There is no love lost between saltwater and metal surfaces; some might even say it’s a “corrosive” relationship. Corrosion in and of itself is a natural process, a reduction-oxidation reaction, that converts a metal in its manufactured state back to its natural oxidation state. Or to put it another way; it’s the destruction of metal by its environment.
Cathodic protection systems have been used to reduce the corrosion of metal surfaces, both exterior and interior) on a wide range of structures in an even wider range of environments since the early 1800’s. The most common application process of cathodic protection is a passive protection technique (galvanic) which uses a “sacrificial” sheath which corrodes in place of the protected surface. Often referred to as passive protection.
For many larger boats and structures where passive protection just won’t do, impressed current cathodic protection(ICCP) systems are widely accepted as a superior alternative to sacrificial systems Requiring less frequent replacement, ICCP systems can also reduce the costs associated with fuel and maintenance making them the preferred choice of ship owners.
Typically referred to as CAPAC systems (a brand name which has become the generic name for the system – like Kleenex has for tissue) they work by supplying DC current directly to the submerged surface, which the system itself regulates and monitors, stopping the corrosion process before it even has a chance to start.
As opposed to passive cathodic systems, which work because of their ability to balance the electrical potential of the protected surface, ICCP systems rely on DC currents. The electrical potential remains uniform as a result of the DC current being forcibly sent through the hull converts the entire structure into an electrical circuit.
Every size and type of sea-faring vessel has benefited from ICCP; cruise ships, oil tankers, recreational boats, and semi-submersibles to name just a few, all reap the benefits associated with CAPAC systems.