Ground coats

Oxide s Ground coats Cover coats Aluminum enamels ... 

The dry powder process has several additional advantages over the wet process. For example, much less waste of enamel occurs because the dry over-spray is airborne and recycled in a closed system. No-pidde ground coats have broadened the apphcation of both wet-process and dry-process systems. These enamels are appHed over cleaned-only metal. Thus the problems of disposing of pickling acid wastes containing iron sulfates and nickel wastes are eliminated (see Metal surface treatments) (7). 

Residual Compressive Stress. Residual compressive stress ia commercial ground coat enamels varies with enamel thickness ... 

Two general types of sheet steel are in current use, viz. cold-rolled mild steel and decarburised steel. A typical analysis for cold-rolled steel is 0-1% C, 0-5% Mn and 0-04% S. It can be obtained in regular, deep drawing or extra-deep drawing grades. This type of steel is normally used with a ground-coat including cobalt and nickel, as shown in Table 16.1. 

Vitreous enamel is normally applied to the prepared metal or over a ground-coat by spraying or dipping. Alternative wet techniques are used, of which the most common has been electrostatic wet spraying. Electrophoretic deposition from the slurry has been found to be highly suitable for some components. 

Aluminum does not require a ground coat. Enamel is generally applied by spraying, with firing accomplished by heating to 450-550°C (850-1040°F) for 2-10 min. 

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