In phosphate (bonderizing), a property-enhancing conversion layer is applied by chemically altering the surface. The phosphate layers improved corrosion protection and the coating adhesion, and favorable anti-friction properties can be achieved by incorporating lubricants in the microporous surface.
We phosphate zinc-plated and cadmium-plated steels as well as components made of aluminum and zinc in accordance with DIN 50942. To phosphate aluminum, we use fluoride-containing phosphating solutions that help dissolve the oxide layer of the aluminum. To improve adhesion to aluminum, we recommend yellow passivation. Depending on the purpose, three phosphate baths can be used:
Zinc phosphating yields the best corrosion protection and is frequently used as a pretreatment before powder coating. The arising zinc phosphate layers approximately 7-15 µm thick are very effective in protecting steel from rust creep.
Iron phosphate layers approximately 1 µm thick are less effective in preventing corrosion, but they are preferred because of their superior anti-friction properties during subsequent cold forming. Iron or alkali phosphating is used for example for deep drawn parts.
Manganese phosphate layers can withstand very high pressures and are particularly suitable for incorporating lubricants due to their microcapillary structure. Manganese phosphating is therefore preferred for friction bearings, intake bushes and similar applications that are subject to high loads.