Aluminium coatings casting

Bernal, N., and Tierra, P. (1988). Hot-dip zinc-5% aluminium coatings on fabricated steel and cast iron components. 15th Int. Galv. Conf., ZDA, London, pp. GF5/1-8. 

This type consists of a propeller or disk-type wheel within a mounting-ring panel or cage. The wheel or housing is constructed from either sheet metal, cast aluminium, plastic, or plastic-coated material. It may be a direct drive with the wheel on the motor shaft or belt driven. 

The bath is normally at a temperature in the range 620-710°C, depending on whether the coating material is an aluminium-silicon alloy (for use in high-temperature conditions) or pure aluminium (for corrosion prevention). It is heated by inductors, by resistance heaters or by an external flame. The pot will usually be refractory lined unless cast-iron pots are needed to ensure adequate heat transfer from an external flame. As molten aluminium is extremely aggressive towards ferrous metals, replacement of cast-iron pots is fairly frequent. Refractory-lined pots obviously do not have this drawback, although the bath hardware, in particular the sinker roll and support mechanism, will still be attacked and need replacement at intervals. 

The rubber coating can be from 2 mm to 50 mm thick or more in certain cases depending on the application, and can be bonded to mild steel, stainless steel, cast iron and aluminium. 

The most common types of coatings are enamels and glazes based on silicate systems. The term enamel is used for coatings on a metal base (steel, cast iron, aluminium, etc.) whereas glazes arc similar coatings on the surface of ceramic materials. 

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