In impressed cathodic protection, direct current is applied to the metal structure with a rectifier and auxiliary anodes.
In mild steel structures, steel will be driven by external current of a cathodic protection system to a status of immunity against corrosion whereas passivated steel will be maintained in a region of perfect passivity.
Benefits of the Savcor Impressed Current Cathodic Protection (ICCP)
Cathodic Protection can be applied to any metallic structure that is in contact with an electrolyte. Cathodic Protection is commonly used in structures such as wharfs, jetties, ship hulls, foundation of offshore wind mills, offshore oil drilling platforms and exterior of pipelines buried in soil or water. Especially, corrosion of steel piles and steel sheet piles immersed in water can be stopped by installing a properly designed and engineered Cathodic Protection System.
The most vulnerable areas in sea water structures are the splash zone and tidal zone. The corrosion rates of those areas typically vary between 0.1-0.3 mm/year. However, much higher corrosion rates are commonly recorded. The atmospheric zones of e.g. the sheet piles cannot be protected with a Cathodic Protection System due to lack of electrolyte. Best protection can be achieved in the most vulnerable zone against corrosion, tidal zone. Combined with a coating solution Savcor Cathodic Protection will provide a long lasting and economical protection for any steel structure in a corrosion aggressive environment.
Chloride ingress from de-icing salt or sea water will lead to an increased risk of corrosion. Once chlorides have destroyed the protective oxide layer from steel surface, corrosion will initiate leading to material loss. Corrosion products which take more space than original rebar, will eventually cause cracks in concrete and later spalling of concrete.
Cathodic Protection (CP) is a well-known and proven method to extend the service life of the reinforced concrete structures in case of chloride contaminated concrete corrosion. Cathodic Prevention is usually applied during the building process or the ordinary concrete repairs. Cathodic Protection System in concrete consist of external DC power source, non-soluble anodes, cabling, reference electrodes and a control unit.
In new structures, the anodes can be installed directly to the steel reinforcement prior to concrete casting. When installing the CP during construction, savings in the CP installation shortens the payback time considerably, especially, in a corrosion intensive environment.
Furthermore, when protecting a pristine structure, the protection current requirement is much less than the amount of current required to stop an on-going active corrosion.
With old concrete structures all the damaged concrete needs to be removed before system installation. The cathodic protection system stops the corrosion progress but it does not repair already deteriorated structure. The Cathodic Protection is usually installed together with the repair work.
The protection current in a Cathodic Protection System is fed from the rectifiers to the metal surface through the anodes immersed into the process liquid. Cathodic current creates a passive oxide layer on the surface of e.g. stainless steel and makes it corrosion resistant, even in the harshest environments. General-, crevice-, pitting- and stress corrosion cracking can be prevented by the Savcor Cathodic Protection. When installed into an old equipment, cathodic protection stops corrosion already in action.
The bleaching filters in the pulp industry are typical examples of the equipment where corrosion can be prevented by Cathodic Protection. The rotating filter drum is a very expensive part of the filter that greatly benefits from CP. Naturally also the inlet vat and the filter vat will be protected to prevent leaks.
In the process industry, all sorts of chemicals are stored e.g. in stainless steel tanks and vessels. Every now and then the process conditions change to more aggressive and the tank begins to corrode. Process temperatures can increase or the concentration of aggressive ions such as chlorides are getting higher when the water circulation becomes more closed. Instead of replacing a corroding tank with a more noble and expensive material or lining it with some corrosion resistant coating the most cost effective solution is to install a CP System. Usually the installation is very fast and the down-time is much less than in any coating application or overlay welding.
Heat exchangers used for cooling or heating also corrode. If the corrosion problem is on the liquid side, there is a possibility of utilizing Savcor CP. The steam side lacks the conducting electrolyte and a CP is not an option.
Copyright © 2020 Savcor Oy info(at)savcor.com