Sciencemadness Discussion Board

Why does gold turn gray

Romix - 20-5-2021 at 04:02

Sometimes gold plated PCBs turn gray in acetic acid, and also coppery colored.
Also saw this happen when gold plated heatsinks been boiled in sodium hydroxide solution.
Same happened when I left some jewelry in a concentrated solution of table salt. It turned gray.
How to explain this phenomenon? Gold not going any where, when I boiled it in 3% nitric gold returned.
And in one of the Dusan's new videos he boiled gold plated pins in HCl to remove solder, all of his pins turned gray too.
What if the same will happen with Eco Goldex? You can't tell if the gold went in to the solution or plated gray.
Not going to use it, don't want to pour cyanide based chemicals down the drain and don't know how to dispose of it.

Romix - 20-5-2021 at 04:37

https://www.youtube.com/watch?v=r3cZrHwfCHk