Understanding the Different Types of Coated Steel

Main Product Groups

The most common coated steel products are metal coated steels. Their manufacture typically uses cold- rolled steel (although a small percentage is made from hot rolled coil or sheet) which is then coated with zinc or with tin. A further coating is often added to zinc-coated steel in a subsequent process step to produce colour-coated steels.

Zinc Coated Steels

There are several distinct types of zinc coating (or galvanizing). These are

Continuous hot dip galvanizing: in this process, a cold-rolled coil or sheet in immersed in a pot of molten zinc. A common manufacturing technique for hot dip galvanizing steel is the Sendzimir process (which uses a small quantity of aluminium in the china epoxy powder coating). Continuous hot dip galvanizing is presently the most popular method of producing coated steels. Typical applications of these steels include construction (roofs, walls - often as sandwich panels), auto body components (exposed panels), fabrication (metal cabinet frames and walls), agriculture (outhouses, livestock buildings, silos), heating and ventilation (casings, air ducts); and it is very common for the galvanized steel to be further coated (see below) for many of these uses.

Hot dip batch galvanizing - used for small lots in a non-continuous batch process. Typical products can include lighting poles, antenna poles, radio towers, road barriers, power transmission lines, camera poles, motorway crash barriers, pedestrian bridge systems, garden frames, galvanized wire or mesh, street furniture, advertising poles, boilers, ducts, welded tubes and other profiles, etc. The usual production process involves dipping the shaped steel fabrication into a molten bath, which can be up to 12 metres in length.

Electrolytic galvanizing - a somewhat popular coating technique producing a zinc coated steel with a coating of 25-100 g/m2 per side - although capital costs, operating costs and market preferences have swung demand away from electro galvanizing towards continuous hot dip galvanizing in recent years.