Zinc plays a very important part among various metallic coatings applied to iron and steel to provide protection against corrosion. This process of applying the zinc coatings is called galvanizing.

It is very much useful for all types of articles and utensils, e.g.: buckets, washtub, bar, tube, wire etc. Hot-dip galvanizing is one of the most commonly applied zinc coatings. In this process zinc coating is obtained by immersion of the materials or articles in a bath of molten zinc. The zinc combines with the iron, so that iron-and-zinc alloy crystals are formed which provide a firmly adhering coating. The characteristic crystalline surface patterns presented by hot-dip coatings are known as spangles; their size and shape are influenced by the surface condition of the steel, the impurities present in the bath, the rate of cooling, etc. Other types of Zinc-coating process are electrogalvanizing, metal spraying & sherardizing. These coatings are less in use compare to Hot-dip galvanizing.

For successful completion of hot-dip galvanizing first of all the steel must be free of oil, grease, dirt, scale, and corrosion products. Preparatory treatment includes all of the following: degreasing with a suitable solvent, pickling with acid, rinsing, treatment with a flux, and drying. The object of pickling is to remove any oxide film by the action of hydrochloric or sulphuric acid. Castings to which molding sand still adheres may have to be subjected to mechanical cleaning treatments such as grit blasting or tumbling, the latter being an operation in which small articles are mixed with an abrasive and rotated in a cylindrical drum. The flux, usually a mixture of zinc chloride and ammonium chloride, serves to remove any remaining traces of impurities and increases the wettability of the steel surface. Certain metals such as tin and aluminum may be added to the bath, they promote fluidity, and tin imparts brightness to the coated material.

Sherardizing is a process for forming intermetallic compounds of iron and zinc on a steel surface. This is formed by heating it in the presence of zinc dust below the melting of the zinc. This process is more often used for small articles such as bolts, nuts, chains, valves etc.

Other process, which is known as Sendzimir process, is used for the galvanizing of steel strip. Following methods to be kept in mind while functioning of this process. The strip is unwound from a coil 1. At 2 the oil or grease adhering to it is removed by oxidation (heating). In the next stage 3 the strip is annealed and the oxides are reduced by ammonia. Then follows cooling to 500°C 4 and immersion of the strip in the zinc bath 5, which is kept molten at about 450°C by the temperature of the steel strip. On leaving the bath, the strip is cut 6 or coiled 7.