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Electroplated gold turns red
We are using Printed Wired Board with a selective electroplated gold realized with a deposition of gold over nickel over copper.
The Gold bath contain 99.7% pure gold, 0.25% Cobal (to have 180hv hard gold).
Actually we have a problem because the gold surface turn red if in contact with environment (originally we receive them as clean yellow). The boards are finished with olse OSP (Organic surface Preservative) studied not to remain on gold. Any idea about what kind of pollution can come from the plating process or PWB manufacturing final stages that can give this effect?Alessio Agresti
electronics manufacturing - Bologna, Italy
First of two simultaneous responses -- 2004
This could also be a problem of surface topography instead of contamination. The reflectivity and wave length of the incident rays change by the surface condition. Check if the red color remains after a soft and bright mechanical polishing.Guillermo Marrufo
Monterrey, NL, Mexico
Second of two simultaneous responses -- 2004
A good place to look is at the Nickel plating. If it is porous the copper migrates into the Gold. A chemical analysis of the Gold surface can determine this.Tom Gallant
- Long Beach, California, USA
October 15, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. Dear Ladies and Gentlemen,
I have a plating work shop in biggest jewellery manufacturers' complex in Istanbul-Turkey.
My problem is when we electro-plate 23k gold on 18k rings, it sometimes turns red-ish after a while. l will be very thankful if anyone can solve my problem.
A. Hi Mehmet,
Gold deposit turning reddish could be due to:
1. Gold porosity leading to corrosion.
2. Poor final water rinse after gold plating.
3. Gold plating bath is contaminated with metallic impurities, such as copper or iron, which co-deposit with gold during electroplating.
This can be because of many things but usually is due to low gold content in the bath, poor water rinse. Implement final hot water rinse and, if possible, anti-tarnish.
- Mumbai, India