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Why does gold plating tarnish?

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Q. I have observed that the gold plating has some darkening areas over the nickel plated copper base material.

What causes this effect? We all know that gold is a very inert metal & does not corrode or rust. In this case, it should not tarnish. Under what circumstances or condition does this problem arises?

Your advice is greatly appreciated.

Thank you

Maung San Zaw
- Singapore


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A. Hi,

Gold as such will not tarnish. It is inert. The tarnish-like appearance is due to underlying surface getting corroded or oxidized. If the thickness of gold is not adequate and if the coating is porous, the corrosion taking place in the underlying surface may seem like tarnish. Ensure that you have adequate thickness build up of gold, to put an end to your problem.

Good luck ...

Karthik
- Singapore

Goldie book
Gold Plating Technology

Reid & Goldie


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Q. I need to know how to clean tarnished gold plated bracelets.

Thanks,

Desiree Rubinstein
- New York


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A. Gold does NOT tarnish. if you wish, post a detailed picture and we'll advise further.

Fred Luhn
- S. Ozone Park, New York


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A. Hi,

If you have nickel plating as a finish to plate gold onto it will normally not tarnish even if you only deposit 0,1 micron of gold. This could mean that the gold plating solution has contamination, which tarnished. If you have nickel-free plating and plate gold onto copper or bronze the tarnish would come from the base if the gold plating is too thin to form a uniform layer without pores.

Good luck and all the best,

kastner Trudy Kastner
electroplating service
Durban, KZN, South Africa


July 1, 2009

Q. Can anyone tell me if pure gold (such as a necklace) tarnishes in a swimming pool water that has chlorine?

Minou Sadeghi
- San Diego, California


July 6, 2009

A. Hi, Minou. My understanding is that 24 karat gold will not tarnish; but jewelry is usually made of a lower karat which contains copper or nickel or silver or other metals, and a lot of gold jewelry will tarnish in chlorine. However, the tarnish layer is probably thin and a jeweler can probably restore the shine with some polishing. But don't wear gold jewelry into a swimming pool.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

Polishing Sticks


January 14, 2011

A. Gold plating has only little effect on nickel materials, but it's best on gold, silver, and copper. Heavy plating can be used.

Janice O.
- Philippines

March 10, 2013

Q. I dropped my 24-Kt. Gold bracelet into a "Tarn-X" solution by mistake. When I finally took it out, it was still gold; however, it had a dull layer (that looked tarnished). I want to know what household items I can use to restore the bracelet without having to take it to a jeweler. What about jewelry cleaner; will that help?

Thanks!

Roz- Johnson
- Richmond, Virginia, USA


March 11, 2013

A. Hi Roz. I'm surprised that 24 kt gold would tarnish as 24 kt gold is extremely chemical resistant. Are you sure it's 24 kt?

Don't mess with further chemical treatments. Try buffing off the discoloration with a jewelry cloth and a very mild abrasive like light duty rubbing compound.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
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