Finite element calculation of crack propagation in type 304 stainless steel in diluted sulphuric acid solutions

The crack propagation rate of Type 304 stainless steel in diluted sulphuric acid solutions was modelled based on finite element calculations of the chemical and electrochemical conditions within the crack and an analytical expression for the crack-tip strain rate. The slip/dissolution/repassivation mechanism was assumed. The influence of various variables - dissolved oxygen, sulphuric acid content, stress intensity, crack length, temperature, flow rate, sensitization and yield strength - was studied and found to be in agreement with experimental observations. The model was calibrated against one data point. The effect of temperature on thermal conductivity, electrode reaction kinetics, equilibrium constants, yield strength and crack geometry was considered and the thermal activation energy for the crack propagation rate could almost fully be accounted for.