To remove rust from oil-free materials and expose the surface, the material is immersed in an acid bath. It chemically removes the rust and oxide layers on steel, revealing the clean surfaces underneath. For this process, hydrochloric acid (HCl) solution is used prior to hot-dip galvanizing.

To prevent the release of acid vapors from the HCl baths, the tops of the tanks are sealed in a way that does not hinder the process.