Corrosion mechanisms in aqueous solutions containing dissolved H2S. Part 1: Characterisation of H2S reduction on a 316L rotating disc electrode

► Reduction reactions occurring during steel corrosion by CO2 and H2S are examined. ► H2S enhances the cathodic reactions in water similarly as CO2. ► CO2 produces additional cathodic current of chemical nature (buffer effect). ► On the contrary H2S provides an additional electrochemical reaction. ► The additional current should correspond to the reduction of H2S or HS− to 1/2 H2.