Original Date: 01/26/1998
Revision Date: 01/18/2003
Information : Powder Coating Technology
Corpus Christi Army Depot (CCAD) has installed a powder coating system that is being used to apply corrosion and fretting resistance coatings on selected, approved aerospace components. Powder coating technology is an alternative method to liquid coating protection for materials. The technology uses no solvents, and as a result, reduces the pollution of the environment from Volatile Organic Compounds (VOCs).
The existing industry-wide liquid-coating process uses paints that contain VOCs which are detrimental to the environment and require special processing equipment and facilities to protect the paint operator. The process is equipped with a spray booth containing an exhaust for the release of the VOCs, filters to collect over-spray, explosion proof equipment, and fresh air respirators for the operator’s safety. Parts are typically sprayed with a primer and a topcoat containing high VOC solvents. Not only is the current industry process unfriendly to the environment, it presents a health hazard to the operator and results in high maintenance costs.
CCAD began exploring powder coating technology because of Environmental Protection Agency environmental laws. In 1995, a batch booth system was installed and brought into operation to apply corrosion and fretting resistance coatings on selected, approved aerospace components. The process uses a powder coating. The powder is usually held in a hopper that is bombarded with dry and clean air, making the powder act like a fluid. This powder fluidization allows for easy flow. The powder is then pumped from the hopper through an electrostatic system where it is charged and sprayed onto a grounded part. Because of the electrostatic charge, the powder clings to the part. Once the part is fully coated, it is routed to an oven for curing. A cool-down period is usually required after parts are cured. Proper powder cure is usually obtained when the part has been properly pre-treated (cleaned and etched), properly grounded, and the powder is dry and clean. Booths are equipped with over-spray filters (some with reclamation capabilities). Part application dictates the type of powder material used. Typical parts that CCAD is planning to coat are magnesium, aluminum, and steel aerospace components. With powder coatings, it is possible to control the thickness by controlling the amount of charge applied.
CCAD is pursuing powder coating technology to augment its other efforts to preserve the environment. In addition, the Depot is currently in the process of testing powders to be used on many powertrain components that use liquid epoxy coatings.
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