CREVICE PROTECTION POTENTIAL FOR 90-10 COPPER NICKEL

The potential and pH variations for a simulated ″crevice″ on 90-10 Cu-Ni in 0. 1 M NaCl at pH 10. 3 were determined for a range of external potentials, and related to the experimental potential pH diagram for the alloy in 0. 1 M NaCl. The range of values of steady state potential and pH for ″crevice″ samples undergoes a discontinuity at an external potential of 0. 140 plus or minus 0. 010 volts (SHE). The electrode potential at which this discontinuity occurs has been called the ″crevice protection potential″ . This crevice protection potential corresponds closely to the potential of the intersection of the ″corrosion region″ on the experimental potential-pH diagram and the locus of the primary passivation potential as a function of pH for the alloy.