This paper reports the hydrogen permeation behavior of an X-70 pipeline steel in a synthetic near neutral pH field solution under both galvanostatic and potentiostatic conditions. The hydrogen flux through the steel exposed to the solution is influenced by the chemical reactions at the steel surface on the charging side. Results from tests done under potentiostatic and galvanostatic conditions were compared to predictions based on different boundary conditions assumed in solving Fick’s diffusion equations. Constant concentration boundary conditions gave the best fit. It was also found that the diffusible hydrogen generated in a near neutral pH soil environment is likely to be 3 to 10 times lower than the minimum hydrogen concentration required to initiate hydrogen blistering in pipeline steels.

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