Omar Abu-Shanab

Autodeposition Coatings: How and Why They Perform

Autodeposition coatings are thin, highly corrosion resistant organic coatings that are deposited in a chemical reaction with a metal surface. Because the autodeposition process deposits a coating only on metallic surfaces, coating of just the metal portion of metal-plastic or metal-rubber assemblies is possible. The overall autodeposition process includes stages of clean, water rinse, coat, reaction rinse, and cure. The use of a reaction rinse after the autodeposition stage is unique among coating processes and allows new properties to be introduced to the coating before curing. This paper will briefly review the general chemistry of autodeposition, and then focus on how corrosion performance and physical characteristics of a recently developed epoxy-acrylic autodeposition coating are designed into the product and how the autodeposition process controls these properties. The role of the organic polymer and the reaction rinse in all the properties will be discussed. In general, physical properties, such as flexibility, hardness, UV durability, and chemical resistance are affected by the polymer design. On the other hand, corrosion properties are largely conferred by the chemistry of the reaction rinse.