Stainless steels are widely used as metal components owing to self-protection in aggressive environments, provided by an extremely thin surface oxide film enriched in chromium oxide. Yet, despite decades of research, the mechanisms distributing the chromium enrichment at small length scale are poorly understood, although it may cause loss of stability and local failure of the corrosion resistance. Here, we apply high resolution surface analysis to investigate at small time and length scales the nucleation and growth mechanisms of the surface oxide on a model stainless steel. Starting from an oxide-free surface, we report the direct observation of the oxide nucleation and local oxidation of chromium, which governs the nanoscale heterogeneity of the growing surface oxide by chromium pumping from the atomic terraces to the steps for preferential Cr(III) oxide nucleation and subsequently by segregation from the atomic planes below to grow the Cr(III) layer incompletely saturating the stainless steel surface. This work provides new insight on corrosion chemistry, by evidencing local chemical and structural defects self-generated at the nanoscale by the building process of the protective oxide barrier, and affecting the passive film stability.

由于在腐蚀性环境中具有自我保护作用，不锈钢被广泛用作金属部件，而这种保护是由富含氧化铬的极薄的表面氧化膜提供的。然而，尽管进行了数十年的研究，但是尽管其可能导致稳定性损失和耐腐蚀性的局部破坏，但人们对铬在小长度尺度上富集的机理仍知之甚少。在这里，我们应用高分辨率表面分析来研究在较短的时间和长度范围内模型不锈钢表面氧化物的形核和生长机理。从无氧化物的表面开始，我们报告了对铬的氧化物成核和局部氧化的直接观察，它通过从原子阶跃到优先的Cr（III）氧化物成核的步骤以及随后从下面的原子平面中析出以生长不完全浸透不锈钢的Cr（III）层来控制正在生长的表面氧化物的纳米级异质性。表面。通过证明由保护性氧化物阻挡层的构建过程在纳米尺度上自生的局部化学和结构缺陷，并影响钝化膜的稳定性，这项工作为腐蚀化学提供了新的见解。