Corrosion Behavior of Electrophoretically Coated Cold Rolled, Galvanized and Galvannealed Steel Sheet for Automobiles - Adaptability of Cataphoretic Primer to Zinc Plated Steel

The corrosion behavior of cold rolled-, galvanized and galvannealed steel sheet was investigated. Unpainted, ED painted and three-coat painted specimens were used. Cataphoretic primer prevents corrosion on the underlying steel more effectively than an anaphoretic primer. Cathodically electropainted cold rolled steel exhibits a good film adhesion in all tests. In alternately wet and dry conditions cathodically electrodeposited zinc plated steels show a better adhesion property than anodically electrodeposited ones. Upon consideration of actual car driving conditions, it was concluded that zinc plated steels, as well as cold rolled steel, are suitable for cathodic painting system.