Galvanic interactions between SLM-built and cast aluminium alloy interfaces in hybrid structures: a microstructural and electrochemical study

Hybrid aluminium configurations, consisting of selective laser melting (SLM)-built regions incorporated with traditionally cast substrates, give outstanding prospects for tailored functional and mechanical performance. This study examines the galvanic corrosion performance of aluminium hybrid systems comprising SLM-built regions of varying compositions on cast substrates. The electrochemical evaluations, such as open circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS), were carried out in a 1 M hydrochloric acid (HCl) solution to determine the galvanic coupling across the built–substrate interface, supported by SEM/EDS and XRD analyses. Outcomes showed that galvanic performance was hugely affected by both microstructural alterations and local compositional rising, with greater silicon content in the SLM section initiating the development of cathodic intermetallic phases that deepened localized anodic dissolution in the nearby cast matrix. The corresponding cast substrate with refined passive layers showed greater resistance to galvanic attack, whereas galvanic current was significantly higher at interfaces comprising SLM regions with higher Si content. These discoveries emphasize the necessity of microstructural compatibility and organized compositional changes in reducing galvanic corrosion in hybrid aluminium systems, thereby supporting their engagement in aerospace and marine environments.