A synergistic effect of dissolved oxygen, $$HCO_3^-$$ H C O
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A synergistic effect of dissolved oxygen, HCO3− , and Cl− on the electrochemical corrosion behavior of X70 pipeline steel in the oilfield soil environment Fei Xie1,2 · Zeqi Wang1 · Dan Wang1,2 · Siwen Yin1 Received: 26 March 2020 / Accepted: 6 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The pipeline corrosion phenomenon in the Liaohe oilfield has become severe in recent years, and X70 steel has been extensively employed as a high-strength pipeline material in this oilfield. Therefore, in this study, the electrochemical corrosion of X70 steel in the simulated Liaohe oilfield soil solution was investigated under the combined action of dissolved oxygen (DO), HCO−3 , and Cl−. The corrosion behavior of X70 steel was examined by both the orthogonal test and the fitting analysis. It was found that DO, HCO−3 , and C l− had profound influences on the corrosion behavior of X70 steel. When concentrations − − of HCO3 , and Cl were stable in the solution, both current corrosion density and corrosion rate gradually increased with the increasing DO concentration. When concentrations of DO and Cl− were constant, the current corrosion density also increased with the increasing HCO−3 concentration. When concentrations of DO and HCO−3 were constant, the current corrosion density decreased significantly with the decreasing C l− concentration. In the soil solution, the corrosive effect of C l− ions were found − to be the least among all three factors, whereas HCO3 ions had the greatest influence on the corrosion behavior of X70 steel. Keywords X70 pipeline steel · Dissolved oxygen · HCO−3 · Cl− · Pitting corrosion
1 Introduction Pipeline transportation is seen as the most economical and safe mode of transportation in China and even in the world. Most pipelines in transportation are built in in the ground. The soil itself is a complex system, and its corrosion on pipelines is also the result of the comprehensive action of various factors [1]. Buried pipelines are generally protected by coatings to avoid corrosion [2]. However, due to construction processes, environmental changes, internal and external stresses, and other factors, coatings are sensitive to damage [3]. Ruptured pipelines cause fatal accidents and incalculable economic losses [4]. Anion and cation * Fei Xie [email protected] * Dan Wang [email protected] 1
College of Petroleum Engineering, Liaoning Shihua University, Fushun 113001, China
Liaoning Key Laboratory of Oil and Gas Storage and Transportation Technology, Fushun, China
2
concentrations, pH value, temperature, humidity, stress, salinity, and microorganisms in soil have different effects on pipeline corrosion [5–8], and their analytical methods are also different [9]. Caceres et al. [10] studied the effects of dissolved oxygen (DO) and NaCl on carbon steel and found that all kinetic parameters, except for AC current density and Tafel slope, were significantly dependent on the concentrations of DO and NaCl. Due to pitting corrosion, oxidation kinetic par
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