Rick:

Plating is a process of adding electrons to a metal ion in solution causing
it to revert to the metallic state.  The differences in types of plating are
due to where the electrons come from.

In flash plating, aka "electroplating", the electrons are delivered by
connecting the part to a rectifier, which "pumps" them in.

In immersion plating, the electrons are donated by the substrate metal, in
this case Nickel, as it becomes an ion, and goes into solution, while the
receptor Gold ions deposit as the metal.

I would suspect that for a given thickness (and immersion plating is self
limiting in thickness, once all the Nickel is covered, plating stops)  flash
plating would have more tendency to be porous, thus opening up the
possibility of Nickel corroding, and the oxide coming through on to the Gold.


Good luck

Rudy Sedlak
RD Chemical Company

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