Providing Cathodic Protection Solutions since 1950

Cathodic protection is commonly used to mitigate corrosion damage to buried or submerged metal surfaces. It is used all over the globe to protect a wide range of structures, including but not limited to:

• Pipelines and piping,
• Water treatment plants,
• Above and underground storage tanks (internal & external)
• Ship and boat hulls
• Offshore production platforms,
• Reinforcement bars in concrete structures
• Jetties & harbours

Electrochemical corrosion is generally caused when two dissimilar metals (by material or environment) are submerged in an electrolytic substance such as water (fresh or sea), soil, or concrete. A pathway is created through which free electrons move from the more active metal (anode) to the less active metal (cathode).

A reaction at the surface of the cathode allows oxygen to combine with the steel to produce ferrous hydroxide, i.e. rust.

For corrosion to occur, four elements must be present: a host site from which current flows, a destination site where no current flows, a medium capable of conducting current (such as water, concrete, or soil), and a return path between the host and destination site.

Cathodic protection connects the base metal at risk (the cathode; typically steel) to the anode that provides a supply of electrons to the cathode.

The technique of providing cathodic protection to steel preserves the steel by installing an anode which provides free electrons. These electrons flowing to the cathode prevents the less active steel from corroding.

Yes. There are two basic types of cathodic protection: galvanic (or sacrificial), and impressed current cathodic protection.

The galvanic anode method of protection uses a metal more active than the base metal to ‘sacrifice’ ions. These ‘sacrificial anodes’ (usually alloys such of magnesium, aluminium, or zinc) have a more negative electrochemical potential than the base metal.

These systems have limited life-spans, as the galvanic anode protecting the base metal will continue to degrade over time until the anode is no longer capable of supplying protection. Galvanic anode systems are self-regulating with current output changing with local conditions.

Impressed current cathodic protection systems consist of inert anodes that are connected to a power source, that provides a perpetual source of electrical current flow. The most common anode materials are activated titanium (MMO) and silicon iron. The current flow is created using a transformer rectifier unit which converts AC power to DC. This method has a much longer design life than galvanic anodes as the anodes are inert.

A galvanic anode remains active through its lifetime which is typically 10 to 20 years.

An impressed current system is typically designed for a lifetime of 25 to 30 years. However, where anodes cannot be easily replaced the design can be increased to over 50 years.

Cathodic protection systems need to be checked on a frequent basis to ensure they are still operating correctly and protecting the structure. Competent personnel and specialist equipment are required to perform inspections.