Insulating and protective layer created by phosphate crystals over the steel surfaces is done via Phosphate Coating. Although it provides a short-term protection over corrosion, it is mainly used where lubrication is needed and as a pretreatment before painting. There are two types of phosphate coating.
Paint adhesion is high over zinc phosphate coated surfaces. It is possible to get corrosion resistant surface using this way. The color of coating can vary from light gray to dark gray according to mechanical process before phosphate coating or to the type of steel alloy.
Manganese phosphate acts as a layer on metal surface. It is mainly used in moving mechanisms like gears, pistons and guns due to oil suction feature and keeping this oil on its structure for a long time. Natural color of the coating can vary from dark gray to black according to mechanic process which is done to the part before the phosphate coating.
Coating performance is calculated by Surface Appearance, Coating Weight and Corrosion Resistance tests.
MIL-DTL-16232G Type M, Type Z Class 1 ,2,3 and 4 (These are the main international standards, it can also be customer standards as well.)