Phosphate - Steel Protection

This heavy zinc coating reacts with the metal surface improving paint adhesion and preventing the spread of under paint corrosion. Heavy manganese and light zinc coatings are also available. Phosphate coated items, when dipped in oil, impart great rust protection. These coatings are available to military and commercial specifications.

Applications for Phosphate Coatings

Test Panels after Phosphate and Oil.
Test Panels after Phosphate and Oil.

Manganese Phosphate

Phosphate conversion coatings are most commonly used on steel but can also be used on zinc, cadmium, silver and tin. It serves as a conversion coating in which a dilute solution of phosphoric acid and phosphate salts are applied via immersion and chemically reacts with the surface of the part being coated to form a layer of insoluble, crystalline phosphates.

Phosphate coatings are often used to provide corrosion resistance, however, phosphate coatings on their own do not provide this because the coating is porous. Therefore, oil or other sealers are used to achieve corrosion resistance. This coating is called a phosphate and oil (P&O) coating. Zinc and manganese coatings are used to help break in components subject to wear and help prevent galling.

Military Specification MIL-DTL-16232G Type M, Classes 1, 2, 3 and 4 MIL-STD-171

Zinc Phosphate

This process provides a micro-crystalline Zinc Phosphate coating on ferrous metals. Zinc is used extensively on fasteners with excellent results. It can be used as a base coat for painting and is applied at 160°F-200°F. It is a porous surface that can absorb and maintain a post application of oil or wax. Phosphate conversion coatings are most commonly used on steel but can also be used on zinc, cadmium, silver and tin. It serves as a conversion coating in which a dilute solution of phosphoric acid and phosphate salts are applied via immersion and chemically reacts with the surface of the part being coated to form a layer of insoluble, crystalline phosphates.

This coating is called a phosphate and oil (P&O) coating. Zinc and manganese coatings are used to help break in components subject to wear and help prevent galling.

Coating weight thicknesses are in the range of 1500 - 2500 mg/sq.ft. (.0002" to .0006")

Military Specification MIL-DTL-16232G Type M, Classes 1, 2, 3 and 4, MIL-STD-171