The passive film of iron showed n-type semiconductor characteristic in borate buffer solution, and its donor concentration increased slightly after tensile strain in the present study. However, comparing with solution-annealed sample, the anodic passive film formed on tensile-strained one was highly protective. The more dislocations on tensile-strained sample promoted the diffusion of iron and oxygen vacancy. Moreover, more donor density (mainly oxygen vacancies) promoted the diffusion of oxygen. They all facilitated tensile-strained sample to form Fe2O3 and thicker passive film on the surface. More Fe2O3 and thicker passive film on the surface of tensile-strained iron could improve corrosion resistance. Copyright © 2014 John Wiley & Sons, Ltd.