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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Gold plating color change - tarnish problem
Q. We are having a quick tarnishing problem with our gold plating. We put 1-micron gold plating (using IWG's MC218) over 925 silver material. After micron gold plating we do flash-gold plating for color purposes over micron gold layer.
As we complete the plating process the color comes out ok (14k hamilton color). However when we touch the plated piece around 30 seconds the color changes and becomes a dark orange color. When we steam-clean the piece the color goes back to the original 14k hamilton color. Also if the piece is left out for a few days the color change as well. It looks like an oxidization problem. Our vendor couldn't solve the problem so far and still working on it. But I thought some of you guys may have an idea as well.
Your help will be appreciated.
Regards
Plating shop - Istanbul, Turkey
October 10, 2010
A. Hi Cem,
Did you try without 14K flash gold to confirm the problem is not related to thick gold? If the problem is confirmed due to 14K flash gold, then possible causes maybe:
1. Gold conc in flash gold bath is too low or other metallic elements (to contribute the 14K gold color, such as indium, cadmium, iron, copper, etc) concentration are too high and/or out of optimum ratio.
2. Contamination of flash gold bath (organic or inorganic).
3. Poor rinsing/drying after flash gold.
4. Rectifier output (ripple, etc) and/or wrong current setting.
Regards,
David
David Shiu
- Singapore
A. An anti tarnish dip (not lacquer) may help.
Regards
T.K. Mohan
plating process supplier - Mumbai, India
October 13, 2010
Q. Thank you for your recommendations. We discovered that the color change was because of cyanide left overs on the surface. Now we are cleaning the items by washing in water over 80 °C. This is a really time consuming process. Is there any other way you can recommend for cyanide destruction?
Thanks
Cem
- Istanbul, Turkey
October 24, 2010
A. Hi, Cem. I am not immediately understanding why hot water rinsing is such a time-consuming process, but you could try ultrasonic rinsing. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hello, did you solve the problem?
I have the same issue. Gold plate looks bright yellow straight out of bath, turns dark orange as soon as I try to clean it with water. I guess it's cyanide residue, but no idea how to remove it. Hot water doesn't seem to help either.
- California
December 16, 2024
Ed. note: This forum was built as a gathering place for sharing tips, pics, anecdotes, & opinions to promote camaraderie.
When engagement is requested by strangers withholding their names, readers may be less likely to engage.
A. Hi Rose. Cem said hot water worked for him; we'll try to advise him of your posting, but his was 14 years ago.
Please search the site for "cyanide spot-out", but both Asif Nurie and Robert Probert said the first thing to try is a dip in a diluted acid -- acetic, oxalic, or sulfuric have all been suggested from time to time.
But please try your best to fully describe your own situation because "same issue" is almost never quite the same. For example if your parts are not silver, or are castings it may actually a very different problem than Cem's :-)
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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