NUMERICAL ANALYSIS OF HYDROGEN DIFFUSION AND DISTRIBUTION AT CORROSION DEFECT ON AGED PIPELINES FOR HYDROGEN SERVICE

Using existing natural gas pipelines to transport hydrogen blended natural gas is an important way to achieve efficient hydrogen transportation. However, the existing pipelines may contain corrosion defects, which can affect the diffusion and distribution behavior of hydrogen atoms, further resulting in hydrogen embrittlement and pipeline failure. This study applied the numerical analysis method to simulate the hydrogen atom redistribution in interstitial lattice sites and in trapping sites of X52 steel pipeline with corrosion defect by coupling stress field and hydrogen diffusion field. It was found that under applied tensile strain, the hydrogen atoms accumulated at corrosion defect due to local stress concentration. The maximum lattice concentration was located on the outer pipe wall, and the maximum trapped concentration occurred at the defect center. And both of them elevated with tensile strain and initial concentration increasing, although there was a difference of several orders of magnitude between them. The increase of temperature reduced the maximum concentration. Besides, the maximum hydrogen concentration in trapping sites also increased with the higher binding energy. The proposed model can be used to determine the hydrogen concentration and distribution behavior at corrosion defect for HE prediction of corroded pipeline.