In-situ study on hydrogen permeation inhibition by corrosion inhibitors during localized corrosion via permeating hydrogen signal

Corrosion inhibitors provide excellent protection for oil and gas pipelines and associated equipment. However, research on corrosion inhibitors has primarily focused on evaluating macroscopic corrosion rates, while their inhibitory effect on hydrogen permeation has been largely overlooked. In this study, using spatially resolved scanning Kelvin probe (SKP) technology, we comparatively analyzed the effectiveness and underlying mechanisms of oleic imidazoline (OIM) and 2-mercaptopyrimidine (2-MP) in inhibiting hydrogen permeation. The results demonstrated that both inhibitors reduced the permeating hydrogen signal in a concentration-dependent manner. Notably, 2-MP exhibited superior performance to OIM. In the SKP tests, 300 ppm of 2-MP almost eliminated the permeating hydrogen signal. OIM primarily acts by suppressing localized corrosion, thereby reducing hydrogen generation at the source. In contrast, 2-MP functions through a dual mechanism involving both corrosion inhibition and a direct barrier effect against hydrogen penetration, facilitated by its stable adsorbed film. These findings provide a theoretical basis for designing bifunctional inhibitors with both corrosion inhibition and hydrogen resistance.