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The copper sulfate test is a visual method of determining the existence of free iron in specifically stainless steel. In many cases, the copper sulfate test is used as a pass/fail examination of a passivation process on a part or stock material, but it can also be used as a test to determine if passivation is necessary in the first place. //
http://everyspec.com/MIL-STD/MIL-STD-0700-0799/MIL_STD_753C_1117/
The method is specifically designed to work with stainless steel alloys with a minimum of 16% chromium as stated in the document.
The procedure is as follows:
- Prepare test solution – Dissolve 8 grams of copper sulfate in 500 ml of distilled water in which 2 – 3 ml of sulfuric acid has been added.
This will take approximately 5 minutes and should be mixed completely before using. It is noted in the documentation that solutions older than 2 weeks shall not be used for the test. The dilution by weight of the test is 1.6% which is on the lower end of the copper sulfate solution dilution.
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Swab the surface to be inspected with test solution – keep surface wet for a period of 6 minutes.
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Carefully rinse and dry the surface such that no copper deposits are removed.
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Copper deposits indicate the presence of metallic iron.
