Silver Plate Corrosion

[faulkma]

We have some copper pieces silver plated and the plating becomes tarnished when exposed. Is this normal? Does it effect the conductivity of the electrical joint when applied.

thanks

 

[IRstuff]

If it didn't tarnish, it probably wasn't silver.

TTFN

FAQ731-376

 

[faulkma]

Thanks but the plating was almost Black. Is this normal?

 

[IRstuff]

What was it exposed to?

TTFN

FAQ731-376

 

[faulkma]

not sure, just the outside elements.

 

[btrueblood]

Black tarnish is from sulfur oxides. Either there's a lot of coal smoke where you are, or the plating layer was porous and some residual sulfuric acid from the process remained to bubble out later to speed tarnishing.

 

[IRstuff]

I ouwld be only a little surprised that it turned black, since that seems a bit extreme, but that might just depend on what specific environment it got exposed to.

As for electrical conductivity, it would affect it, UNLESS, you are able to break through the tarnish to get to the metal underneath. As a general rule, this is discouraged, as the tarnish can still spread, since you don't have a clean interface, so "stuff" can still get in.

TTFN

FAQ731-376

 

[kenvlach]

This seems to be an environment requiring precious metal plating, e.g., hard gold, platinum, rhodium or an alloy thereof (Ir,Pt, Rh). An intermediate layer of nickel may be needed as a diffusion barrier (between copper & gold).