What type of anode is used primarily in unheated water storage tanks?

The use of aluminum anodes in unheated water storage tanks is primarily due to their efficiency and effectiveness in preventing corrosion. Aluminum anodes have a higher electrochemical potential compared to other metals and are particularly suitable for use in environments where the water is unheated. They are lightweight, have a good current output, and are highly reactive, which makes them effective at sacrificing themselves to protect the tank from corrosion.

Additionally, aluminum anodes are less prone to hydrogen gas evolution in low-temperature water, making them safer and more effective in these applications. When used in water tanks, aluminum anodes can help extend the life of the tank itself by mitigating the corrosive effects caused by the water and any impurities it may contain.

In comparison, other materials like graphite, carbon, and platinum are not typically used for sacrificial anodes in this context. Graphite and carbon may not provide sufficient electrochemical activity for effective cathodic protection and platinum is an expensive and inert material that would not serve well as a sacrificial anode under typical conditions found in water storage tanks.