Combined dual-exposure test and DFT investigations into effects of interstitial hydrogen on oxide film of Alloy 600 in high temperature water

The influence of interstitial hydrogen (Hi) in the oxide film of Alloy 600 was investigated using in-situ H charging via dual-exposure test and DFT calculations. H charging modified the oxide film by reducing the oxide particles in the outer oxide layer and transforming the inner oxide film from an uneven thickness and element distribution to a thicker oxide film with a homogenous element distribution. DFT calculations revealed that Hi enhanced the Cr-O interaction while facilitating electron loss in Ni. Additionally, Hi obviously enhanced O diffusion along the Ni-Cr surface, promoting the initial oxidation stage of the Ni-Cr surface.