. The
mance
acidified sodium chloride environment gives results closer to
experience in cooling water and process water environments.
7.2 Acidified Sodium Chloride Test—Test Method G123
should be used to evaluate all alloys for resistance to chloride
stress corrosion cracking. The specimen design suggested in
Test Method G123 should be used, if possible. This design is
based on the Practice G30 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 G123 and entered on the summary results sheet. See
Fig. 3.
7.3 Magnesium Chloride Test, Optional—Alloys that do not
FIG. 1 Summary Results Form - Alloy Description crack in the acidified sodium chloride environment may be
G157 − 98 (2005)
tested in a magnesium chloride test. The test environment is 8. Report
described in Practice G36. U-bend specimens similar to those
8.1 The results of these tests are to be reported as specified
suggested in Test Method G123 should be used with triplicate
in the test method referenced. The summary results sheets
replication.Thetestshouldberunfor30daysoruntilcracking
shown in Figs. 1-3 provide a convenient form to present the
is observed. The specimens should be removed at convenient
results in a consistent format.
intervals not to exceed three days during exposure and exam-
ined for cracking. The time to first crack is reported. Metallo-
9. Keywords
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
9.1 chemical process industry; crevice corrosion; general
crack morphology or, in the case of surviving specimens, that
corrosion; iron-base corrosion resistant alloys; nickel-base
no microcracks are present. The result of this test is to be
corrosion resistant alloys; stress corrosion cracking
reported on the summary results sheet (Fig. 3).
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 X1.2.5 Anitrogen sparging system, which is used for initial
deaeration in tests at temperatures below boiling and in
X1.1.1 Thistestmethoddescribesasuggestedprocedurefor
non-oxidizing solutions, should be capable of sparging nitro-
corrosion tests to determine the relative resistance of wrought
genattherateof100mL/min.Adevicetopreventbackflowof
iron- and nickel-based alloys to corrosion in selected media.
test solution into the gas supply system should be included.
These tests are intended to provide corrosion data suitable for
preliminary evaluation prior to testing for specific chemical
X1.3 Test Specimens
applications.
X1.3.1 The specimens should be made from sheet, plate, or
X1.1.2 Each alloy is tested in the as-manufactured condi-
strip produced by commercial methods.
tion;as-weldedspecimensmaybeincluded.(SeeX1.3.10.2for
when only the as-welded condition need be tested.)
X1.3.2 Materialfromwhichthespecimensaremadeshould
be in the annealed condition, the final heat treatment being
X1.1.3 Specimen evaluation procedures provide for mass
done after any cold rolling. Temperature of the final heat
loss measurements for evaluation of general corrosion and low
treatment and method of cooling should be reported.
power surface microscopic examination for presence of local-
ized corrosion, such as pitting, stress corrosion, intergranular
X1.3.3 Thickness of the sheet materials used for specimens
attack, end-grain corrosion, and preferential weld attack.
should be between 1.5 and 4.8 mm (0.06 and 0.188 in.).Width
of the specimens should be 20 mm (0.8 in.) and the length 50
X1.2 Apparatus
mm (2.0 in.).
X1.2.1 A1000 mL Erlenmeyer flask equipped with a reflux
X1.3.4 Specimens are to be cut to size by a machining
condenser, a sparger with a fitted glass disc for deaerating
operation.Ifshearedspecimensareused,theshearededgesare
certain solutions, a specimen support system, and a means for
to be removed by grinding or machining; the amount of metal
controlling the temperature of the contents of the flask are
removed by machining should equal the thickness of the
recommended for all tests.
specimen.
X1.2.2 AllcomponentsoftheapparatusdescribedinX1.2.1
X1.3.5 All specimens should be abraded to provide a
which are in contact with the test environment (liquid and gas
uniformsurfacefinishfreeofscaleanddirt,andtoremoveany
phases) are to be made of glass or polytetrafluoroethylene
sharp edges or burrs due to machining or drilling operations.
(PTFE) or other inert nonconductive material.
The final step in this abrading operation should be done with
X1.2.3 The temperature-regulating device used for tests at
wet No. 80 or dry No. 120 grit abrasive paper. Exercise care to
temperatures other than the boiling temperature should be
avoid overheating the surface. This step should be omitted
capable of controlling the temperature of the contents of the
when the intent of the test is to evaluate mill finish or other
flask to within 61°C of the selected test temperature.
surface conditions.
X1.2.4 The specimen support system should be designed so
X1.3.6 Specimens should be stamped with identifying let-
that the specimen is separated from the flask and its internal
ters and numbers, using clean, hardened steel stamps.
components. The specimen is to be maintained in a vertical
position, totally immersed in the test solution. One desirable X1.3.7 Specimens should be measured prior to test and the
support system is to use an individual glass cradle for each total exposed area, including edges, calculated and reported to
2 2
specimen. the closest 65 mm (0.1 in. ).
G157 − 98 (2005)
X1.3.8 Following the abrasive treatment, the specimens Add water to a 1.5 L beaker, then carefully and slowly add
should be cleaned with a magnesium oxide paste or detergent the reagent acid to the beaker while stirring the mixture.When
solution to remove any residual dirt or grease, rinsed in water, cool, measure 600 mL into each flask for the test.
and dipped in acetone and air dried. X1.4.4.2 Sulfuric Acid Solution—Use sulfuric acid 95 to
98%, specific gravity 1.84 min. Prepare 800 mL of each
X1.3.9 The dried specimens should be weighed to an
solution using volumes shown as follows:
accuracy of at least 60.2 mg. Weighed specimens should be
Desired % mL Concentrated Acid mL Reagent H O
stored in a desiccator for at least 24 h before use. 2
10 72 1148
60 608 680
X1.3.10 Two kinds of specimens may be used: (1)as
manufactured specimens and (2) as-welded specimens.
Add water to a 1.5 L beaker, then carefully and slowly add
X1.3.10.1 As-Manufactured Specimens—These specimens
concentrated acid to flask with constant stirring. In the case of
should be prepared according to the procedure described in
the 60% solution, it is desirable to cool the mixture to 30°C
X1.3.1-X1.3.9. after about half of the acid has been added to avoid boiling.
X1.3.10.2 As-Welded Specimens—The principal reason for
Then complete the acid addition.When cool, measure 600 mL
usingthesespecimensistoevaluatethecorrosionresistanceof
into each flask for the test.
the weld deposit. However, where the corrosion resistance of
X1.4.4.3 Ten Percent Nitric Acid Solution—Use nitric acid
the weld deposit is equal to, or better than, that of the parent
69 to 70%, specific gravity 1.416 to 1.424. Prepare 1200 mL
metal, a welded specimen can be used in lieu of the as-
of the 10% solution as follows. Measure 1083 mL of water
manufactured specimen and thus avoid running an additional
into the flask. Then carefully and slowly add 128 mL of the
test. The welded specimens should be prepared from material
concentrated acid to the water with constant stirring. When
described in X1.3.1 and X1.3.2. The minimum thickness of
cool, measure 600 mL into each flask for the test.
material for these specimens should be 3.0 mm (0.12 in.). The
X1.4.4.4 Fifty Percent Formic Acid Solution—Use formic
weld should be made so that it will be in the center of the
acid88%minimum(specificgravity1.201min).Prepare1200
specim
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