Powder Coating Process

Powdercoating is the electrostatic application of powdered paint pigments to an object. The process is a long and painstaking one - at least in the preparation.

Surface preparation is extremely important. First the part undergoes a standard degreasing. Then, the old finish is removed with bead blasting with glass beads. All rust and old finish must be removed.

Next the part is dipped in a chemical cleaner to remove other contaminants and residues.

Areas that are to remain unpowdered at this stage (cylinder walls, threads, etc) are plugged with high temperature rubber plugs or taped over with high temperature tape. Then, the part is hung in the oven and pre-baked. This facilitates out gassing of any gasses lingering in the pores of the metal.

To prevent dust from attaching, the part is moved to the spray booth as soon as it has cooled down from the pre-bake and is hung on metal hooks. The booth is electrically grounded and the metal hook is attached to the booth, so the hook and object are grounded.

When turned on, the computerized sprayer base unit mixes air with the powder and supplies this aerated mix to the gun, where the powder receives a positive electrical charge as it exits the tip in a fine, directional spray. The part attracts the powder like a magnet. The operator can regulate the air pressure, the volume of powder and the amount of electrostatic charge to achieve the most manageable spray.

Depth of coating should range from 1.5 to 4 millimeters. Powdercoating tightly conforms to the contours of the surface it is covering.

Once the proper amount of powder has been applied, the hook bearing the part is carefully removed from the spray bin and hung in the oven. The piece bakes at about 400 degrees for 15 to 20 minutes. When the piece is removed from the oven, it is fully cured, and needs only to cool for handling.

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