Metal Coatings of Steels Sep18

Metal Coatings of Steels...

Metal Coatings of Steels  Metallic coated steels are defined as a steel substrates coated with a layer of zinc, Zn/Al (zinc/aluminum) alloy, Zn/Si (zinc/silicon) alloy, or pure Al etc. The schematic arrangements of metal coating structure with and without passivation is shown in Fig 1, Fig 1 Metal coating structure with and without passivation  Metal coatings of steels enhance the life and the performance of the steels. They provide the most effective and economical way of protecting steels against corrosion. Metal coated steels offer unique combination of properties which include high strength, formability, light weight, corrosion resistance, aesthetics, recyclability and low cost. There are several processes for metal coating of steels as given below. The hot dip coating process, whereby the steel strip is immersed in a bath of molten metal. The composition of the molten metal (Zn, Zn/Al, Al/Si, or pure Al etc.) determines the nature of the metal coating. The electro-galvanizing process, in which metal is deposited electrolytically on the cold steel strip. Coating under vacuum, such as PVD (physical vapour deposition), CVD (chemical vapour deposition) etc. Hot dip coating processes are the most popular processes for the metal coating of steel strips. Normally continuous coating lines are employed for the production of the metal coated steel products. Metallic coated steels produced in continuous coating lines have experienced a remarkable growth and continues to be used in increasingly varied new fields. This is due to their outstanding economic, technological and environmental advantages. .The wide range of metallic coated steel products available today meets the requirements of all sectors. The following are the parameters which govern the choice of the metal coated steel material. Quality or grade of the steel substrate Type of metal coating Mass or thickness of the metal coating Surface...