Hydrogen diffusion process in the oxides formed on zirconium alloys during corrosion in pressurized water reactor conditions

•The oxide film in pre-transition is divided into two sub-layers, an external one, highly permeable to hydrogen and an inner protective one.•The pre-transition oxide layer presents two H-oxide interaction sites in consistency with the subdivision of the oxide layer.•Apparent diffusion coefficient of hydrogen in the inner oxide was estimated around 2.10−14cm2/s at 360°C.