Study On Corrosion Behavior Of Long-distance Pipelines In The Northwest Of West To East Gas Transmission

With the rapid development of society,pipeline transportation has become the most important transportation mode in the modern era.West-East Gas Transmission is one of the important transportation pipelines in China.In recent years,because the West-East Gas Pipeline has been buried in the soil for a long time,the soil environment in different locations has been different,causing a certain degree of corrosion damage to the pipeline at different locations,which seriously threatens the normal transportation of pipelines.This paper mainly studies the corrosion behavior of long-distance pipelines in the northwest section of the West-East Gas Pipeline,analyzes the causes of the corrosion,and determines the research scheme,experimental methods and actual operating conditions.The temperature and pH of the main corrosion factors in the soil were selected for the study.The electrochemical corrosion behaviors of X70 pipeline steel in soil simulation solutions in four regions of Shaanxi,Xinjiang,Gansu,and Ningxia were studied by means of electrochemical tests,scanning electron microscope observations,and weight loss methods.Polarization curves and AC impedance spectra were obtained..Through various factors of the corrosion test of buried pipelines,comparative analysis of polarization curve test results to determine the impact of various factors on the corrosion potential of the test material Ecoor and annual corrosion rate.By means of AC impedance spectroscopy,an equivalent circuit was established to analyze each factor and determine the influence of each factor on the corrosion behavior and the degree of significance.The experimental results show that with the decrease of pH and the increase of temperature,the resistance in the soil simulation solution continuously decreases,the corrosion rate of X70 steel increases,and the corrosion becomes more severe.At pH 5,the corrosion rate reached a maximum.In the Ningxia section of the soil the most serious corrosion.With the increase of infiltration time,the corrosion rate of X70 in the soil simulation solution in four areas is constantly decreasing,and the number of corrosion pits is continuously increasing.After the test,the microscopic corrosion morpHology of the sample after removing the product film was observed,and local corrosion of the sample occurred.In orthogonal experiments,the influence of temperature and SO₄^2-on corrosion rate is most significant.