ASTM B368-97(2003)e1
(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)
SIGNIFICANCE AND USE
The CASS test is widely employed and is useful for specification acceptance, simulated service evaluation, manufacturing control, and research and development. It was developed specifically for use with decorative, electrodeposited nickel/chromium and copper/nickel/chromium coatings. Use of the test has improved the quality of electroplated parts and led to the development of new and superior electroplating processes.
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 B 537 and E 50, Specifications B 456 and B 604, and Test Method B 602.
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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
e1
Designation:B368–97(Reapproved 2003)
Standard Test 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.
e NOTE—Sections 8.1 and 10.1.12 were editorially updated in July 2003.
1. Scope B 456 Specification for Electrodeposited Coatings of Cop-
per Plus Nickel Plus Chromium and Nickel Plus Chro-
1.1 This method prescribes the conditions required in
mium
copper-accelerated acetic acid-salt spray (CASS) testing for
B 537 Practice for Rating of Electroplated Panels Subjected
specification purposes. The standard does not specify the type
to Atmospheric Exposure
of test specimen or exposure periods to be used for a specific
B 602 Test Method for Attribute Sampling of Metallic and
product, nor the interpretation to be given to the results.
Inorganic Coatings
1.2 This method is applicable to evaluating the corrosive
B 604 Specification for Decorative Electroplated Coatings
performance of decorative copper/nickel/chromium or nickel/
of Copper Plus Nickel Plus Chromium on Plastics
chromium coatings on steel, zinc alloys, aluminum alloys, and
D 1193 Specification for Reagent Water
plastics designed for severe service. It is also applicable to the
E 50 Practices forApparatus, Reagents, and Safety Consid-
testing of anodized aluminum. The suitability of this test and
erations for Chemical Analysis of Metals, Ores, and
correlation of results with service experience should be deter-
Related Materials
mined before it is specified for coating systems or materials
other than those mentioned in this paragraph.
3. Significance and Use
NOTE 1—The following standards are not requirements. They are
3.1 The CASS test is widely employed and is useful for
referenced for information only: Practices B 537 and E 50, Specifications
specification acceptance, simulated service evaluation, manu-
B 456 and B 604, and Test Method B 602.
facturing control, and research and development. It was devel-
1.3 This standard does not purport to address all of the
oped specifically for use with decorative, electrodeposited
safety concerns, if any, associated with its use. It is the
nickel/chromiumandcopper/nickel/chromiumcoatings.Useof
responsibility of the user of this standard to establish appro-
the test has improved the quality of electroplated parts and led
priate safety and health practices and determine the applica-
to the development of new and superior electroplating pro-
bility of regulatory limitations prior to use. For more specific
cesses.
safety precautionary information see 8.1.
4. Apparatus
2. Referenced Documents
4.1 The apparatus required for the CASS test consists of a
2.1 ASTM Standards:
fog chamber, a salt-solution reservoir, a supply of compressed
B 117 Practice for Operating Salt Spray (Fog) Apparatus
air, one or more atomizing nozzles, specimen supports, provi-
B 162 Specification for Nickel Plate, Sheet, and Strip
sion for heating the chamber, and necessary means of control.
4.2 The size and detailed construction of the apparatus are
optional, provided the conditions meet the requirements of this
ThismethodisunderthejurisdictionofASTMCommitteeB08onMetallicand
method. The construction of the apparatus is described in the
Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on Test
Methods.
appendix of Test Method B 117. For the CASS test, however,
Current edition approved May 10, 2003. Published July 2003. Originally
approved in 1961. Last previous edition approved in 1997 as B 368 – 97.
The CASS test was developed by the initiative of the Research Board of the
American Electroplaters Society under AES Project 15. Annual Book of ASTM Standards, Vol 02.05.
2 5
Annual Book of ASTM Standards, Vol 03.02. Annual Book of ASTM Standards, Vol 11.01.
3 6
Annual Book of ASTM Standards, Vol 02.04. Annual Book of ASTM Standards, Vol 03.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
e1
B368–97 (2003)
regulator valve minimizes the possibility that the nozzle will be operated
the requirements for air pressure and temperature are typically
at its critical pressure.
0.08 to 0.12 MPa and 60 to 65°C, respectively. The actual air
pressure will be that required to produce the proper collection
7. Test Specimens
rate (see 8.3.1).
4.3 The apparatus shall be constructed so that drops of 7.1 The type and number of test specimens to be used, as
well as the criteria for the evaluation of the test results, shall be
solution that accumulate on the ceiling or cover of the chamber
do not fall on the specimens being tested. Drops of solution defined in the specifications covering the material or product
being tested or shall be mutually agreed upon between the
that fall from the specimens shall not be returned to the
solution reservoir for respraying. purchaser and the supplier.
4.4 Materials of construction shall not affect the corrosive-
ness of the fog, nor be themselves corroded by the fog. 8. Procedure
8.1 Preparation of Test Specimens— Clean metallic and
5. Test Solution
metallic coated specimens. Unless otherwise agreed upon,
5.1 Prepare the salt solution by dissolving 5 parts by weight clean decorative copper/nickel/chromium or nickel/chromium
of salt in 95 parts of water conforming to Specification D 1193,
coatings immediately before testing by wiping significant
TypeIV.Thesaltshallbesodiumchloride(NaCl),ACSreagent surfaces with a cotton pad saturated with a slurry containing 10
grade, or equivalent. The pH of this solution shall be between
gofpuremagnesiumoxidepowder(ACSreagentgrade)in100
6.0 and 7.0. Impurities or contam-ination of either the salt or mL of distilled water. Upon rinsing in warm running water, be
the water, or both, should be suspected if the pH is outside of
sure that the clean surface is free of water break. Anodized
this range (Note 2). aluminum parts may be cleaned with inhibited 1,1,1-
5.2 Add 0.25 g of reagent grade copper chloride (CuCl
trichloroethane or other suitable organic solvent (seeWarning).
2·2H O) to each litre of the salt solution; dissolve and mix Do not clean organic and other nonmetallic coated specimens.
thoroughly.
Other methods of cleaning, such as the use of a nitric-acid
5.3 The pH of the salt-copper solution shall be adjusted to solution for the chemical cleaning or passivation of stainless
the range of 3.1 to 3.3, as measured on a sample of the steel specimens, are permissible when agreed upon between
collected spray, by the addition of glacial acetic acid, ACS the purchaser and the supplier. Take care that the specimens
reagent grade, or equivalent (Note 3). The pH measurement after cleaning are not recontaminated by excessive or careless
shall be made electrometrically at 25°C. Before the solution is handling. Protect the cut edges of plated, coated, or multilay-
atomized, it shall be free of suspended solids (Note 4). ered materials and areas containing identification marks or in
contact with the racks or supports with a coating that is stable
NOTE 2—A solution having a specific gravity of 1.030 to 1.040, when
under the conditions of the test, such as wax, stop-off lacquer,
measured at a temperature of 25°C, will meet the concentration require-
or pressure-sensitive tape. (Warning—1,1,1-Trichloroethane
ment. It is suggested that a daily check be made.
should be used in a well-ventilated area away from open
NOTE 3—TheinitialsolutionmaybeadjustedtoapHof3.0to3.1,with
the exception that the pH of the collected fog will be within the specified flames.)
limits.Adjustment of the initial pH for makeup solution is based upon the
8.2 Positioning of Specimens—Position the specimens in
requirements to maintain the required pH of the collected samples. If less
the CASS test chamber during the test so that the following
than1.3ormorethan1.6mLoftheglacialaceticacidarerequiredperlitre
conditions are met:
of sodium chloride and copper solution to attain the specified pH, some
8.2.1 Support or suspend the specimens 15 6 2° from the
discrepancy in the system may be suspected (the purity of the water or
vertical and preferably parallel to the principal direction of
salt, or both; the accuracy of the pH meter; the general cleanliness of the
system; etc.).
horizontal flow of fog through the chamber, based upon the
NOTE 4—The freshly prepared salt solution may be filtered or decanted dominant surface being tested. Support or suspend automobile
before it is placed in the reservoir, or the end of the tube leading from the
parts, however, so as to expose all significant surfaces at the
solution to the atomizer may be covered with a double layer of cheese
general level of the condensate collectors. If the position on the
cloth to prevent plugging of the nozzle.
automobile is vertical, place the part in an incline position 15°
from vertical to allow surface wetting by the condensate. If the
6. Air Supply
position on the automobile is facing down, rotate the part
6.1 The compressed air supply to the nozzle or nozzles for
approximately 180° to test the significant surface. If there are
atomizing the test solution shall be free of oil and dirt (Note 5).
several significant surfaces at different angles, expose each
Pressure shall be adequate to provide a specified condensate
surface of one or more specimens.
rate. Pressure of 0.10 6 0.02 MPa has been found satisfactory
8.2.2 Make sure the specimens do not come in contact with
(Note 6).
each other or any other metallic material or any material
NOTE 5—The air supply can be freed of oil and dirt by passing it capable of acting as a wick.
through a water scrubber or at least 60 cm of suitable cleaning material,
8.2.3 Placeeachspecimensoastopermitfreesettlingoffog
such as sheep’s wool, excelsior, slag wool, or activated alumina. Com-
on all specimens.
mercial filters for compressed air may be used.
8.2.4 Make sure the salt solution from one specimen does
NOTE 6—Atomizing nozzles may have a critical pressure, at which an
not drip on any other specimen.
abnormal increase in the corrosiveness of the salt fog occurs. If the critical
8.2.5 Place the specimens in the chamber just prior to
pressure of a nozzle has not been determined with certainty, control of
fluctuationintheairpressurewithin 60.0007MPabyinstallingapressure bringing the test chamber to the required temperature and
e1
B368–97 (2003)
when measured at 25°C, will meet the concentration requirement. The
turning on the air, since storage in an idle chamber overnight,
concentration may also be determined as follows: Dilute 5 mL of the
or for other significant length of time, can affect test results.
collected solution to 100 mL with distilled water and mix thoroughly;
NOTE 7—Suitable materials for the construction or coating of racks and
pipet a 10-mLaliquot into an evaporating dish or casserole; add 40 mLof
supports are glass, rubber, plastic, or suitably coated wood. Bare metal
distilled water and 1 mL of 1% potassium chromate (K CrO ) (ACS
2 4
should not be used. Specimens are preferably supported from the bottom
reagent grade with less than 0.005% chloride) and titrate with 0.1 N silver
ortheside.Slottedwoodenstripsaresuitableforthesupportofflatpanels.
nitrate (AgNO ) (ACS reagent grade) solution to the first appearance of a
Suspension from glass hooks or waxed string may be used as long as the
persistent red coloration.Atest solution that requires between 3.9 and 4.9
specified position of the specimens is obtained. If necessary, such
mL of 0.1 N Ag NO solution will meet the concentration requirements.
suspension may be made by means of secondary support at the bottom of
NOTE 12—It has not been found necessary to check copper concentra-
the specimens.
tion of the collected solution.
NOTE 13—Factors that may contribute to dilution and evaporation of
8.3 Conditions in the Salt-Spray Chamber—Maintain the
condensate and make it difficult to control the concentration are lower
exposure zone of the CASS test chamber at a temperature of
temperature, inadequate cover insulation, and prolonged storage of test
4961°Cduringtheexposureperiod(Note8).Afterclosingthe
solution at above room temperature.
test chamber, bring the temperature to 49°C before the fog is
turned on. The test duration shall commence when the tem- 8.3.2 Direct or baffle the nozzle or nozzles so that none of
perature is 49 6 1°C and fog is present in the chamber. Heat
the spray can impinge directly on the test specimens.
the air supply by passing fine bubbles through heated distilled 8.4 Continuity of Test—Unless otherwise specified in the
or deionized water (see Specification D 1193, Type IV) so that
specification covering the material or product being tested, the
the temperature of the air after expansion at the nozzle is 49 6 test shall be continuous for the duration of the entire test
1°C. Record the temperature within the exposure zone of the
period. Continuous operation implies that the chamber be
closed cabinet (Note 9) twice a day at least 7 h apart (except closed and the spray operating continuously, except for the
Saturdays, Sundays, and holidays, when the salt-spray test is short daily interruptions necessary to inspect, rearrange, or
not interrupted for exposing, rearranging, or removing test remove test specimens, to check and replenish the solution in
specimens or to check and replenish the solution in the the reservoir, and to make necessary recordings as described in
reservoir). 8.3. Schedule operations so that these interruptions are held to
a minimum.
NOTE 8—This can be best accomplished by preheating the chamber to
8.5 Period of Test—Designate the period of test by the
49°C before starting solution atomization.
specifications covering the material or product being tested or
NOTE 9—Asuitable method to record the temperature is by a thermom-
eter that can be read from outside the closed cabinet. The recorded as mutually agreed upon between the purchaser and the
temperature must be obtained with the salt-spray chamber closed to avoid
supplier.
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 spec
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.