Zinc caustic is a chemical compound that has various uses in industries, such as in the production of adhesives, plastics, and textiles. The term "zinc caustic" is not typically used in everyday language, and therefore, there are no standard antonyms for it. However, if we consider the individual words zinc and caustic separately, we can come up with some antonyms. For zinc, antonyms could include words such as copper, silver, or gold, which are all metals. For caustic, antonyms could include gentle, mild, or soothing, which are all words that describe the opposite of harsh and corrosive substances.