Structure of Coating
The formation of the galvanized coating on the steel surface is a metallurgical reaction, where the zinc and steel combine to form a series of hard intermetallic layers. The outer layer is, typically, 100% zinc which covers the surface after withdrawal from the molten zinc bath.
The gamma, delta and zeta alloy layers are all harder than the base steel they are metallurgically bonded to, which gives hot dip galvanizing its great abrasion resistance.
The galvanizing process naturally produces coatings on the corners and edges which are at least as thick as the coating on the rest of the article. As the reaction between iron and zinc is a diffusion reaction, the crystalline structure of the coating forms perpendicular to the steel surface.
Three types of protection for steel
When left unprotected, steel will corrode in almost any exposed environment. One of zinc’s most important characteristics is its ability to protect steel against corrosion and no other material provides such efficient and cost-effective protection for steel.
Barrier protection, cathodic protection and the zinc patina are what provide the galvanized coating its long-lasting protection.