The corrosion and passivation behavior of carbon steel AISI 1020 in borate buffer pH 8.4 were studied in terms of a superposition model for corrosion partial reactions, applied for experimental polarization curves measured using two different cell arrangements of a batch and a flow cell. It was found that the kinetics of both the hydrogen evolution and iron oxidation reactions are affected by the hydrodynamic conditions at the electrode surface in combination with an strong influence of the borate buffer concentration in the active-transition region. Supporting facts with experimental interpretation are presented to explain this behavior. (C) 2016 The Electrochemical Society. All rights reserved.