What Does Linear Anode Mean?
A linear anode is a metal electrode or a set of metal electrodes that is used in cathodic protection systems. Linear anodes are usually made from noble metals such as titanium or niobium. They are used in both methods of cathodic protection — impressed current cathodic protection (active) systems and sacrificial anode (passive) systems.
Corrosionpedia Explains Linear Anode
Linear anodes are used in cathodic protection systems to prevent a specific metal from rusting. The idea behind cathodic protection is that the linear anode is the metal to be corroded, acting as the anode in a galvanic cell, where the metal to be protected is the cathode. This is achieved by placing it in contact with the metal to be protected.
Sacrificial anode systems are less complicated. They require only a material anodic to the protected steel in the environment of interest. Sacrificial anodes are coupled to the structure under protection and conventional current flows from the anode to the structure as long as the anode is more "active" than the structure. During the flow of current, all the corrosion occurs on the anode which "sacrifices" itself in order to offer protection from corrosion to the structure.
With an impressed current system, the current is impressed by a power supply developing a high potential difference between the surface to be protected and an anode. The power source must be able to deliver direct current (DC). A series of anodes installed in the ground are referred to as a groundbed. Fewer anodes are required for impressed current systems than are required for a galvanic system of equal current capacity. Impressed current systems tend to have a low initial cost with higher operating and maintenance costs than a galvanic system.