Iron–chromium and nickel–chromium binary alloys containing sufficient quantities of chromium serve as the prototypical corrosion-resistant metals owing to the presence of a nanometre-thick protective passive oxide film^{1,2,3,4,5,6,7,8}. Should this film be compromised by a scratch or abrasive wear, it reforms with little accompanying metal dissolution, a key criterion for good passive behaviour. This is a principal reason that stainless steels and other chromium-containing alloys are used in critical applications ranging from biomedical implants to nuclear reactor components^9,10. Unravelling the compositional dependence of this electrochemical behaviour is a long-standing unanswered question in corrosion science. Herein, we develop a percolation theory of alloy passivation based on two-dimensional to three-dimensional crossover effects that accounts for selective dissolution and the quantity of metal dissolved during the initial stage of passive film formation. We validate this theory both experimentally and by kinetic Monte Carlo simulation. Our results reveal a path forward for the design of corrosion-resistant metallic alloys.

^{由于存在纳米厚的保护性钝化氧化膜1、2、3、4、5、6、7、8}，含有足够量铬的铁铬和镍铬二元合金可作为原型耐腐蚀金属. 如果该薄膜受到划痕或磨损的影响，它会在几乎不伴随金属溶解的情况下进行改造，这是良好被动行为的关键标准。这是不锈钢和其他含铬合金用于从生物医学植入物到核反应堆部件等关键应用的主要原因^9,10. 解开这种电化学行为的成分依赖性是腐蚀科学中一个长期悬而未决的问题。在此，我们基于二维到三维交叉效应开发了合金钝化的渗流理论，该理论解释了钝化膜形成初始阶段的选择性溶解和金属溶解量。我们通过实验和动力学蒙特卡罗模拟验证了这一理论。我们的结果揭示了设计耐腐蚀金属合金的前进道路。