Development Of A Cathodic Protection System Using A Galvanic Anode Method

ABSTRACT

The development of a Cathodic Protection System for a mild steel pipe using a magnesium anode was investigated. The pipe was externally coated with three layers of polykene tape wrapping and the soil resistivity was determined using the Wenner four pin method; a value of 2177Ωcm was obtained. The design parameters for the developed Cathodic Protection System were: total current of 0.0153mA; current density of 0.01mA/m 2 ; protection current of 0.0153mA; protection voltage of 0.95Volts. The experimental values of 0.02mA/m 2 current density; 0.0154mA protection current; 0.9Volts protection voltage obtained compared favourably with the design parameters with negligible differences and these may have occurred as a result of :- (i) variation in the soil resistivity and (ii) the introduction of a safety and utilization factor to give room for safety and utilization of some reactions in the soil that can induce increase in the corrosion rate. This can cause the value of the protection potential obtained to fall below the optimum value prior to the end of the design life of the pipe. The protection potential of -890mV to -1080mV obtained is in the range of (-850mV to -1150mV) for a protected mild steel. This confirmed that the mild steel pipe was cathodically protected.