Abstract A mathematical model is proposed for modeling the chemistry and the potential distribution in a corrosion fatigue crack, along with the crack propagation rate, in sensitized stainless steel in boiling water reactor (BWR) coolant environments. Mass transport by diffusion, ion migration, and convection (due to movement of crack walls) was considered. Anodic and cathodic processes, hydrolysis, oxide solubility, and water dissociation are included in the model. The model takes into account oxygen transport and depletion in the crack and transport processes in the external environment, and it recognizes the fact that the specific rate (rate per unit area) of metal dissolution at the crack tip surface is well above that on the crack sides. We show that the pumping effect induced by fatigue influences the concentration and potential distributions within the crack and crack propagation rate.