Microstructure and Hydrogen Permeation Resistance of Zirconium Hydride Coated by Micro Arc Oxidation Process in Na5P3O10 Solution

A dense and continuous coating with less cracks and holes was obtained by micro-arc oxidation (MAO) process in an electrolyte composed of Na5P3O10+NaOH+Na(2)EDTA under the constant voltage mode. The surface and cross-sectional morphologies, phase structures and chemical composition of the coatings were characterized by scanning election microscopy (SEM), X-ray diffraction (XRD) and energy disperse spectroscopy (EDS), respectively. The hydrogen permeation performance of the oxide films was evaluated by vacuum dehydrogenation experiment and XRD. The results show that the obtained coating with an average thickness of 78 mu m contains a transition layer, a dense layer and a loose layer. The coating is mainly composed of M-ZrO2, T-ZrO2 and C-ZrO2, and M-ZrO2 accounts for about 90%. The PRF (permeation reduction factor) value of the oxide film reaches up to 11.7, which indicates that the ZrO2 ceramic coating formed on the surface of ZrH1.8 has a superior hydrogen anti-permeation effect.