apply phosphate coating to metal workpiece

Prevent steel or iron workpieces from rusting and other corrosion by applying a protective phosphate coating to the metal surface through a chemical reaction of phosphate salts and a dilute solution of phosphoric acid with the surface of the coated workpiece, forming a protective layer of insoluble, crystalline phosphates, usally iron. Phosphate coatings are usually applied to car bodies in their manufacturing process.