Galvanized iron sheets...

Galvanized iron sheets Galvanization is the process of applying a protective zinc coating to steel or iron in order to prevent it from rusting. The term is derived from the name of Italian scientist Luigi Galvani. Galvanized iron (GI) sheets are steel sheets which are basically coated with zinc and include a range of hot dip galvanized and electro-galvanized steel sheets. Zinc weathers at a very slow rate, so the coating generally has a long life. Zinc has a greater electro-negativity than iron and hence provides cathodic (or sacrificial) protection to the steel. This results in the zinc corroding in preference to the steel if the coating is chipped or damaged to expose the base metal. Besides acting as galvanic protector, The other functions of the zinc layer are as follow: To retain the steel intact with its full initial strength. To provide the surface a more pleasing appearance. To increase the life of any suitable organic finishing system applied over it. To protect the steel from corrosive attack in most atmospheres, acting as a continuous and lasting shield between steel and the atmosphere. The texture of galvanized steel sheet is shown in Fig 1 Fig 1 Texture of galvanized iron sheet Process of galvanizing The process of galvanizing steel sheet was developed simultaneously in France and England in 1837.  Both of these methods employed a ‘hot dipping’ process to coat steel sheet with zinc. Galvanizing is carried out on cold rolled sheets/cold rolled strips. Galvanizing process is broadly divided into hot dipping and electro-galvanizing. The hot dip process is more suitable for heavy coating weights, and electro-galvanizing for lighter coatings. For reasons of efficiency, galvanizing of cold rolled strip is more common than galvanizing of cold rolled sheets. Hot dip galvanizing – The principle of the process consists...