The evolution of the open-circuit potential, cupric ion concentration and electrochemical impedance during immersion of Cu OFP in deoxygenated borate buffer solution (pH 7.3) in a closed cell featuring a Pd membrane was monitored at 25 degrees C for up to 3000 h (ca. 4 months). It was demonstrated that the steady-state rest potential of a copper electrode is very close to that of a cupric ion selective electrode for most part of the duration of the respective experimental runs and therefore can be considered to be determined by traces of divalent copper in the aqueous solution. No evidence of sustained corrosion of copper was found by the methods employed. The results were interpreted by a kinetic model previously proposed for shorter exposures with the addition of the disproportionation reaction of monovalent copper to explain the persistence of soluble divalent copper at longer exposure times. A hypothesis on possible hydrogen formation by a catalytic mechanism involving adsorbed CuOH is advanced and a preliminary estimate of the upper limit of hydrogen production rate is obtained using calculation results from the kinetic model. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.078302jes] All rights reserved.