ASTM B368-97
(Test Method)Standard Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)
Standard Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)
SCOPE
1.1 This method prescribes the conditions required in copper-accelerated acetic acid-salt spray (CASS) testing for specification purposes. The standard does not specify the type of test specimen or exposure periods to be used for a specific product, nor the interpretation to be given to the results.
1.2 This method is applicable to evaluating the corrosive performance of decorative copper/nickel/chromium or nickel/chromium coatings on steel, zinc alloys, aluminum alloys, and plastics designed for severe service. It is also applicable to the testing of anodized aluminum. The suitability of this test and correlation of results with service experience should be determined before it is specified for coating systems or materials other than those mentioned in this paragraph. Note 1-The following standards are not requirements. They are referenced for information only: Practices B537 and E50, Specifications B456 and B604, and Test Method B602.
1.3 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. For more specific safety precautionary information see 8.1.1.
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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: B 368 – 97
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Method for
Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing
(CASS Test)
This standard is issued under the fixed designation B 368; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope to Atmospheric Exposure
B 602 Test Method for Attribute Sampling of Metallic and
1.1 This method prescribes the conditions required in
Inorganic Coatings
copper-accelerated acetic acid-salt spray (CASS) testing for
B 604 Specification for Decorative Electroplated Coatings
specification purposes. The standard does not specify the type
of Copper/Nickel/Chromium on Plastics
of test specimen or exposure periods to be used for a specific
D 1193 Specification for Reagent Water
product, nor the interpretation to be given to the results.
E 50 Practices for Apparatus, Reagents, and Safety Precau-
1.2 This method is applicable to evaluating the corrosive
tions for Chemical Analysis of Metals
performance of decorative copper/nickel/chromium or nickel/
chromium coatings on steel, zinc alloys, aluminum alloys, and
3. Significance and Use
plastics designed for severe service. It is also applicable to the
3.1 The CASS test is widely employed and is useful for
testing of anodized aluminum. The suitability of this test and
specification acceptance, simulated service evaluation, manu-
correlation of results with service experience should be deter-
facturing control, and research and development. It was devel-
mined before it is specified for coating systems or materials
oped specifically for use with decorative, electrodeposited
other than those mentioned in this paragraph.
nickel/chromium and copper/nickel/chromium coatings. Use of
NOTE 1—The following standards are not requirements. They are
the test has improved the quality of electroplated parts and led
referenced for information only: Practices B 537 and E 50, Specifications
to the development of new and superior electroplating pro-
B 456 and B 604, and Test Method B 602.
cesses.
1.3 This standard does not purport to address all of the
4. Apparatus
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4.1 The apparatus required for the CASS test consists of a
priate safety and health practices and determine the applica-
fog chamber, a salt-solution reservoir, a supply of compressed
bility of regulatory limitations prior to use. For more specific
air, one or more atomizing nozzles, specimen supports, provi-
safety precautionary information see 8.1.1.
sion for heating the chamber, and necessary means of control.
4.2 The size and detailed construction of the apparatus are
2. Referenced Documents
optional, provided the conditions meet the requirements of this
2.1 ASTM Standards:
method. The construction of the apparatus is described in the
B 117 Practice for Operating Salt Spray (Fog) Apparatus
appendix of Test Method B 117. For the CASS test, however,
B 162 Specification for Nickel Plate, Sheet, and Strip
the requirements for air pressure and temperature are typically
B 456 Specification for Electrodeposited Coatings of Cop-
0.08 to 0.12 MPa and 60 to 65°C, respectively. The actual air
per Plus Nickel Plus Chromium and Nickel Plus Chro-
pressure will be that required to produce the proper collection
mium
rate (see 8.3.1).
B 537 Practice for Rating of Electroplated Panels Subjected
4.3 The apparatus shall be constructed so that drops of
solution that accumulate on the ceiling or cover of the chamber
do not fall on the specimens being tested. Drops of solution
This method is under the jurisdiction of ASTM Committee B-8 on Metallic and
Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on
that fall from the specimens shall not be returned to the
General Test Methods.
solution reservoir for respraying.
Current edition approved Oct. 10, 1997. Published March 1998. Originally
4.4 Materials of construction shall not affect the corrosive-
published as B 368 – 61 T. Last previous edition B 368 – 85 (1997).
The CASS test was developed by the initiative of the Research Board of the ness of the fog, nor be themselves corroded by the fog.
American Electroplaters Society under AES Project 15.
Annual Book of ASTM Standards, Vol 03.02.
3 5
Annual Book of ASTM Standards, Vol 02.04. Annual Book of ASTM Standards, Vol 11.01.
4 6
Annual Book of ASTM Standards, Vol 02.05. Annual Book of ASTM Standards, Vol 03.05.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
B 368
5. Test Solution clean decorative copper/nickel/chromium or nickel/chromium
coatings immediately before testing by wiping significant
5.1 Prepare the salt solution by dissolving 5 parts by weight
surfaces with a cotton pad saturated with a slurry containing 10
of salt in 95 parts of water conforming to Specification D 1193,
g of pure magnesium oxide powder (ACS reagent grade) in 100
Type IV. The salt shall be sodium chloride (NaCl), ACS reagent
mL of distilled water. Upon rinsing in warm running water, be
grade, or equivalent. The pH of this solution shall be between
sure that the clean surface is free of water break. Anodized
6.0 and 7.0. Impurities or contam-ination of either the salt or
aluminum parts may be cleaned with inhibited 1,1,1-
the water, or both, should be suspected if the pH is outside of
trichloroethane or other suitable organic solvent (see 8.1.1). Do
this range (Note 2).
not clean organic and other nonmetallic coated specimens.
5.2 Add 0.25 g of reagent grade copper chloride
Other methods of cleaning, such as the use of a nitric-acid
(CuCl ·2H O) to each litre of the salt solution; dissolve and
2 2
solution for the chemical cleaning or passivation of stainless
mix thoroughly.
steel specimens, are permissible when agreed upon between
5.3 The pH of the salt-copper solution shall be adjusted to
the purchaser and the supplier. Take care that the specimens
the range of 3.1 to 3.3, as measured on a sample of the
after cleaning are not recontaminated by excessive or careless
collected spray, by the addition of glacial acetic acid, ACS
handling. Protect the cut edges of plated, coated, or multilay-
reagent grade, or equivalent (Note 3). The pH measurement
ered materials and areas containing identification marks or in
shall be made electrometrically at 25°C. Before the solution is
contact with the racks or supports with a coating that is stable
atomized, it shall be free of suspended solids (Note 4).
under the conditions of the test, such as wax, stop-off lacquer,
NOTE 2—A solution having a specific gravity of 1.030 to 1.040, when
or pressure-sensitive tape.
measured at a temperature of 25°C, will meet the concentration require-
8.1.1 Caution—1,1,1-Trichloroethane should be used in a
ment. It is suggested that a daily check be made.
well-ventilated area away from open flames.
NOTE 3—The initial solution may be adjusted to a pH of 3.0 to 3.1, with
8.2 Positioning of Specimens—Position the specimens in
the exception that the pH of the collected fog will be within the specified
limits. Adjustment of the initial pH for makeup solution is based upon the the CASS test chamber during the test so that the following
requirements to maintain the required pH of the collected samples. If less
conditions are met:
than 1.3 or more than 1.6 mL of the glacial acetic acid are required per litre
8.2.1 Support or suspend the specimens 15 6 2° from the
of sodium chloride and copper solution to attain the specified pH, some
vertical and preferably parallel to the principal direction of
discrepancy in the system may be suspected (the purity of the water or
horizontal flow of fog through the chamber, based upon the
salt, or both; the accuracy of the pH meter; the general cleanliness of the
dominant surface being tested. Support or suspend automobile
system; etc.).
parts, however, so as to expose all significant surfaces at the
NOTE 4—The freshly prepared salt solution may be filtered or decanted
before it is placed in the reservoir, or the end of the tube leading from the general level of the condensate collectors. If the position on the
solution to the atomizer may be covered with a double layer of cheese
automobile is vertical, place the part in an incline position 15°
cloth to prevent plugging of the nozzle.
from vertical to allow surface wetting by the condensate. If the
position on the automobile is facing down, rotate the part
6. Air Supply
approximately 180° to test the significant surface. If there are
6.1 The compressed air supply to the nozzle or nozzles for
several significant surfaces at different angles, expose each
atomizing the test solution shall be free of oil and dirt (Note 5).
surface of one or more specimens.
Pressure shall be adequate to provide a specified condensate
8.2.2 Make sure the specimens do not come in contact with
rate. Pressure of 0.10 6 0.02 MPa has been found satisfactory
each other or any other metallic material or any material
(Note 6).
capable of acting as a wick.
8.2.3 Place each specimen so as to permit free settling of fog
NOTE 5—The air supply can be freed of oil and dirt by passing it
through a water scrubber or at least 60 cm of suitable cleaning material, on all specimens.
such as sheep’s wool, excelsior, slag wool, or activated alumina. Com-
8.2.4 Make sure the salt solution from one specimen does
mercial filters for compressed air may be used.
not drip on any other specimen.
NOTE 6—Atomizing nozzles may have a critical pressure, at which an
8.2.5 Place the specimens in the chamber just prior to
abnormal increase in the corrosiveness of the salt fog occurs. If the critical
bringing the test chamber to the required temperature and
pressure of a nozzle has not been determined with certainty, control of
turning on the air, since storage in an idle chamber overnight,
fluctuation in the air pressure within 60.0007 MPa by installing a pressure
or for other significant length of time, can affect test results.
regulator valve minimizes the possibility that the nozzle will be operated
at its critical pressure.
NOTE 7—Suitable materials for the construction or coating of racks and
supports are glass, rubber, plastic, or suitably coated wood. Bare metal
7. Test Specimens
should not be used. Specimens are preferably supported from the bottom
7.1 The type and number of test specimens to be used, as
or the side. Slotted wooden strips are suitable for the support of flat panels.
well as the criteria for the evaluation of the test results, shall be
Suspension from glass hooks or waxed string may be used as long as the
defined in the specifications covering the material or product specified position of the specimens is obtained. If necessary, such
suspension may be made by means of secondary support at the bottom of
being tested or shall be mutually agreed upon between the
the specimens.
purchaser and the supplier.
8.3 Conditions in the Salt-Spray Chamber—Maintain the
8. Procedure
exposure zone of the CASS test chamber at a temperature of
8.1 Preparation of Test Specimens—Clean metallic and 496 1°C during the exposure period (Note 8). After closing the
metallic coated specimens. Unless otherwise agreed upon, test chamber, bring the temperature to 49°C before the fog is
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
B 368
turned on. The test duration shall commence when the tem- the spray can impinge directly on the test specimens.
perature is 49 6 1°C and fog is present in the chamber. Heat
8.4 Continuity of Test—Unless otherwise specified in the
the air supply by passing fine bubbles through heated distilled
specification covering the material or product being tested, the
or deionized water (see Specification D 1193, Type IV) so that
test shall be continuous for the duration of the entire test
the temperature of the air after expansion at the nozzle is 49 6
period. Continuous operation implies that the chamber be
1°C. Record the temperature within the exposure zone of the
closed and the spray operating continuously, except for the
closed cabinet (Note 9) twice a day at least 7 h apart (except
short daily interruptions necessary to inspect, rearrange, or
Saturdays, Sundays, and holidays, when the salt-spray test is
remove test specimens, to check and replenish the solution in
not interrupted for exposing, rearranging, or removing test
the reservoir, and to make necessary recordings as described in
specimens or to check and replenish the solution in the
8.3. Schedule operations so that these interruptions are held to
reservoir).
a minimum.
8.5 Period of Test—Designate the period of test by the
NOTE 8—This can be best accomplished by preheating the chamber to
specifications covering the material or product being tested or
49°C before starting solution atomization.
NOTE 9—A suitable method to record the temperature is by a thermom- as mutually agreed upon between the purchaser and the
eter that can be read from outside the closed cabinet. The recorded
supplier.
temperature must be obtained with the salt-spray chamber closed to avoid
a false low reading, because of wet-bulb effect when the chamber is open. NOTE 14—Typical exposure periods are: 6, 16, 22, 48, 96, 192, 240,
Automatic control of temperature in the chamber and a continuous record 504, and 720 h.
of temperature are desirable.
8.6 Cleaning Tested Specimens—Unless specified in the
8.3.1 Place at least two clean fog collectors within the
specifications covering the material or product being tested,
exposure zone so that no drops of solution will be collected
carefully remove specimens at the end of the test, rinse gently
from the test specimens or any other source. Position the
in clean, running, warm water (38°C, max) to remove salt
collectors in the proximity of the test specimens, one nearest to
deposits from their surfaces, and then dry immediately. To dry
any nozzle and the other farthest from all nozzles. A preferred
the specimens use a stream of clean, compressed air at 0.25 to
arrangement is shown in Fig. 1. Make sure that the fog is such
0.30 MPa gage pre
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