This specification covers Navistar’s requirements for two types of conversion phosphate coatings applied by chemical treatment primarily for adhesive wear resistance and corrosion resistance.

Type M (formerly designated as Type A) - Manganese phosphate base coating used for corrosion protection, anti-galling and lubricity. Manganese phosphate coatings are the hardest, while providing unbeatable corrosion and abrasion protection. In comparison to zinc phosphate coatings, manganese phosphate coatings offer continued wear protection after the breaking in of components that are subject to wear. These coatings are applied only by immersion. Use of manganese phosphate is especially useful in projects that require sliding of parts, such as automotive engines and transmission.

Type Z (formerly designated as Type B) –Zinc phosphate base for corrosion resistance. They can be applied by immersion or spraying. Zinc phosphate is a lighter alternative to manganese phosphate. Zinc phosphate coatings are typically used to retain rust preventive oils and waxes. The coatings provide good corrosion protection by bonding the final finish (stain, oil, wax or paint) to the treated material. The treatment produces a uniform coating and is particularly good for corrosion protection of threaded areas and parts that have small holes or recesses.

Proprietary phosphate systems used as paint-bond systems under painted parts are not included in this specification.

APPLICATION

This specification covers Navistar’s requirements for phosphate coatings applied to metal parts for corrosion resistance, lubricity, or as a foundation for subsequent coatings or paint. Phosphate coatings prevent galling and scoring and facilitate the break-in of gears, rocker arms, and bearings, etc. Phosphate coatings, with oil films applied, is used on fasteners to provide both torque control and limited corrosion resistance.