In situ multiscale XCT degradation study of PEO-modified WE43 scaffolds: Correlating microstructure with hydrogen evolution

The degradation of magnesium-based implants for bone regeneration leads to hydrogen gas evolution, prompting local pH shifts, oxidative stress, and reduced mechanical integrity, factors that collectively impair cell function and tissue healing. While numerous studies aim to mitigate hydrogen release, few provide three-dimensional (3D), real-time visualization of hydrogen bubble formation in direct relation to scaffold microstructure. In this study, we present a multiscale in situ imaging approach to address this gap. Time-resolved tomography was employed to monitor hydrogen bubble nucleation and growth during magnesium scaffold degradation in simulated body fluid (SBF). Simultaneously, X-ray nano-tomography revealed scaffold microstructural features, such as intermetallic precipitates, porosity, and grain oxide inclusions, at high spatial resolution. These features not only influence degradation behavior but also play a role in the formation and uniformity of the plasma electrolytic oxidation (PEO) layer, which serves as a protective barrier. By integrating both datasets, we correlated specific microstructural characteristics with hydrogen bubble dynamics and local degradation performance. Our findings identify the degradation initiation sites and the underlying corrosion mechanisms within a 3D scaffold architecture. This combined methodology provides unprecedented insights into the interplay between microstructure, degradation and PEO layer, supporting the development of more reliable, long-lasting magnesium-based implants. Unlike previous studies that have focused on post-mortem surface characterization or overall corrosion rate measurements, this work enables in situ, time-resolved 3D observation of hydrogen evolution within additively manufactured Mg scaffolds, establishing direct correlations between LPBF-induced microstructure, PEO layer uniformity, and local degradation mechanisms. • Microstructure of Mg scaffolds governs PEO layer formation and uniformity. • Precipitate-rich regions lead to porous and non-uniform PEO layers. • Uniform PEO layers reduce H 2 release and support biocompatibility. • In situ XCT of powder melting behavior reveals how oxides are distributed in the microstructure. • In situ XCT of scaffold degradation captures early-stage differences in hydrogen evolution.