Letter 12080

Effects of muriatic acid solution on copper and bronze

My most recent project is a table set which consists of square steel tubing and ornaments which have been roughly plated with either copper or bronze. I have had excellent luck oxidizing mild steel with a vinegar water solution. What effect will a diluted Muriatic Acid [link is to product info at Amazon] solution have on the copper and bronze.

Bud Morgan
fabrication - Goodyear, Arizona

Bud,
Dilute muriatic (hydrochloric) acid would temporarily give a shine to the brass deposit, albeit a somewhat "matte" one. Once you applied it, however, there would be no way of getting ALL of the muriatic out of the brass pores. You said it was plated onto a steel base-alloy, therefore, the acid chlorides would eventually start to leach iron from the steel base toward the surface. You would end up with a nice greenish hue on your brass deposit. I would stick with the vinegar (acetate) solution, followed by hand-buffing.

Randy Fowler
Metal Surface Technologies, LLC

Cleveland, TN, USA

Hi,

I see you are talking about the effect acid has on metal. I also have a question about this. I'm active in a living history group and have therefore made a chainmail hauberk for myself. I used galvanized wire for this purpose. But after completing the hauberk I realized that galvanized wire wasn't very authentic. So now I want to use acid to strip the hauberk of its zinc layer. What kind of acid should I use to do so and at the same time not damage the wire itself?

Thanks!

Bertus Brokamp
- Utrecht, the Netherlands

Hydrochloric acid will attack zinc very rapidly and steel more slowly. If you can obtain "inhibited" hydrochloric acid, which is designed to lessen the attack on steel, the results will be better.

Ted Mooney, P.E.
finishing.com
Brick, New Jersey

May 24, 2009

The galvanised (zinc) coating will prevent any signs of corrosion and keep your chainmail looking good. But, that said, as mentioned above, inhibited hydrochloric acid (which is used to remove deposits in boilers and water heaters) will remove the zinc readily and should have a negligible effect on the underlying steel. But you must then attempt to keep the chainmail as dry as possible to prevent corrosion as it will no longer have any protection against rusting. But a little rusting may add to the authenticity of the armor.
Make sure that you get the inhibited acid - most water treatment companies can supply it.

Barry Eslick
- Centurion, Gauteng, South Africa

November 15, 2009

Regarding the possible rusting of chainmail, one method of removing rust in the "olden days" involved placing the item in a wooden barrel with a quantity of sand, putting on a lid of sorts, then rolling the barrel across the ground for a time.

I've not yet put this to practice, but when the time comes, I have ideas for a contraption similar to a hobbyist's rock tumbler, but on a larger scale.

Ernest Hubbard
- Cloquet, Minnesota