MIL–DTL–16232
Phosphate coatings are a crystalline conversion coating for steel and other metals that is formed on a ferrous metal substrate. The process of Phosphate coating is employed for the purpose of pretreatment prior to coating or painting, increasing corrosion protection and improving friction properties.
TYPES
Type M : Manganese Phosphate
Type Z : Zinc Phosphate
CLASSES
Class 1 : Supplementary Preservative treatment or coating.
Class 2 : Supplementary Treatment with lubricating oil conforming to MIL-PRF-16173,Grade 3 or MIL–PRF–3150.
Class 3 : No supplementary treatment.
Class 4 : Chemically converted ( may be dyed to color as specified )With no supplementary coating or coating as specified .