Cathodic protection systems, often used in conjunction with an appropriate coating system, prevent corrosion by causing direct current to flow from discrete electrodes known as 'anodes' through the surrounding environment (sea water, sediment, soil etc) onto the structure to be protected. This direct current overcomes the naturally occurring current generated as a result of the corrosion process and renders the structure cathodic - hence the name 'cathodic protection'.

There are two methods of applying cathodic protection. The first is the impressed current method, involving discrete, relatively inert anodes isolated from the structure and connected to a direct current power source The second method involves the use of galvanic anodes, made from specially formulated alloys, which are directly attached to the structure to be protected As these anodes are more electronegative than the structure, a galvanic cell is created, which generates the necessary protective current.

1. Impressed Current Systems

AARAV INTERNATIONAL 's engineering expertise includes the design of complete impressed current protection systems and advice on the most appropriate materials and equipment Detailed design and supply of complete systems can be undertaken on a turnkey basis or as a job specific materials supply/consultancy service.

Impressed current anodes can be produced in a wide and growing range of materials. For most environments there is no clear cut choice of material, however, the most commonly used anode types are silicon iron, mixed metal oxide, platinized titanium and graphite. AARAV INTERNATIONAL can supply systems using any of these materials or many others.

Typical applications for impressed current systems include buried structures such as pipelines, cable conduits, tanks, piling structures and foundations; non-buried structures such as jetties; water and sewage treatment plants, pipeline interiors, water tanks, condensers and heat exchangers.

2. Galvanic Anode Systems

AARAV INTERNATIONAL's engineering expertise includes the design of complete galvanic anode systems and advice on the most appropriate materials.

Of all the galvanic anode materials available to the corrosion engineer, magnesium anodes have the highest driving potential with respect to steel structures. For this reason, in higher resistivity electrolytes such as soil and fresh or brackish water, magnesium anodes are generally used in preference to zinc or aluminum alloys.

Magnesium galvanic anode systems are particularly suitable for external protection of buried pipelines, storage tanks, tank bases and immersed moorings, and for internal protection of storage tanks, condensers and treatment plant.