The effects of boron on the microstructure and intergranular corrosion behavior of UNS S31254 (S31254) austenitic stainless steels were investigated. The sensitivity to intergranular corrosion in the samples was determined by an altered double loop electrochemical potentiokinetic reactivation method. The microstructure characterization showed that the S31254 steels only precipitated sigma (sigma, Fe-Cr-Mo-Ni) phases during the aging process, but boron addition decreased the amount of s phase precipitation, reduced the size of the s phases, and promoted the formation of small Laves phases at the grain boundaries. The precipitated s phases lead to surrounding zones depleted of Cr and Mo, leading to intergranular corrosion. The S31254 alloy with added boron slows down the intergranular corrosion, due to microstructure manipulation at the grain boundaries. (C) 2019 The Electrochemical Society.