Question

Tha silver or copper coated with gold is

Answer 1

A barrier metal layer is used to counter this effect. 
Copper, which also migrates into gold, does so more slowly than silver.
The copper is usually further plated with nickel.
A gold-plated silver article is usually a silver substrate with layers of copper, nickel, and gold deposited on top of it.
the process of covering the metals like copper, silver by gold is called gold plating.

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