Consequences of mobile and trapped hydrogen on the dissolution kinetics and pitting processes of an austenitic stainless steel

The effect of cathodic hydrogen charging on corrosion behaviour of an AISI 316 L austenitic stainless steel in acidified sodium chloride is studied. A large set of electrochemical and physico-chemical methods allows to demonstrate that the oxide initial growth steps are little affected while the dissolution kinetics increase drastically in relation to hydrogen oxidation. This effect is mainly reversible with hydrogen desorption, highlighting the role of mobile hydrogen. Defects induced by hydrogen could be responsible for a small irreversibility. Hydrogen promotes the pitting processes, but seems to have few impacts on the passive film composition and thickness.