中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 10 No. 6 December 2000 |
（1. Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001, P.R.China;
2. Engineering Department, Kyoto University, Kyoto 606-8283,Japan）
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=kt1/2+ C, and that Pb in the film increasesk, on the other hand, Ag in the film decreaseskof the melanizing rate.
Key words: zinc sulfate bath; melanization; semi-conductive property
