Effect of Soil Conductivity on the Design of Cathodic Protection Systems Used in the Prevention of Pipeline Corrosion

Abstract

One of the most influential factors affecting the rate of corrosion of a buried pipeline and the design of the cathodic protection systems is the conductivity of the soil. The present paper is designed to study the effect of this factor on the design of cathodic protection systems, i.e. the current required to achieve comprehensive protection. Several corrosive environments were studied within the laboratory. The classification of environment corrosivity approved by ASTM was the base of the categorization of these environments. These environments were simulated by adding certain amount of distilled water mixed with weighed amount of sodium chloride to the soil. Several runs were carried out, whereas the conductivity of the soil and the linear polarization curves for the cathode and the anode were obtained during each run. The boundary element method (BEM) was used to compute the total current required using linear polarization curves as the boundary conditions for calculations. The BEASY software based on BEM was used to compute the total current required. The relationship between the total current and the soil conductivity values were drawn. Two equations governing and controlling this relationship were derived.