Metal corrosion is an electrochemical phenomenon that affects every metal due to their interaction with the environment. On the surface of the structure affected by the corrosion process we can identify areas with cathodic properties and areas with anodic properties, where the corrosion process is active. Either ground or water can surround the structure and act as electrolytes, allowing the transfer of ions generated by the electrochemical reaction. The metal itself can act as an electrical connection allowing the electronic transfer.
All these 4 elements must exist simultaneously to trigger the pipes deterioration process:
ANOD
CATHOD
ELECTROLYTE
WIRED CONNECTION
We need to intervene at least on one of these 4 components to stop or slow down the corrosive process.
To date there are many different approaches to this problem. The first one consists in the isolation of the electrolyte structure through plastic coatings or through applying specific paints before the implementation. This process isolates the material from the environment, interrupting the electrochemical phenomenon.
In case of corrosion resulting from galvanic coupling due to the electrical contact of metals with different electrochemical potential, such as high-strength steels matched up with carbon steels, or in case of substitution of pipes sections in current distribution networks, it will be possible to interrupt the wired connection using insulating joints or flanges or to implement in the engineering process an accurate selection of materials.
Another option consists into transforming the anodic areas on the surface of the structure into cathodic ones, where the corrosion can’t occur due to cathodic protection.
Cathodic protection (CP) is an electrochemical technique able to slow down the corrosion of a metallic surface granting it the role of an electrolytic cell’s cathod.
Inside the system, in addition to the 4 elements, we can introduce a new anod which polarizes the surface of the metal granting it the role of an electrolytic cell’s cathod. The system can be made using galvanic anodes (sacrificial anodes) or through impressed-current plants.
