Purpose – The purpose of this paper is to characterize the pitting behaviour of sigma-phase-containing duplex stainless steel and investigate the correlation between magnetic susceptibility and pitting potentials. Design/methodology/approach – Use an alternating current (AC) magnetic susceptometer to trace the change in magnetic susceptibility associated with sigma phase formation and systematic study of the effects of sigma precipitation on pitting parameters as obtained using the anodic potentiodynamic polarization test. Findings – The precipitation of sigma phase impairs the general and pitting corrosion resistance of duplex stainless steel. The pitting potential, the corrosion potential and the AC magnetic susceptibility have good correlations. Unlike the pitting potential and the corrosion potential, the passive current and the corrosion current do not seem to possess any trend with annealing time. Originality/value – The correlation between AC magnetic susceptibility and pitting parameters has not been reported in the literature before.