Pre Treatment

Express Coatings offer pre treatment services including, shot blasting, de-greasing and iron phosphate coating.

Phosphating

The Phosphating process is a complex chemical one which involves converting the surface layer of metal into strong insoluble metal phosphate. Phosphating creates a rust resistant layer and gives a good key for any coating to be applied. It also gives protection against corrosion. Phosphating solutions usually consist of iron or zinc phosphates dissolved in dilute phosphoric acid, as the solution is applied to the product the reaction between the acid and metal creates a metallic phosphate which becomes insoluble on the surface and forms a layer which is metallic in colour. Phosphating consists of a 3 stage cycle:

Stage 1
The Phosphating solution is heated and sprayed onto the surface, it will remove all oil and grease by emulsification and chemically convert the surface to an iron phosphate coating. This will improve paint adhesion and enhance corrosion resistance.

Stage 2
The passivate solution is then added to de-mineralise the water and all parts are rinsed with the solution, this is a reactive seal ensuring a complete coating for the powder or paint to adhere to.

Stage 3
Parts are rinsed in water to remove excess solution from them.