Copper-accelerated acetic acid-salt spray (CASS) testing used 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.

Solution: dissolving 5 parts by weight of salt in 95 parts of water conforming to Specification D 1193, the salt shall be sodium chloride (NaCl), ACS reagent grade, or equivalent.

The pH of this solution shall be between 6.0 and 7.0. Impurities or contam-ination of either the salt or the water, or both, should be suspected if the pH is outside of this range.

Add 0.25g of reagent grade copper chloride (CuCl2·2H2O) 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. The pH measurement shall be made electrometrically at 25°C. Before the solution is atomized, it shall be free of suspended solids.