Aluminum phosphate sealing to improve deuterium permeation resistance of α-Al2O3 coating prepared by MOD method

Abstract

α-Al2O3 coatings prepared by metal-organic decomposition (MOD) method were sealed by aluminum phosphate adhesive. The sealed MOD α-Al2O3 coatings with a thickness of about 51 μm and the main phases in the sealed coatings are α-Al2O3 and orthophosphate AlPO4. The aluminum phosphate adhesive showed good penetration into the coatings and effectively filling the defects, such as pores and cracks, in the α-Al2O3 coatings. The automatic scratch test result showed that the alumina coatings have a bonding strength greater than 100 N and aluminum phosphate sealing treatment has little effect on the adhesion of the Al2O3 coatings. The electrochemical hydrogen (ECH) permeation and deuterium gas-driven permeation (GDP) results showed that the aluminum phosphate sealing treatment could be a promising way to improve the hydrogen/deuterium permeation resistance of the thick MOD coatings. A microscopic model was proposed to understand the sealing mechanism of aluminum phosphate adhesive precursors.