The corrosion behavior of a 17Cr multiphase martensitic stainless steel quenched (1000°C, water cooling) and tempered at different temperatures was determined using the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. The specimen tempered at 550°C showed the highest degree of sensitization. For the specimen treated at 600°C, a healing process was observed, followed by a second sensitization at 625°C coincident with an increase in the austenite volume fraction. This phase was quantified using the magnetic method and an increase in this phase was observed with the tempering temperature. The DL-EPR results were correlated with surface aspects obtained by atomic force microscopy.