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采用恒电流法测定了添加Ga元素前后的Al-Zn-Bi系合金在人造海水中的开路电位、工作电位和电流效率,观察了该试验过程后合金的表面腐蚀形貌;利用极化曲线和电化学阻抗谱研究了该阳极合金在3.5%NaCl溶液中腐蚀过程的演变规律。结果表明:Ga能使Al-Zn-Bi系合金开路电位负移,工作电位稳定,电流效率升高,腐蚀形貌更加均匀;Ga可均匀固溶于铝合金中,并与回沉积的阳离子形成Ga基汞齐,使得阳极合金的活化控制步骤由第二相粒子优先溶解-脱落机理转变为金属阳离子的溶解-再沉积机理,促进阳极合金的均匀溶解,从而提高其综合电化学性能;等效电路RL(Cs(CpRp)(Q1Rd1)(LRa))和RL(Cs(CpRp)(Q1Rd1)(LRa)(Q2Rd2))能较好地表征两种合金的腐蚀行为和活化机理。
The open circuit potential, working potential and current efficiency of Al-Zn-Bi alloys before and after addition of Ga element were measured by galvanostatic method. The corrosion morphology of the alloy after the addition of Ga element was observed. The polarization curves and Electrochemical impedance spectroscopy was used to study the evolution of the corrosion process of the anode alloy in 3.5% NaCl solution. The results show that Ga can make the open-circuit potential of Al-Zn-Bi alloys negatively shifted, the working potential is stable, the current efficiency is increased and the corrosion morphology is more uniform. Ga can be uniformly dissolved in aluminum alloy and form with the deposited cations Ga-based amalgam, the activation control of the anode alloy is changed from the preferential dissolution-exfoliation mechanism of the second phase particles to the dissolution-redeposition mechanism of the metal cation to promote uniform dissolution of the anode alloy to improve its comprehensive electrochemical performance. The corrosion behavior and activation mechanism of the two alloys are well characterized by the circuits RL (Cs (CpRp) (Q1Rd1) (LRa)) and RL (Cs (CpRp) (Q1Rd1) (LRa) (Q2Rd2)).