Throughout most of history, metalworkers have used paint to protect and embellish their work. But paint can be scratched relatively easily, and it can break down when exposed to extreme temperatures and ultraviolet (UV) rays. To overcome these limitations, consider using powder coating instead of paint for your next metal project.
Powder coating creates an extremely tough, durable finish and can be used on steel, zinc and aluminum as well as other materials. The powder, primarily composed of ground plastic polymers and referred to as “paint” in the industry, surpasses paint in resisting acids, solvents, impact and abrasion. It’s highly resistant to UV degradation, making it ideal for any metal item that’s to be used outdoors, and it’s available in hundreds of combinations of colors, sheens and effects. From basic black to metal flake to deep, rich, wet-look tones, almost any color you can imagine can be created with the powder-coating process.
Whether you plan to finish dozens of metal spindles for a deck railing or just a single piece of lawn furniture, you owe it to yourself to investigate this unique and fascinating process. We worked with Club member Bill Stallone, owner of Quick Turn Powder Coating in Shakopee, Minnesota, to walk us through and explain its benefits.
The principle
Powder coating is based on the principle that objects with opposite electric charges (positive and negative) attract one another. Powder particles are negatively charged by passing through a special electrified spray gun. The metal object to be coated is cleaned in a phosphate bath and then grounded, creating a positive charge. When the spray gun is activated, the powder follows the electrical field and adheres to the metal object. The coated item is then placed in an oven and baked at about 400 degrees for about 10 minutes, at which point the powder melts, flowing into a beautiful and durable finish.
Most powder will cover about 30 square feet per pound. Prices range from $3 to $5 dollars a pound for a basic triglycidyl isocyanurate (TGIC) polyester powder (the most common type) up to $13 a pound or more for specialized powders such as metal flake or other custom finishes.
Professional powder-coating facilities operate as either batch-booth or line processors. With batch-booth processing, individual items that have been cleaned and dried are hung in a large booth, where they are manually sprayed. The booth is then wheeled into a large oven, where the parts are baked at the required temperature.
Line processing uses a motorized conveyor to transport the parts along an automated track that incorporates the cleaning, spraying and baking process. Line processing is faster and more consistent, but in general it’s set up to handle large runs of parts rather than single items. In general, line processing can’t accommodate long parts such as automotive frames or parts that weigh more than 200 pounds.
The powder-coating process is environmentally friendly, as the powder contains no solvents or other harmful chemicals, and the process produces very low levels of hazardous waste. For example, Quick Turn produces less than 50 pounds of hazardous waste a year —an amount that’s less than what the average American household generates in the same time period. Even the powder overspray can be collected and reused.
The process
Powder coating can be used on virtually any metal object that can withstand the baking temperature. Outdoor furniture, metal railings and spindles, decorative objects, cast iron, doorknobs, metal cabinet hardware and automotive, motorcycle and bicycle parts can all be powder coated.
Before taking an object to be powder coated, call the company you intend to use and discuss the project. Some companies don’t accept small jobs, and some aren’t set up to handle large items. Remove any loose paint, and clean any grease or dirt from the object. If you have the ability and the tools, grind or blast any rust that has accumulated on the object. If the item is too rusty or dirty for you to effectively clean, most powder-coating companies can recommend a local blasting or dipping service that can remove all of the rust, grime and old paint.
Remember that a little elbow grease can result in big savings in the end, and the quality of the finished powder coating depends on thorough preparation and cleaning. But whether you choose a single basic color or an exotic, multilayer application, the results will be a stunning finish that can withstand years of use.
SOURCES
Craftsman (No. 00917288000 powder-coating system), 800-377-7414
Eastwood (powder-coating guns and supplies) 800-343-9353
Quick Turn Powder Coating