(1. 中南大學(xué) 粉末冶金國家重點(diǎn)實(shí)驗(yàn)室，長沙 410083；
2. 中南大學(xué) 化學(xué)化工學(xué)院，長沙 410083)
摘 要: 采用開路電位、循環(huán)極化曲線、電化學(xué)阻抗譜及腐蝕形貌表征等研究不同時(shí)效制度下Al-6.2Zn-2.3Mg- 2.3Cu鋁合金分別在3.5%NaCl(質(zhì)量分?jǐn)?shù))以及10 mmol/L NaCl + 0.1mol/L Na2SO4溶液中的電化學(xué)腐蝕行為。結(jié)果表明：4種時(shí)效制度處理后，擠壓鋁合金耐局部腐蝕能力由大到小的順序依次為T76+T6、T76、T77、T6。試樣在10 mmol/L NaCl+0.1mol/L Na2SO4溶液中主要發(fā)生點(diǎn)蝕，從循環(huán)陽極極化曲線上可以觀察到明顯的點(diǎn)蝕電位和點(diǎn)蝕轉(zhuǎn)換電位；在3.5%NaCl溶液中發(fā)生點(diǎn)蝕和晶間腐蝕。利用點(diǎn)蝕電位φb以及點(diǎn)蝕電位與自腐蝕電位的差值(φb-φcorr) 表征局部腐蝕發(fā)生的難易程度，自腐蝕電位和再鈍化電位的差值(φcorr-φrep)表征局部腐蝕的發(fā)展程度。另外，表征了試樣的硬度和導(dǎo)電率等性能，發(fā)現(xiàn)與峰時(shí)效相比，三級時(shí)效處理后的合金的硬度并無顯著降低，且T76+T6態(tài)的硬度稍大于T77態(tài)的。可見擴(kuò)大三級時(shí)效的回歸時(shí)間窗口、降低回歸溫度，可使合金同時(shí)獲得更優(yōu)異的強(qiáng)度和耐蝕性能。
關(guān)鍵字: Al-6.2Zn-2.3Mg-2.3Cu鋁合金；時(shí)效制度；電化學(xué)腐蝕；腐蝕形貌
（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
