Corrosion of Paint
233
4. Higher initial cost than other spraying techniques
5. A need to exercise extra care to avoid excessive buildup of paint that
causes solvent entrapment, pinholes, runs, sags, and wrinkles
7.7.1.5 Powder Coating
Powder coatings have grown in popularity as anti-pollution coatings
because of the absence of solvents. Coating thicknesses of 25 to 250 μm can
be obtained.
Automotive bodies, electric components, and housing materials, wire and
cables make use of this process. Polyethylene and epoxy resins are the predominant types of paints used. At the present time, the following procedures are used:
1. Pouring method (flock coating)
2. Rotational coating of pipes
3. Fluidized bed
4. Dipping in nonfluidizing powders
5. Centrifugal casting
6. Rotational molding
7. Electrostatic powder spraying
8. Electrostatic fluidized bed
9. Pouring or flowing of fluidized powder
10. Electrogas dynamics powder spraying
11. Flame spraying of thermoplastic powders
Powder coating was developed in the 1950s and is a method for applying
finely divided, dry, solid, resinous coatings by dipping products in a fluidized
bed or by spraying them electrostatically. The fluidized bed is essentially a
modified dip tank. During the electrostatic spraying method, charged particles adhere to grounded parts until fused and cured. In all cases, the powder coating is heated to its melt temperature, where a phase change occurs,
causing it to adhere to the product and fuse to form a continuous coating.
The fluidized bed powder coating is a dipping process using dry, finely
divided plastic materials; a tank having a porous bottom plate forms the
fluidized bed. The plenum below the porous plate uniformly supplies lowpressure air across the plate, which suspends the finely divided plastic powder particles. Products that are preheated above the melt temperature of the
material are dipped into the bed where the powder melts and fuses into a
continuous coating. Thermosetting powders often require additional heat to
cure the film on the product.
233
4. Higher initial cost than other spraying techniques
5. A need to exercise extra care to avoid excessive buildup of paint that
causes solvent entrapment, pinholes, runs, sags, and wrinkles
7.7.1.5 Powder Coating
Powder coatings have grown in popularity as anti-pollution coatings
because of the absence of solvents. Coating thicknesses of 25 to 250 μm can
be obtained.
Automotive bodies, electric components, and housing materials, wire and
cables make use of this process. Polyethylene and epoxy resins are the predominant types of paints used. At the present time, the following procedures are used:
1. Pouring method (flock coating)
2. Rotational coating of pipes
3. Fluidized bed
4. Dipping in nonfluidizing powders
5. Centrifugal casting
6. Rotational molding
7. Electrostatic powder spraying
8. Electrostatic fluidized bed
9. Pouring or flowing of fluidized powder
10. Electrogas dynamics powder spraying
11. Flame spraying of thermoplastic powders
Powder coating was developed in the 1950s and is a method for applying
finely divided, dry, solid, resinous coatings by dipping products in a fluidized
bed or by spraying them electrostatically. The fluidized bed is essentially a
modified dip tank. During the electrostatic spraying method, charged particles adhere to grounded parts until fused and cured. In all cases, the powder coating is heated to its melt temperature, where a phase change occurs,
causing it to adhere to the product and fuse to form a continuous coating.
The fluidized bed powder coating is a dipping process using dry, finely
divided plastic materials; a tank having a porous bottom plate forms the
fluidized bed. The plenum below the porous plate uniformly supplies lowpressure air across the plate, which suspends the finely divided plastic powder particles. Products that are preheated above the melt temperature of the
material are dipped into the bed where the powder melts and fuses into a
continuous coating. Thermosetting powders often require additional heat to
cure the film on the product.