EXPERIMENTAL STUDY OF CHANGES IN CONTACT RESISTANCE OF UNDERGROUND PIPELINE COATINGS

Abstract

The purpose of this experimental study was to determine the reduction in contact resistance of underground pipeline coatings over time, as well as to analyze the effect of cathodic protection on pipeline coatings. Investigation was carried out in the laboratories USPTU under normal conditions with the use of special facilities, developed on the basis of GOST R 5116 – 98 «Assessment of the contact resistance». Experiment bears out that, CP current intensify the deterioration of the coating, i.e. form all experiments the use of cathodic protection about 100 times decreased the contact resistance of pipeline coatings during the first of operation, compared with operation without cathodic polarization. Therefore, it is requested to consider the necessity of applying cathodic protection on pipelines once again. In the operation of field pipelines special problems with external corrosion is not observed. Alternative means of electrochemical pipeline protection would be the use of anodic grounding according to patents № 125673 and № 146246 along the entire pipeline in the most dangerous places after appropriate investigations. It is known that the negative effect of cathodic polarization on the properties of the metal pipeline is the magnetization of metal, the increasing speed of occurrence of Stress Corrosion Cracking (SCC) and others. In addition, in previous decades, many studies have found reduction of individual properties of the protective coating when applied cathodic polarization: it's a decrease in adhesion and an increase in water permeability and others. Now it's proven that integral R пер decreases about 100 times in the first year of operation. Conducting large-scale field experiments will allow the industry to draw definitive conclusions.