(1. 中南大学 粉末冶金国家重点实验室，长沙 410083；
2. 中南大学 化学化工学院，长沙 410083)
摘 要: 采用开路电位、循环极化曲线、电化学阻抗谱及腐蚀形貌表征等研究不同时效制度下Al-6.2Zn-2.3Mg- 2.3Cu铝合金分别在3.5%NaCl(质量分数)以及10 mmol/L NaCl + 0.1mol/L Na2SO4溶液中的电化学腐蚀行为。结果表明：4种时效制度处理后，挤压铝合金耐局部腐蚀能力由大到小的顺序依次为T76+T6、T76、T77、T6。试样在10 mmol/L NaCl+0.1mol/L Na2SO4溶液中主要发生点蚀，从循环阳极极化曲线上可以观察到明显的点蚀电位和点蚀转换电位；在3.5%NaCl溶液中发生点蚀和晶间腐蚀。利用点蚀电位φb以及点蚀电位与自腐蚀电位的差值(φb-φcorr) 表征局部腐蚀发生的难易程度，自腐蚀电位和再钝化电位的差值(φcorr-φrep)表征局部腐蚀的发展程度。另外，表征了试样的硬度和导电率等性能，发现与峰时效相比，三级时效处理后的合金的硬度并无显著降低，且T76+T6态的硬度稍大于T77态的。可见扩大三级时效的回归时间窗口、降低回归温度，可使合金同时获得更优异的强度和耐蚀性能。
关键字: Al-6.2Zn-2.3Mg-2.3Cu铝合金；时效制度；电化学腐蚀；腐蚀形貌
（1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China）
Abstract:The electrochemical corrosion behavior of extruded Al-6.2Zn-2.3Mg-2.3Cu Al alloy was investigated. The open circuit potential (OCP), cyclic polarization curve and electrochemical impedance spectroscopy (EIS) were performed in 3.5% (mass fraction) NaCl and 10 mmol/L NaCl+0.1 mol/L Na2SO4 solutions. The results show that the resistance to localized corrosion of various ageing processes according to decreasing order is T76+T6, T76, T77, T6, as deduced from electrochemical parameters, such as OCP, corrosion potential, repassivation potential, pitting potential, pitting transition potential, linear polarization resistance, corrosion current density and charge transfer resistance of EIS. Corrosion morphologies indicate that pitting corrosion is the main corrosion form for Al-6.2Zn-2.3Mg-2.3Cu alloy in the solution of 10 mmol/L NaCl+0.1 mol/L Na2SO4, which can be terrified by the occurrence of pitting potential and pitting transition potential in its cyclic polarization curves. Being different from 10 mmol/L NaCl+0.1 mol/L Na2SO4, the pitting corrosion and intergranular corrosion (IGC) can be observed in 3.5% NaCl solution. φb, (φb-φcorr), and (φcorr-φrep) were used as criteria to evaluate the localized corrosion. Additionally, the influence of ageing process on the hardness and conductivity was also discussed. T76+T6 shows the least decline of hardness comparing to T6 and the best corrosive resistance amongst the four ageing processes.
Key words: Al-6.2Zn-2.3Mg-2.3Cu alloy; ageing process; electrochemical corrosion; corrosion morphology
