Aluminium is a suitable metal to use as a sacrificial anode. When two different metals are placed in salt water, they form an electronic current. Aluminium is paired with a less reactive metal like bronze. A sacrificial anode is an anode that is used to protect other metals. Aluminium is suitable for both freshwater and seawater which makes it the most popular metal for anodes. Magnesium anodes may be suitable for freshwater too but they perform poorly in seawater. Only high quality aluminium metal should be used to make anodes for the best performance.
Uses of Aluminium Anodes in Boats
The hull of a boat is made from bronze or steel which is protected using aluminium. Aluminium anodes are used to protect the boat's hull from corroding. The aluminium anode will corrode over time. Magnesium anodes may be used on the hull in freshwater only. Zinc anodes can be used instead of aluminium in salty water. Zinc anodes get corroded faster than aluminium anodes. Aluminium anodes need to be replaced annually to effectively protect the noble metal. Alternatively, the anodes can be changed when they are half their original size.
Aluminium anodes can last longer in salt water compared to zinc anodes. The anodes used should be from reputable sources. They need to meet the requirements stipulated by the military or marines. Following the stated requirements will save you from corrosion related expenses in future. Aluminium anodes do not form an artificial film from its reaction with water. Zinc anodes form an insulating field of zinc peroxide. This leaves the cathode open for corrosion.
Properties That Make Aluminium Suitable
1. Electrical Potential
Aluminium has a high negative voltage which translates to higher protection for the cathode. The larger the electrical difference between the cathode and the anode, the more protection that the cathode gets from the aluminium anode. Basically, aluminium should be paired with a metal which has a lower voltage than aluminium to increase its effectiveness as a sacrificial anode. Magnesium anodes have a higher electrical potential but perform poorly in seawater.
2. Current Potential
Aluminium anodes have the highest current potential compared to zinc and magnesium anodes. The current potential relative to the mass and surface area of an anode determines the longevity of the anode. Therefore, aluminium anode will last longer protecting the other terminal.
Aluminium is an efficient metal to use as an anode. It is highly reliable in fresh and salty water. Aluminium anodes can be changed annually which reduces the maintenance cost of anodes.