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Recently, Vibration Damping Steel Sheet (VDSS) has been increasingly used for automobile parts such as dash boards and partition panels. VDSS is also used in oil pans, but the rquirements in this application are much stricter than those in other auto applications. The material must remain sound (show no wall break) and not delaminate during deep drawing press forming. In service, it must be oil tight at the welded drain nut and must maintain good adhesion characteristics at high temperatures of 60-120°C. The VDSS with a thermoplastic resin core used to date in oil pans provides poor baking durability and heat durability in high temperature service. For use in oil pans, the authors therefore developed a new VDSS material comprising two extra deep drawing class steel skin sheets (of ultra low carbon steel) and a thermosetting polyester resin core layer containing metal powder.

Al2O3 -dispersed Zn-Co-Cr alloy electroplated has been developed for automobile use. Optimum coating composition ranges from 0.5 to 2.0wt% for Co, 0.3 to 1.0wt% for Cr, and 0.1 to 2.0wt% for Al2O3. The coating showed excellent corrosion resistance with and without paint. Superior anti-corrosive property of the coating results from the formation of the mechanically and chemically stable corrosion products, ZnCl2 −4Zn (OH)2, and the passivation in anodic polarization. The coating also showed good stone chipping resistance as well as paintability, formability, and weldability. Accordingly Al2O3 -dispersed Zn-Co-Cr alloy electroplated is suitable for application to both unexposed and exposure parts, including interior and exterior surfaces.

A new organic composite-coated steel sheet with bake-hardenability has been developed. The steel sheet consists of Zn-Ni alloy electroplated layer, chromate and zinc powder free organic film. To obtain better formability (anti-powdering) and weldability, the thickness of the organic film is reduced to 0.8∼1.5µm (1.0∼2.0g/m2). The addition of bake-hardenability to this organic coated steel sheet was realized by controlling the amount of residual solute carbon in continuous annealed extra low carbon steels.

A new organic composite-coated steel sheet “Zincrometal-KII” has been developed. The steel sheet consists of a specially improved thin zinc rich paint on Zn-Ni alley electroplated layer of low coating weight. Corrosion resistance, formability and weldability were investigated. (1) In two cyclic corrosion tests, consisting of salt spray, salt water immersion, drying and humidity, red rust initiation time of the flat part in unpainted condition of KII was about one and half times longer and its thickness reduction was reduced into less than about two third as compared to the conventional organic coated steel.