Research of efficiency of security of cathodic protection from corrosion for pipelines prepared for reconstruction with method «pipe in pipe»

The questions of organization of cathodic protection against corrosion of pipelines laid by the «pipe in pipe» method are considered. The variants of the organization of the cathodic corrosion system for pipelines laid by this method are determined. A laboratory stand simulating a pipe-in-pipe gasket with the installation of coppersulphate electrodes of comparison of small size between the pipes has been prepared. Laboratory studies to verify the protection of the main pipeline under various schemes of organization of cathodic corrosion protection were carried out. The conditions that must be observed when laying the pipeline to ensure the operation of the cathodic protection system, the main ones are the presence of electrolyte in the medium between the pipelines, as well as the absence of direct electrical contact between the pipelines. Negative features of joint protection of both pipelines are revealed. The optimal schemes of organization of cathodic corrosion protection during pipeline laying by this method, which are schemes with the use of extended anode grounding between pipelines or schemes without cathodic protection of external pipe, are determined. Solutions are proposed to eliminate the «failure» of the protective potential in contact with the metal between the pipelines, which consists in laying an extended anode grounding and local displacement of the potential of the internal pipeline relative to the external one.