In a cathodic protection system, what does the term "anode" refer to?

In a cathodic protection system, the term "anode" refers to the source of protective current. The primary role of the anode is to provide the electrons necessary to protect a metal structure from corrosion. When an anode is connected to a cathodic protection system, it is typically made from a metal that has a more negative electrochemical potential than the structure being protected. The anode sacrifices itself (becomes consumed) while supplying electrons to the cathode (the structure), thereby preventing corrosion.

This protective current flows from the anode to the cathode, helping to inhibit the electrochemical processes that would otherwise lead to the deterioration of the metal structure. Understanding the function of the anode is crucial for properly designing and operating a cathodic protection system to ensure effective corrosion control.

Other terms mentioned in the options represent different components or concepts within the system. For instance, the structure being protected relates to the cathodic part of the system, the return path for the current is necessary for completing the circuit but does not define the anode, and the control device for the system relates to the operational management of the cathodic protection rather than its source of protective current.