How to test for good passivation/phosphating?

[ndsram]

HI,

I wondering whether there is any test for testing the passivation on the surface of the metal. Normally Salt Spray Test has been carried out for testing coating on the surface of the metal, however when I asked my supplier who carry out passivation for our product, they replied that salt spray test is not the correct test to perform for passivated surface. So may I request you whether can you recommend any test for passivated metal surafce

BR
N D Senthil Ram

 

[swall]

Proper passivation on stainless can be verified with a copper sulfate soak. Mix 8g CuSO4 in 500ml of distilled water with 2-3ml of H2SO4. Immerse the subject parts for 6 minutes. If no copper plates out, the parts are properly passivated.

 

[ndsram]

Thank you for your reply
I could say that my material is NdFeB magnet which is highly corrosive. S for this material I cannot use H2SO4. Please let me know whether is there any standard for testing the passivation