Can sacrificial metals prevent the rusting of an old car?
In general, sacrificial anodes only work when all parts of the structure are submerged in something that will conduct electricity. For the zinc sacrificials used in boats, water acts as the conductive medium. For the magnesium sacrificials used in your example, the ground itself will actually conduct charge. If you just bolt sacrificials to a car’s body, they won’t do much because the entire structure of the car isn’t surrounded by a conducting medium.
