Cathodic protection for disks of various diameters

In a simplified disk model for cathodic protection, the maximum disk size t hat can be protected completely is calculated for the case that the anode i s infinitely far away. Results calculated for potential-dependent hydrogen evolution and iron dissolution are compared with that for an assumed unifor m current density and an allowed window of variation of electrode potential . Attempting application of a voltage that yields equal average hydrogen an d iron current densities leads to iron corrosion near the center and hydrog en generation near the edge of the disk, with large values of these current densities for large disks. Another approach is to suppress only iron corro sion by applying a sufficiently negative protecting voltage. Suppressing th e iron current leads to an enormous hydrogen generation near the edge of la rge disks. (C) 2001 The Electrochemical Society. All rights reserved.