物理化学学报 >> 2008, Vol. 24 >> Issue (08): 1465-1470.doi: 10.3866/PKU.WHXB20080823

研究论文 上一篇    下一篇

6063铝合金三价铬化学转化膜的制备与电化学性能

余会成; 陈白珍; 石西昌; 李兵; 吴海鹰   

  1. 中南大学冶金科学与工程学院, 长沙 410083; 中南大学现代分析与测试中心, 长沙 410083; 广州有色金属研究院, 广州 510651
  • 收稿日期:2008-02-29 修回日期:2008-04-22 发布日期:2008-08-06
  • 通讯作者: 余会成 E-mail:doyhc@126.com

Preparation and Electrochemical Properties of Trivalent Chromium Coating on 6063 Aluminium Alloy

YU Hui-Cheng; CHEN Bai-Zhen; SHI Xi-Chang; LI Bing; WU Hai-Ying   

  1. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, P. R. China; Center of Modern Testing and Analysis, Central South University, Changsha 410083, P. R. China; Guangzhou Non-Ferrous Metal Research Institute, Guangzhou 510651, P. R. China
  • Received:2008-02-29 Revised:2008-04-22 Published:2008-08-06
  • Contact: YU Hui-Cheng E-mail:doyhc@126.com

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摘要： 以硫酸铬钾及磷酸为原料在6063铝合金上制备了三价铬化学转化膜. 采用极化曲线及交流阻抗技术研究了不同条件下三价铬转化膜的电化学性能. 结果表明, 温度为30-40 ℃、沉积时间为9 min、pH值为2.0-3.0、KCr(SO4)2为15-25 g·L-1及H3PO4的浓度为10-20 g·L-1的条件为最优条件. Tafel极化曲线结果表明化学转化膜比基体铝合金具有更正的腐蚀电位(Ecorr)、小孔腐蚀电位(Epit)和更低的腐蚀电流(icorr), 说明化学转化膜具有良好的耐腐蚀性能. 利用交流阻抗谱的数据建立了等效电路模型, 并拟合出了腐蚀参数, 如表面电阻(Rcoat)及电容(Ccoat), 电荷转移电阻(Rct)及双电层电容(Cdl)等. 三价铬化学转化膜的交流阻抗谱结果与极化曲线的电化学测试结果相吻合.

关键词: 转化膜, 铝合金, 三价铬, 电化学, 腐蚀阻力

Abstract: Chromium (Cr3+) conversion coating was prepared on 6063 aluminium alloy using chromic potassium sulfate and phosphoric acid. Tafel polarization curves and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical properties of the coating formed under different conditions. The optimum conditions were obtained as following: temperature was 30-40 ℃, deposition time 9 min, the pH was adjusted to 2.0-3.0, the KCr(SO4)2 and H3PO4 concentrations were controlled within 15-25 g·L-1 and 10-20 g·L-1, respectively. The polarization result showed that the coating had more positive corrosion potential (Ecorr) and pitting corrosion potential (Epit), and lower corrosion current density (icorr), indicating that the coating formed under the optimum conditions had better corrosion resistance. To explain the electrochemical properties of the coating, a simple equivalent circuit was designed. Electrochemical parameters of EIS, such as the resistance (Rcoat) and capacitance (Ccoat), the charge transfer resistance (Rct) and double layer capacitance (Cdl), were obtained by fitting the EIS plots. The results of EIS were in good agreement with those of Tafel polarization curves.

Key words: Conversion coating, Aluminumalloy, Trivalent chromium, Electrochemistry, Corrosion resistance