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Body in White (BIW) is a major assembly in an automobile. It is made of sheet metal components that are welded together by Resistance Spot Welding (RSW). This bare metal assembly is put through a process called Cathodic Electrodeposition (CED) for an anti-corrosive coat that lasts for the entire lifetime of the automobile. The CED process is a complex multi-stage process which includes rinse cycles, phosphate cycles, coat cycles and baking. These multistage setups are custom built to the automobile manufacturer’s requirement based on their product geometries and production volumes. Due to the high cost of establishment, these are typically restricted to production plants, except for smaller single stage setups. Smaller CED setups for component level coating with single stage vertical dipping stations can serve as a potential alternative to low volume builds and prototype builds.

Phosphating is the most preferred surface treatment process used for auto body sheet panel before painting due to its low-cost, easy production process, good corrosion resistance, and excellent adhesion with subsequent paint layer. There are different phosphating processes used for ferrous metal like zinc phosphating, iron phosphating, di-cationic & tri-cationic phosphating, etc. Among these phosphate coatings, the best corrosion resistance and surface adhesion are achieved by tri-cationic phosphate coatings (zinc-nickel-manganese phosphate). Many new technologies of phosphating are evolving. Key drivers for this evolution are increasing demand for higher corrosion resistance, multi-metal car body processing in same phosphating bath and sustainability initiatives to reduce the carbon footprints. We have evaluated two of these recent technologies.

In sheet metal painting for various applications like tractor and automobiles, most attractive coating is metallic paints. It is widely applied using 3 coat 2 bake or 3 coat 1 bake technology. Both options, results in high energy consumption, higher production through put time and lower productivity in manufacturing process. During various brainstorming and sustainability initiatives, paint application process was identified to reduce burden on environment and save energy. Various other industry benchmarking and field performance requirement studies helped to identify critical quality parameters. There was collaboration with supplier to develop monocoat system without compromising any performance and aesthetic properties. This resulted in achieving better productivity, elimination of two paint layers, substantial reduction in volatile organic content, elimination of one baking cycle and energy saving.