Core-shell particle engineering overturns conventional purity-corrosion dependence in Mg alloys

Magnesium (Mg) alloys offer high weight-saving potential for transportation technologies; however, their use remains constrained by poor corrosion resistance, which is strongly dependent on alloy purity. The presence of impurities, such as iron (Fe), severely degrades the corrosion resistance of Mg alloys. Herein, we present an alloy design strategy that substantially improves the corrosion resistance, even when using low-purity Mg. Our method produces core-shell particles, where an Fe-rich core is encapsulated by an Fe-depleted shell embedded in the Mg matrix. This shell acts as a local microscavenger that isolates the core and suppresses impurity-triggered corrosion, resulting in corrosion resistance achievable only when using ultrahigh-purity Mg. This approach provides a practical pathway for the development of high-performance Mg alloys without relying on costly purification.