Prediction of corrosion fatigue crack growth rate in alloys. Part II: effect of electrochemical potential, NaCl concentration, and temperature on crack propagation in AA2024-T351

Abstract

Abstract We report here on the prediction of corrosion fatigue crack growth rate (CFCGR) for Aluminum Alloy 2024-T351 in aqueous environments under cyclical sinusoidal loading. Using the General Corrosion Fatigue Model (GCFM) described in Part I, the CFCGR was calculated as a function of environmental variables, including the electrochemical potential, NaCl concentration, loading frequency, stress intensity factor range, and temperature, in addition to the contribution from mechanical fatigue. Based on the influence of the environment, the changes in the potential drop down the crack enclave and the corrosion current density in a 1:1 electrolyte were also calculated from which the CFCGR was estimated. Corrosion fatigue crack growth in this alloy is readily understood in terms of the competition between environmental factors as described by the differential aeration hypothesis and the hydromechanics (advection) of the system resulting from the cyclical opening and closing of the crack.