The best anode material is an aluminum anode,as far as the environment is concerned, aluminum is a better alternative than zinc because it does not contain cadmium and has no damage to the environment.

The three most reactive materials used for sacrificial anodes are zinc, aluminum, and magnesium, which have different properties and uses.

First, electric potential. When immersed in water, all metals produce a negative voltage (compared to a reference electrode). The lower the voltage, the higher the activity of the metal, e.g. -1.6 V for magnesium anode, -1.1 V for aluminum anode, -1.05 V for zinc anode.

Now compare these voltages to metals commonly used in the ocean: bronze: -0.3 V, steel: -0.6 V, and aluminum: -0.75 V, if used in hulls, stern drives, or outboard motors. Reference electrode: Silver-chloride (Ag/AgCl) reference electrode.

To provide protection, the highest possible voltage difference needs to be between the sacrificial anode and the metal to be protected. For example, if zinc is used to protect a bronze propeller, then a "drive or protection voltage" of -0.75V is sufficient. If an aluminum anode is used, the voltage increases to -0.8V. The magnesium anode is increased to -1.3V. The larger the voltage difference, the more protection you get. However, some materials (aluminum) may be "overprotected", more on this later.

Second, the current capacity. The anode creates a voltage difference, which drives the flow of current between the anode and the metal being protected. The larger the capacity, the longer the protection time. For a particular anode, the rate of current depends on the surface area of the anode, and the lifetime depends on the mass. For an anode of the same size, its relative capacity is: zinc: 100 days; Magnesium: 30 days; Aluminum anode: 130-150 days. So if you replace the "100 days" zinc anode with a magnesium anode, it will only last for 30 days. Aluminum anodes can be used for 130 to 150 days.