This is the katone protection of the car body against corrosion. The point is that negative potential is applied to the protected part of the car, and the protective detail is positive. The result is the rusting of the protected part, the so-called "sacrificial electrode". To protect against corrosion, a small negative potential is applied to the vehicle body (great potential can increase the rate of rust) and the sacrificial anode is a small positive. Ruin the part under the hood is the sacrificial anode. Different parts of the sacrificial anodes can play different parts on different models of cars. Like the hinged door.
