Low temperature UV assisted sol-gel preparation of ZrO2 pore-sealing films on micro-arc oxidized magnesium alloy AZ91D and their electrochemical corrosion behaviors

In this paper, a unique UV assisted low temperature sol-gel method was developed to prepare ZrO2 pore-sealing film on the micro-arc oxidation (MAO) layer coated magnesium alloy. It was found that 100 degrees C UV irradiated ZrO2 film (UV-ZrO2) showed a denser surface, as compared with those prepared by traditional sol-gel route and heat treated at 100-425 degrees C. Correspondingly, the magnesium alloys with UV-ZrO2 sealed MAO layer showed an enhanced anti-corrosion property. The photochemistry analysis indicated that UV light can break the organic species at low temperature, resulting in the amorphous ZrO2 film with more flat surface. Therefore, this kind of ZrO2 films irradiated by UV light at low temperature can play a good sealing role in protecting the MAO layer coated magnesium alloys from corrosion. (C) 2019 Elsevier B.V. All rights reserved.