Sodium chloride solution preparation
The multi-purpose reagents of the salt spray test chamber use chemically pure or above. Sodium chloride is dissolved in distilled water or deionized water with a conductivity not exceeding 20uS / cm, and its concentration is 50g / L ± 5g / L. At 25 degrees, the density of the prepared solution is in the range of 1.025 5 ~ 1.040 0. There are unused test methods for the salt spray test chamber, and each unused test method has a different solution preparation method.
Neutral salt spray test (NSS test)
Adjust the pH value of the salt solution prepared with sodium chloride solution to be between 6.5 and 7.2. The pH value can be measured with an acidity meter. As a daily test, a precision pH test paper with a measurement accuracy of 0.3 can also be used. The pH of the solution can be adjusted with hydrochloric acid or sodium hydroxide.
The loss of carbon dioxide in the solution during spraying may result in a change in pH. Corresponding measures should be taken, for example, heating the solution to more than 35 degrees before sending it into the instrument or preparing a solution from fresh boiling water to reduce the carbon dioxide content of the solution Must change the pH value.
Acetic acid salt spray test (AASS test)
Add an appropriate amount of glacial acetic acid to the salt solution prepared according to the sodium chloride solution to ensure that the pH value of the collected solution in the salt spray test chamber is 3.1 ~ 3.3. If the pH of the initially prepared solution is 3.0 ~ 3.1, the pH of the collected solution is generally in the range of 3.1 ~ 3.3. The pH value is measured with an acid meter. As a daily test, a precision pH test paper with a measurement accuracy of 0.1 can also be used. The pH of the solution can be adjusted with glacial acetic acid or sodium hydroxide.
Copper accelerated acetate spray test (CASS test)
In the salt solution prepared by adjusting the pH, copper chloride (CuCl2 · 2H2O) was added, and its concentration was 0.26g / L ± 0.02g / L (that is, 0.205g / L ± 0.015g / L anhydrous copper chloride). The method of adjusting the pH of the solution is the same as the acetate spray test (AASS test)
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