Phosphate Coating or Parkerizing

Parkerizing is a procedure for plating a thin phosphate, coating that serves as a base or primer, for enamels and paints on iron & steel.

The parts to be processed are first degreased and cleaned free from rust, oil grease, scale, etc. and therefore immersed or dippid in a solution of manganese dihydrogen phosphate which has a temperature of 90oC and is held there for around 45 min. Throughout the dipping period, the phosphate from manganese dihydrogen phosphate decomposes and phosphate separates out and forms a reasonably thick coating on steel parts.

Parkerizing being a heavier coating, provides reasonable corrosion protection for indoor use. Thus, it is essential to apply oil or paint to such surfaces after parkerizing to insure a long life and good finish or else rusting and corrosion shall ultimately occur.

This procedure is widely utilized in the automotive and electrical appliance industries to prepare automobiles, refrigerators, washing machines, outdoor fittings and similar products to receive an organic finish.