P. E. Yudin, O. S. Bondareva, and I. S. Trofimov

USING TRANSIENT RESISTANCE MEASUREMENTS TO CALCULATE THE DIFFUSION COEFFICIENT OF THE WATER MEDIUM IN THE INTERNAL AND EXTERNAL POLYMER COATINGS OF OILFIELD PIPES

The recent development of stages in the degradation of internal corrosion-resistant coatings on pipes is necessary for predicting their trouble-free service life. The current absence of in-line inspection methods for pipes with internal coatings imposes additional requirements for the accuracy of life cycle assessment. The first stage of operation involves polymer saturation with the transported fluid, and the time it takes is directly related to the diffusion coefficient. Using reference data is not appropriate since they are provided for typical resins without special fillers. Internal and external pipe coatings involve creating a composite layer ensuring minimal environmental penetration to the metal substrate, which is achieved through the use of special resins, hardeners, and inorganic fillers. There are many methods for determining the diffusion coefficient; however, all are used for research purposes, and they are not included in regulations for coatings. This study proposes a new method for calculating the diffusion coefficient using data on transient resistance obtained in accordance with the requirements of GOST 51164-98 (a standard industry regulatory document, with testing procedures mastered by all testing laboratories). The correctness of the results is confirmed by comparison with reference data for similar polymer materials. The paper also demonstrates that the obtained values significantly depend on temperature and suggest tightening the current experiment requirements.

Acknowledgment: We are grateful to Prof. A. P. Amosov, head of the Department of Metal Science, Powder Metallurgy, and Nanomaterials at the SSTU, for his criticism of our manuscript. We also appreciate the assistance from the staff of the Samara RPC LLC in obtaining the experimental data.

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