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Copper & silver plate in one pickle


#1

I don’t normally work with copper, but tonite was just hammering out
some bracelet shapes and tossed 2 copper pieces and 2 silver pieces
into the pickle. The copper pieces plated silver…and the
silver pieces plated copper. I used copper tongs and haven’t had any
problem w/ last silver pieces finished. Curious what happened and is
there an easy way to get this plating off?

Thanks for any input.

Liane Redpath


#2

Liane, A bit of hanky-panky going on in your hot tub when you weren’t
looking? Roxy


#3

The plating wont be that thick but will need emery paper or the like
to remove it. Your pickle will normally dissolve the oxides from the
surface of your work leaving a clean metal. However, when you put 2
different metals in the bath and in contact with each other you get
a cathodic reaction that dissolves the metal of the most reactive and
deposits the metal from the salts of the least reactive hence your
plating. Some people do this on purpose to recover the precious
metal in the bath.

The reason you dont normally get problems with your tongs is mecause
they are harder to dissolve as a metal than the would be as a metal
oxide and the contact time shorter.

|Nick Royall


#4

Hello Liane -

I haven’t posted on Orchid in years… ! :slight_smile:

If your piece that received a “plated” coating of copper is still in
process and could be reheated with the torch - then, you could
lightly heat the piece enough so it will gently “quench” in a clean
pickle solution and the “plating” will easily be removed. You could
repeat the process if needed - focusing just on certain areas, with
the heat.

In my experience, the only other way to remove the unwanted metal
coating is to physically abrade the surface. Using a small medium
natural bristle brush (3/4") on the flex shaft - with bobbing
compound - works great to remove small, unwanted areas of coating.

This brush has a good amount of flexibility, along with enough
strength of abrasion, to get into areas that are harder to reach and
can quickly remove the unwanted “plated” metal coating without
removing much metal or creating scratches (by sanding). The stiff
natural bristle brush was a little stiff for my preference.

It is recommended to have separate pickles for different metals -
but that isn’t always possible. Where I teach, the students often
solder multi metals. When the multi metals are soldered in the same
piece, physically removing the unwanted metal on the surface is the
only way to clean the piece.

So, if it is possible to heat the piece again, reheating and
quenching in clean pickle works quickly and beautifully. Hope this
info is useful…

Aloha,
Cynthia


#5

Not sure if this is safe or not…but I tried it and it worked so
thought I’d pass it on.

An instructor em’d me and said to make a mixture of half pickle, half
hydrogen peroxide. Put the copper plated silver pieces in it. In less
than 10 minutes the copper plating lifted and I was elated as I knew
there was no way I could get into all the nooks with emery or sand
paper. However, I could not get the silver plate to lift off the
copper. She mentioned in a classroom situation accidental plating
happens all the time.

Liane Redpath Worlund


#6
However, I could not get the silver plate to lift off the copper. 

Nitric acid etches silver but has little effect on copper. A quick
etch in nitric should do the trick (though I’ve never seen copper get
silver plated in pickle).

Noel


#7
Nitric acid etches silver but has little effect on copper. A quick
etch in nitric should do the trick (though I've never seen copper
get silver plated in pickle). 

Copper is rapidly dissolved by nitric acid.

James Binnion
James Binnion Metal Arts


#8
Nitric acid etches silver but has little effect on copper. 

Actually, nitric acid has more effect on copper than other acids.
With concentrated nitric acid, poisonous nitrogen dioxide is
produced. In dilute acids, you get nitric oxide, which isn’t as bad,
but eventually oxidizes to the poisonous form.

Probably you’re thinking of the nitrate etchants, like ferric
nitrate.

Al Balmer
Pine City, NY


#9

Ok, since people I respect tell me I am wrong, it must be true,
though I wonder why we use ferric chloride to etch copper if nitric
acid does it so well.

A quick etch in nitric, as i suggested, will still take off the
silver, especially if the nitric is relatively dilute, the way I use
it for etching silver. But maybe it will remove too much. Since I
have never needed to remove silver plating from copper, I guess I
should have stayed mum.

Noel


#10
I wonder why we use ferric chloride to etch copper if nitric acid
does it so well. 

It’s safer.

Al Balmer
Pine City, NY