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Minnesota Technology Magazine - Fall/Winter 2006

Up Front

Ask Mr. Technology

Questions answered, myths exploded, problems solved.

Q.We need to get some equipment painted, but one of our employees mentioned we should consider powdercoating. What exactly is powdercoating, and how does it work?

Image of chemical model A.Powdercoating is a relative newcomer to the world of metal finishing. First developed in the 1950s, it gained enormous popularity in manufacturing plants, and customized finishing shops as well. In a nutshell, powdercoating is a process in which a dry powder consisting of finely ground particles of pigment and plastic resin is given an electrostatic charge and sprayed on the part to be coated. Because of the charge, the powder clings to the part. After spraying, the part is placed in a curing oven; the heat melts and fuses the powder to a uniform coating. Because the powder doesn't contain the volatile organic compounds found in most liquid paints, powdercoating is an environmentally friendly process that provides a durable finish.

When you take a part to the powdercoater's shop, it will first be sandblasted to remove existing surface coatings and roughen the underlying metal.Doing so improves the powdercoating's adhesion. Any areas that you don't want coated— for instance, any polished metal accents or close-tolerance openings—will be covered with special tape that withstands the high heat to come later. After its been sandblasted and taped, the prepared piece goes to the powdercoating booth, where it is placed on an electrically grounded holding fixture.The powdercoating technician wields a 50,000-volt or more electrostatic applicator that sprays the tiny, highly charged resin particles onto the part,where they adhere much like dust clings to a TV screen.

After the coating is applied, the part is cured in a high-temperature industrial oven. As the metal heats, the powder melts and bonds to the surface.The part continues to bake in the oven after the melt, assuring that all resin particles have fully bonded to the surface.

Outside the environs of this column, Mr. Technology goes by the name William Gurstelle. He's a Minneapolis-based freelance writer and frequent contributor to Minnesota Technology. Send your questions to him at editor@mntech.org.