To understand the chloride (Cl)-induced initiation mechanism of localized corrosion of Aluminum (Al) alloys, we apply density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations to investigate the interactions between Cl and hydroxylated α–Al₂O₃ surfaces, mainly (0001) orientation, under aqueous electrochemical conditions. Hydroxylated alumina surfaces thermodynamically stable in aqueous environments are constructed based on DFT calculations for both the single-crystal and bicrystal configurations. AIMD simulations suggest a Cl anion can only be stabilized on these surfaces by substituting a surface hydroxyl (OH) group. This substitution is thermodynamically favorable at sites on surface terminations of grain boundaries (GBs) in bicrystal configurations but not favorable at sites on single-crystal surfaces. Electronic structure analyses show that the different adsorption behaviors originate from the higher sensitivity of the Al–OH bond strength to the local coordination than its counterpart of the Al–Cl bond. The adsorbed Cl significantly increases the thermodynamic driving force for Al cation dissolution from alumina surfaces into the aqueous electrolyte, which can initiate localized corrosion.

为了了解氯化物（Cl）诱导的铝（Al）合金局部腐蚀的引发机理，我们应用密度泛函理论（DFT）计算和从头算分子动力学（AIMD）模拟来研究Cl与羟基化α- Al之间的相互作用₂ ö ₃在水性电化学条件下的表面，主要是（0001）取向。基于DFT计算，对于单晶和双晶构型，构建了在水性环境中热力学稳定的羟基氧化铝表面。AIMD模拟表明，只能通过取代表面羟基（OH）来使Cl阴离子稳定在这些表面上。在双晶构型中，这种取代在晶界（GBs）的表面末端上的位点在热力学上是有利的，但在单晶表面上的位点上则是不利的。电子结构分析表明，不同的吸附行为源于Al-OH键强度对局部配位的敏感性高于其Al-Cl键对应物的敏感性。