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Non-Tarnish FINISH
Some clearcoating solutions 
We import belt buckles from India. What FINISH absolutely ensures there will be NO-TARNISH? Lacquered Brass, Gold Plate ....... Zinc... I have seen many tarnished samples....
Nela Kash- Los Angeles, California, USA
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Precious metals (gold, rhodium) don't tarnish. But even then the precious metal has to be thick enough and properly applied in order that an undercoat does not tarnish through any porosity in the top coat. Even then there is the possibility of stains that are not tarnish but may look like tarnish.
There is nothing you can specify which will put all of your QA people out of work though :-)
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
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Nela Kash,
This is a very general letter. Here are some questions you need to answer, then go to a Plating consultant if you still need a solution to your problem.
- What is the base metal.
- What is the plating process sequence.
- What is the final plated deposit.
- Which lacquer is used.
- How is it applied. The process.
- What is the mode of drying.
- What is the mode of packaging
What is the type of tarnish observed. How long does the part remain tarnish free. The problem of tarnish is solvable with Proper identification of causal factors, Patience, Right technique and a choice of the right materials.
Regards,
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Asif Nurie Atlanta Global  New Delhi, India |
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Firstly, if the product is a cheap brass casting,with any porosity, an initial plating with nickel should seal the metals pores prior to gold plating. Make sure to use the maximum plating time for both. On the subject of lacquering, there are products that will withstand corrosion and abrasion if baked and dipped two or three times.
Mark Hunter- N.S.W., Australia