Corrosion Resistance of Ti Coatings, Cr Coatings, and Ti/Cr Multilayer Coatings Prepared on 7050 Aluminum Alloy by Magnetron Sputtering

Abstract

Al7050 aluminum alloy substrates were coated with Cr, Ti, and Ti/Cr multilayer films via direct current magnetron sputtering to enhance their corrosion resistance. A comprehensive analysis, employing SEM and XRD, characterized the coatings’ morphology and composition, while electrochemical experiments assessed their corrosion performance. The Cr coating, despite exhibiting the largest thickness (588 nm), revealed a porous microstructure with inherent structural weaknesses. Conversely, the Ti coating, while possessing a dense structure, presented a significantly reduced thickness (96 nm). The Ti/Cr multilayer coating, with a thickness of 242 nm, achieved an optimal balance between structural density and overall thickness. Critically, the layered architecture of the Ti/Cr multilayer coating effectively impeded crack propagation and facilitated the formation of tortuous corrosion pathways. This intricate pathway morphology significantly hindered the diffusion of the corrosive medium, resulting in a notably low corrosion current density of 3.83 × 10−7 A·cm−2. Comparative analysis revealed that the corrosion current density of the Ti/Cr multilayer coating was substantially lower than that of both the Cr and Ti coatings, demonstrating improvements of 2386% and 222%, respectively. These findings underscore the pivotal role of the multilayer structure in augmenting the corrosion resistance of aluminum alloys by providing a superior barrier to corrosive medium.