Background Laser powder bed fusion (LPBF) is a 3D printing technique that rapidly and selectively melts metal powder via laser irradiation which then solidifies in the prescribed pattern before a new layer of powder is spread across the surface and the process repeats. LPBF is the most common 3D printing method used with stainless 316L alloys. It offers advantages in the biomedical field by improving mechanical properties such as fracture toughness and strength, enabling complex, patient-specific geometries and reducing material waste, crucial for applications like stents and implants. Nevertheless, consideration of corrosion behavior is crucial in assessing the longevity of these materials in aqueous environments.

Methods Various corrosion tests were conducted on LPBF-produced stainless steel alloys. These tests included polarization scans in acidic environments to assess corrosion resistance, mass loss testing in ferric chloride and sodium chloride solutions to measure susceptibility to localized corrosion, and galvanostatic etching in ammonium persulfate to identify microstructural sites prone to selective attack. Transmission electron microscopy was used to analyze local chemical composition differences at a microscale. Scanning electron microscopy and optical microscopy characterized the microstructure, focusing on features susceptible to localized corrosion.

Results Corrosion testing showed lower rates for LPBF-produced material compared to conventionally processed stainless steel, suggesting enhanced corrosion resistance. However, post-test analysis revealed various localized corrosion forms, including dissolution through cellular structures formed during the rapid solidification inherent to LPBF. Transmission electron microscopy uncovered local variations in elements critical to corrosion resistance like chromium and molybdenum, impacting corrosion behavior. These findings emphasize the complexity of corrosion mechanisms in LPBF materials and the importance of detailed microstructural analysis.

Conclusion The study identified lower corrosion rates in LPBF-produced stainless steel alloys but also highlighted localized corrosion pathways through cellular structures, pores formed due to inadequate metal fusion, and other microstructural features inherent to the LPBF process. Advanced microscopy techniques revealed elemental variations influencing corrosion behavior. Future research should explore diverse environments, long-term corrosion performance, and predictive models linking microstructure to corrosion behavior. Addressing these challenges is vital for developing corrosion-resistant materials for biomedical applications and enhancing device performance in clinical settings.