It was shown that chromium in deaerated sulfuric acid exhibits two stable corrosion potentials, depending whether the metal had previously been in contact with air or subjected to activation by cathodically evolving hydrogen. Electrochemical polarization measurements, as well as measurements of the actual metal dissolution rate at the corrosion potentials, anodic or cathodic polarization, using the analytical determination of Cr ions in the solution, weight-loss of metal, or volumes of hydrogen evolved, showed that hydrogen can evolve on chromium by three different reaction mechanisms. The first one is the electrochemical hydrogen evolution reaction from H+ ions at the bare chromium surface obtained by cathodic activation. This reaction and the active anodic dissolution of chromium determine one stable corrosion potential. The second reaction is the reaction of H+ ions on the oxidized chromium surface which, coupled with the anodic dissolution of passivated chromium determines the other stable corrosion potential. The third one is the "anomalous" or chemical reaction of chromium with water molecules and hydrogen ions whereby hydrogen is liberated. This is a potential independent reaction, occurring on the bare metal surface, and which is at pH <2 several times faster at the corrosion potential than the electrochemical hydrogen evolution reaction. The consequence is that the overall corrosion rate is several times faster than that determined by the usual electrochemical methods. The applicability of the different methods of measuring electrochemical corrosion rates and cathodic current efficiencies in chromium plating is discussed. Also, a possible role of the "anomalous" chromium dissolution in corrosion fatigue and stress corrosion cracking of stainless steels is considered. (C) 2004 Elsevier Ltd. All rights reserved.