Study on hydrogen permeation behavior of Q235 pipeline steel under stray current interference from urban rail transit system

Purpose Stray current generated from rail transit system poses great integrity threat on surrounding buried metal pipelines, especially for oil and gas pipelines. Apart from corrosion damage, hydrogen damage will also occur in widely distributed cathode area on the pipeline surface due to locomotive operating conditions and location. However, limited studies focus on the hydrogen permeability characteristics of Q235 pipeline steel under stray current interference. The purpose of this paper is to study hydrogen permeation behavior of Q235 steel under stray current interference from urban rail transit system. Design/methodology/approach Since hydrogen permeation is prerequisite for inducing hydrogen damage, this study deals with hydrogen permeation behavior of Q235 pipeline steel under direct stray current interference. Besides, the impact of surface defect and pH value on the hydrogen permeation behavior was also studied with electrochemical techniques. Nonlinear fitting was conducted with high accuracy to explore the quantitative relationship between hydrogen permeation process and influencing factors. Findings Experimental results show that stray current flowing into metal substrate could obviously promote hydrogen permeation process, and surface defect and decreasing pH value could also enhance hydrogen permeation effect. Hydrogen penetration kinetic parameters: hydrogen flux J and diffusion coefficient D were found to be positively correlated with increasing amplitude of stray current density and area of surface defect, and negatively correlated with the increasing environmental pH value. Originality/value This study clarifies main influencing factors of external environment on the hydrogen permeation under stray current interference. Experimental results of this study are of great significance for daily maintenance of buried gas pipelines adjacent to rail transit system and prevention of hydrogen-induced cracking from the perspective of influencing factors.