Phosphate coating is a type of conversion coating formed by a controlled chemical reaction between a metal surface and a phosphating solution. The result is a thin but robust phosphate layer on the surface.
Benefits of Phosphate Coating
- Excellent base layer for paint and subsequent coatings
- Increased corrosion resistance
- Friction-reducing effect, particularly with manganese phosphate
Coating Weight and Common Types
Phosphate coatings are generally classified by coating weight rather than thickness. Zinc phosphate coatings, the most common type used as a paint base, typically run 2-30 g/m², while heavier manganese phosphate coatings used for wear and friction reduction on machined parts can reach 5-30 g/m² or more. These ranges are broadly consistent with specifications referenced in standards such as TT-C-490 and ISO 9717.
Application Methods
Phosphate coating can be applied by immersion or spray, with the most suitable method chosen based on part size and production volume.
