Simulation of hydrogen diffusion in pipeline steel under pre-cracks and sour environment

Purpose: In this work, the influences of different field operating parameters (pH and partial pressure of H2S) and crack types (isolated and cluster cracks) are investigated on the distribution of hydrogen concentration in pipeline steel. Design/methodology/approach: A numerical simulation based on the finite element method was performed using the COMSOL Multiphysics software to achieve the objectives. Findings: Hydrogen concentration and total hydrogen flux are increased when pH decreases and [Formula: see text] increases. Besides, the crack flanks are the most appropriate areas for hydrogen diffusion. Accordingly, the areas including step-wise cracking absorb more atomic hydrogen, and the space between the upper surface of the crack and the outer wall is no longer protected. Furthermore, the computational results reveal how a blister on the top of a cluster crack can be crucial by providing enough area for hydrogen to diffuse, and the area between the crack top surface and the outer wall could no longer be protected from hydrogen flux. Originality: Evaluation of hydrogen concentration in different areas of isolated and cluster cracks under different field operating conditions (pH and [Formula: see text] is not yet understood, which is discussed in this study.