Hot Dipping

It is a rapid, inexpensive process which allows forming coating for corrosion-resistant metals onto base metals by dipping in molten bath of low melting metals as, tin, zinc and lead, and sometimes aluminium at less cost than by electroplating. The procedure is widely utilized for zinc coating on iron and steel. The coating of strip, sheet, wire and pipe is done on continuous bases while other shapes have to be immersed in the bath in batches.

The metal coating by hot dipping is built up of two layers. The first layer is built of alloy of base and coating metal that adheres to the surface. The outer layer is the pure metal. This is of interest to note down that the first metal adheres to the base surface by formation of intermetallic compound that is brittle. Such metals that do not make intermetallic compound might not be directly coated. Lead is one such instance and for this reason lead-tin alloy in molten state is utilized for coating steel.

Tin is very commonly utilized as coating material as it readily makes compounds with other metals. Food containers built in steel, copper and brass are frequently tin coated because of non-toxic nature of tin.