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1.2μm /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。
The components in trivalent chromium plating solutionarecomplex. The existing forms of key componentsin trivalent chromium solution and their effect on chromium electrodeposition were studiedby theoretical calculations and plating experiments. The results indicate that 98% of both urea and formic acid in the molecule formare combined with Cr(Ⅲ) to formactive Cr(Ⅲ) complexes. According to the equilibrium conformation diagram of Cr(Ⅲ) complexes, higher electrochemical activity of Cr(OH)L2+than CrL3+isascribed tothelarger distance between water molecules and chromium ion. The electrodeposition rate ofCrisenhanced by increasing the concentration of active Cr(Ⅲ) complexes. The maximum ratereachesup to 1.2 μm/min. Boric acid existed in the form of B(OH)3, and the optimum pH buffer range is8?10. For Al3+, the optimum pH buffer rangeare3~3.5. When 0.6 mol/L Al3+isadded, the value of thehcorner/hcenteris decreasesfrom 11 to 2. In the presence of 1 mol/L boric acid, the value decreasesfrom 5 to 3.Thismeansthatthe effect of Al3+on the improvement of coating uniformityis greater.
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