ВЛИЯНИЕ ТЕМПЕРАТУРЫ НА ЭЛЕКТРОХИМИЧЕСКИЕ ПАРАМЕТРЫ ВНУТРЕННИХ АНТИКОРРОЗИОННЫХ ПОКРЫТИЙ

The paper examines the effect of temperature on the electrochemical characteristics of the inner epoxy-phenolic anticorrosive coating of tubing using the high-pressure electrochemical cell (HPHM) developed by the authors, which provides measurements by the method of electrochemical impedance spectroscopy according to the in situ principle. The tests were carried out at a temperature of 90 °C, a pressure of 80 atm (PH₂S = 10 atm, PN₂ = 70 atm) for 30 days, followed by a gradual decrease in temperature to 80 °C. Equivalent electrical circuits were selected from the obtained impedance curves and changes in their parameters were analyzed. It was found that the most intensive decrease in coating resistance occurs at the initial stage of testing: during the first three days, coating resistance decreased from 9.70 to 6.72 MOhm ∙ cm ². Subsequently, the degradation rate significantly decreased, and changes in CPE1 parameters indicate that the main water absorption of the coating occurred in the first hours or days of testing. Starting from the third day, elements characterizing the processes in the sub-film area appear in the equivalent scheme, which is associated with the formation of corrosion products under the coating. After the completion of the high temperature tests and the subsequent lowering of the temperature from 90 to 80 °C, the resistance of the coating increased from 4.86 to 27.23 MOhm· cm ², and the resistance of the sub-film region increased by more than 10 times. The results obtained indicate a significant effect of temperature on the measured electrochemical parameters of the coating due to changes in the mass transfer rate and electrochemical processes. It has been shown that conducting electrochemical studies directly under the influence of operational factors on an in situ basis allows obtaining more reliable information about the actual state of protective coatings compared to measurements after the tests are completed. The developed high-pressure electrochemical cell can be used for comparative assessment of protective properties of various types of internal coatings and study of mechanisms of their degradation under conditions as close as possible to operational ones.