SCC of AZ31B alloy was studied in NaCl solutions at different potentials and chloride concentrations using the slow strain rate technique. A combination of pre-exposure tests followed by immediate straining or straining after a dry air exposure delay helped to weight the relative importance of anodic damage accumulation versus increased hydrogen charging during open-circuit potential pre-exposure. The dependence of ductility with pre-exposure time and the fracture surface of embrittled samples suggest that hydrogen embrittlement of AZ31B was controlled by hydrogen diffusion.