Zinc plating is a common coating on hardware items such as screws and nuts. It is primarily used to provide a protective barrier against oxidation. However, if this plating is incompatible with other types of hardware, as can often happen, it must be removed. A caustic bath in a highly concentrated acid or base will allow you to remove zinc plating from your hardware so that it will be more useful and more compatible with other components.
Add the HCl or NaOH to a glass beaker until there is a large enough volume to submerge your hardware completely. Be sure to wear latex gloves while handling acids or bases as these substances are extremely corrosive.
Place the items you wish to be stripped in the acid or base bath. Let the items sit for 12 hours.
Use a glass ladle or other corrosive resistant tool to remove the items from the bath. If the glossy zinc coating is not fully removed, submerge the items again for an hour and check them again.
Place the items on a glass or ceramic plate and allow them to air dry. If you wish to speed the drying process, wipe them down with a paper towel, being sure to wear your latex gloves for protection.
Add the universal indicator to the corrosive bath. This will allow you to determine the pH of the bath and thus the steps you will need to take to neutralize it. If you are using HCl, the mixture will turn red (indicating an acidic solution), if NaOH is being used, it will turn blue or purple (indicating a basic solution.)
Add Milk of Magnesia to the bath if you are using HCl. If NaOH is being used, add vinegar. Add these substances until the bath turns green. This will indicate that the mixture is neutral and is safe to dispose.
Sodium hydroxide is the active ingredient in lye.
Be careful not to leave the items in the corrosive bath for longer than 12 to 15 hours as the bath can corrode the metal underneath the zinc plating.