Why pre-treatment is the most important step

Powder does not stick to a dirty surface. Grease from machining, fingerprints, the oxide layer and residue from transport — all of it stands between the metal and the coating. If the surface is not properly prepared, the film will look good on delivery and start to flake after the first winter.

That is why the durability of powder coating is measured on the pre-treatment, not on the powder. Our pre-treatment of the aluminium surface is tested at 1000 hours in a salt spray chamber.

Stages of pre-treatment

Degreasing — removal of oil, grease and machining residue
Rinsing — removal of degreasing agent residue
Etching and removal of the oxide layer from aluminium
Conversion coating — a chemical layer that bonds the metal and the powder
Final rinse with demineralised water
Drying before the part enters the booth

The salt spray test

The salt spray chamber is an accelerated corrosion test: the sample stands in a mist of salt water and it is recorded when the first trace of corrosion appears, usually around a scribe cut made deliberately in the film. A result of 1000 hours is the result asked for on aluminium in architectural use.

Tested	1000 h in a salt spray chamber
Material	Aluminium
Final rinse	Demineralised water

Zinc primer for steel

Mild steel that goes outdoors gets a zinc primer here as the base under the powder: a zinc-rich layer that takes over the role of a galvanised base. In many cases it is an adequate substitute for hot-dip or electro-galvanising, and it is done in the same plant, without sending the part out to be galvanised.

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