Regulating the Degradation and Cytocompatibility Behavior of Additively Manufactured Pure Zinc Through Post‐Processing Surface Treatments

ABSTRACT Zinc‐based biodegradable metals are promising implant materials, and additive manufacturing offers a powerful route for their patient‐specific fabrication. However, process‐induced surface defects can accelerate degradation and compromise biocompatibility, rendering post‐processing essential. In this study, four post‐processing strategies—chemical polishing (CP), hydroxyapatite sandblasting (SB), electrochemical polishing (EP), and mechanical polishing (MP)—were systematically investigated for the first time to regulate the degradation behavior and cytocompatibility of laser powder bed fusion (LPBF) fabricated pure Zn. MP generated the smoothest surface, whereas SB, CP, and EP increased roughness or introduced defects. In vitro immersion tests revealed over an order‐of‐magnitude difference in degradation rates: CP and EP exhibited the highest corrosion rates (2.1 and 1.2 mm year −1 , respectively), whereas MP yielded the lowest (0.16 mm year −1 ). Comprehensive electrochemical analyses combined with surface and corrosion product characterization revealed that corrosion resistance is governed not simply by surface roughness but primarily by the integrity of the inner dense passive layer. Cytocompatibility correlated strongly with Zn 2+ release: MP maintained excellent cell viability (> 70%) and low lactate dehydrogenase (LDH) release (< 30%) even at 50% extract concentration, meeting biosafety requirements. In contrast, SB improved cytocompatibility only at a 25% extract concentration, whereas CP and EP showed no improvement at any tested concentration. Overall, MP is identified as the most effective post‐processing strategy for enhancing surface quality, controlling degradation, and ensuring biocompatibility in additively manufactured zinc implants. These findings provide important guidance for the surface engineering of LPBF biodegradable Zn‐based biomaterials.