Anodic protection (AP) otherwise referred to asAnodic Control is a technique to control thecorrosion of a metal surface by making it theanode of anelectrochemical cell and controlling theelectrode potential in a zone where the metal ispassive.
Anodic protection is used to protect metals that exhibit passivation in environments whereby thecurrent density in the freely corroding state is significantly higher than the current density in the passive state over a wide range of potentials.[1][2]
Anodic protection is used forcarbon steelstorage tanks containing extremepH environments including concentratedsulfuric acid and 50 percentcaustic soda wherecathodic protection is not suitable due to very highcurrent requirements.
In anodic protectionpotentiostat is used to maintain a metal at constant potential with respect to reference electrode. Out of three terminals of the potentiostat one is connected to tank to be protected, another to an auxiliary cathode (platinum) and the third to reference electrode. Thus, a potentiostat maintains a constant potential between tank and reference electrode.
An anodic protection system includes an externalpower supply connected to auxiliarycathodes and controlled by a feedback signal from one or morereference electrodes.[3] Careful design and control is required when using anodic protection for several reasons, including excessive current when passivation is lost or unstable, leading to possible accelerated corrosion.