Mechanisms of hydrogen evolution on chromium

Abstract

In this work, the mechanisms of hydrogen evolution on the metal chromium in a solution of 0.1 M Na2SO4 + H2SO4, pH 1 to pH 7 were analysed. In the pH < 3 range, hydrogen is evolved according to three different mechanisms, depending on the experimental conditions: electrochemical evolution of H2 by reaction of H+ ions according to the Volmer-Heyrovsky mechanism, on the bare chromium surface, during chemical dissolution of chromium by the Kolotyrkin mechanism, which does not depend on the electrode potential, and electrochemical hydrogen evolution by the Volmer-Heyrovsky mechanism, but on the passive chromium. At pH values greater than 3, the fourth mechanism of hydrogen evolution is observed, that is electrochemical reaction of water molecules on the surface of oxide covered chromium surface.

Keywords

• chromium
• corrosion
• chemical dissolution
• hydrogen evolution