GALVANIZATION
Galvanizing is the process of coating of zinc or iron or stainless steel sheets. Process: The iron or stainless-steel article surface is first cleaned by acid pickling with dilute H2SO4 solution for 15-20 minutes at 60-90 degree celsius. This treatment removes any scale, rust (oxide layer) and impurities on the metal surface. The article is then washed well with water and dried. It is then dipped in the bath containing molten zinc maintained at 425-430 degree celsius. The surface of the bath is kept covered with a flux, i.e. ammonium chloride, which is used for cleaning the surface of the metal and also to prevent oxide formation. When the article is taken ort, it is found to have been coated with a thin layer of zinc. In order to get uniform thickness, it is passed through a pair of hot rollers, which removes any superfluous (excess) of zinc. Then, it is annealed at a temperature of 650 degree celsius and finally, cooled slowly. Uses: It is most widely used for protection of iron fr