자동차 외장용 부품에 적용 가능한 3가 Cr도금의 황산욕과 염산욕의 비교 연구

Abstract

Experimental study of trivalent Cr plating to select a practical plating solution suitable for plating exterior parts of automobiles such as micro-porous MP plating of radiator grill was performed and following results could be derived. According to the analysis of trivalent Cr chloride baths on plating properties, the maximum plating rate, 0.3㎛/min was possible at 10A/d㎡ current condition. The plating efficiency was over 15% and the maximum plating thickness was 5㎛. In case of a trivalent Cr sulfate baths, on the other hand, the maximum plating rate, 0.03㎛/min was obtained at 5A/d㎡ current condition. The plating efficiency and the maximum plating thickness were below 5% and 0.3㎛, respectively. As a test result of corrosion resistance of trivalent Cr platings, platings of sulfate baths appeared a more satisfactory result than platings of chloride baths. Trivalent Cr plating of sulfate baths showed corrosion pits of typical MP coatings on the plating surface. Pits size decreased as plating thickness increased. Trivalent Cr plating of chloride baths lost luster, showing a number of micro pits spread over the entire plating surface. Moreover, micro cracks were found when the plating thickness was over 0.3㎛.