[en] Highlights: • Influence of quenching and partitioning process on stainless steel was studied. • Pitting potentials of experimental steel partitioned at 350 and 450 °C were higher. • Retained austenite and M_3C carbides existed in matrix of experimental steel. • Retained austenite is beneficial for the corrosion resistance of stainless steel. - Abstract: A 0.3C–13Cr martensitic stainless steel (MSS) was subjected to quenching and partitioning (Q&P) treatment. Due to the different thermodynamic condition from the standard constrained carbon equilibrium (CCE), both the carbides precipitation and the interface migration occur during the partitioning step in the Q&P treatment. However, a sufficient amount of austenite is still retained in the Q&P treated MSS. After being partitioned at 350 °C and 450 °C, the Q&P treated MSS exhibits better corrosion resistance than the same steel treated via conventional quenching and tempering (Q–T) treatment.