(中国科学院 过程工程研究所 湿法冶金清洁生产技术国家工程实验室
绿色过程与工程重点实验室，北京 100190)
摘 要: 通过理论计算和电镀实验研究镀液核心组分存在形式及其对铬电镀的影响规律。结果表明:络合剂脲或甲酸98%以上是以分子形式与Cr(Ⅲ)离子形成三价铬活性络合物。根据三价铬络合物平衡构象图发现:相比于CrL3+，Cr(OH)L2+更高的电化学活性归因于较大的水分子-中心铬离子距离。通过增加三价铬活性络合物浓度，能显著提高铬电镀速率，可高达1.2 μm /min;缓冲剂硼酸主要以B(OH)3的形式存在，最佳pH缓冲范围为8~10，而Al3+最佳的pH缓冲范围为3~3.5。加入0.6 mol/L Al3+使铬镀层边缘和中心厚度之比(hcorner/hcenter)从11降低至2;而加入1 mol/L硼酸仅使hcorner/hcenter从5降低至3，Al3+改善镀层均匀性的作用更为明显。
关键字: 镀液组分;三价铬活性络合物;电镀速率;镀层均匀性
（Key Laboratory of Green Process and Engineering,
National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology,
Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China）
Abstract:The components in trivalent chromium plating solution are complex. The existing forms of key components in trivalent chromium solution and their effect on chromium electrodeposition were studied by theoretical calculations and plating experiments. The results indicate that 98% of both urea and formic acid in the molecule form are combined with Cr(Ⅲ) to form active Cr(Ⅲ) complexes. According to the equilibrium conformation diagram of Cr(Ⅲ) complexes, higher electrochemical activity of Cr(OH)L2+ than CrL3+ is ascribed to the larger distance between water molecules and chromium ion. The electrodeposition rate of Cr is enhanced by increasing the concentration of active Cr(Ⅲ) complexes. The maximum rate reaches up to 1.2 μm/min. Boric acid existed in the form of B(OH)3, and the optimum pH buffer range is 8-10. For Al3+, the optimum pH buffer range are 3~3.5. When 0.6 mol/L Al3+ is added, the value of the hcorner/hcenter is decreases from 11 to 2. In the presence of 1 mol/L boric acid, the value decreases from 5 to 3. This means that the effect of Al3+ on the improvement of coating uniformity is greater.
Key words: bath component; active Cr(Ⅲ) complexes; electrodeposition rate; coating uniformity
