Summary for copper plating unexpected effects Discussion
Copper plating unexpected effects are explained mainly as current-density problems and possible contamination. Eric Slighton described a hobby setup using copper sulfate root killer, sulfuric acid drain cleaner, salt, and glycerine, with a copper pipe anode and a plated wire cathode. Trevor Crichton said the copper anode likely had too low a current density to dissolve cleanly, while the cathode was likely run too hard, causing “burning” and poor adhesion; he also noted the cathode should be chemically clean, suggesting a scrub with chalk followed by a dip in 10% caustic soda. Another reply warned that root killer and drain cleaner are poor substitutes for proper plating chemicals: some root killers may not contain copper sulfate, drain cleaner may be caustic rather than sulfuric, and battery acid is a safer acid source than drain cleaner, though still hazardous.
Q. Hi,
Out of curiosity, I set up a basic copper plating arrangement, 200 g copper sulphate
⇦ on
eBay or
Amazon [affil link] (root killer), 30 ml sulfuric (acid drain cleaner
⇦ on
or
Amazon [affil link] ), and .1g salt all mixed with deionized water to make 1 liter. I also added 1/2 ml of glycerine (polyethylene glycol I believe) thinking that this might work as brightener. The anode was copper pipe. It worked pretty well for my simple purposes, but I noticed a couple of unexpected things that I hoped others might be able to shed light on.
1) the copper pipe anode turned dark brown after operation, whereas I expected it to turn a bright copper color as it dissolved. Any idea why?
2) a loose white film formed on the anode (over the brown copper) Any idea what it might be?
3) I did most plating at a voltage under 1/2 volt, but when I tried more I got a lot of loose grains forming. In the most extreme case, I dipped an inch or so of wire in as cathode and passed a couple of amps through. in minutes it formed a pencil thick coating that was loosely attached with color ranging from black to deep rust to copper color. The coating easily came off as a loose granular paste. I presume it is mostly copper crystals (though it did not look like clean bright copper). Any idea what this is?
Thanks for any thoughts.
Eric Slighton
hobbyist – San Francisco, California
2004
A. You need to have more similar areas for the anode and cathode. It sounds as if the current density on the copper anode was too low, resulting in poor dissolution of the copper and the anode was too high, resulting in “burning”. When the cathodic current is too high, you can get poor adhesion. Ideally you should also make sure the cathode is chemically clean; to do this you should give it a good scrub with chalk, followed by a dip in 10% caustic soda ⇦liquid caustic soda in bulk on
Amazon [affil link]
solution and then a two minute dip in 10% sulfuric acid. Good rinsing is essential. As a general guide, copper should be plated at about 25-40 A/ft2.
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
A. Hi,
Trevor has answered Eric’s questions but I will add, for the benefit of others who may read between the lines and proceed based on it, that it is best to not use products for purposes for which they were not intended. Some root killers have no copper sulfate in them, some might have other stuff in addition to the copper sulfate. It’s better to just get copper sulphate crystals rather than root killer.
Most drain cleaner is not sulfuric acid but caustic, and what is acid-based is awfully powerful stuff. You’re better off with battery acid. It’s not that battery acid is safe (read the warning labels) it’s just not quite as dangerous as drain cleaner.
Luck & Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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