IRRADIATION EFFECTS ON THE ELECTROCHEMISTRY AND CORROSION-RESISTANCE OF STAINLESS-STEEL

Nickel (Ni) ion radiation at 500 degrees C was shown to have a strong effect on the surface electrochemistry and intergranular corrosion (IG C) of stainless steel (SS). Measured current densities in a 1 N sulfur ic acid (H2SO4) solution at room temperature were increased at active- passive, passive, and transpassive potentials. Radiation effects on th e current decay behavior and susceptibility to IGC were similar for a fine-grained (FG) SS alloy and for a very large-grained (LG) SS. Radia tion-induced segregation (RIS) at the surface was believed to promote higher currents at short times, whereas segregation at grain boundarie s was responsible for IG attack. Analytical electron microscopy (AEM) measurements revealed chromium (Cr) and iron (Fe) depletion plus Ni an d silicon (Si) enrichment at grain boundaries in irradiated specimens. Si enhanced dissolution at transpassive potentials, whereas Cr deplet ion did the same at active-passive and passive potentials.