Effect of protection current intermittence on cathodic protection of carbon steel

The paper reports the results of a preliminary research study on the effects of protection current intermittence on the cathodic protection conditions of buried or immersed pipelines. It is well known that cathodic protection has chemical and electrochemical beneficial effects on carbon steel, which do not disappear instantly in correspondence to the current interruption. According to this premise, laboratory tests of intermittent cathodic protection in which the current has been interrupted cyclically were carried out on carbon steel specimens in soil-simulating solution. The effects of the duration of the current-off time, the number of on-off cycles, and of the applied current density have been studied. Potential has been monitored weekly and the residual corrosion rate was calculated by means of a simple electrochemical model.