It depends on what the object in question is for (decoration or durability)
and what time period it was done.
Way back in the early 90's when I worked at a plating facility for the
printing industry (Tide soap boxes, Marlboro cigarette boxes as an example)
they used to copper plate large and heavy steel (or aluminum which needed
another step) cylinders. The copper layer was then diamond engraved with the
design for each color and then a heavy chrome plating was done for wear to
keep the design from getting damaged from printing rolls of paper or what
have you. No nickel plating at all back then. A final QC test was spinning
the cylinder and running sandpaper over it to spot imperfections (shiny
spots that show indentations where no design was) that would show up during
printing , if it passed it went to the onsite printer for a proof print
otherwise acid bath to remove the chrome then the lathe to cut off the
designs and back to copper plating again. The chrome plating was pretty
thick.
-----Original Message-----
From: Brent Hilpert via cctalk
Sent: Thursday, July 20, 2017 3:02 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Removing Pitting and Rust From an Enclosure
A copper layer can perform some filling and smoothing function in a plating
job.
Its perhaps more significant purpose however (as I understand it in my
limited experience with having plating done*), is to provide an oxygen
barrier for the steel substrate.
(* OT, FWIW: I once went through the trial, albeit educational, of having a
chrome Scott radio chassis replated. Longer tale.
A proper chrome plate job is not chrome on steel, it's copper on the steel,
then nickel, and finished with a few atoms of chrome.)
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