Galvanized steel iron-zinc alloy layer

The adhesion is good compared with electroplated coatings. Thickness can be varied as desired from 5 pm to more than 70 pm. However, the coating is not alloyed with the steel, nor does it have the hard, abrasion resistance iron-zinc alloy layers of galvanized or sherardized coatings. Conversion coatings can be applied. 

Zinc and its alloys are widely used because they have low melting points and can be easily cast. Therefore, various objects are made from zinc and its alloys. Zinc is widely applied to iron and steel as a protective coating by the process known as galvanization that consists of coating an iron object with a thin layer of zinc. Relative to iron, zinc is an anode, so it is preferentially oxidized. If the coating is broken, the zinc continues to corrode rather than the iron object. When iron is coated with a less reactive metal such as tin, a break in the coating causes the more easily oxidized iron to be corroded at an accelerated rate. 

In galvanized steel constructions, blasting is also necessary to provide a coatable surface. The sweep-blasting method is used in which the zinc surface is roughened without removing a significant amount of the zinc layer. When constructions made of aluminum alloys are coated, their surfaces must be blasted with iron-free blasting materials. 

Industrially, the most important property of zinc metal is its ability to form an alloy with iron so that a thin adherent layer can be applied to the surface of iron workpieces. The zinc coating, obtained either by hot-dip galvanizing or aqueous electrogalvanizing, considerably extends the service life of steel constructions. In addition, zinc alloys can be easily cast into intricate shapes that are used extensively in household goods and automotive equipment, building, and construction utilities. Other important areas are brasses, batteries, tires, and other rubber goods. Furthermore, zinc is now known to be an essential nutrient that is indispensable for human health as well as for many species of animals and plants, and it is therefore used in pharmaceuticals, fertilizers, and animal feed. 

---