Zinc-Phosphate is preferred as under electrostatic powder coating, especially when high corrosion resistance is required. 

 

Zinc-Phosphate can be evaluated as a basis for lubrication, subsequent coating operations, or coat processing in order to strengthen the corrosion resistance. Zinc-Phosphate plating is also applied on metal surfaces. This type of plating acts as a conversion plating in which a dilute solution of phosphoric acid and phosphate salts is chemically reacted with the surface of the coated part to form a layer in which the insoluble crystalline phosphates are applied by spraying or dipping technique. The main types of phosphate coatings are manganese, heat resistant and zinc. Manganese Phosphates can be used as standard or surface lubricated and can be applied by immersion only. Iron-Phosphates are typically used as a base substrate for plating or coating, and can be applied by dipping or spraying. Zinc-Phosphates are used to prevent rusting of a lubricant base coat and as a paint or coating base, and can also be applied by dip or spray.