Remove the Zinc from Galvanized Parts...

[TechShopJim]

Sometimes you find a steel part, fastener, hinge, or other piece of hardware that is just perfect for your project, but you have to weld it or paint it. Unfortunately, it is galvanized. If you weld galvanized parts, you'll get zinc poisoning (resulting in a splitting headache and maybe other long-term problems). What do you do?

Simply soak the part in pool acid, also known as muriatic acid or hydrochloric acid (the type of acid that is in your stomach). This is not to be confused with battery acid, which is sulfuric acid.

Muriatic acid will burn you really badly if it gets on your skin, and will permanently blind you if you get it in your eyes, and mess up your lungs if you breathe the fumes, so take ALL possible precautions and DO NOT UNDERESTIMATE what this acid will do to you! Work outdoors, and have a garden hose with the water turned on nearby in case you need to flush acid off of you or in the case of a spill.

To remove the galvanized zinc coating from your part, put just enough muriatic acid in a plastic bucket to cover your part (never use metal), and lower the part into the acid slowly. I usually tie a plastic string to the object so I can retrieve it later.

As the zinc comes into contact with the acid, it will foam up and produce a LOT of fumes, so be careful. The acid can also get quite hot during the reaction. In my experience, it takes about 10 minutes to boil the zinc off the part, but I have left parts in the acid overnight with no damage to the underlying steel.

Your results may vary, so work safely and have pare parts on hand.

[lens42]

If you are not in a hurry, a much less noxious method than pool acid is to use plain vinegar. I have used vinegar to strip both galvanized coatings as well as the shiny zinc coating on hardware store bolts. You can speed things up with a little bit of heat (I shine a 60 Watt incandescent spotlight on the container) but I usually just let the pieces soak overnight and by morning they are clean. BTW, vinegar will work pretty well removing rust as well. Vinegar is of course not poisonous, but one thing to be careful about is to carefully clean up any little splashes. I ruined a pair of parallels that I had nearby because I didn't noticed that they got splattered when I dropped my nuts and bolts into the vinegar cup. By the next morning they were very rusted.

[Neil]

Muriatic acid is by far the faster method but in addition to the important safety tips pointed out by TechShopJim you should make sure to do this in the absence of any ignition source. The gas evolution observed here is the formation of hydrogen. The acetic acid method also produces H2 but at a much slower rate. In the event of a spill always flush with plenty of water. Never decide to get clever and attempt to neutalize the acid with bicarbonate. Many people have made this mistake only to realize that the addition of bicarb results in CO2 formation causing much of the HCl fumes to be agitated up into the surrounding area.