Metal Finishing Guide Book

2012-2013

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coating materials and application methods ELECTROCOATING BY LISA E. MERLO PPG INDUSTRIES INC., SPRINGDALE, PA. Electrocoat (also called E-coat, electrodeposition, or electrophoretic coating) is a widely used coating technology that has provided superior levels of performance on a vast array of industrial metal objects for over 40 years. Electrocoat technology has evolved dramatically since the early 1960s when it was first commercialized as an automobile body primer. Today, over 98% of all car bodies produced globally utilize an electrocoat primer. New end uses for electrocoat continue to be found annually; examples include automotive parts and accessories, appliances, heat exchangers, decorative plated objects,and heat-sensitive components. Current commercially available electrocoat systems offer superior performance using processes and materials that are both environmentally friendly and economically efficient. Major advantages of the electrocoat process include: total coverage of complex parts with unsurpassed film uniformity; material transfer efficiencies routinely in 95 to 99% range; highly automated, closed-loop systems with excellent productivity and low operating costs; fast line speeds and high part racking densities; very low air and wastewater emissions that foster environmental compliance; and totally enclosed system leading to a cleaner and safer paint application method. THE ELECTROCOAT PROCESS There are four major steps in the electrocoat process: cleaning and pretreating, electrocoating, postrinsing, and baking (see Fig. 1) Cleaning and Pretreating The cleaning and pretreating of metal prior to the electrocoat bath are critical steps in the process of providing a high-performance paint finish. Alkaline cleaners are employed frequently to remove dirt and oils found on industrial metal parts in manufacturing. Aluminum objects generally receive a conversion coating prior to electrocoat and can be electrocoated simultaneously with ferrous parts. Phosphate (iron and zinc) pretreatments are used to provide adhesion be- Fig. 1. The electrocoat process has four major steps: pretreat, coat, rinse, and bake. 257

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