Hot-dip galvanizing — Principle

Zinc is one of the most widely used metals for corrosion protection, not only for galvanizing, but also for electro-galvanizing, metallizing, zinc-rich paints, vapor deposition and sherardizing.

By covering the steel with zinc, a hot-dip galvanizing coating provides dual protection: on the one hand, physico-chemical, due to the barrier effect that isolates the steel from the atmosphere, a barrier that lasts due to the formation of protective zinc salts; on the other hand, electrochemical, due to the cathodic protection provided by zinc against iron.

The galvanized coating is not simply a deposit of zinc on the steel surface. A metallurgical reaction of double diffusion occurs between zinc and iron, leading to the formation of layers of Fe-Zn alloys, intermetallic compounds linked both to the characteristics of the steels to be galvanized and to the operating conditions.