On the Mechanism of Cathodic Protection

Abstract

Changes in the distribution of anodic sites on steel and aluminum surfaces have been monitored by applying a pH-indicating dye and observing how the color pattern on the surface changes as cathodic protection is applied. In addition, cathodic polarization curves for steel in seawater have been correlated with 120-day weight loss measurements and surface morphological observations for specimens receiving various levels of cathodic protection. The results are discussed in terms of the Mears and Brown, Hoar, and LaQue theories of cathodic protection and their implications as to the criteria for cathodic protection and the consequences of underprotection.