1. Zinc phosphating is a crystalline coating consisting crystals of varying composition and sizes separated by intercrystalline zones (voids) and these areas may act as possible weak spots on the surface in case of contact with corrosion agents – mainly moisture.
  2.  Passivation seals these exposed areas as well forms a protective film on phosphate crystals surrounding the voids.
  3.  Passivation normally and conventionally is carried with compositions of hexavalent chromium, but now chrome free passivations also serves the purpose.
  4. Concentrations used in the range of 0.02 to 0.2% 5.