What best describes an anode?

An anode is best described as active because it is the electrode where oxidation occurs during an electrochemical reaction. In the context of cathodic protection and corrosion prevention, an active anode means that it participates in the corrosion process by sacrificing itself to protect another structure, such as a metal pipeline or tank. This active behavior is essential for the function of sacrificial anodes, which are commonly used to prevent corrosion in metallic structures by corroding preferentially, thus preserving the integrity of the protected structure.

Passive, inert, and noble have different meanings in electrochemistry. While a passive anode does not actively participate in the electrochemical reaction and a noble anode can resist corrosion (often used in context to describe materials), the defining characteristic of the anode in a depth of its function is its active role in the anodic process. An "active" description effectively encompasses the role of the anode in relationships with other electrodes and its essential purpose in cathodic protection systems.