Effect of Mixed β, γ Irradiation on the Pitting Corrosion of AISI 316L Steel in Artificial Seawater at Various Chloride Ion Concentrations. Part 1: Testing at 25°C

AISI 316L steel, which is used as a structural material for the adsorption columns at the Fukushima Daiichi NPP, is subjected to electrochemical investigations to determine its susceptibility to pitting corrosion in diluted and saturated artificial seawater solutions. The investigations are conducted in accordance with the recommendations of Russian standard GOST 9-912–89 at 25°C in artificial seawater solutions with a chloride ion concentration of ~100, ~10 000, and ~29 000 ppm when the steel is in contact with natural clinoptilolite in the absence and presence of mixed ionizing β, γ radiation from the 137Cs and 90Sr radionuclides at a total absorbed dose rate of ~4.9 × 10–2 Gy/s. The values of free corrosion potential Ecor, pitting potential Eb, pitting corrosion repassivation potential Erp, and minimum galvanostatic pitting corrosion potential Epc; pitting resistance indicators ΔEpc, ΔEb, and ΔErp and their dependences on the Cl– ion concentration and mixed ionizing β, γ radiation have been determined. Metastable pittings and their radii are analyzed as functions of the scan potential and the chloride ion concentration with and without irradiation.