single-piston brake calipers : original plating

[Bukowski]

I have been cleaning up some single-piston calipers. I washed/degreased the floating frame as a test case, including Goof-Off, then started testing brass brushes. They managed to get it shiny-looking.

so now I am wondering about the original plating, which I think is zinc. Is there a way to tell immediately when the wire brush is scraping it all off? I imagine if I let it sit in a moist atmosphere, a coating of red rust will indicate the zinc is all gone.

How thick would the original plating be, anyways?

also, a pre-emptive comment : I know about the Pelican Parts-promoted brake caliper restoration services, but I am not interested in that with this question, but thanks.

[Tervuren]

I used power wire brushes until there was no more rust, cleaned, and painted. I didn't bother plating. Mine were already rusted through whatever coating they had in places.