Influence of soil parameters on coating damage evolution of X52 pipeline steel under cathodic protection conditions
© 2014 by NACE International. In this study, the influence of soil parameters on coating and metallic substrate damage evolution has been characterized by electrochemical impedance spectroscopy (EIS). Intact and defective coating conditions have been simulated to study the damage transformation of a coal tar coating of a pipeline both in the real soil environment and in an NS4 soil simulation solution. Quantitative estimation of coating on a steel X52 pipe under cathodic protection (CP) conditions has been performed by using the transmission line model (TLM). The results show that a compact soil layer can be formed on the intact coating surface, which increases the impedance at the initial time of experimental conditions. With time, water and ions transport and distribute through the soil and coating interface and reach the steel surface, a process which is considered as the first stage of damage evolution. This transport mechanism transition is reflected in the EIS signal and is quantified by TLM.
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