Hi Andy,  I heard a different thing.  I have always understood that the
nickel is what protects the underlying metal.  Chrome plating is very
porous and doesn't offer any corrosion protection at all.  It is just
there for it's shiny looks.

The process of chrome plating that I read about is called "triple
chrome plating".  First the item is plated with a thick layer of copper.
This copper is then buffed to a mirror like shine.  The copper layer is
thick enough to fill minor scratches.  It serves a similar purpose as
high build primer does in automotive painting.  Then the nickel is
plated over the copper to provide corrosion protection.  Finally,
a thin layer of chrome is added to add the shiny look.

Ben Haass