Galvanizing, or galvanization, is the term used for the process of applying a layer of zinc to steel or iron, in order to create a protective coating. It is commonly used as a method of protecting metals from corrosion as the layer of zinc prevents the metal from oxidizing.
There are several ways in which galvanizing can protect the base metal. Firstly, it creates a protective layer which protects the base metal from corrosion by offering sealed protection from the surrounding environment. The zinc will prevent elements such as water getting through, unless it is scratched or damaged badly enough to expose the metal underneath. The outer layer of zinc usually slows the corrosion of the base metal too, preserving its longevity through ‘galvanic corrosion’.
There are several methods of galvanizing.
The method of hot-dip galvanizing involves submerging the base metal in molten zinc, to produce a thick and robust ‘outer shell’. This method is quick to perform, which makes it economically attractive, but it is not suitable for use on everything and can be inconsistent in the results it produces.
Pre-galvanizing has similarities to hot-dip galvanizing and involves cleaning sheet metal before immersing it in hot, molten zinc. Large steel coils can be quickly galvanized using this method, with more reliable and uniform results than hot-dip galvanizing. However, once the coil is cut to produce smaller pieces of metal uncoated edges are left exposed.
Electro-galvanizing utilises an electric current to deposit zinc ions on the base metal, as opposed to melting the zinc like other methods. The zinc ions are deposited on the positively charged base metal, and in a similar way to pre-galvanizing this method is popularly used on large rolls of sheet metal. This method offers a consistently uniform coating, but it is generally thinner than the results obtained using the method of hot-dip galvanizing.
Although the process of galvanizing offers a lengthy period of protection, some damage is inevitable if exposed to the elements and over the years the coating will degrade. If proper measure are taken, such as regular paint coatings and maintenance then the life of the galvanized steel can be prolonged.