Dense Al2O3 sealing inhibited high hydrostatic pressure corrosion of Cr/GLC coating

Abstract The corrosion failure of amorphous carbon (a-C) coatings is commonly ascribed to the existence of growth microdefects, which serve as pathways for corrosive fluids to permeate the substrate. Atomic layer deposition (ALD) is renowned for its ability to augment the corrosion resistance of metallic materials. Graphite-like carbon (GLC) is one of the amorphous carbon materials dominated by hybridized sp 2 -C bonds. In this study, an ALD-deposited Al 2 O 3 layer is specially introduced on the Cr/GLC multilayer coating to solve the aforementioned corrosion risk of a-C by taking the sealing conception for defects. Compared to the as-deposited Cr/GLC coating, the coating encapsulated with Al 2 O 3 layer depicts the reduction of corrosion current density over two orders of magnitude under a wide pressure range of 0.1 ~ 15 MPa. Particularly, the presence of released Cr n+ and Fe n+ in the corrosion solution is significantly diminished, accompanying with a small quantity of Al n+ generated in sealed coating during corrosion. Microstructural analysis and electrochemical results identified that both the dense Al 2 O 3 layer offered strong safeguard for Cr elements released from multilayers, whilst amorphous carbon network inhibited the likelihood chloride penetration induced by partially infiltrated Al 2 O 3 , which made the synergistic contributions to the enhancement of corrosion resistance for Cr/GLC coating for deep-sea applications.