Electrochemical Corrosion Behavior of Hybrid SLM–Cast Aluminum Structures Under Extreme pH Conditions in 3.5 wt% NaCl

This study investigates the corrosion behavior of hybrid aluminum structures fabricated by integrating selective laser melting (SLM) with conventional casting, under extreme pH conditions (2 and 12) in a 3.5 wt% NaCl solution. Separate analyses were conducted on the SLM-built and cast portions of the hybrid samples to assess their electrochemical responses. A comprehensive set of techniques such as Open Circuit Potential (OCP), Electrochemical Impedance Spectroscopy (EIS), chronoamperometry, and Potentiodynamic Polarization (PDP) were employed. Additionally, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) were used for post-corrosion surface and phase characterization. Outcomes revealed that the alkaline environment (pH 12) initiated more aggressive localized corrosion in both regions, driven by unstable passive film formation and microstructural susceptibility. On the other hand, the acidic condition (pH 2) led to a more uniform corrosion pattern with relatively moderate deterioration. These discoveries pinpoint the vital role of environmental pH, alloy chemistry, material selection, and microstructural uniformity in governing the corrosion resistance of hybrid AM–cast aluminum systems, with implications for performance in marine and industrial settings.