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In response to the increasing demand for organic-silicate composite coated steel sheet with bake hardenability, we developed EZN-UCII, which allowed the coating to be cured in the temperature range where bake hardenability could be maintained. It was said that improved perforation corrosion resistance of automotive body panels was achieved through the development of EZN-UCII. In recent years, the most important objective with respect to the corrosion resistance of automotive body panels has been to improve cosmetic corrosion resistance of the outer panel. The cosmetic corrosion resistance can be improved by applying an organic-silicate composite coating on Zn-Ni plated steel sheet. EZN-UCII, however, could not be applied to the automotive outer panel because the inferior appearance of the cationic e-coat made it worthless for use on the exposed side of the outer panel.

A new method of evaluating the anti-cratering properties of precoated steels has been developed which detects minute differences among materials. The anti-cratering properties of precoated steel sheets are evaluated by measuring the variation of current with electrodeposition time (current-time profile) at the initial stage of cathodic electrocoat deposition. Although some current peaks were observed in the current-time profiles, the slight differences of anti-cratering properties in precoated steel sheets were able to be evaluated by measuring the last current peak height. In the case of cratering at high applied voltage, the peak height of the last current peak was high and the variation of the current was vigorous. On the other hand, when few craters were generated, the last current peak height was low.

To improve the performance of zinc-rich painted steel sheets, such as Zincrometal®, we at first developed Zn-Ni plated steel sheet with a thin (about 1μm) organic-silicate composite film entirely different from a zinc-rich paint film. This product (EZN-UC) is superior to zinc-rich painted steel sheet in corrosion resistance, anti-powdering property and weldability. This product (EZN-UC), however, is not able to provide bake hardenability due to the high curing temperature of the film. In response to increasing demand for the product with bake hardenability, we have developed new organic-silicate composite coated steel sheet (EZN-UCII), which allows the coating to be cured in the temperature range, where bake hardenability can be maintained.

To improve the performance of zinc rich paint coated steel sheet, such as Zincrometal, we have developed Ni-Zn plated steel sheet coated with a new organic-silicate composite entirely different from a zinc rich paint film. The new product is superior to zinc rich paint coated steel sheets in corrosion resistance, powdering resistance, and weldability due to the excellent performance of the thin (about 1 µm) organic-silicate composite film. It is produced on a new coil coating line, equipped with induction curing ovens. Moreover, we have developed a modified organic-silicate composite coated steel sheet with bake hardenability.