On the implication of mobile hydrogen content on the surface reactivity of an austenitic stainless steel

The Influence of hydrogen on the corrosion behavior of an AISI 316 L austenitic stainless steel in borate buffer solution is studied after a cathodic pre-charging step. A high amount of hydrogen is absorbed and forms a concentration gradient from the surface to the bulk with a path length of about 80 mu m. The surface reactivity in the passive regime after the cathodic charging and during the hydrogen desorption is investigated with a large set of electrochemical and physico-chemical technics: electrochemical polarization, EIS, Mott-Schottky analysis and XPS. This approach allows to demonstrate that surface reactivity increases drastically with hydrogen absorption. This effect is mostly due to mobile hydrogen and is mainly reversible with its desorption. Hydrogen absorption and desorption have a small impact on the passive layer composition and thickness. However, the hydrogen induces an increase in the dissolution rate, which is discussed based on the Point Defect Model. Present results suggest that the impact of hydrogen on the surface reactivity is a consequence of a strong increase in the mobility of anionic vacancy and/or hydrogen oxidation.0 2021 Elsevier Ltd. All rights reserved.