Impressed Current Cathodic Protection
Engineering services have found impressed current cathodic protection necessary with no exceptions in construction of metal structures. The structures requiring this protection most are exposed to weather and/or water. Pipelines, ships and bridges must have protection of an attached inferior metal to receive corrosion and therefore protect the valued metal in its core or main construction.
Protection occurs when inferior metal, being of lower electrolyte compound, is attached to the structure’s metal which has higher electrolytes, and therefore the electrical corrosive reaction occurs on the sacrificial lesser metal and the valued metal of the structure is protected. Where electrolyte resisting strength is higher in large metal structures, sufficient current cannot provide protection. Therefore the impressed current cathodic protection is incorporated, consisting of having anodes attached to DC power sources, and sometimes a transformer connected to AC power or alternative power such as solar, wind, or gas powered generators. Learn more about What is Electrochlorination?
Pipelines require anodes arranged in grounding beds of vertical holes or other geological fissures effective for grounding. The protection of pipelines is mandatory for many types, such as hazardous waste and pipelines under water.
Ships have cathodic protection by anodes attached to hulls and ICCP systems can be installed in large vessels. Since regular inspection and maintenance requires the removal of ships from the water, it is simple to replace galvanic anodes often. Smaller boats or yachts without metallic hulls have galvanic anodes to protect lower areas, relying on solid connections of electricity between the anode and what it is protecting. DC power supplies are in the ship with anodes on the hull outside.
Some ships require special work, like aluminium hulled boats with fixtures of steel creating cells so aluminium acts as an anode and makes corrosion worse. Aluminium or zinc anodes are used to offset differences between aluminium hulls and the steel.
Galvinized steel is not actually impressed current cathodic protection. Galvanizing is hot-dip coating steel with a layer of zinc metal. The steel is exposed because the zinc is marred, the zinc coating forms a cell with steel and the steel is protected, called localized cathodic protection.
Steel imbedded in concrete must be protected in a slightly different procedure but with the same scientific principle for cathodic protection.
The auto industry cannot as of 2013 manufacture cathodic protection in their vehicles although they have been working intensely in their laboratories attempting to develop the procedure successfully.