There are two predominant types of galvanized steel: hot-dipped galvanized and electroplate galvanized. The hot-dipped process takes a steel surface and dips it in molten pure zinc. Zinc plating or electroplating takes a steel surface and applies a thin coating of zinc using an electric current. Electroplating is a thinner less resilient surface and is not recommended for exterior use or heavily trafficked interior use.
Hot Dip Galvanized Steel
Hot-dipped galvanizing uses an immersion technique whereby the steel is dipped in a bath of molten zinc. The duration of immersion in the bath determines the thickness obtained. A metallurgical bond is formed between the zinc surface and the steel.
This bond provides the major difference between electroplating and hot-dipped zinc. Hot-dipping creates an intermediate alloy layer between the highly pure zinc and the steel. This intermediate layer provides a significant amount of the corrosion protection to the steel base material. The outer, pure zinc layer acts as a barrier to protect the steel and gives the metal its characteristic color and spangle appearance. The inner layer provides a transition zone that resists attack on the base steel by sacrificial action.