This solution from nautism (engines and hulls of boats, for example) makes it possible to concentrate the corrosion on this sacrificial anode which one we will have to replace once deteriorated. The effectiveness of these anodes is such that today it allows many boats (fishing, tourism, ...) to navigate without any protection against corrosion. This is the case of silver gray raw aluminum boats that can be seen in some ports.
The principle of the sacrificial anode is to use a piece with a metal whose electrical potential is very low. The foil circulating in salt water (conductive) will behave like an electric battery. The anode will then give its ions instead of aluminum and will corrode in priority.