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Anti tarnish for copper coating on imitation jewellery


Q. I do imitation Rose gold ( which is an alloy of Cu-Ag). I WANT A GOOD Anti tarnish, not E-coat which has to withstand 1% polysulphide test, so that glitter/sheen of the jewellery stone should not diminish.

Panjala Mukesh Goud
Employee - Hyderabad, India
September 4, 2025


"The Chemistry of Benzotriazole Derivatives"
benzotriazole
on eBay or Amazon
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A. Hi Panjala

Is there an ASTM, ISO. or other standard governing this 1% polysulphide test you are speaking of? I understand what polysulphide is, and that it can blacken and otherwise corrode copper, but I'm not understanding how you conduct this test or interpret the results.

The best copper preservatives to forestall tarnishing of copper are sodium benzotriazole and related compounds, and they are quite routinely applied to copper surfaces, but I don't know whether they will get you past the requirements of a test that I'm not familiar with.

Luck & Regards,

ted_yosem
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted is available for instant help
or longer-term assistance.


The test is supposed to be for silver plating on top of copper wire. After the procedure, the surface turns black from reaction with the copper base metal when the silver plating is not fully protecting the copper. Since you are plating a copper-silver alloy instead of unalloyed silver, the ASTM B298 test may not work no matter what you do. Perhaps I am wrong and the alloy plate layer does not discolor in the test procedure. If that is the case, your best bet is to plate a thicker coating.

Jon Barrows
Jon Barrows, MSF, EHSSC
Kansas City


Thank you! This Poly Sulphide is Nothing but Sulphurated Potassh (Liver of Sulphur). This is one way of testing Copper/Silver top layers for Tarnish test. When copper-coated piece is dipped in benzoTriAzole solution, piece dried, and subjected to 1% Polysulphide test, it has tarnished to black. Tried other Anti Tarnish solutions ... not withstanding polysulphide test.

Panjala Mukesh Goud [returning]
- Hyderabad, Telangana
September 19, 2025




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