School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
ACS Appl Mater Interfaces. 2012 Mar;4(3):1225-32. doi: 10.1021/am201345v. Epub 2012 Mar 7.
Using reactive force-field (ReaxFF) and molecular dynamics simulation, we study atomistic scale chloride ion adsorption and transport through copper oxide thin films under aqueous conditions. The surface condition of passive oxide film plays a key role in chloride ion adsorption and facilitates initial adsorption when surface corrosion resistance is low. Using implemented surface defects, the structural evolution of the copper oxide film from thinning to breakdown is investigated. In addition to chemical thinning of passive film, extended defects in the metal substrate are observed, at high concentration of adsorbed chloride ions. The initial stage of breakdown is associated with rapid depletion of adjacent chloride ions, which creates a locally deficient environment of chloride ions in the solution. The dissolved copper cations gain higher charge upon interaction with chloride ions. Owing to the increased Coulomb interactions resulted from dissolved copper ions and locally low density of chloride ions, far-field chloride ions would diffuse into the local corrosion sites, thereby promoting further corrosion.
使用反应力场（ReaxFF）和分子动力学模拟，我们研究了在水相条件下氯化物离子通过氧化铜薄膜的原子尺度吸附和传输。在吸附氯化物离子时，被动氧化膜的表面状态起着关键作用，并且当表面耐腐蚀性较低时，有利于初始吸附。利用所实现的表面缺陷，研究了氧化铜薄膜从减薄到击穿的结构演变。除了钝化膜的化学减薄外，在吸附了高浓度氯化物离子的金属基底中还观察到了扩展缺陷。击穿的初始阶段与相邻氯化物离子的快速耗尽有关，这会在溶液中形成氯化物离子局部缺乏的环境。溶解的铜阳离子在与氯化物离子相互作用时获得更高的电荷。由于溶解的铜离子引起的库仑相互作用增加以及局部低浓度的氯化物离子，远场的氯化物离子会扩散到局部腐蚀部位，从而促进进一步的腐蚀。
