Exacerbation of the mild steel corrosion process by direct electron transfer between [Fe-Fe]-hydrogenase and material surface

• Hydrogenase increased the corrosion process of mild steel in Tris-HCl medium.
• The surface of mild steel was attacked at grain boundaries with hydrogenase.
• In presence of hydrogenase, pits were with a square shape and depth up to 10 μm.
• Enzyme activity and concentration had a major role in the corrosion increase.
• Hydrogenase is proved to induce cathodic depolarization on mild steel.

The influence of [Fe-Fe]-hydrogenase from Clostridium acetobutylicum on the anaerobic corrosion of mild steel was studied and the use of a dialysis bag to contain the enzyme in the close vicinity of the electrode surface led to conclusive tests. Electrochemical measurements (open-circuit potential monitoring, corrosion rate evolution, impedance), and surface and medium analysis, all confirmed the strong effect of hydrogenase to exacerbate the corrosion process. Electrolysis performed at a cathodic potential proved that hydrogenase catalysed the electrochemical reduction of protons or water into dihydrogen by direct electron transfer, demonstrating the involvement of hydrogenase in cathodic depolarisation.