What is Manganese phosphate coating

Manganese phosphate coating has the highest hardness and superior corrosion and wear resistances of general phosphate coatings.
Manganese phosphating is extensively employed to improve the sliding properties of engine, gear, and power transmission systems. The use of manganese phosphated coatings for improved corrosion resistance can be found in virtually all branches of the metal working-industry. Typical examples mentioned here include motor vehicle components in brake and clutch assemblies, engine components, leaf or coil springs, drill bits, screws, nuts and bolts, washers, anti-vibration washers, tools, magnet cores, casting interiors and many other small items.

Manganese phosphate coatings for conferment of good corrosion resistance, whether a post-treatment such as oil application is to be used or not, are invariably applied by the immersion method.

Manganese phosphating is mainly by immersion. Treatment times range from 5-20 minutes, the optimum time depending on the surface condition. The bath operating temperature is around 95°C and only in special cases can satisfactory coatings be formed at temperatures around 80°C.

The phosphated components, after drying, are immersed in the oil or lubricant baths for 0.5-2 minutes, allowed to drain. The thickness of the resulting oil film depends on the oil used and its concentration.