Always wear eye protection before dropping anything into acid. Some things may have something on them which will give the same effect as dropping water in molten lead! I have a small scar near my eye from about 22 years ago to prove this. Secondly although the acid may prove whether or not your metal has zinc in it, it won't remove it. In order to do so, i would think the metal would have to be pure powder and be put through many soakings and cleanings.