(中國(guó)科學(xué)院 過程工程研究所 濕法冶金清潔生產(chǎn)技術(shù)國(guó)家工程實(shí)驗(yàn)室
綠色過程與工程重點(diǎn)實(shí)驗(yàn)室，北京 100190)
摘 要: 通過理論計(jì)算和電鍍實(shí)驗(yàn)研究鍍液核心組分存在形式及其對(duì)鉻電鍍的影響規(guī)律。結(jié)果表明:絡(luò)合劑脲或甲酸98%以上是以分子形式與Cr(Ⅲ)離子形成三價(jià)鉻活性絡(luò)合物。根據(jù)三價(jià)鉻絡(luò)合物平衡構(gòu)象圖發(fā)現(xiàn):相比于CrL3+，Cr(OH)L2+更高的電化學(xué)活性歸因于較大的水分子-中心鉻離子距離。通過增加三價(jià)鉻活性絡(luò)合物濃度，能顯著提高鉻電鍍速率，可高達(dá)1.2 μm /min;緩沖劑硼酸主要以B(OH)3的形式存在，最佳pH緩沖范圍為8~10，而Al3+最佳的pH緩沖范圍為3~3.5。加入0.6 mol/L Al3+使鉻鍍層邊緣和中心厚度之比(hcorner/hcenter)從11降低至2;而加入1 mol/L硼酸僅使hcorner/hcenter從5降低至3，Al3+改善鍍層均勻性的作用更為明顯。
關(guān)鍵字: 鍍液組分;三價(jià)鉻活性絡(luò)合物;電鍍速率;鍍層均勻性
（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
