The salt spray tester is a kind of artificial simulation of the salt spray environment. Compared with the exposure test under atmospheric conditions, it has significant advantages: the corrosive environment can be controlled, the environmental reproducibility is good, and the test time is significantly shortened. This test is aimed at the surface treatment of various materials, including metal plating, chemical coatings, baking varnishes, automobiles, motorcycles, hardware wares, screws, springs, magnetic materials, organic and inorganic coatings, anodizing, anti-rust oil and other industries. Test the corrosion resistance of its products. The salt spray test we usually do is generally divided into three ways: neutral salt spray test, acetate spray test, copper accelerated acetate spray test. Today we mainly explain the three tests. What are the same and different solutions?
First, the cover layer, neutral salt spray test (NSS test)
a. The salt solution is prepared by using sodium chloride (chemically pure, analytically pure) and distilled or deionized water at a concentration of (5% ± 0.1) (mass percent). The collected liquid after atomization shall not be reused except for the blocking part of the baffle;
b. The pH of the salt solution before atomization is between 6.5 and 7.2 (35 ± 2 ° C). When preparing a salt solution, a chemically pure solution of dilute hydrochloric acid or sodium hydroxide may be used to adjust the pH, but the concentration still meets the requirements of point a.
Second, metal coating, copper accelerated acetate spray test (CASS test)
a. Dissolve sodium chloride in distilled or deionized water at a concentration of 50 ± 5 g / L.
b. Add copper oxide (CuC12.2H2O) to a solution at a concentration of 0.26 ± 0.02 g / L (ie 0.205 ± 0.015 g / L anhydrous copper chloride).
c. Add an appropriate amount of glacial acetic acid in the solution a to ensure that the pH of the salt spray collection in the test chamber is 3.1 to 3.3. If the pH of the solution before the spraying is 3.0 to 3.1, the pH of the collection is generally 3.1 to Within the scope of 3.3. The pH value of the solution is measured with a pH meter, and a precision pH test paper which can be read by a pH meter and can read a change in pH of 0.1 can be used as a daily test. The pH of the solution can be adjusted with glacial acetic acid or sodium hydroxide.
d. To avoid nozzle clogging, the solution must be filtered before use.
Third, the metal coating, the acetate spray test (ASS test) eliminates the "b" step in the "two" process.
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