ABSTRACT
The best strategy to control corrosion of an active metal is to apply a protective surface coating. The surfaces of manufactured metal forms, including sheet, plate and sections, are seldom suitable for the application of coatings. The chapter discusses the cleaning and preparation of metal surfaces including, descaling steels, cleaning aluminium surfaces and preparation of aluminium substrates for electrodeposits. Manual methods such as grinding, shot and sand blasting and flame cleaning are slow, subjective and costly. Electrodeposition provides a convenient means of applying a protective coating of one metal on another. The chapter also discusses application and principles of electrodeposition, including cathodic and anodic reactions, hydrogen discharge, throwing power and illustrative selection of deposition processes. In hot-dipping, a solid metal is immersed in a liquid bath of another metal and withdrawn with an adherent film of the liquid that solidifies on cooling. The process is most useful for applying coatings of zinc, tin or aluminium to steel.
