A study is made of the electrochemical behavior of a chromium-and phosphorus-bearing iron alloy and phosphides of iron and chromium. It is established that a high (more than 10 at. %) phosphorus content has a positive effect on the passivability of the alloy and the phosphides. It is conjectured that phosphorus forms a covalent bond with chromium and that compounds of the Cr-P type accumulate on the surface during dissolution, thereby facilitating passivation of the alloy.