Alpha localized radiolysis and corrosion mechanisms at the iron/water interface: Role of molecular species

Abstract

This paper is devoted to the iron corrosion phenomena induced by the α (4He2+) water radiolysis species studied in conjunction with the production/consumption of H2 at the solid/solution interface. On one hand, the solid surface is characterized during the 4He2+ ions irradiation by in situ Raman spectroscopy; on another hand, the H2 gas produced by the water radiolysis is monitored by ex situ gas measurements. The 4He2+ ions irradiation experiments are provided either by the CEMHTI (E = 5.0 MeV) either by the ARRONAX (E = 64.7 MeV) cyclotron facilities. The iron corrosion occurs only under irradiation and can be slowed down by H2 reductive atmosphere. Pure iron and carbon steel solids are studied in order to show two distinct behaviors of these surfaces vs. the 4He2+ ions water irradiation: the corrosion products identified are the magnetite phase (Fe(II)Fe(III)2O4) correlated to an H2 consumption for pure iron and the lepidocrocite phase (γ-Fe(III)OOH) correlated to an H2 production for carbon steel sample. This paper underlined the correlation between the iron corrosion products formation onto the solid surface and the H2 production/consumption mechanisms. H2O2 species is considered as the single water radiolytic species involved into the corrosion reaction at the solid surface with an essential role in the oxidation reaction of the iron surface. We propose to bring some light to these mechanisms, in particular the H2 and H2O2 roles, by the in situ Raman spectroscopy during and after the 4He2+ ions beam irradiation. This in situ experiment avoids the evolution of the solid surface, in particular phases which are reactive to the oxidation processing

Radiation-Induced Chemical Changes to Iron Oxides

“…A number of recent studies have observed enhanced radiation decomposition of water when associated with various solid oxides. − Iron oxides have a number of interesting biological and geological applications; a number of papers have examined radiation effects on stainless steel, , carbon steel, − magnetite, and pure iron ,− under a variety of atmospheres, but radiation effects on the molecular level at iron oxide surfaces are not completely understood. Currently, stainless steel containers are being proposed for long-term radioactive waste storage .…”

“Impact of γ-radiation on carbon steel anaerobic corrosion and H2 production.”

“…6), which passivate and protect the carbon steel coupons surface. The identification of magnetite as predominant corrosion product has previously been observed in several carbon steel anoxic corrosion studies performed either under un-irradiated conditions [6,8,9,[31][32][33][34] or under irradiation [14,23,[35][36][37]. In previous studies dealing with long term anoxic corrosion under irradiation [14,38] such progressive magnetite formation has been associated to corrosion rate decrease.…”