Atomistic mechanisms of non-monotonic acidic corrosion at the SiO2 surface: An ab initio molecular dynamics study

초록

Silicon dioxide (SiO2), a primary component of cement and concrete, is a cornerstone material in numerous industrial fields, including chemical processing and civil infrastructure, and it often serves as a protective or binding phase. However, the long-term stability of SiO2-based materials in acidic environments remains a critical concern, as the fundamental atomistic mechanisms of corrosion are poorly understood. This study bridges this knowledge gap by employing a multiscale simulation approach. Extensive ab initio molecular dynamics (AIMD) simulations elucidate the interaction between alpha-quartz and hydrochloric acid at the atomic level. Our investigation reveals a critical, non-monotonic dependence of corrosion on acid concentration. While proton attack and Si-O bond weakening intensify with concentration, a surprising suppression of corrosion occurs at the highest level. This discovery unveils a previously unidentified "passivation-like" effect, where high Cl-ion coverage sterically hinders proton access to the surface. Furthermore, we correlate this peak corrosion resistance with a strain-induced contraction of the Si-O bond and minimized silicon mobility. More importantly, classical molecular dynamics (MD) simulations for larger time and length scales were performed to further confirm the non-monotonic trend, and identified that there is an optimal corrosive concentration that maximizes HCl diffusion and interfacial accumulation, as evidenced by density profiles and mean square displacement analysis. Adsorption energy calculations further reveal that this concentration corresponds to the most thermodynamically favorable adsorption of HCl at the interface. Beyond this optimum, increased concentration hinders diffusion and reduces corrosive ability. Collectively, our multiscale results fundamentally challenge the conventional linear corrosion model. The results of this work are expected to help advance our understanding of the atomic-level corrosion mechanism, which could be potentially used for developing more durable construction and engineering materials.

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