Long-term in vitro immersion corrosion mechanism of pure zinc fabricated by laser powder bed fusion

Pure zinc has emerged as a promising biodegradable metal for biomedical applications; however, its long-term in vitro corrosion behavior remains inadequately understood, particularly when produced via laser powder bed fusion (L-PBF). In this study, the corrosion behavior of L-PBF-fabricated pure zinc was systematically investigated during immersion in simulated body fluid (SBF) for up to 28 days, with emphasis on the evolution of corrosion products, formation of layered structures, and the influence of intrinsic fabrication defects. The results reveal the formation of a distinct multilayered corrosion product structure, where the outer layers predominantly consist of calcium phosphate compounds, Zn 5 (OH) 8 Cl 2 ·H 2 O, and Zn 5 (CO 3 ) 2 (OH) 6 , while the inner layer is mainly composed of ZnO/OH, magnesium oxide, or magnesium carbonate phases. Notably, the corrosion process proceeds through four distinct stages, which are significantly affected by L-PBF-induced defects and grain boundary features, jointly shaping the local electrochemical environment and corrosion dynamics. These findings advance the fundamental understanding of corrosion mechanisms in L-PBF-processed biodegradable zinc and highlight their implications for the design of customized biomedical implants.