Tarnishing of palladium plating

 

Hi,

I have a palladium (pure palladium) plated part that has tarnished, i.e. the surface has gone brown. The brown layer is quite evenly distributed across the part, and the color is darker round the edges. The layer can be scratched off. I suspect it's an oxide layer, but what is the possible cause for that?

If the Palladium is turning brown, it must be a very thin coating, and the underlying base metal is corroding through.

I'm afraid that you're confronted with the so-called "brown powder effect". This is caused by the fact that pure Palladium has a tendency to attract organics on the surface which finally form a brown film.

About this phenomenum are literature studies available. I've never seen it personally in practice but quite a lot about it has been published in the past.

Kind regards,