Spray-applied zinc-aluminium coating

PRINCIPLES OF APPLYING COATINGS BY METAL SPRAYING Table 12.6 Physical properties of sprayed zinc and sprayed aluminium... 

Coatings up to more than 500 /im (3 200 g/m zinc) can be applied to suit requirements, but with aluminium it is usually best to spray 100-200/xm more than 200 /xm is unnecessary. In manual spraying, the uniformity of the coating depends on the skill of the operative. Spraying in horizontal overlapping lines gives more uniform thickness than the cross-hatch technique. 

Thermal sprayed Aluminium/Zinc/Indium - A proprietary variation on thermal sprayed zinc that uses an alloy to enhance the current rather than a humectant. A 300 micrometre thick coating is applied by arc spray. Approrimately 35,000 m had been applied up to May 2003. Adhesive zinc sheet - A proprietary system consisting of rolls of zinc 0.25 mm thick, 25 mm wide with a conductive gel adhesive on one side. The installed system can be painted. The edges must be sealed against water ingress as the gel can swell and leak. 

This is the case, for instance, for K2Sip6 which in an aluminothermic reaction provides in situ the Al-Si clad (molten fiUer metal) normally used for controlled atmosphere brazing (CAB) of aluminium. In the case of zinc, the primary objective is not only to form a clad but to obtain a homogeneous diffusion layer into the aluminium, which is needed for some applications and which would have to be otherwise applied by costly intensive methods like electrochemical galvanization, plasma coating or thermal spray coating. 

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