New Methods for the Corrosion Monitoring of Underground Pipelines According to the Measurements of Currents and Potentials

It is shown that the method of contactless current measurement (CCM) makes it possible to perform rapid monitoring of the state of corrosion protection in different sections of underground pipelines, determine the state and detect defects in the insulation of underground pipelines (UGP). The method of simultaneous measurements of direct-current and alternating-current voltages enables us to determine the polarization potential (with removal of the Ohmic component) which is regarded as the main criterion for the monitoring of electrochemical corrosion protection of the metal in conducting media. The realization of this method in the equipment aimed at measuring the polarization potential makes it possible to detect defects of the insulation both by using an alternating current (Pearson method) and according to the potential drop on the surface of soil (gradient method). The use of a GPS modulus in the developed BVS-K installation guarantees the possibility of automatic determination of the geographic coordinates and the time of measuring the current and depth of the underground pipelines, which strongly facilitates the procedures of processing and documentation of the results of inspection, in particular, in the course of determination of the current density, current losses, and the “pipe–ground” transient resistance in different sections of the underground pipeline. The contactless current measurements together with the measurements of the polarization potential enable us to determine the distributions of densities of the currents of corrosion protection, the resistivities of soils around the pipe, and the protective insulation in different sections of the underground pipeline.