Integrated steps of the process are degreasing, rinsing, activation, phosphating and passivation.
Activation step is needed before Zn phosphate treatment its function is to allow crystals creation of fine−crystalline zinc phosphate coatings, particularly on degreased surfaces by an alkaline cleaner. Proper activated the surface guarantees an uniform coating phosphate, appropriate size of crystals and mass of the coating.
2.Tri cationic phosphating
Zinc phosphate is an inorganic chemical compound used as a corrosion resistant coating on metal surfaces either as part of an ED Coating process. The phosphate process produces an hard, electrically non-conducting surface, coating that adheres tightly to the underlying metal. This layer protects the metal from corrosion and improves the adhesion to paint. The basic phosphate process consists in an etching reaction and formation of the surface coating.
Passivation is the next step after the last water rinsing bath. The aim of the process is the seal inaccurate phosphate coatings produced by incorporating zirconium ions in a shell. This process improves the corrosion resistances of treated metal surfaces which are to be painted or electrostatically powder coated.