Electrostatic-Based Cathodic Protection Modeling

A corrosion engineer is often faced with the design of complex cathodic protection systems. Cathodic protection (CP) is defined as the application of an electrical current to suppress the corrosion (anodic or oxidation) reaction. When steel (or iron) corrodes, the reaction is Fe ← Fe⁺² + 2e⁻ (anodic or oxidation reaction). The reaction is suppressed through CP by using an external energy source or sacrificial material to make the reaction shown above unfavorable. If we are using an outside energy source, which is actually an external current source, we call it Impressed Current Cathodic Protection (ICCP). Design of an ICCP system involves establishing the optimal location and functional parameters for anodes and reference cells on the structure that the engineer is trying to protect. One of the more challenging aspects of this design effort is the ability to predict the distribution of current from one or more anodes to the structure protected. There are various empirical methods for making such estimates as well as comprehensive, computer-based software for modeling complex structures. However, a reasonable estimate of current distribution can be made on the basis of the principles of electrostatics using a common commercial spreadsheet program. This modeling approach proves to be simple to use, is inexpensive compared to the other modeling software on the market and gives meaningful results in a very short period of time.