What is it?

Hot dip galvanizing is the process of coating mild steel by submerging it into molten zinc for the purpose of protecting it against corrosion.

Mild steel is a strong and relatively cheap material for use in a variety of industries and a host of applications from tiny brackets to large structural beams.  The one major problem with it is its tendency to rust.

The most cost effective, simple and durable way of beating the rust is hot dip galvanizing.  The reason that hot dip galvanizing is the most durable coating for steel is that the molten zinc actually bonds with the steel during the galvanizing process creating zinc-iron alloy layers of protection that are harder than the steel itself and will not rust.  So, unlike paint, the galvanized coating does not merely sit on top of but becomes a part of the steel itself.

The British Standard for Hot Dip Galvanizing is BS EN ISO 1461:2009 (Hot dip galvanized coatings on fabricated iron and steel articles) and covers the general properties and testing methods of hot dipping steel in zinc.

Cross section of steel showing hardness.
Cross section through galvanized steel showing the surface which is zinc only, underneath which there is the tough zinc-iron alloy followed by the steel substrate.