Nanostructured Coating for Additively Manufactured AlSi10Mg Alloy

Additively manufactured AlSi10Mg alloys are increasingly used in lightweight engineering applications but require improved surface protection to achieve long-term durability in aggressive environments. In this work, a submicrometre multifunctional nanostructured coating was developed for additively manufactured AlSi10Mg using a two-step process consisting of impulse anodizing followed by atomic layer deposition (ALD). Impulse anodizing produced a porous anodic aluminium oxide (AAO) layer that was subsequently infiltrated and sealed with an Al2O3/TiO2 nanolaminate deposited by ALD. The coating morphology was investigated using scanning and transmission electron microscopy, while corrosion performance was evaluated by neutral salt spray (ISO 9227), linear sweep voltammetry and electrochemical impedance spectroscopy. In this proof-of-concept study, the nanostructured coating showed no visible corrosion after 168 h of neutral salt spray exposure and reduced the mass change by approximately one order of magnitude. Electrochemical measurements showed the strongest barrier response for the nanostructured coating, with reproducible EIS responses across four independently measured specimens and retention of high impedance after 24 h of immersion. Micro-Vickers hardness increased from 167 HV0.1 for the uncoated substrate to 281 HV0.1 after nanostructured coating, corresponding to a 69% improvement in the effective hardness response of the coating/substrate system. The coating also modified the visible reflectance depending on the initial surface finish. For the investigated specimens and experimental conditions, these results demonstrate that impulse anodizing followed by ALD nanolaminate deposition is a promising route for producing nanostructured coatings for additively manufactured aluminium components with improved corrosion protection and modified surface hardness and optical properties.