镧铈混合稀土对AM60B镁合金电化学行为的影响

Effect of Lanthanum-Cerium Mixed Rare Earth on Electrochemical Behavior of AM60B Magnesium Alloy

摘要: 本文采用析氢实验、Mott-Schottky分析和电化学测试技术研究了3.5% NaCl溶液中La、Ce混合稀土对AM60B镁合金电化学性能的影响，并探讨其作用机理。结果表明，AM60B镁合金的析氢腐蚀电流密度降低、腐蚀电位升高、腐蚀电流密度降低、容抗弧值增大、电荷反应电阻R_ct增大、双电层电容C_dl降低，镁合金的电化学性能提高，其原因归结于添加的La、Ce混合稀土元素细化了α-Mg晶粒、减弱了β相的电偶腐蚀作用，加之镁合金表面形成致密的La₂O₃和CeO₂复合氧化膜，有效地阻隔Cl⁻向镁合金表面渗入，抑制了镁合金的溶解。Mott-Schottky曲线测试结果表明，少量添加La、Ce混合稀土AM60B镁合金在−1.9 V~−1.0 V的电位区间曲线呈线性，呈n-型半导体特征，供体密度N_D减小，平带电位E_FB负向移动，添加稀土La、Ce的镁合金耐蚀性得到提高。

Abstract: The effect of La, Ce mixed rare earth in 3.5% NaCl solution on the electrochemical properties of AM60B magnesium alloy was studied by hydrogen evolution experiment, Mott-Schottky analysis and electrochemical test, and its mechanism was discussed. The results show that the hydrogen evolution corrosion current density of AM60B magnesium alloy decreases; the corrosion potential increases; the corrosion current density decreases; the capacitance arc value increases; the charge reaction resistance R_ct increases; and the double layer capacitance C_dl decreases, which improves the electrochemical properties of magnesium alloy, which is due to the addition of La, Ce mixed rare earth elements to refine α-Mg grain and weaken the galvanic corrosion of β phase. The occasional corrosion, coupled with the formation of dense La₂O₃ and CeO₂ composite oxide films on the surface of magnesium alloy, effectively blocks the infiltration of Cl⁻ into the surface of magnesium alloy and suppresses the dissolution of magnesium alloy. The results of Mott-Schottky curve show that the potential range curve of a small amount of La, Ce mixed rare earth AM60B magnesium alloy is linear in the range of −1.9V - −1.0V, showing n-type semiconductor characteristics; the donor density N_D decreases and the flat band potential E_FB moves negatively. The corrosion resistance of magnesium alloy with rare earth La, Ce was improved.