Background to corrosion on buried and immersed structures

Corrosion occurs on many buried and immersed metallic structures such as pipelines, jetties and storage vessels. The majority of this corrosion is of an electro-chemical nature, caused by forces within the metal trying to return it to its original state.

Four components are required to create electrochemical corrosion:

• an anode (i.e. the point at which energy leaves the metal and the corrosion occurs);
• a cathode (i.e. the point at which the energy is received to prevent corrosion);
• a metallic contact, between the anode and cathode;
• an electrolyte, soil, water etc.

Substantial sums are spent in order to try to reduce or eliminate corrosion. The application of coating systems on metal is normal as it can remove the metal from the electrolyte and can reduce or prevent corrosion completely. However, this is not always possible as:

• standards of construction vary;
• damage can occur to a coating system during construction, and later during the life of a structure.

As a result of these failings in what is considered the primary corrosion prevention system, it is necessary to have a secondary method of corrosion prevention. In most instances Cathodic Protection (CP) can be applied. Essentially the concept of CP is to connect secondary metals of known properties (anodes) to a create a cathode, resulting in corrosion at the anode and subsequent protection at the cathode.

The world market for cathodic protection is large and number of firms are involved. These deal with various aspects of the market including system design, pre-construction site surveys, manufacture and supply of components, installation of systems, management and commissioning of systems, operation and maintenance of systems and specialist surveys.

Cath-Tech International was formed in 2002 and is based in Lincolnshire UK. In this time the company has become a major provider of specialist pipeline survey and monitoring services in both the UK and overseas. The Managing Director of Cath-Tech International Ltd, Peter Martin, has been involved with the industry in excess of 25 years, and has extensive UK and International experience.

Cath-Tech International Ltd are a major partner and a distributor for Cathodic Technology Limited of Canada for whom we promote the sale and use of the world leading HexcorderTM Dataloggers and GPS Current Interrupters.

We also can provide Technical support for CPDM Software manufactured by American Innovations Ltd