What Is Electrostatic Metal Painting?
You may have noticed that the paint finish on your metal filing cabinet, or another manufactured metal object, seems almost impossibly smooth and perfect. In many cases, the pristine paint jobs we associate with certain metal products are the result of a process known as electrostatic metal painting.
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Static Electricity
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The principle that allows electrostatic metal painting to work is a well-known phenomenon; it's the same principle that explains why you get a shock when touching a metal object after walking across a carpeted floor. In both cases, the principle at work is static electricity. Static electricity occurs whenever an electric charge is built up on the surface of objects, usually as a result of objects coming together and then separating. In the case of the carpeted floor, the friction between our shoes and the carpet builds up an electric charge in the body, which is then discharged upon touching a grounded object (a doorknob, for instance). We experience this electric discharge as a mild electric shock.
Preparation
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Before the power of static electricity can be harnessed in the process of electrostatic metal painting, the metal surface to be painted must be cleaned of impurities that can interfere with the proper accumulation of charge. This cleaning is usually accomplished by sandblasting or by a chemical cleaning process.
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Painting Process
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After the metal surface has been cleaned and prepared, the electrostatic metal painting process can begin. This process uses a dry powder mixture, composed of colored pigments and protective resins, to coat the surface in lieu of paint. The powder is electrically charged in a high-voltage, low-amperage pneumatic spray gun. The charged powder is then sprayed onto the cleaned painting surface, which has been electrically grounded. The charged pigment and resin particles are strongly attracted to the grounded surface, just as the static charge in your body after a walk across a carpet is attracted to the grounded doorknob, leaving you with a shock.
Heat Curing and Types
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Although the static charge is enough to hold the pigment and resin particles in place temporarily, it is not a permanent arrangement. The particles are permanently fused to the surface in a curing oven, which melts the coating and creates the familiar ultrasmooth finish. Depending on the intended use of the metal object, there are different formulations of the pigment and resin mixture available. For outdoor use, the mixture will likely feature polyester and urethane resins, which offer good weather durability. For an indoor item, a corrosion-resistant epoxy resin is more likely to be used.
Benefits
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There are many benefits for undergoing this multistage process. The aesthetic quality of the finish on electrostatically painted items is superior; unlike liquid paints, no brush marks, bubbles, drips or imperfections will result. Also, the heat-cured coating is more durable than a traditionally painted surface, and better able to resist weathering, corrosion and chemical or solvent staining. Finally, the electrostatic metal painting process avoids the use of harsh solvents common in the traditional painting industry.
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References
- Photo Credit red office #2 image by Val Thoermer from Fotolia.com
