GI STRUCTURE

Galvanization or galvanisation (or galvanizing as it is most commonly called in that industry) is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which parts are submerged in a bath of molten zinc. Galvanizing protects in three ways: It forms a coating of zinc which, when intact, prevents corrosive substances from reaching the underlying steel or iron. The zinc serves as a sacrificial anode so that even if the coating is scratched, the exposed steel will still be protected by the remaining zinc. The zinc protects its base metal by corroding before iron. For better results, application of chromates over zinc is also seen as an industrial trend.

•  The size of crystallites in galvanized coatings is a visible and aesthetic feature, known as "spangle". By varying the number of particles added for heterogeneous nucleation and the rate of cooling in a hot-dip process, the spangle can be adjusted from an apparently uniform surface (crystallites too small to see with the naked eye) to grains several centimetres wide. Visible crystallites are rare in other engineering materials.