Process-Induced multiscale features and their impact on the corrosion kinetics of additively manufactured SS316L

The accelerated development of metal additive manufacturing (AM) underscores the critical influence of process-induced multiscale features; spanning from the nanoscale to the macroscale; on corrosion behavior and electrochemical performance. While melt-based AM methods such as laser powder bed fusion (LPBF) have been extensively evaluated, the corrosion performance of components produced via bound metal deposition (BMD), a sinter-based extrusion AM technology, remains largely unexplored. Motivated by this gap, the interplay between BMD's multiscale features, microstructural characteristics, and surface electrochemistry is examined, and a comprehensive multiscale corrosion analysis of BMD-fabricated SS316L is presented, with performance benchmarked against LPBF and wrought counterparts in a CO2-saturated brine. Using an integrated characterization approach covering four distinct scales; nanoscale (TEM-EDS elemental segregation, SKPFM surface potential mapping), microscale (EBSD), mesoscale (cross-sectional SEM), and macroscale (XCT volumetric porosity assessment); coupled with electrochemical testing (EIS, PDP) and post-corrosion surface analysis (XPS and SEM/EDS). The results revealed that BMD-fabricated SS316L outperforms both LPBF and wrought counterparts despite higher bulk porosity (1.4% for BMD vs. 0.15% for LPBF). BMD samples exhibited enhanced corrosion resistance (4.06 mmpy corrosion rate for BMD vs. 11.48 mmpy for LPBF) due to a uniform equiaxed grain structure, the absence of nanoscale segregation, and a stable Cr/Mo-oxide-enriched passive film. This work establishes a multiscale framework for corrosion evaluation and expands the industrial applicability of BMD in critical, corrosion-sensitive environments.