Proposed here is that CF and SCC mechanisms may interact synergistically as each is dependent on the electrochemically-active surface area (ECSA) at a crack tip. A phenomenological model is developed for the effects of crack tip strain rate, film-rupture and repassivation rates on ECSA. Analysis of hold-time CGR data provides a method of separating cyclic- and static-load hold-time effects on ECSA. Five model parameters, each having physical interpretation, are found to have reasonable magnitudes.