Creation of insoluble phosphates in conjunction with preservative agents increases resistance to corrosion. Phosphate treatment represents surface treatment by itself or it´s used as pretreatment under painting coats or by metal forming.
Passivation of ferrous and non-ferrous metals increases resistance to corrosion, especially before painting coats.
Chemical colouring of metals
Chemical processes most frequently create sulphides, oxides etc. on surface, whereby decorative appearence or the antiquing af metal (verd-antiqu) can be accomplished. The most widespread is blacking of steel, colouring of copper, brass and aluminum.