The present work looks into the influences of sigma phase precipitation on pitting parameters obtainable from the anodic potentiodynamic polarization test and AC magnetic susceptibility of duplex stainless steel (DSS) type 7MoPLUS. The microstructural changes and corrosion morphology associated with sigma phase formation have also been studied using TEM, SEM, optical metallography, and XRD. The AC magnetic susceptibility and the two corrosion potentials (pitting potential Epit and corrosion potential Ecorr) of 7MoPLUS decrease almost in step upon the decomposition of ferrite into sigma phase and secondary austenite. The use of AC magnetic susceptibility for the assessment of the severity of pitting attack of 7MoPLUS is therefore feasible. This conclusion is believed to be applicable to other DSSs whose compositions do not differ too much from that of 7MoPLUS. No correlation between the passive current (Ipass) and the AC magnetic susceptibility of 7MoPLUS could be found. The same is true between its corrosion current Icorr and AC magnetic susceptibility