Corrosion-Driven Tribofilms Enable Spontaneous Antifriction in Magnesium Alloys.

Magnesium (Mg) alloys are attractive lightweight metals but suffer from unstable friction and poor wear resistance. Here we show that the high electrochemical activity of Mg, typically viewed as detrimental, can drive the regeneration of lubricious nanoscale tribofilms during sliding. In deionized water, corrosion continuously supplies interfacial reaction products that repair mechanically disrupted films, converting severe tribo-oxidation in air into a corrosion-modulated self-regeneration process. While dry sliding typically leads to a highly unstable interface, the continuous formation of this regenerative layer in water imparts robust interfacial stability. This pathway reduces wear by more than 60% across the tested Mg-based materials. SiC-reinforced AZ91 Mg composites further stabilize the interface through load sharing, improved water spreading, and regulated aqueous corrosion. The optimized composite forms a uniform amorphous nanoscale tribofilm supported by a nanocrystalline gradient layer, giving a 77.2% wear reduction and outperforming 7050 Al under identical conditions. In contrast, Al-, Ti-, and Fe-based materials do not show comparable regeneration because their surfaces are relatively inert in water. These findings establish controlled corrosion as an active nanoscale design variable for self-adaptive tribological interfaces in Mg alloys.