Nature Materials, Published online: 27 March 2026; doi:10.1038/s41563-026-02563-0Mg3(Sb, Bi)2 is a potential next-generation thermoelectric with cost-effectiveness compared with Bi2Te3; however, it suffers from poor moisture corrosion resistance. Here, an anodic protection strategy is presented that substantially reduces corrosion, enabling the 28-day performance of a module in high-temperature and high-humidity environment.