plating, anodizing, & finishing Q&As since 1989
Stripping plating from welding clamps leaves them copper color
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
August 31, 2021
A. Hi Mark. The chrome on your welding clamps is not hazardous, it's just metal, although you don't want to inhale any dust from anything you sand, grind, or wire brush; so sand it if you can while wearing an N95 mask.
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.
If you get all the plating off because they're rusting, ho are you going to stop them from continuously rusting?
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. If there is copper on your iron or steel part you want removed then hydrochloric acid (muriatic) will not remove it. In fact it might increase its shine.
You can dissolve the copper off the part using a strong alkaline solution like sodium hydroxide.
- San Jose, California
March 15, 2023