What is Hot Dip Galvanising?

Hot Dip Galvanising is a process developed to prevent steel from corroding.

Before the process can take place, the steel goes through a thorough chemical clean; this removes all rust, oil and mill scale from the surface.

When the cleaning process has been completed and the cleaning solution has been rinsed off, the coating process can begin.

The steel is dipped into a bath of molten zinc that has been heated to around 450 °C. The steel is then removed from the bath and left to cool in a passivation tank. When the cooling process is complete, the zinc coating is then metallurgically bonded to the steel.

Its unique characteristics help provide a long maintenance free life for steel.


Hot Dip Galvanizing provides an easy to clean surface which can give a maintenance-free life of over 50 years. (This is dependent on the environment it is being used in). When maintenance eventually becomes necessary, it is straightforward: no complex preparation treatments are necessary.

For many applications, the cost of hot-dip galvanizing is lower than that of applying alternative coatings. The reason is simple: alternatives – particularly painting – are very labour intensive compared with galvanising which is a highly mechanized, closely controlled factory process.

Low initial cost and long life make galvanizing the most versatile and economic way of protecting steel for long periods. There are bonuses from no maintenance or extended maintenance intervals: fewer problems of access in remote areas, difficult terrain or when buildings are closely packed together; also when there are safety restrictions e.g. electricity pylons.

The process is relatively simple, straightforward and closely controlled. The thicknesses (weights) of coatings formed are regular, predictable and simply specified. Our Hot dip galvanizing process is SANS 121/ ISO 1461 approved.

A full protection coating can be applied in hours; a complicated paint system can require a week.

Galvanizing is unique: the hot dip process produces a coating which is bonded metallurgically to the steel. No other coating process has this feature, and as a result, galvanised steel has by far the greatest resistance to mechanical damage during handling, storage, transport, and construction – an important factor where steelwork is to be shipped around the world.

Because it is formed by dipping steel in molten zinc, all parts of the surface of the steel are coated – inside, outside, awkward corners, and narrow gaps which would be impossible to protect in any other way.
The coating actually tends to build up at vital corners and edges – rather than thinning out as do brushed, sprayed and other dipped coatings.

Galvanized coatings protect steel in three ways:

Firstly, the coating weathers at a very slow rate giving a long and predictable life.

Secondly, the coating corrodes preferentially to provide cathodic (sacrificial) protection to any small areas of steel exposed through drilling, cutting or accidental damage; scratches are sealed by weathering products from the zinc.

Thirdly, if the damaged area is larger, the sacrificial protection prevents the sideways creep of rust which can undermine paint coatings.

Hot Dip Galvanizing steel simplifies inspection of the protective finish. The nature of the process is such that if the coating looks continuous and sound, it is! Thicknesses can be easily checked with an electronic probe.

Hot Dip Galvanizing steel is ready for use. No further site surface preparation, painting, touch up or inspection is necessary. Once constructed the galvanized steel is ready for use: and cladding can begin immediately, thus accelerating the construction time.

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