The influence of the applied potential and the concentration of chloride ions on the determination of the critical pitting temperature (CPT) by potentiostatic polarization technique was studied in a duplex stainless steel (DSS) UNS S31803. Applied potentials for the potentiostatic polarization tests (300, 500, 600, 700 or 800 mVAg/AgCl) were chosen among a passive common range observed in potentiodynamic polarization curves obtained for chloride ions concentrations from 0,3 to 5 M, at room temperature. The determination of CPT under less severe test conditions (lower concentrations of chlorides and low applied potentials), lead to high dispersion in CPT values, and a tendency to CPT decrease with more severe test conditions, showing the dependence of CPT values with chloride concentration and applied potential. CPT determination for DSS UNS S31803 presented smaller dispersion and can be considered chloride and potential independent under the testing conditions: 600 mVAg/AgCl with 5 M NaCl, 700 mVAg/AgCl with 3 or 5 M NaCl and 800 mVAg/AgCl with 1 to 5 M NaCl. CPT independent of chloride concentration and potential for DSS UNS S31803 occurs around 50 C. Stable pits characterization by microscopy techniques shows that there are 1 to 3 pits per sample after CPT determination. Stable pits have a lacy-cover morphology, with Feret diameter of approximately 100 μm. It was observed that the higher chloride concentration, the smaller are the formed pits. Another parameter that contributes to the increase in pitting size is the applied potential, an increase in potential leads to larger pits. Under the lacy-cover, pit grows eroding phases and structures preferentially, forming galleries and resulting in a honeycomb structure. These galleries are larger under more severe test conditions (higher chloride concentration and applied potential).