Development of Galvannealed Steel Sheet with Fe-Zn Electroplated Layer for Automotive Bodies

Research work was conducted on the development of two-layer coated steel sheet, a new corrosion-resistant material based on galvannealed steel that can be used in automotive outer panels and can be easily produced to a heavy coating weight as long-life corrosion-resistant steel and electroplated with an iron-rich iron-zinc alloy. As a result, the two-layer coated steel with a 30 g/m² galvannealed coating + 3 g/m²iron-zinc alloy electroplated coating on the exterior surface and a 60 g/m² galvannealed coating on the interior surface was found to be excellent in electrodeposited primer film cratering resistance, wet adhesion and blister resistance, to last long against scab corrosion and perforative corrosion, and to have good press formability and weldability. The method employed for electroplating the iron-rich iron-zinc alloy on the galvannealed coating is also described.