Corrosion fatigue crack nucleation from surface irregularity is modelled as a moving boundary value problem. The model is based on material dissolution proportional to the surface stretch. Dissolution and repassivation processes are forming the geometry of the crack tip, thus creating conditions for strain concentration. No crack growth criterion is used. The interaction between the electrochemical processes and the deformation of the crack tip region is incorporated in continuum mechanical theory. Elastic-perfectly plastic materials under low frequency cyclic load are considered. The model simulates how cracks form and grow in a single continuous process. The resulting natural variation of lengths of the formed cracks makes them grow with different rates. One crack after another falls into a wake behind a larger crack and the crack tip load of the smaller decreases leading to its arrest.