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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 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.