Sc添加对铸造Al-3Cu-1Li合金在酸性NaCl溶液中腐蚀行为的影响

Effect of Sc Addition on Corrosion Behavior of As-cast Al-3Cu-1Li Alloy in Acidic NaCl Solution

摘要:

在2 mol/L NaCl酸性溶液中，研究少量Sc对铸态Al-3Cu-1Li合金腐蚀行为的影响。通过XRD对铸态Al-3Cu-1Li-xSc（质量分数）合金进行相分析，用FE-SEM/EDS和TEM观察了Al-3Cu-1Li合金和Al-3Cu-1Li-0.5Sc合金的显微组织；采用极化曲线、电化学阻抗谱（EIS）、电化学噪声（EN）和浸泡法对合金的腐蚀行为进行了研究，并探讨腐蚀机制。结果表明：含Sc的Al-3Cu-1Li合金晶内富Cu球形相减少，晶界析出W相。随Sc含量的增加，合金腐蚀反应的活化能降低，阴极析氢速率增加，自腐蚀电流密度增加，合金的耐蚀性降低。添加Sc后，合金在空气中形成的表面膜保护作用减弱至消失，使含Sc合金的阻抗谱低频感抗弧逐渐消失。在EN测量期间，不含Sc和含0.1% Sc的合金表面处于“膜破裂-再钝化”状态；含0.3% Sc和0.5% Sc的合金发生严重的局部腐蚀（晶间腐蚀），且与W相有关。

Abstract:

The effect of Sc addition on the corrosion behavior of as-cast Al-3Cu-1Li alloy in 2 mol/L NaCl acidic solution was studied. The phase compositions of as-cast Al-3Cu-1Li-xSc (mass fraction) alloys were determined by XRD. The microstructures of Al-3Cu-1Li alloy and Al-3Cu-1Li-0.5Sc alloy were observed by FE-SEM/EDS and TEM. The corrosion behavior of the alloy was studied by potentiodynamic polarization, EIS, EN and immersion test, and the corrosion mechanism was discussed. The results show that Cu-rich spherical phases are distributed in the grain of Al-Cu-1Li alloy; Cu-rich spherical phase is reduced, and W phase precipitates at the grain boundary of Al-3Cu-1Li alloys containing Sc. Sc can reduce the corrosion reaction activation energy of the alloys, making the corrosion process easier. With increasing the Sc content, cathode hydrogen evolution rate increases, the self-corrosion current density of the alloy increases, and the corrosion resistance decreases gradually. EN and EIS results show that the surfaces of Al-3Cu-1Li alloy and Al-3Cu-1Li-0.1Sc alloy are in the state of “film rupture-repassivation” during 12 h immersion in the solution, and Al-3Cu-1Li-0.3Sc alloy and Al-3Cu-1Li-0.5Sc alloy have severe intergranular corrosion.