Everything You Need To Know About Zinc Phosphate Coating

A chemical reaction on the surface crystallizes zinc phosphate, which then forms a coating. Any phosphating application can use zinc phosphating, which should be applied by spray or immersion.

Spray coating for steel surfaces weighs between 1 and 11 g/m2, while immersion coating weighs between 1.6 and 43 g/m2. Prior to painting, zinc phosphate coatings between 1.6 and 4.5 g/m2 and between 1.6 and 43 g/m2 were applied to steel and zinc, respectively. The company should authorize the type of phosphate coating and the weight of zinc phosphate coating for particular jobs.

What does a coating of zinc phosphate do?

Steel and iron parts are shielded from rust and corrosion by zinc phosphate coating. Its porousness and high bonding qualities enable better and more powerful paint adherence.

Increased corrosion resistance and surface preparation for painting are two common uses for zinc phosphate conversion coatings. In the realm of reinforced concrete, this form of treatment has just recently been developed.

A passive layer of protection forms on the surface of the reinforcing steel implanted in fresh concrete. This layer is made up of -Fe2O3 is strongly adhered to the steel and is created as a result of the high alkalinity of the concrete pore solution (pH 13). Steel is unaffected as long as that oxide deposit is present.

Zinc phosphate coating formation mechanism

In essence, phosphorating is an electrochemical process. Phosphate solution, which is essentially a phosphoric acid-based solution, reacts electrochemically when it comes into contact with steel. At the anodic site, Fe2+ begins to dissolve and liberate electrons, while at the cathodic site, H+ is reduced. Crystals of zinc phosphate are precipitated at the surface as a result of the local pH increase caused by the evolution of hydrogen and consumption of H+ ions.

Zinc phosphate coating's alkaline stability

It is crucial to investigate the zinc-phosphate reinforcing steel's alkaline stability because it will be incorporated into a pH 13 environment. There aren't many published studies on the phosphate coating on reinforcing steel's alkaline stability. The literature demonstrates that the chemical makeup and crystal structure of zinc phosphate coatings determine their alkaline stability.

In addition to effectively preventing reinforcement corrosion, this chemical compound also helps to lessen the aggressiveness of chlorides.