Microstructure can have a significant effect on the resistance to intergranular stress corrosion cracking. Certain grain boundaries are susceptible to corrosion while others have high resistance and may form crack bridging ligaments as the crack deviates around them. To investigate the mechanics of crack bridging, 3D computational model has been previously developed. An extension to the model, to include stress corrosion crack growth kinetics is presented in this paper. An analysis of the effects of resistant grain boundary fraction demonstrates that the bridging ligaments can significantly retard short crack propagation rates. Increasing the fraction of resistant boundaries is shown to improve microstructure resistance by reducing the crack propagation rate.