Phosphate coatings are predominantly applied to ferrous metals. Additionally, it is also used on Zinc and Aluminium for specific applications. These coatings, on their own, are not enough to protect the treated metal surfaces. Their advantage lies in pre-treatment before painting, powder coating, impregnation with enamels, lacquers, oils and waxes.
The coating is thin and adherent to the substrate metal whilst being porous and insulating. As a result, the coating permits “keying” or mechanical interlocking of the applied paint film. In addition, the electrical inertness of the coating localises corrosion under the adjacent unbroken painted areas of the base metal surface. Phosphate coatings may be produced by immersion, brush and spray since surface conversion depends only on contact between substrate and phosphating solution. These coatings are also used in cold forming operations such as drawing, stamping and cold extraction processes.