Phosphate Coating: Heavy

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A coating for medium and low alloy steels. Gray to black in color. Intended uses:

• The "heavy" phosphate coatings covered by this specification are intended as a base for holding/retaining supplemental coatings which provide the major portion of the corrosion resistance.
• "Light" phosphate coatings used for a paint base are covered by other specifications such as TT-C-490. Heavy zinc phosphate coatings may be used when apint and supplemental oil coatings are required on various parts or assemblies. Heavy coating (.0002" - .0004") is for corrosion and wear resistance.

Type M: Manganese phosphate base coating (minimum 16g/mē or 11g/m when specified).

Class 1: Supplementary preservation treatment or coating, as specified.

Class 2: Supplementary treatment with lubricating oil conforming to MIL-L-3150.

Class 3: No supplementary treatment.

Class 4: Chemically converted (may be dyed to color as specified).
With no supplementary coating or supplementary coating as specified.

Type Z: Zinc phosphate base coating (min. 11g/m).

Class 1: Supplementary preservation treatment or coating as specified.

Class 2: Supplementary treatment with preservative conforming to MIL-C-16173 or MIL-L-3150 as alternative for very small parts.

Class 3: No supplementary treatment.

Class 4: Same as Class 3.