Zinc powder is an important electrochemical antirust pigment. The primer made of zinc powder is called zinc-rich primer. Zinc-rich paint is divided into inorganic zinc-rich primer with silicate as binder and organic zinc-rich primer with epoxy resin as binder.
Compared with other metals, zinc has its unique characteristics. It is lighter than iron and has good ductility. It can be alloyed with iron. The important thing is its electrochemical activity. Its standard electrode potential is -0.76V, which is relatively Iron (-0.44V) is active. Zinc can be melted and purified into fine particles of high-purity zinc powder, which is used as the most important antirust pigment in antirust paint. When the coating film is eroded, the zinc powder is corroded first as the anode, and the substrate steel is the cathode, which is protected. The oxidation product formed by the zinc as a sacrificial anode plays a sealing role on the coating, which can still strengthen the coating to the substrate. protection of. In zinc-rich coatings, zinc powder is gradually consumed during the protection process, but at a very slow rate. The formation of its corrosion products reduces the potential difference between the coating and the substrate. When the paint film is damaged, new metal zinc is exposed, and the potential difference increases immediately, resulting in a strong cathodic protection effect. Therefore, the corrosion of zinc-rich paint will not spread from the damage to the surrounding.
