What meaning is the anode in aluminum alloy anode

Sacrificial anode method is a common anticorrosion method.

An aluminum anode, which is an anode block, is used to prevent corrosion. Hang it on a pipe, for example, and it corrodes, whereas iron does not. Because the aluminum is in front of the iron, it protects the pipe from corrosion. This method is called a sacrificial anode.