Powder coating of steel products is a relatively new entrant in finishing techniques. The basic concept is the application of dry paint to a particular part of machinery. One cured coating of paint is the equivalent of two well set rounds of regular paint. In the paints that you use for a house, a medium must be mixed with a powder for the right proportion. In the case of powder coating application is in two forms - the object to be painted is lowered into a fluid bed of powder. In some cases there is an electrostatic charge that is passed through the tray and others there isn't. Another form of powder coating is where powedered paint is charged electrostatically and sprayed on. This is then placed in an oven for the paint particles to melt onto the surface and form a coating.
Powders too are available in two forms. One is the thermoplastic powder which if heated after it is set will melt again. The other is the thermosetting powders which will withstand reheating. This property comes in the curing process where a cross link reaction takes place sealing the paint.
If powder coatings fail in any way, it is only because the surface has not been prepared the right way. Depending on the kind of material, the preparation forms vary. If the material is aluminium then the preparation means is standard - clean the surface, rinse it, etch, rinse again, Chromate/phosphate application, rinse and then a demin rinse. If it is for steel that is to be used on interiors then the process followed is clean, rinse, derust, rinse, iron phosphate, rinse and round up with an acidulated rinse. The weak alkalis remove oils and grease. Etching removes any heavy oxides that may be present.
If an electrostatic spray is being use, then a relevant gun is used as well. Before the powder is introduced to the application gun, it is fluidized. This allows for the grains of paint to be separated and this allows a smoother passage into the gun. Because they are electrostatically charged, they cling onto the surface that they have been spray on. But if you want to coat to set, then it will have to be placed inside an oven which will cause the spray paint molecules to melt creating one cohesive coat.
Powder coating is a job that is meant to be done by experts in the line.
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01 Aug, 2011
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Source: http://goarticles.com/article/The-many-benefits-of-good-powder-coating/5073764/
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