What type of anodes are typically used in reinforced concrete structures?

In reinforced concrete structures, aluminum (Al) anodes are commonly used due to their effectiveness in providing cathodic protection against corrosion. The primary reason for this choice is that aluminum has a high electromotive potential, which helps prevent the corrosion of embedded steel reinforcement. When aluminum anodes are installed, they can sacrifice themselves by corroding preferentially, thus protecting the rebar from oxidative processes that would lead to deterioration.

Aluminum anodes are particularly advantageous in concrete environments because they are lightweight, have a high energy density, and can effectively produce the necessary current density to protect the steel reinforcement, even in highly resistive concrete. This corrosion protection is crucial, as the integrity of the reinforced concrete depends heavily on the condition of its steel components.

Other types of anodes like magnesium, zinc, and iron may also be used in specific applications, but they may not offer the same level of compatibility or effectiveness in concrete as aluminum does. For instance, magnesium anodes could create a more aggressive environment due to hydrogen evolution or may not provide adequate protection in varying pH levels common in concrete. Zinc anodes, while common in some applications, do not work as well in alkaline environments found in concrete.