Powder coating spraying

The sheer variety of processes used to apply coatings to surfaces is fascinating. Melt coatings, solvent based paints, latex formulated with water, reactive coatings such as polyurethanes, polyesters, and epoxies, electrochemical deposition, powder coating, spraying, dipping, and evaporation techniques have aU been employed. " ... 

Powder Coating. Nylon-11 and nylon-12 are used in powder form for anticorrosion coating of metals. Dip coating and electrostatic and flame spraying are used. Dip coating, which involves immersing a preheated article into fluidi2ed nylon powder, is most suitable for automation. 

Almost all PVC powder coatings are appHed by the fluidized-bed coating process. Although some electrostatic spray-grade formulations are available, they are very erratic in their appHcation characteristics. The resistivity of plasticized PVC powders is low compared to other powder coating materials and the appHed powder quickly loses its electrostatic charge. For the same reason, PVC powders show poor appHcation characteristics in an electrostatic fluidized bed and are seldom used in this process. 

Electrostatic Spray Coating. Electrostatic spray coating is the most widely utilized method for the appHcation of powder coatings (see... 

There were over 3000 electrostatic powder spray lines and about 800 other powder coating installations operating in the United States as of 1991. Eor additional general information on the safety aspects of powder coatings, see References 90, 93, and 94. 

Powder coating is a solventless coating system that is not dependent upon a sacrificial medium such as a solvent, but is based on the performance constituents of solid TP or TS plastics. It can be a homogeneous blend of the plastic with fillers and additives in the form of a dry, fine-particle-size compound similar to flour. The three basic methods are the fluidized bed, electrostatic spray, and electrostatic fluidized bed processes (9). 

Other potential applications are ceramic powders coated with their sintering aids, zirconia coated withyttria stabilizer, tungsten carbide coated with cobalt, or nickel, alumina abrasive powders coated with a relatively brittle second phase such as MgAl204 and plasma spray powders without the segregation of alloying elements. 

The use ofDa plasma synthetic route can lead to materials with advantageous new physical characteristics such as high surface area (eg TiOp), spherodised powders and sprayed-on coatings. 

See also Powder coating processes Spray coating processes discrete surface-coating methods, 7 23-24... 

Wire is coated by being passed through a plastic extruder, but most materials are coated with solutions, emulsions, or hot powders. The classic brushing process has been replaced by roll coating, spraying, and hot powder coating. The application of polymers from water dispersions to large objects, such as automobile frames, has been improved by electrode-positon of the polymer onto the metal surface. 

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