how to find plating peeloff

Plating peeloff will contain pieces of the metal.  In severe cases, this will look like foil or sheets of metal.  Sometimes it looks like glitter or small particulates of metal.

Passivate doesn't really peeloff, it sloughs off.  It will remain clear/blue/yellow for the most part with no visible traces of metal.  It tends to look like a gel or slime.