目的 解决现有氯化盐体系和硫酸盐体系三价铬电镀存在的问题。 方法 以甲酸铬为主盐,甲酸铵、尿素和苹果酸为络合剂,通过 Hull 槽试验和方槽试验,研究铬离子、甲酸铵、尿素、苹果酸的浓度以及镀液 pH 值、镀液温度、电镀时间等工艺参数对黄铜表面三价铬镀层形貌、 沉积速率和光亮范围的影响。 结果 甲酸铵和尿素分别与 Cr³⁺形成活性络合物,苹果酸具有 pH 值的缓冲作用。 最佳的工艺条件为:Cr³⁺浓度 0 . 4 mol / L,甲酸铵浓度 0 . 5 mol / L,尿素浓度 0 . 2 mol / L,苹果酸浓度 0 . 05 mol / L,镀液 pH 值3 . 5 ,镀液温度 25 ~ 30 ℃ 。 结论 该甲酸盐三价铬电镀工艺具有较宽的光亮范围,镀层孔隙率低,光亮致密,沉积速率较高,与铜基体结合良好, 结构为混晶态。 在室温、 电流密度为 15 A / dm²的条件下电镀 5min,镀铬层厚度即可达到 1 . 78 μm,满足装饰性镀铬层的要求。

Objective To solve trivalent chromium plating problems existing in chloride system and sulfate system. Methods Chromic formate was used as the main salt, and ammonium formate, urea and malic acid were used as the coordination agents. The effects of different factors, such as the concentration of Cr³⁺, ammonium formate, urea and malic acid, and pH value, temperature and plating time on the morphology, deposit rate and brightening range of trivalent chromium plated brass were studied by using Hull Cell and quadrate cell. Results The results showed that ammonium formate and urea could form active complexes with Cr³⁺respectively, and malic acid could buffer the pH value. The optimal condition was: 0. 4 mol / L Cr³⁺, 0. 5 mol / L ammonium formate,0. 2 mol / L urea concentration, 0. 05 mol / L malic acid, pH value of 3. 5 and temperature of 25 to 30 ℃ . Conclusion This technology of trivalent chromium electroplating in formate system had a wide bright range, and a plating can be gained with low porosity,bright and compact appearance, high deposit rate and excellent binding force with brass, the structure of the plating was mixed crystal. A decorative chromium deposit with a thickness of 1. 78 μm could be obtained after electroplating at the current density of 15 A / dm²for 5 min at room temperature.