A study on cathodic protection against crevice corrosion in dilute NaCl solutions

Potential and current distributions in a cathodically protected crevice between a simulated coating and segmented mild steel electrodes were measured in dilute NaCl solutions. The distributions became more uniform with time due to an increase in solution conductivity and depletion of dissolved oxygen in the crevice. Generally, a negative shift of control potential and an increase in initial solution conductivity and crevice thickness resulted in a higher polarization level on the steel. However, if the control potential is too negative, the polarization level may be lower than that under a suitable control potential because of hydrogen evolution. On the basis of these results, a mechanism of cathodic protection against crevice corrosion in high-resistivity environments was proposed.