Li Xuejiao, Würger Tim, Feiler Christian, Meißner Robert H, Serdechnova Maria, Blawert Carsten, Zheludkevich Mikhail L
Institute of Surface Science, Helmholtz-Zentrum Hereon, Geesthacht 21502, Germany.
Institute of Polymers and Composites, Hamburg University of Technology, Hamburg 21073, Germany.
ACS Omega. 2022 Apr 2;7(14):12412-12423. doi: 10.1021/acsomega.2c01115. eCollection 2022 Apr 12.
Effective protective coatings are an essential component of lightweight engineering materials in a large variety of applications as they ensure structural integrity of the base material throughout its whole service life. Layered double hydroxides (LDHs) loaded with corrosion inhibitors depict a promising approach to realize an active corrosion protection for aluminum and magnesium. In this work, we employed a combination of density functional theory and molecular dynamics simulations to gain a deeper understanding of the influence of intercalated water content on the structure, the stability, and the anion-exchange capacity of four different LDH systems containing either nitrate, carbonate, or oxalate as potential corrosion inhibiting agents or chloride as a corrosion initiator. To quantify the structural change, we studied the atom density distribution, radial distribution function, and orientation of the intercalated anions. Additionally, we determined the stability of the LDH systems by calculating their respective hydration energies, hydrogen-bonded network connected to the intercalated water molecules, as well as the self-diffusion coefficients of the intercalated anions to provide an estimate for the probability of their release after intercalation. The obtained computational results suggest that the hydration state of LDHs has a significant effect on their key properties like interlayer spacing and self-diffusion coefficients of the intercalated anions. Furthermore, we conclude from our simulation results that a high self-diffusion coefficient which is linked to the mobility of the intercalated anions is vital for its release via an anion-exchange mechanism and to subsequently mitigate corrosion reactions. Furthermore, the presented theoretical study provides a robust force field for the computer-assisted design of further LDH-based active anticorrosion coatings.
有效的防护涂层是多种应用中轻质工程材料的重要组成部分，因为它们能在整个使用寿命期间确保基材的结构完整性。负载缓蚀剂的层状双氢氧化物（LDH）是实现铝和镁主动腐蚀防护的一种有前景的方法。在这项工作中，我们结合密度泛函理论和分子动力学模拟，以更深入地了解插层水含量对四种不同LDH体系结构、稳定性和阴离子交换容量的影响，这四种体系分别含有硝酸盐、碳酸盐或草酸盐作为潜在的缓蚀剂，或氯化物作为腐蚀引发剂。为了量化结构变化，我们研究了插层阴离子的原子密度分布、径向分布函数和取向。此外，我们通过计算各自的水化能、与插层水分子相连的氢键网络以及插层阴离子的自扩散系数来确定LDH体系的稳定性，以估计它们插层后释放的概率。获得的计算结果表明，LDH的水化状态对其关键性质如层间距和插层阴离子的自扩散系数有显著影响。此外，我们从模拟结果得出结论，与插层阴离子迁移率相关的高自扩散系数对于其通过阴离子交换机制释放并随后减轻腐蚀反应至关重要。此外，所提出的理论研究为基于LDH的进一步主动防腐涂层的计算机辅助设计提供了一个强大的力场。
