Phosphate
Conversion

Phosphate conversion is the treatment of metals with acidic phosphate
solutions. This process converts the metal
surface into a phosphate coat.
The phosphating process produces a nonmetallic, oil-absorptive coating
on iron and steel surfaces.
Benefit of such coating are as follows:
Permits rapid break-in of moving parts without scuffing or welding by
preventing metal to metal contact between the bearing surfaces.
Increases lubrication of treated surfaces due to the oil-absorptive
coating.
Removes light metal scratches remaining from machining operations.
Retards corrosion.
Promote the adhesion of
paints

Types
of Phosphate Coatings
1. Zinc Phosphate (3 to 5 microns thick, light gray in colour)
2. Manganese Phosphate (4 to 10 microns thick, dark gray in colour)