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What Is Galvanising? - Technical Page

"What is galvansing?" It’s a question we often get asked.

Galvanizing is a process of coating steel or iron with a layer of zinc to protect it from rust and corrosion. The process involves immersing the steel or iron in a bath of molten zinc at a high temperature. This causes a chemical reaction between the zinc and the surface of the metal, resulting in the formation of a layer of zinc-iron alloy on the surface of the steel or iron.

The zinc layer provides a barrier between the metal and the environment, preventing moisture and other corrosive elements from reaching the steel or iron. Galvanizing is commonly used in a variety of industries, including construction, automotive, and manufacturing. It is an effective and relatively low-cost way to protect metal from rust and other forms of corrosion, extending the life of the metal and reducing the need for maintenance and repairs.

The galvanizing process offers:

  • Durability – a permanently bonded tough coating
  • Hygienic – easy to clean surface
  • Long Life – Up to 50 years+ maintenance free
  • Economic – lowest overall cost compared to other coatings

Long life
Galvanizing can give a maintenance-free life of over 50 years. (This is dependent on the environment it is being used in).

Competitive first cost
For many applications the cost of galvanizing is lower than that of applying alternative protective coatings.

Lowest lifetime cost
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.

The process is relatively simple, straightforward and closely controlled. The thicknesses of coatings formed are regular, predictable and simply specified. Galvanizing is one of the few coatings which is completely defined by a British Standard (BS EN ISO 1461).

Coating toughness
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 galvanized steel has by far the greatest resistance to mechanical damage during handling, storage, transport and construction – an important factor where steel work is to be shipped around the world.

Complete coverage
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.

Three-way protection
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.