Search Results

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.

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.