Graph Theory and the Passivity of Iron-Chromium Binary Alloys

Using graph theory, it is shown that the introduction of 70 atom % of into a ‐Cr‐O‐Cr‐ oxide network serves to disjoin the network, or conversely, introduction of 30% atomic concentration of serves to provide a connected ‐Cr‐O‐Cr‐ network. The results of surface analysis show that this concentration of 30 atom % in the oxide film corresponds to 13 atom % chromium in the Fe‐Cr alloy, i.e., the critical concentration of Cr required for passivity in Fe‐Cr binary alloys.