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Copper remains on welding clamps despite muriatic acid bath

(-----) August 31, 2021

Q. I have two Vice-Grip welding clamps that were semi rusty, crusty, and the plating was flaking. Since I have no idea if the plating is chrome, I do not dare sandblast, grind, or wire brush it. I read that muriatic acid might dissolve the chrome. Well, I soaked on clamp for several hours and it seemed to have removed the plating; however, now a copper looking plating remains. Can anyone explain this? Is it copper and will more of the acid bath remove it down to bare steel? Any advice would be greatly appreciated. Peace.

Mark S Lyons
- Glassboro, New Jersey

September 2021

A. Hi Mark. Chrome plating is not hazardous, although you don't want to inhale any dust from anything you sand, grind, or wire brush; wearing an N95 mask, sand it if you can.

You're unlikely to be able to remove the copper with HCl. In fact, even if there were no copper on it in the first place, it would acquire an immersion copper plating on it if any copper were available from another source like the cable, because copper is more "noble" than iron and will replace it ...

Copper is stronger when it comes to grabbing available electrons than iron is, so copper will grab electrons from the iron on the surface, which will reduce dissolved copper to metallic copper, but cause metallic iron to become dissolved iron. Gold is more noble than silver, which is more noble than copper, which is more noble than iron, which is more noble than zinc.

Immersion copper plating is a commonplace, from high school science class demonstrations of iron nails acquiring a copper color when dipped in copper sulphate, to industrial coppering of welding wire.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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