Mil-Spec: MIL-DTL-16232G

Coating for medium and low alloy steels. The zinc and manganese phosphate coating will be uniform in texture, evenly deposited and can be grey to black in color. Provides moderate corrosion resistance and prevents wear.

Type Zinc Phosphate

Zinc phosphate base coating.
Thickness: .0002-.0006”
Type Z shall be a minimum of 11 g/m²

Class Comments
1 Supplementary preservative treatment or coating, as specified.
2 Supplementary treatment with preservative conforming to MIL-PRF-16173, Grade 3 or MIL-PRF-3150.
3 No supplementary treatment.
4 Chemically converted (may be dyed to color as specified) with no supplementary coating or coating as specified.

Type Manganese Phosphate

Manganese Phosphate Base.
Type M shall be a minimum of 16 grams per square meter (g/m²)

Class Comments
1 Supplementary preservative treatment or coating, as specified.
2 Supplementary treatment with lubricating oil conforming to MIL-PRF-16173, Grade 3 or MIL-PRF-3150.
3 No supplementary treatment.
4 Chemically converted (may be dyed to color as specified) with no supplementary coating or coating as specified.

Accelerated corrosion resistance requirement

Coating System Exposure Time Minimum Type Class Salt Spray Hours
M 1 1.5
M 2 1.5
M 3 1.5
M 4 24
Z 1 2
Z 2 2
Z 3 2
Z 4 24