In the case of FeNiCr alloys (without precipitation), we propose an electrochemical method which allows us to obtain a reproducible selective corrosion of grain boundaries (H2SO4-2N-25°C in the transpassive domain). We establish a model of dissolution to explain the morphology of etched grooves. From this model we deduce a parameter α0 which characterizes the intergranular corrosion susceptibility of a given alloy. Electrochemical kinetic allows us to calculate the ratio of the density of active sites at the emergence of the grain boundary and on the surface of the grain. This electrochemical method permits us to study the effects of the segregation phenomena, of composition alloy and of grain boundary structure on intergranular corrosion.