Simulation of coating failures on cathodically protected pipelines - Experimental and numerical results

A cathodically protected buried pipe with coating failures was simulated in two different ways. An experimental model was developed and then a computer program was used to study the same problem. The agreement between the results demonstrates that numerical simulations are applicable to cathodic protection systems in high-reststivity media, Steel coupons were electrically connected to the pipe to simulate coating failures. The ohmic drop (IR)-corrected potential values of the coupons were obtained instantaneously after a brief interruption of the protection current. The potential and current density were calculated over distinct failure areas for three different medium reststivities: 80,000, 15,000, and 500 Omega-cm, The IR drop, which affects the potential measurements, was related to the resistivity of the medium, and a mathematical expression between these parameters was obtained.