Aluminum anodes have several advantages, such as a lighter weight, and much higher capacity than zinc. However, their electro chemical behavior is not considered as reliable as zinc, and greater care must be taken in how they are used. Aluminum anodes will passivate where chloride concentration is below 1,446 parts per million.
One disadvantage of aluminum is that if it strikes a rusty surface, a large thermite spark may be generated, therefore its use is restricted in tanks where there may be explosive atmospheres and there is a risk of the anode falling.
Aluminum and Zinc anodes are suitable for use in marine environments such as harbors’ and jetties and for internal protection of tanks.
Aluminum is one of the preferred materials to be used as sacrificial anode for carbon steel protection. The efficiency of these can be low due to the formation of oxide layer which passivate the anodes. Currently, to improve its efficiency, there are efforts using a new technique called surface modifications.
Anode weight, length, width and height dependent upon lifetime and current output.
Chemical Composition :
COMPOSITION, % (max.)
3.0 – 5.0
0.02 – 0.05
Other elements, each
Other elements, total