Galvanisation: which method is best?

While steel is considered a great construction material because of its strength, it does have flaws in that by nature it’s extremely vulnerable to the elements and can very easily rust when exposed to these elements without being protected first.  To protect it from rusting, steel needs to go through the galvanisation process, which involves applying a zinc based coating to create a protective layer.  Zinc is used because it has a natural resistance to corrosion.

There are two main methods of applying this zinc protective layer, which are completely different in their application and therefore, depending on the intended use of the steel, it’s important to choose the method that will produce the greater benefit.  These methods are commonly known as hot-dipped and electroplating.

The hot-dipping method involves the steel being cleaned chemically first in order to remove any oil and grease from the surface before it is then submerged into a bath of molten zinc at a temperature of around 460°C.  It’s then removed and the zinc is allowed to freeze into a crystalline pattern on the steel’s surface, producing a strong alloy layer.  This then oxidises into a self-protecting matt grey colour with a pure zinc coat as the outer layer.

The benefits of using this method include being able to determine the thickness of the protective coat.  It’s important to make this coat as thick as possible when using steel items outdoors, since there is more chance of corrosion happening out in the elements.

The second option for galvanising steel is electroplating or sometimes it is known as zincplating.  This involves passing an electrical current through a zinc solution to chemically bond a thin layer of zinc to the steel’s surface.  It results in the steel appearing to have a shiny surface.

This is ideal for smaller steel components that do not necessarily require a long life protection because they are intended to be used indoors, where the risk of rusting is reduced due to minimal exposure to corrosive catalysts.  This is because electroplating is limited to a set thickness for the zinc coat, since it relies on the chemical reaction the zinc when an electrical current is applied.  It’s generally a cheaper way to galvanise steel, as opposed to the hot-dipped method.

In accordance to the galvanisation Standard BS EN ISO 1461*, we adopt the hot-dipped process for all the steel components within our systems, including the Park Tegra and Carport range, ensuring that all the welding, cutting and drilling happens beforehand so that a complete protective coat is applied.  What’s more is that we specify the thickness of the zinc coat to be a minimum of 400g/m (56 microns), where the industry average tends to be 200g/m.  This ensures that the steel used in our systems has a lifetime expectancy of 50 years or more.

*BS EN ISO 1461 Standard is available to buy from