Analysis of an Educational Cathodic Protection System with a Single Drainage Point: Modeling and Experimental Validation in Aqueous Medium.

Abstract

Cathodic protection, often taught in curricular units, such as corrosion and materials science, is an important subject in the study of chemical engineering. The implementation of lab setups and experimental activities in this field, are core to promoting understanding of the underlying concepts and to developing “hands-on” skills fundamental to the success of future process engineers. This paper reports the influence of different variables on the electrical potential and current behaviors of an educational cathodic protection system operated with a single drainage point. The system comprised a steel bar cathode connected to a zinc sacrificial anode, both placed in aqueous medium. The study variables were the anode area, the cathode diameter, the NaCl electrolyte concentration and the anode placement. Each variable showed a specific influence on the attenuation curves, allowing us to conclude that: (1) increasing the sacrificial anode area, or decreasing the resistivity of the medium, promotes more electronegative potentials on the structure and higher currents; (2) increasing the cathode diameter decreases the protection capacity; (3) positioning the anode in the middle of the cathode lengthwise gives rise to a more balanced potential distribution; and (4), the attenuation curves, both for potential and current, can be successfully predicted using equations based on Morgan and Uhlig’s work. High correlations were obtained between the experimental and modeling data for all the studied variables.