Aloha, fun & authoritative answers -- no cost, no registration, no passwords, no popups
(as an eBay Partner & Amazon Affiliate we earn from qualifying purchases)

Where the
world gathers for metal finishing
Q&As since 1989

-----

Electroplated gold turns red

2004

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).

31816

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 --

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
2004

Second of two simultaneous responses --

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
2004

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.

Mehmet Refik Atakoglu
- Turkey
October 15, 2012

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.

Regards,
David

David Shiu
- Singapore
October 21, 2012

A. Hi,
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.

Gurudatta Thakur
- Mumbai, India
December 16, 2012

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories: