Semi-conductive properties of melanization of chromate zinc plates

来源期刊：中国有色金属学报(英文版)2000年第6期

论文作者：李宁 黎德育 周德瑞 何局化 Kurachi Mitsuo

文章页码：834 - 837

Key words：zinc sulfate bath; melanization; semi-conductive property

Abstract: The anodic polarization curves of chromate zinc plates were studied under the condition of with and without illumination. It is found that the chromate film of zinc plate is characterized by ann-type semi-conductive property. The illumination on the surface and the addition of Pb in the surface raises the anodic photocurrent and plays a part of thentype property in the film. Contrarily, Ag in the film plays a part of thep-type dopant. The effects of quantitative Pb²⁺ and Ag+in bath on the melanization(black patina) of zinc plate after chromate treatment also has been studied by comparing the lightness differencesΔLby means of a whiteness meter. It is found that the lightness decreasing process (the melanization rate) is consistent with the Wagner equationΔL=kt^1/2+ C, and that Pb in the film increasesk, on the other hand, Ag in the film decreaseskof the melanizing rate.