‘Stunning’ discovery: Metals can heal themselves::Scientists for the first time have witnessed pieces of metal crack, then fuse back together without any human intervention, overturning fundamental scientific theories in the process. If the newly discovered phenomenon can be harnessed, it could usher in an engineering revolution—one in which self-healing engines, bridges and airplanes could reverse damage caused by wear and tear, making them safer and longer-lasting.
Yeah and preventing that from happening in space is rather complex task. Especially on parts that grind against each other causing the existing oxidized layer to wear off.