Highlighting the Influence of Radiolysis at The Interface between 316L Stainless Steel using In Situ Electrochemical Techniques

The study of water radiolysis at the solid/solution interface is an experimental challenge. Here, we present two original and complementary setups: the PATRICIA cell (Passivation - Tribology - Irradiation) and the RADEAU cell.<br/>The PATRICIA configuration allows to study the tribocorrosion of a stainless steel under extreme conditions (proton irradiation, submission to radiolysis product). For instance, a proton beam can irradiate the interface formed by the contact between a liquid and a passivable material (such as 316L stainless steel). An alumina pin can induce friction on the sample's surface. Electrochemical techniques enable the <i>in situ</i> characterization of the evolution of the RedOx potentials of the solution, as well as the evolution of the passive film present on the steel surface. Through the PATRICIA cell, we demonstrated that, regardless of the beam's energy, the corrosion potential remains unchanged. This indicates that it is the highly reactive, short-lived radiolysis products that determine the corrosion potential, rather than just long-lived radiolysis products like H₂O₂. During irradiation, the evolution of resistivity profiles within the thickness of the passive film, obtained from electrochemical impedance spectroscopy measurements, shows that the inner Cr₂O₃ layer of the passive film becomes thinner, leading to a reduction in the corrosion resistance of 316L stainless steel. This evolution could be attributed to the radiolysis of water molecules bound within the passive film.<br/>In the RADEAU configuration, a thin layer of water is irradiated in front of a passivable material. The system's evolution is also monitored through <i>in situ</i> electrochemical techniques. In this geometry, only the water or the system {water + interface} can be irradiated, which allows for the discrimination of the passive layer's role in the corrosion process of 316L stainless steel.<br/>These two complementary setups enable the <i>in situ</i> study of the interface's role in the mechanisms of steel corrosion.