Luca Magagnin, Alberto Palamini, Luca Nobili, Politecnico di Milano, Milano, Italy
Aluminum alloys 6082 and 7075 are widely employed in transportation and structural applications due to their low density and good corrosion resistance. A duplex surface treatment consisting of anodizing followed by diamond-like carbon (DLC) deposition was investigated to enhance both corrosion and wear resistance while preserving the lightweight advantages of aluminum alloys.
The study focused on optimizing anodizing conditions to produce hard, thick, and homogeneous anodic interlayers suitable for subsequent DLC coating. After appropriate pretreatment sequences, samples were anodized in different electrolytic baths under controlled conditions. The anodized films were characterized by Vickers microhardness testing, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) to evaluate morphology, thickness, and chemical composition. The hardest anodic layers for each alloy were selected, with and without sealing in boiling water, and subsequently coated with DLC using Plasma Assisted Chemical Vapor Deposition (PACVD). The corrosion and wear performance of the treated specimens was assessed by linear potential scan voltammetry and wear resistance testing, respectively, and compared to untreated alloys. The results demonstrated that specific anodizing conditions produced significantly improved interlayers that enhanced DLC effectiveness. In particular, sealed samples anodized under optimized electrolyte compositions exhibited superior resistance to both corrosion and wear. The duplex anodizing/DLC system proved to be an effective strategy for tailoring surface properties of 6082 and 7075 alloys, providing a balanced combination of hardness, electrochemical stability, and tribological performance suitable for advanced engineering applications.