ASTM G2-88(1996)e1

e1
Designation:G2–88 (Reapproved 1996)
Standard Test Method for
Corrosion Testing of Products of Zirconium, Hafnium, and
Their Alloys in Water at 680°F or in Steam at 750°F
This standard is issued under the fixed designation G 2; 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.
e NOTE—Section 18 was added editorially in April 1996.
1. Scope 3.1.3 Grade A water—purified water having a pH of 5.0 to
8.0 and an electrical resistivity of not less than 1.0 MV·cm.
1.1 This test method covers (1) the determination of mass
3.1.4 Grade B water—water prepared with deionized or
gain, and (2) the surface inspection of products of zirconium,
demineralized water having a minimum electrical resistivity of
hafnium, and their alloys when corrosion tested in water at
0.5 MV·cm.
680°F or in steam at 750°F.
3.1.5 The stated values of pH and electrical resistivity are to
1.2 This test method is to be utilized in its entirety to the
be met after the measured values are corrected to 77°F.
extent specified herein as a product acceptance test.
3.1.6 high mass gain coupons—zirconium alloy specimens
1.3 This test method may be used on wrought products,
that have been specially heat-treated to produce a mass gain
castings, powder metallurgy products, and weld metals.
higher than the maximum specified as acceptable value used
1.4 A complete metric companion to this test method has
for verifying the severity of the test.
been developed, Test Method G 2M. Therefore, no metric
3.1.7 reagent grade—The grade of chemicals normally used
equivalents are shown. However, since the mass gain and
for analytical purposes.
surface area of the specimen and the electrical resistivity of
water are always measured or calculated in SI units, these are
4. Summary of Test Method
given in SI units.
4.1 Specimens of zirconium, hafnium, or their alloys are
1.5 This standard does not purport to address all of the
exposed to high-pressure water or steam at elevated tempera-
safety concerns, if any, associated with its use. It is the
tures for 72 or 336 h. The corrosion is normally measured by
responsibility of the user of this standard to establish appro-
the gain in mass of the specimens and by the appearance of the
priate safety and health practices and determine the applica-
oxide film on the specimen surfaces. In some instances, such as
bility of regulatory limitations prior to use. For specific
weld evaluation, mass gain measurements are either impracti-
precautionary statements, see Section 9.
cal to make or not required. When so specified, appearance of
2. Referenced Documents the specimen shall be the sole criterion for acceptance.
2.1 ASTM Standards:
5. Significance and Use
D 888 Test Methods for Dissolved Oxygen in Water
5.1 This test method is primarily used as an acceptance test
E 29 Practice for Using Significant Digits in Test Data to
3 for products of zirconium, hafnium, and their alloys. This
Determine Conformance with Specifications
standard has been widely used in the development of new
3. Terminology alloys, heat treating practices, and for evaluation of welding
techniques.
3.1 Definitions of Terms Specific to This Standard:
5.2 Specimens are normally tested after careful etching and
3.1.1 control coupons—zirconium alloy specimens of
rinsing. Specimens with as-manufactured surfaces may also be
known performance used to monitor the validity of the test.
tested without further surface removal.
3.1.2 etching—a process for removal of surface metal by
5.3 When tubing with a second material clad on the inner
action of acids in water.
surface is to be tested, the inner cladding shall be removed
prior to the test.
This test method is under the jurisdiction of ASTM Committee G-1 on
Corrosion of Metals and is the direct responsibility of Subcommittee G 01.08on
6. Interferences
Corrosion of Nuclear Materials.
Current edition approved Jan. 29, 1988. Published March 1988. Originally
6.1 Autoclave loads that have one or more specimens
published as G 2 – 67. Last previous edition G2–81.
showing gross oxidation may affect results on other specimens
Annual Book of ASTM Standards, Vol 11.01
in the autoclave by contamination of the environment.
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
G2
7. Apparatus order to accelerate cooling upon completion of testing.
7.1 The apparatus consists of equipment for (1) etching the
10. Sampling, Test Specimens, and Test Units
specimens when required, (2) measuring the specimen surface
10.1 The size and the quantity of the test specimens, the
area and mass, the water resistivity and pH, test temperature
method of selection, surface preparation, and test acceptance
and pressure, etch and rinse temperature, and (3) performing
criteria shall be specified in the product specification or by
the water or steam corrosion test at elevated temperature and
agreement between the purchaser and the seller as stated in the
pressure.
purchase contract.
7.1.1 Etching—An acid bath, a flowing rinse, and a deion-
10.2 Each specimen and control coupons shall be individu-
ized water rinse are needed for proper metal removal and
ally identified.
stain-free rinsing. Polyethylene or polypropylene tanks are
commonly used with a bottom feed for flowing water rinses.
11. Preparation of Apparatus
Specimen hangers are generally made of Type 300 series
11.1 General requirements for new or reworked autoclaves
stainless steel. When many specimens are processed, a me-
and parts of autoclaves previously used for testing materials
chanical dipper for the etching process is useful.
other than to this standard are as follows:
7.1.2 Autoclaves, constructed of Type 300 series stainless
11.1.1 Before specimens are tested in a new or reworked
steel or nickel base alloys such as UNS grade N06600 or
autoclave, or in one having new valves, tubing, gaskets, etc.,
N06690 and are manufactured to conform to ASME (American
which contact the test specimen, clean the apparatus thor-
Society for Mechanical Engineers) and government regulations
oughly, wipe with reagent grade ethanol or acetone, and rinse
governing unfired pressure vessels. The autoclave is fitted with
twice with Grade B water. Dry the autoclave or auxiliary
devices for measurement and control of pressure and tempera-
equipment by vacuum cleaning or drain and wipe with a clean,
ture, safety devices, and venting valves. Control systems for
lint-free cloth, and inspect carefully to ensure freedom from
pressure and temperature adequate to meet the requirements of
contamination. There shall be no visible contamination, such as
this standard are needed. Sample holders and other internal
lubricant, residues, dust or dirt, loose oxides or rust, and oil or
accessories are also constructed of Type 300 or 400 series
grease film on the water surface, internal surface, gasket, or
stainless steel, or nickel-base alloys such as UNS grade
head surfaces.
N06600 or N06690.
11.1.2 Clean all new and reworked fixtures and jigs to be
NOTE 1—If autoclave heating is performed in an oven, the oven and not
used in the autoclave, rinse in hot Grade B water. Autoclave the
the autoclave will have the automatic temperature-control equipment.
fixtures and jigs for at least 1 day at 750°F in 1500 psi steam
7.1.3 Measuring Equipment, capable of measuring speci- or at 680°F in water. Inspect the parts for corrosion product. If
men dimensions to 0.002 in. and a balance capable of weighing
corrosion product is found or electrical resistivity of the
−4
specimens to 1 3 10 g are needed. residual water after the test measures less than 0.1 MV·cm, the
parts should be cleaned and autoclaved again.
8. Reagents and Materials
11.2 General requirements for autoclaves and parts in con-
8.1 Argon Gas, welding grade.
tinuous use for corrosion testing under this standard are as
8.2 Grade A Water.
follows:
8.3 Grade B Water. 11.2.1 With Grade B water rinse all autoclaves, fixtures,
8.4 Detergents and Solvents, for specimen cleaning includ-
parts, and jigs that have been in continuous use and have
ing reagent grade ethanol and reagent grade acetone. shown satisfactory behavior in prior tests. Inspect the fixtures
8.5 Hydrofluoric Acid (HF), reagent grade.
and jigs for corrosion products after each test and rework and
8.6 Nitric Acid (HNO ), reagent grade. re-prepare items showing loose corrosion product.
8.7 Sulfuric Acid (H SO ), reagent grade.
2 4
12. Calibration and Standardization
8.8 Nitrogen Gas, for purging or controlling oxygen con-
tent. 12.1 High Mass Gain Coupon Preparation—These coupons
8.9 Argon-Hydrogen Mixed Gas, for purging or controlling shall be selected from a previously tested lot. The selected
oxygen content. material shall be heat treated to produce the desired mass gain.
Heating for8hat 1652 6 5°F and cooling to 572 6 5°F at a
9. Hazards
rate not exceeding 6°F/min will normally produce the desired
9.1 The chemicals used in preparing specimens for this test
mass gain.
are hazardous. Detailed information on safe handling of 12.2 Autoclaves:
organic compounds, acids and products of zirconium, hafnium,
12.2.1 Prior to use for product acceptance testing, an auto-
and their alloys should be obtained from competent sources. clave shall be profiled thermally as in 12.4.2 and shall
9.2 High-temperature, high-pressure autoclave operation demonstrate acceptability by testing at least three control
must be in accordance with government regulations and coupons, one each at the top, middle, and bottom of useful
manufacturer’s instructions. volume. The test results shall be incorporated in the certifica-
9.3 Hydrogen gas used for addition to the autoclave steam tion document for the autoclave acceptance test. When desired,
supply must be handled in accordance with guidelines for high mass gain coupons may also be used.
explosives and flammables. 12.2.2 Establishing Mass Gain Mean and Standard Devia-
9.4 Do not add cold water directly to the autoclave vessel in tion of Control Coupons—The control coupon lot and, when
G2
desired, the high mass gain coupon lot mass gain mean and 12.2.3.2 The mean value of each control coupon is the mean
standard deviation shall be established by a minimum of one for the three tests.
autoclave test as follows: 12.2.3.3 The standard deviation for the control coupon lot is
12.2.2.1 Randomly select 12 specimens from the control calculated by the (n-1) method using the data from all of the
coupon lot or the high mass gain coupon lot respectively. control coupons taken from the same material lot.
12.2.2.2 Prepare all specimens per the pretest requirements 12.2.4 The new or used autoclave is considered acceptable
of this test method. if each control coupon mass gain is reproducible within the
12.2.2.3 Locate the 12 or 24 specimens in a fixture or jig, in previously established control coupon mean mass gain 63
accordance with Fig. 1, and place the fixture or jig inside the standard deviations.
useful volume of the autoclave. 12.3 Use of Control Coupons:
12.2.2.4 Complete the steam or water corrosion test in 12.3.1 Each autoclave run used for acceptance of product
accordance with any one of the four methods in 14.3. shall contain at least three control coupons with one at the top,
12.2.2.5 Remove specimens and weigh in accordance with one at the middle, and one at the bottom of the specimen load.
the requirement of this test method. 12.3.2 The control coupons may be as manufactured or
12.2.2.6 Calculate and establish the mass gain mean and etched before testing, but if etched, the surfaces should exhibit
standard deviation (n-1 method) of each set of coupons for the no stains, pits, or areas of abnormal etching attack.
test method used. 12.3.3 An autoclave test is considered acceptable only if
12.2.2.7 For product acceptance tests the mean value and each post-test control coupon mass gain is not less than the
standard deviation for the control coupons may be the value established mean value minus 3 standard deviations and the
visual appearance of each control coupon is equal to or better
established in 12.2.2.6 or may be calculated periodically using
all accepted values determined over the preceding 3-month than the product acceptance standard. If a control coupon
post-test mass gain exceeds the mean value plus 3 standard
period but not less than 21 values.
12.2.3 An alternative method for establishing the mass gain deviations, or the specified mass gain value, and one or more
test specimens from the corresponding location in the auto-
mean and standard deviation for the control coupons which are
used repeatedly is: clave failed to meet the mass gain acceptance criterion, the
failed specimen(s) may be discarded and a new test made to
12.2.3.1 Expose the control coupons to be used in three
different tests, once each in the top, middle, and bottom of an determine conformance.
12.3.4 Control coupons may be reused after removal of
autoclave, and determine mass gain.
oxide film.
12.4 Calibration:
12.4.1 The temperature measurement and recording systems
used to determine conformance shall be calibrated at least
every 6 months and shall not deviate more than 65°F from
calibration standards traceable to NBS or other known national
standards.
12.4.2 Vertical thermal profiles of the autoclaves at the test
temperatures shall be made at least once in each 6-month
period, or whenever the heaters or the control thermocouples
are adjusted or replaced. The axial extent of the autoclave used
for performing the product acceptance testing shall be re-
stricted to the volume shown to be within 65°F of the recorded
autoclave temperature, after temperature compensation for
calibration of the thermocouples. This volume is considered
the useful volume. The profile thermocouples may be located
at the center or near the radial extremity of the autoclave
volume.
12.4.3 Pressure-measuring devices shall be calibrated annu-
ally and the recorded reading shall be within 650 psi of the
calibration standard over the range used for testing.
13. Conditioning
13.1 Test Water Quality—The water used to conduct the
corrosion test shall be Grade A water and have an oxygen
content not exceeding 45 ppb. The oxygen content specifica-
tion may be met either by direct measurement using the
appropriate method in Test Methods D 888 or by the use of
Venting Method A or B of 14.3.
13.2 Autoclave Load Restrictions—The surface area of
FIG. 1 Control Coupon and High Mass Gain Coupon Positioning
for Establishing Mass Gain Mean and Standard Deviation specimens loaded in a static autoclave shall not exceed 0.1
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