Influence of the protective potential distribution of a steel underground pipeline on electrochemical corrosion processes

Purpose. To distinguish the influence of inserts, with high resistance to the flow of electric current, which causes deviations of the protective potential along the length of the pipeline from its classical form. Obtaining analytical dependencies in the form of a transfer function that relates the input and output signal. That allows predicting dangerous deviations of the protective potential, the combination of which indicates a worsening of corrosion protection. Methodology. To achieve this purpose, the methods of theoretical analysis, mathematical and computer modeling, and spectral analysis of signals are used. The initial information characterizing the operating modes of adjacent cathode stations is obtained and verified based on the data from monitoring the protective potential along the tracks of underground steel pipelines of various designs. The parameters taken into account in the calculations include the geometric dimensions of the pipeline, soil condition, insulation resistance, etc. By analyzing the results of measurements obtained with the help of a recording voltmeter “PRIMA 2000” and a detector “Sprut-17”, the growth of corrosion risks arising from the repair of a damaged section of an underground steel pipeline using polyethylene pipes is established and analyzed in detail. Findings. A modeling of the operating modes of adjacent cathodic protection stations, between which there is a section of polyethylene pipeline, with the electrical parameters of an underground steel pipeline is performed. Based on the information obtained, attention is drawn to possible rational energy operation modes of adjacent cathodic protection stations, the main task of which is to reduce the corrosive effects of the polyethylene section of the underground pipeline. Originality. The paper is to substantiate the possibility of such a negative impact of a polyethylene insert in a steel pipeline, which increases the corrosion hazard. The dependence is obtained of the protective potential of cathodic protection stations in sections of the pipeline with polyethylene inserts from the operating modes of the electrical system with energy converters and their voltage generation algorithms at the output of cathodic protection stations. Practical value. The paper analyzes the signals of rectifiers of cathodic protection stations and power switches commutation modes that are aimed at improvement of the complex corrosion situation on low and medium pressure pipelines, which are characterized by heterogeneity of structure, especially within populated areas. The proposed modes of operation of adjacent cathodic protection stations reduce the level of corrosion hazard caused by the massive introduction of polyethylene pipes and their widespread use for repairing damaged sections of steel pipelines.