A phosphate layer is chemically generated by immersing the workpieces into a heated and acidic zinc, manganese, zinc-calcium or tri-cation phosphate solution. A chemical reaction occurs through the pickling attack of the metal surfaces with the substrate. This is followed by hydrogen-formation and a shift in pH value on the metal surface. Low solubility phosphates are formed, uniformly distributed across the metal surface as permanently anchored crystallites.
Properties of a phosphate coating: