Phosphate Coatings

Phosphate coatings consist of crystalline, non-reflective, water insoluble metal phosphates that are very adherent to the base metal. Phosphate coatings are measured by coating weights such as gm2 or mgft2. They can be associated in three main categories:
ZINC PHOSPHATE
Heavy zinc phosphate that has the ability to retain rust inhibiting oils, preservatives, or other specified finishes. MIL-DTL-16232, Type Z
Lighter zinc phosphate has a smoother crystal structure and is normally not oiled as it is used as a base for paint.
DOD-DTL-16232, Type Z
TT-C-490, Various Types and Methods
DOD-P-50002, Type Z