Corrosion Protection

Galvanising is the process in which corrosion protection is provided to steel product by coating it in zinc. This can be achieved either through a hot dip process, or electrolytic. In the former, a cold reduced product passes through a series of heat treatments in which it is annealed and the surface is cleaned prior to the strip being passed continuously into a bath of molten zinc at 440°C.

The coating mass is controlled as a result of the strip then passed through a set of air (or nitrogen) knives which force surplus zinc back in the bath. The action of these knives is controlled by a meter that is set according to the coating mass actually required. The alternative method of coating is to do it electrolytic; in this case the feedstock is an annealed and temper rolled cold reduced product.

Generally speaking, the coating masses so applied are much lighter than by hot dipping. If steels are to be post-galvanised as part of the manufacturing process this should be stated at the time of ordering.