Acta Metall Sin  2020, Vol. 56 Issue (2): 137-147    DOI: 10.11900/0412.1961.2019.00237
 Current Issue | Archive | Adv Search |
Corrosion Behavior of X80 Steel Welded Joint in Simulated Natural Gas Condensate Solutions
CHEN Fang,LI Yadong,YANG Jian,TANG Xiao,LI Yan()
School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao 266580, China
Abstract

Carbon steels are widely used as transportation pipelines in oil and gas fields and welding is one of the main ways of connecting pipeline steel. The welded joints are easily corroded due to the difference in composition, structure and properties of the various components. The effect of content of HAc, Cl-, ethylene glycol (MEG) and temperature (T) on the corrosion behavior of welded joint of X80 steel in a simulated natural gas condensate saturated with CO2 was studied by the orthogonal experimental design, weight loss experiment and electrochemical experiment. It is demonstrated that the corrosion rate of the welded joint is significantly higher than that of the base metal because of the formation of macroscopic corrosion galvanic cells, and the corrosion of the weld metal as an anode region is accelerated to become a weak link of the welded joint. The significance of the four factors on the corrosion process is: c(HAc)>T $\gg$c(Cl-)>c(MEG), c(HAc) and T are the main factors affecting the corrosion behavior, and c(Cl-) and c(MEG) are secondary factors. Base metal and weld metal corrosion tendencies increase with increasing temperature. Because ferrous acetate is less protective as a corrosion product, as the c(HAc) increases, the impedance of the base metal and weld metal decreases, and the corrosion rate increases. Based on the results of orthogonal experiments, a multivariate linear regression equation was established.

 ZTFLH: TG172
Fund: National Natural Science Foundation of China(41676071);Fundamental Research Funds for the Central Universities(18CX05021A)
Corresponding Authors:  Yan LI     E-mail:  yanlee@upc.edu.cn