Effect of surface preparation by high-temperature hydrogen annealing on the passivation of Ni-20 at.% Cr alloy in sulfuric acid

•Investigation of native and passive surface films formed on Ni-20 at.% Cr alloy surfaces.•Surface analysis by in situ electrochemical measurements combined with advanced ex situ surface analysis.•Mechanistic understanding of the effects of high-temperature hydrogen annealing pretreatment.•Enhanced corrosion resistance of electrochemically passivated surface by high-temperature hydrogen annealing pretreatment.•Increase in Cr enrichment of initially weakly protected sites of the inner barrier layer.