The λ irradiation-enhanced corrosion of stainless and mild steels by water in the presence of air, argon and hydrogen

Abstract

When air-saturated pure water was λ-irradiated in the presence of air to high doses (10 2–10 3 Mrad) in sealed stainless steel containers hydrogen and oxygen were formed. The amounts were less than one tenth of the maximum possible for continuous aqueous radiolysis but the increase in oxygen appearing as gas was less than that equivalent to the hydrogen formed from the water present, indicating that metallic corrosion had occurred. In the absence of radiation no change in gas composition was observed. When the air in solution and in the gas space was replaced by argon or by hydrogen, radiolysis and corrosion were virtually suppressed. When the container was made of mild steel or strips of mild steel were initially introduced into a sealed stainless steel container containing air and water, oxygen was consumed on irradiation, and hydrogen was formed, together with a suspended brown oxide. In the absence of radiation oxygen was consumed and hydrogen was formed but both at a lower rate than in the presence of radiation. In this case, unlike the case of stainless steel, the formation of hydrogen was not prevented by replacing the air present with argon. The rate of product formation from either system in the presence of air was found to be proportional to dose-rate, in the range 0.2–2 Mrad h −1 and mass changes of the solids, when measurable, corresponded to the oxygen deficit in the gas phase if the oxide was taken to be Fe 3O 4. The effects are greater than hitherto reported. These results are interpreted on the basis of the surface reactions of transient radiolytic products, and product formation is analysed mathematically in terms of a multispecies reaction scheme (33 reactions) involving diffusion to the surface.