The combination of cathodic protection and coating can provide the most economical and effective protection for underground or underwater metal structures. A good coating protects more than 99% of the outer surface of the structure from corrosion. Underground or underwater metal structures are usually coated with a protective coating before use to insulate the metal from the dielectric environment.

The combined application of cathodic protection technology and coating can effectively solve this problem. Cathodic protection on the one hand can effectively prevent coating lesions have corrosion, prolong the service life of coating, coating on the other hand, can greatly reduce the requirement of protection current, improve the protection of current distribution, increase the protection radius, has made it more economic and effective, for the cathodic protection on bare or poor anticorrosion coating of underground or underwater metal structures, Cathodic protection is even the only alternative to corrosion protection.

The cost of the cathodic protection usually only protected metal structure cost 1% ~ 5%, and the service life of the structure can be double or even several times to extend because of this, therefore, the technique to get general recognition of the people, and has set up a ship, in port engineering, Marine engineering, petrochemical, electric power, municipal and other fields to get more and more widely used, promising prospects.