Metal Finishing Guide Book


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al. 5. Water is the primary solvent. 6. The coatings can be spray applied with standard application equipment. 7. Touch-up and repair is possible, although this should first be con firmed by experimentation. 8. The coatings are available in a wide range of colors and gloss levels, and can be used for texture finishing. 9. The coatings meet industry standards for many top-of-the-line ap plications, such as computers, business machines, lighting fixtures, ap pliances, automotive, coil, etc. 10.The coatings are available as primers and topcoats, although the coating can sometimes be applied directly to metal without the need for a primer. 11. The coatings have a lower fire hazard and lower toxicity than solvent-based systems. 12.Costs are lower for reducing solvents and cleanup. Disadvantages 1. The coatings require a high-temperature oven, 121���204��C (240���400��F), for more than 10 minutes. 2. A larger energy supply (and cost) is required. 3. The coatings are not for use on plastics, and other heat-sensitive sub strates, except perhaps some high-temperature plastics. 4. Performance on porous castings is unreliable due to outgassing, un less special precautions are taken to minimize the problem. 5. Touch-up may require a second bake or use of another air-dry coating. 6. The coatings are not applicable where parts such as machined surfaces have tight dimensional tolerances and cannot tolerate warpage. 7. Surface cleanliness is more critical than for solvent systems. 8. As with most resin systems, which cure at elevated temperatures, color changes can occur if the coating is overbaked. CONCLUSIONS Discussed here is a comprehensive selection of waterborne coating technologies that can be used in a wide range of industries. Waterborne coatings can be applied to most types of substrates ��� metal, plastic,wood, glass, and masonry surfaces. These coatings are commercially available at low VOC levels and satisfy even the most stringent regulations. Depending on the resin system and coating formulation, a full spectrum of physical and chemical performance properties can be expected; therefore, companies that now need to get into compliance with the air-quality regulations can and should consider waterborne coatings as possible candidates. 189

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