According to electrochemical theory the oxidizing potential or the potential drop between a corroding metal surface and the solution across the double layer determines the rate and specific mode of corrosion attack. In an environment such as a reactor, the oxidation potential is determined by the intersection of the local anodic and cathodic polarization curves. The potential of a corroding alloy, such as austenitic stainless steel can be referred to as the corrosion potential. The corrosion potential is then determined by the net reaction of metal oxidation and all of the oxidizing and reducing species present in the environment. The effect of each species on the net corrosion potential is determined by its concentration and kinetic response (the shape of each polarization curve). The oxidation potential of a non-corroding electrode like platinum is determined similarly except that the current from oxidation of the metal is zero. Thus the potential of the platinum electrode is responsive simply to the presence and relative reaction of oxidizible and reducible species in the environment. The kinetic response of the platinum and corrosion electrode may be different with regard to the oxidizing and reducing species in the environment. For example the response time and potential sensitivity may vary on the stainless steel and platinum electrode for changes or steady-state concentrations of dissolved O2, H2, or H2O2.
