Galvanised Steel

Zinc Coating, commonly called galvanising, is still one of the most common metallic coating processes for steel. Galvanising describes various methods of adding a metallic zinc coating to steel to give it cathodic protection; also known as galvanic protection.

Galvanised steel is classed as a “Z”-coating and has a bold crystalline pattern or spangle, a random geometric pattern that resembles frost on a window.

There are many processes for galvanising, but only products dipped or immersed in a bath of molten zinc can be called hot-dipped galvanised, the process used for the metallic coating of steel roof and wall cladding.

The thickness of the coating can be more precisely controlled on a continuous coil galvanising-line than it can be with other methods.

The standard coating weight for unpainted galvanised coil and sheet used for roof and wall cladding is 450 g/m², designated Z450, but other coating weights are available. The coating weight for products intended for painting is 275g/m², and it is designated Z275.

Since the advent of ZM coatings, minimised spangle zinc coated products, typically used for painting, are now designated with the “M” after the weight, e.g., Z275M.

The process of zinc coating by electro-plating gives a much thinner protective film and is not considered suitable for painted or unpainted cladding materials exposed to the weather.