Аннотация:In the case of buried Oil and Gaz pipelines, the metal in soil is exposed to corrosive processes that may eventually cause ruptures with the consequent environmental and economic damages.
The pipe coating is the main barrier against external corrosion, and it provides an excellent protection.
Once coating is damaged, the metal surface is exposed to the medium electrolyte (soil or water), metal loses mass and, if this condition remains for some time, corrosion occurs, which may result hydrocarbon leakage. Therefore, external and internal inspections of pipelines are needed to assess integrity and determine if any variations during the process of exploitation has occurred.
The quality of the insulator coating determines the optimal strategy of the pipeline maintenance and the appropriated performance of the cathodic protection (CP) system. Generally, to estimate the coating quality, electrical and electromagnetic (EM) non-destructive test (NDT) methods are applied on surface.
The main threat in pipeline systems in Mexico is the extremely corrosive soil characterized by a high clay content and low resistivity. Pipelines interconnections including pipes out of service and the short distance between parallel pipelines compared to their depths, reduces the possibilities for effective electrical or EM inspection based on surface measurements. Because of this, it is necessary to have inspection techniques that can determine coating electrical resistance as a quantitative parameter of the coating quality.