Phosphating, or conversion coating, is the application of an iron or
zinc phosphate coating to the substrate. Conversion coating can be a
very critical part of the pretreatment process, adding significantly to
the performance of the finished coating.
A phosphate coating converts the metal substrate to a uniform, inert surface, which improves bonding, minimizes the spread of oxidation if the coating is scratchedand improves the overall corrosion resistance
of the final part.