Carbon CoatingCarbon coating is a process used in the aluminium extrusion and glass making industries for applying a non-stick carbon coating to materials or moulds. An aluminium billet is forced into the extrusion mould at very high pressures. If no surface coating is applied to the surface of the billet the aluminium will adhere to the ram and stop the continuation of the process. Applying a thin layer of carbon between billet and ram stops this from happening. In glass moulding, a similar problem arises with the molten glass sticking to the mould. The traditional solution to this problem is to apply a graphite solution to the mould, which prevents the product sticking. This process is manual, expensive and messy, the alternative is to coat the mould with carbon providing a non-stick surface. The carbon is applied from an air-acetylene flame. The flame is deliberately set to an acetylene rich condition and the unburned carbon is deposited onto the work. For aluminium extrusion an automatic process has been developed which lights the torch from a pilot jet when the billet passes on its way to the ram chamber and extinguishes it after the appropriate amount of carbon has been deposited. Carbon coating is quick, clean and cost efficient compared with the alternative processes.
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