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We have developed a new dry film lubricant with friction properties superior to those of conventional dry film lubricants by optimizing the glass transition temperature of the binder resin and adding polyethylene wax and inorganic lubricants. As described in this paper, the new dry film lubricant was applied as a coating on hot rolled steel sheets and galvannealed steel sheets in thicknesses ranging from 1.5 to 2.5 μm. The influence of the dry film lubricant and a rust preventive lubricant oil on the press formability of these steel sheets was investigated. A comparison of the press formability of high strength steel sheets with the dry film lubricant and sheets with the rust preventive lubricating oil suggested that application of the new dry film lubricant expands the use of high strength steel sheets and galvannealed steel sheets in automotive body panels.

The corrosion mechanism of zinc coated steel sheets in automotive bodies was studied in field vehicle tests and several types of accelerated tests. Perforation corrosion starts in unpainted areas of lapped parts, and proceeds in the following steps: i) galvanic protection by the Zn coating, ii) protection by corrosion products, and iii) corrosion of the steel substrate and perforation. Although the corrosion processes were the same in all the cases tested, the corrosion rate depended significantly on the environment, such as atmospheric exposure conditions and the part of the automotive body. In accelerated corrosion environments, Zn coating is largely ineffective against perforation corrosion because galvanic protection and protection by corrosion products cannot be maintained over the long term.

Materials used in automobile and motorcycle fuel tanks must provide good press formability and good seam weldability in addition to good internal and external corrosion resistance. Chromate-treated steel sheets, which contain Cr(VI), possess high corrosion resistance and have been successfully used for many years. Recently, however, Cr(VI) has been recognized as a harmful chemical which affects the human body. In reply to the social requirement of eliminating Cr(VI), Excelzinc Nickel GT has been developed to meet those requirements. Furthermore, Excelzinc GP accomplishes an excellent internal and external corrosion resistance in addition to the performance of Excelzinc Nickel GT by applying a gasoline-resistant resin layer for the tank inside and a lubricant resin layer for the tank outside. The properties of these new products meet all requirements for fuel tanks.