Intestinal bacteria-accelerated corrosion of biodegradable Zn–Mg alloys: Composition-dependent degradation behavior

Zinc-based alloys are promising biodegradable materials for gastrointestinal devices, yet their degradation behavior in the complex, microbe-rich intestinal environment remains poorly understood. In this study, the corrosion behavior and underlying mechanisms of pure extruded Zn, Zn–0.03Mg, and Zn–0.05Mg alloys were systematically investigated in the presence of two representative intestinal bacteria, Lactobacillus acidophilus and Lactobacillus plantarum. Microstructural analysis revealed that trace Mg addition significantly refined the grain size of Zn alloys. Mechanical testing demonstrated that the yield strength of Zn–Mg alloys increased by approximately 3-fold compared to pure Zn, with nearly double the elongation after fracture. Electrochemical measurements, hydrogen release tests, weight loss analysis, and surface characterization showed that microbial activity accelerated the corrosion rate by 3–5 times. Notably, Mg incorporation effectively suppressed corrosion under both sterile and microbial conditions. Mechanistic analysis revealed that the acidic environment generated by bacterial metabolism was the primary driver of enhanced degradation. This work establishes a “structure–property–corrosion” relationship, offering a theoretical foundation for the mechanical optimization and degradation control of zinc-based biodegradable implants for gastrointestinal applications.