In recent years, as air and water pollution has increased, the quality of the circulated water in evaporative condensers and cooling towers has declined. As regulations limit the use of many corrosion inhibitors for the hot dip galvanizing process, such as chromates, the passivation process for protection has become even more critical.
Passivation is a treatment process that forms a very thin protective layer that reduces chemical activity with air and water or other material that comes into contact with a surface. The passivation process varies depending on the type of material to be protected and the substances with which they contact. The most common circumstance is passivation for coils and casings for evaporative condensers and cooling towers. Passivation provides maximum protection from corrosion on newly installed evaporative condensers and cooling towers that have hot dipped galvanized steel tube coil surfaces. Hot dip galvanizing produces a coating of zinc-iron intermetallic alloy layers on steel with the outer layer being purely zinc.