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Vibration damping steel sheets (VDSS), which have sandwich structures with intermediate layers of resin, have been studied. The most important characteristics of VDSS for inner panels of automotive vehicles are the vibration damping properties, press formability and spot weldability. Vibration damping properties, which are quantified by loss factor,η, were influenced by both tanδ, which indicates damping capacity of resins, and elastic modulus of core resin. From a view point of vibration damping properties, resins with larger tanδ and relatively lower elastic modulus were favorable. Because these mechanical characteristics vary considerably with temperature, it is important to select the most suitable resin for the service temperature range. The relationship between noise reduction effect and loss factor of VDSS were also studied. It was experimentally confirmed that noise reduction effect of VDSS is proportional to the logarithm of their loss factor.

In search for new corrosion-resistant coatings in application for body panels, chassis & power-train materials, exhaust systems and fuel tanks, a unique molten-salt electrodeposition process has been developed. Ultra-smooth lustrous Al-Mn alloy-coatings with amorphous structure were electroplated on a moving steel-strip at high current densities up to 80 A/dm2 in a continuous bench-scaled electroplating apparatus. Amorphous Al-25wt%Mn alloy-plated steel can be as readily stamped, spot-welded and arc-welded as cold-rolled steel sheets. Al-Mn alloy pre-coated steel exhibited excellent corrosion-resistance in a variety of severe corrosive environments. Industrial-scale batch electroplating apparatus, capable of plating sheet size of 1 m x 1 m, is now under construction, and engineering developments for full-sized continuous strip plating facilities are under way.

In order to investigate the corrosion resistance of organic composite-coated steel sheets ( OCS ) in a real automotive environment, many kinds of corrosion tests were performed on test pieces and real automotive doors. Tests with a corrosive solution including iron rust were introduced to simulate the real corrosive environment of automotive doors. The relationship between the components of OCS and the corrosion resistance in the rust-including tests was examined. In addition, electrochemical studies were performed. Results indicate OCS has much better corrosion resistance than plated steel sheets with heavier coating weight in all tests. OCS shows excellent corrosion resistance in rust-free corrosive solution, however, some types of OCS do have corrosion concerns in rust-including tests. It became clear that these OCS types have an organic coating with lower cross-linking.

In order to improve the performance of zinc-rich painted steel sheets such as Zincrometal®, a thin organic coated steel sheet with excellent performance has been developed. The new pre-painted steel sheet (Tough Coat-III) consists of Zn-Ni alloy electroplated steel as a substrate and a thin organic coating system without containing a large amount of electric conductive pigments. The organic coating includes a special chromate film containing electric conductive pigments and a thin epoxy resin film (about 1µm thickness). The chromate film is design to be reduced at low baking temperature, using reducing agent. Therefore TC-III shows nearly 100% Cr insolubility with maintaining bake-hardnability. The corrosion resistance of TC-III was investigated by cyclic corrosion tests and by impedance measurements. TC-III exhibits excellent corrosion resistance, especially after forming.