An analysis is made of the effects of solution resistance and cathodic polarization on the current distribution in the cathodic protection of metals. Two of Kasper’s formulas relating to the effect of resistance are discussed. Hoar and Agar’s formula relating resistance and polarization to current distribution, presented as a background, was modified and used as the basis of a partially quantitative treatment of the relative importance of resistance and polarization in influencing current distribution. It is shown that resistances can have a much greater effect in this respect than polarization.
An experimental method of obtaining the current density on various parts of a large cathode is described and data obtained by this method are presented. These show the distribution of current on a large cathode in sea water as affected by the magnitude of applied current and by shields around the anode. Solution resistances are calculated from the data and compared with Kasper’s formulas. Using previously published data for the resistance of paint films, calculations are presented showing the effect of paint films on current distribution. The advantages of good paint coatings in cathodic protection and the difficulties of cathodically protecting unpainted structures are discussed.
5.2.1
