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Environmental Test Chambers for ASTM B368 CASS

Environmental Test Chamber for ASTM B368 Cyclic Accelerate Salt Spray Test


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,electrodepositednickel/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.

ASTM B368 Standard Test Method for Copper Accelerated Acetic Acid Salt Spray(Fog) Testing (CASS Test) this test 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.

This test 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 mentioned other than those mentioned in this paragraph.

The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 
 
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.

The apparatus required for the CASS test consists of a fog chamber, a salt-solution reservoir, a supply of compressed air, one or more atomizing nozzles, specimen supports, provision for heating the chamber, and necessary means of control.
 
The size and detailed construction of the apparatus are optional, provided the conditions meet the requirements of this test method. The construction of the apparatus is described in the appendix of Test Method B117. For the CASS test however, the requirements for air pressure and temperature are typically 0.08 to 0.12 MPa and 60 to 65C, respectively. The actual air pressure will be that required to produce the proper collection rate (see 8.3.1).
 
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 that fall from the specimens shall not be returned to the solution reservoir for respraying.4.4 Materials of construction shall not affect the corrosiveness of the fog, nor be themselves corroded by the fog.

Prepare the salt solution by dissolving 5 parts by weight of salt in 95 parts of water conforming to Specification D1193.Type IV. The salt shall be sodium chloride (NaCI), ACS reagent grade, or equivalent.
 
The pH of this solution shall be between6.0 and 7.0. Impurities or contamination of either the salt or the water, or both, shall be suspected if the pH is outside of this range (Note 2). No adjustment should be made.
 
Add 0.25 g of reagent grade copper chloride (CuCl,-2H,0) to each liter of the salt solution; dissolve and mix thoroughly.
 
The pH of the salt-copper solution shall be adjusted to the range of 3.1 to 3.3, as measured on a sample of the collected spray, by the addition of glacial acetic acid, ACS reagent grade, or equivalent (Note 3). The pH measurement shall be made electrometrically at 25°C. Before the solution is atomized, it shall be free of suspended solids.
 
The compressed air supply to the nozzle or nozzles for atomizing the test solution shall be free of oil and dirt (Note 5) Pressure shall be adequate to provide a specified condensate rate.
 
The type and number of test specimens to be used, as "well as the criteria for the evaluation of the test results, shall be defined in the specifications covering the material or product being tested or shall be mutually agreed upon between the purchaser and the supplier.
 
Preparation of Test Specimens- Clean metallic and metallic coated specimens. Unless otherwise agreed upon, clean decorative copper/nickelchromium or nickelchromium coatings immediately before testing by wiping significant surfaces with a cotton pad saturated with a slurry containing 10 g of pure magnesium oxide powder (ACS reagent grade) in 100 mL of distilled water.