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 (IGC) of stainless steel (SS). Measured current densities in a 1 N sulfuric acid (H2SO4) solution at room temperature were increased at active-passive, passive, and transpassive potentials. Radiation effects on the current decay behavior and susceptibility to IGC were similar for a fine-grained (FG) SS alloy and for a very large-grained (LG) SS. Radiation-induced segregation (RIS) at the surface was believed to promote higher currents at short times, whereas segregation at grain boundaries was responsible for IG attack. Analytical electron microscopy (AEM) measurements revealed chromium (Cr) and iron (Fe) depletion plus Ni and silicon (Si) enrichment at grain boundaries in irradiated specimens. Si enhanced dissolution at transpassive potentials, whereas Cr depletion did the same at active-passive and passive potentials.