They never talked about this in my RPD class that I just finished, but this came from the polident website...
Can partials be soaked in Polident® 5 Minute?
Yes, you can soak partials and orthodonic retainers in Polident® 5 Minute denture cleanser. We recommend Polident® Partials because it is specially designed to be less harsh on the metal portion of the partial or retainer.
If you have any doubts, maybe you should try it on an inconspicuous piece of car bumper metal...Chromium Cobalt - that's the same stuff they make clasps out of...