SIGNIFICANCE OF HYDROGEN EVOLUTION DURING CATHODIC PROTECTION

摘要

Current requirement and calcareous scale properties on carbon steel are investigated as a function of applied potential, flow rate and time in natural seawater. The current requirement is dominated by oxygen reduction during the initial stage of polarization after application of cathodic protection. However, as the calcareous scale deposits, oxygen reduction reaction rate decreases, and hydrogen evolution becomes the dominating cathodic process. Furthermore, the rate of hydrogen evolution appears to become catalyzed by the presence of the calcareous scale deposit. Maximum Ca/Mg ratio in the calcareous deposit gives the best protection and current requirement. The maximum is determined by the applied potential and seawater flow rate.