Influence of Thermal Oxide Layers on the Hydrogen Transport through the Surface of SAE 1010 Steel

Most research on the hydrogen embrittlement of steel dealt with the interaction of hydrogen with the metal bulk microstructural features, whereas the first contact with hydrogen-containing environments occurs at the metal surface. Steel (when un-polarized) is always covered with an oxide layer, varying in composition and thickness. The impact of the oxide layer on the hydrogen transport is, however, not fully understood. This study focused on the effect of controlled pre-formed thermal oxide layers at the exit side on the hydrogen transport through the surface of SEA 1010 steel, considering two distinct thermally produced oxide types as test cases. Results demonstrated that thermal oxides can greatly limit hydrogen diffusion, with bilayers (hematite/magnetite) having a greater effect compared to magnetite layers. Increased oxide thickness resulted also in greater limiting diffusion. The main objective of this manuscript is to provide experimental evidence concerning the effect of oxide layers on the hydrogen transport through steel. Model thermal oxide layers were used to emphasize the importance of considering the surface characteristics when investigating hydrogen transport through metallic components.