Common surface treatments for metal parts

Metal is used in all kinds of applications and products. It can look good on its own, especially with a polished surface, but can also corrode and be marked by water and other contaminants. For this reason, it often receives some form of surface treatment, which not only protects it but also enables it to have a variety of different finishes.

Let’s look at some of the most common finishes you will encounter and where and how are they likely to be used.

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Perhaps the most common surface finish you will see is paint – just pop out and have a look at your car. This can be applied in a number of ways; for example, spraying is common, as are dipping and powder coating. Paint offers a wide choice of colour and surface texture options, is easy to apply, and can be retouched should the surface become damaged.


Another of the more common surface treatments available from specialists such as, anodising is applied to aluminium. The process electrically converts the surface to aluminium oxide, which can then have other surface finishes applied. You will commonly find this type of finish on items such as door handles and letterboxes.


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Electroplating works by applying a thin layer of one metal on top of another. It does this by passing a positive electrical current through a tank containing ions of the coating metal and a negative current through the part to be plated. Chrome is the most common, but plating can be carried out using gold, copper and more. You will most often see electroplating on bathroom fittings, taps and car parts.


Galvanizing is one of the most frequently used means of preventing steel from rusting. It involves a hot dip process whereby the steel is dipped in a vat of molten zinc, producing a distinctive, mottled surface. You will see this in household items such as bins and buckets. Other treatments, such as paint, can be applied on top of a galvanized surface; for example, car bodyshells are usually galvanized before painting.

Chemical treatments

These involve using chemicals to create a surface oxidisation on the metal. This is typically done for corrosion protection, to change the colour of the surface, or to provide a primed surface for painting.