A full-lifetime model for the biodegradation of molybdenum under physiological conditions

Molybdenum (Mo) is an emerging material for resorbable metallic implants due to its favorable biocompatibility and mechanical properties. Understanding its complete degradation behavior under physiological conditions is critical for predicting in vivo performance. Here, we present a macroscopic, kinetic model that quantitatively describes the degradation pathway of Mo, including sequential formation of oxide phases (MoO 2 and MoO 3 ) and the subsequent dissolution of the final soluble species. The model is based on coupled first-order rate equations, with parameters that can be directly identified from experimental data. Fits to corrosion measurements and in vitro dissolution experiments reveal excellent agreement with the model, capturing both the oxide formation kinetics and the solubility-driven release of molybdenum into the medium. This approach enables the quantitative separation of multi-stage oxidation and dissolution processes, providing a predictive framework for the complete service life of molybdenum-based implants.