Both techniques aim to bring the average electrochemical potential of a chain of metals towards values such that each of them tends to be incapable of reacting chemically and turning into oxide.
This is achieved by imposing a current circulation between the sacrificial element ( passive protection ) or the electrode ( active protection ) and the metals to be protected against corrosion.
There are many fields of application for cathodic protection: from marine (nautical, naval, offshore, inshore, industrial, etc.) to terrestrial (aqueducts, gas, oil pipelines, etc.) as well as all those applications where a specific defence against electrochemical corrosion is required.
The anodes that we find installed in specific locations on vessels are part of a passive cathodic protection system.
The operating principle is very simple: the alloy of which the anode is composed, having an electrochemical potential lower than all metals used in the marine industry, triggers an electrochemical process that circulates an electric current from the anode to the cathode (the metal structure to be protected).
The migration of electrons from the anode to the structure to be protected makes the anodic alloy capable of reacting with other substances dissolved in water (OH groups) and transforming into soluble or insoluble oxides.
This complex phenomenology leads the anode to become less and less efficient as time passes until the moment when replacement becomes essential.
Anode efficiency is ensured by introducing chemical elements called activators into the alloy.
The other important function of activators is to fix the electrochemical potential of the anode at values determined on the galvanic scale.
Sacrificial anodes do not require a power supply to function, and no special maintenance is required either. The only care that needs to be taken is to replace them according to the times correctly indicated in the cathodic protection plan.
Sacrificial anodes can be used in: ships, tanks, offshore facilities, port installations, power plants, chemical plants, underground facilities.