Paint types solids coatings

The corrosion rate of a bare sprayed coating is comparable to that of solid zinc or aluminium, although the greater surface area exposed may cause apparent corrosion rates to be a few per cent higher. For most uses, however, the sprayed coating is sealed or painted and achieves the much higher corrosion resistance associated with duplex coatings. The extra life depends on the sealer or on the thickness and type of paint used, and on the environment. 

Mineral wool/cement board—Perforated and solid sheet metal and ladder-type cable trays can be completely enclosed with 1 in (25 mm) minimum thickness mineral wool/cement board panels, or equivalent. The panels should be secured with stainless steel screw and stainless steel bands in (19 mm) wide by 0.02 in (0.5 mm) thick, located no more than 18 in (450 mm) apart. In freezing climates the fireproofing panels should be given a weatherproof coat of paint. The structural strength of the metal cable tray should be adequate to support the weight of the fireproofing. 

Figure 12. Light stability of a two-coat high-solid paint (silver metallic) with a benzotriazole and a HALS type stabilizer. Exposure Florida, 5 south, black box, unheated.

Most paints are supplied as liquids that are applied by different methods, using various types of equipment (see Chap. 8). The properties and uses of powder coatings are described in Section 3.4. Once applied, the wet paint film must dry to a hard solid film. Paints that dry at ambient temperature (air-drying paints) may be force-dried at temperatures up to 100 °C. Other types of paints require higher temperatures (120-220°C) for film formation that involves reaction of two and more binder components. Thus, the paint formulator has to consider both the properties of the liquid film and those of the final dry film. Liquid film properties have to be considered during storage, application, and curing. 

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