Our Cathodic Protection Systems and Services are a proven and reliable method of achieving corrosion control of metals and alloys. Corrosion is a progressively destructive and often potentially hazardous process. Often challenging to identify until well advanced, corrosion is frequently identified when it is too late. Identifying corrosion on submerged or buried equipment and structures is even more critical, which makes Cathodic Protection (CP) so important particularly in the oil & gas, power generation, and petrochemical industries.
Often working in conjunction with protective coatings or vapor phase corrosion inhibitors (VpCI), Cathodic Protection Systems are a proven, highly reliable way of controlling corrosion. The method was initially developed to be used in the shipping industry, but today it is used across all industries where safety, environmental protection, and the long-life is paramount.
Pipelines (On-and Offshore): Distribution and Transmission Oil and Gas, Petrochemicals and Water.
Storage Tanks and Vessels: Above and Below Ground Internal Surfaces and External Surfaces Bases Undersides.
Production Facilities & Refineries: Oil, Gas and Water Wells, Pipeline, Flow-lines, Process Plant, Heat Exchangers, Fire Water Mains and Services.
Power Stations: Intake Screens, and Pumps, Condenser Boxes and Cooling Water Pipe-Work.
Inshore & Offshore Marine Structures: Production and Exploration, Platforms, Rigs, Jackets and Vessels, Harbours, Jetties and Marine Bases, Sheet and Tubular Piling – Ships, Barges Baots Buoys and Fenders.
As with many things the history of cathodic protection has its foundations in the industrial revolution and is connected with four historic scientists and inventors, Alessandro Volta, Sir Humphry Davy, Michael Faraday, and later Thomas Edison.
Alessandro Volta first observed and recorded the effects of electric current on the oxidation of metals in 1802 stating “The oxidation strongly increases on the metal from which the current goes out from to go into the surrounding water or other oxidant liquids. The oxidation decreases or is eliminated on the metal in which the current goes in and on which hydrogen is released “.
In 1806, Sir Humphrey Davy advanced his idea of a favourable effect on the corrosion of copper in seawater in contact with zinc, tin, or iron, but it wasn’t for almost another 2O years, that his idea was practically realized, with his basic principles of cathodic protection being applied to the HMS Samarang, where iron castings called anodes were installed upon the copper-clad hull, which had after only three years of use began to show signs of corrosion damage. The iron anodes then went on to sacrifice themselves, to protect and dramatically reduce corrosion of the copper cladding, and working Sacrificial Anode Cathodic Protection (SACP) was born.
Sir Humphry was assisted in his work by Michael Faraday, what today we might call a laboratory technician. Following the death of Sir Humphry, Faraday continued and further developed his research and work and in 1834 discovered the relationship between corrosion weight loss and electric current, creating the foundation upon which cathodic protection as we know it today is built.
Later the late 19th Century, Thomas Edison devised and unsuccessfully experimented with the first application of Impressed Current Cathodic Protection (ICCP) on ships, but it was not until 1920’s and 1930’s that both sacrificial anode and impressed current systems were widely used on pipelines in the United States of America before spreading globally in popularity and use across most industrial sectors.
Cathodic protection (CP) is an electrochemical method used to control the corrosion of a metal surface immersed in an electrolyte by making it the cathode of an electrochemical cell.
There are two types of cathodic protection systems, sacrificial anode, and impressed current cathodic protection:
Figure 2 – Typical Sacrificial Anode System
Sacrificial anode systems work by connecting anodes of more negative potential to the metal or metallic structure needing protection. Typically for steel, these anodes will be made from magnesium alloys and zinc alloys for soil and freshwater applications, for use in seawater, zinc alloys and aluminium alloy anodes are used.
Figure 2 – Typical Sacrificial Anode System
Sacrificial anode systems work by connecting anodes of more negative potential to the metal or metallic structure needing protection. Typically for steel, these anodes will be made from magnesium alloys and zinc alloys for soil and freshwater applications, for use in seawater, zinc alloys and aluminium alloy anodes are used.
The main factor in the choice of what system is to be used is the overall cost. Generally speaking, both types of system can be applied to any given situation but subject to the size of the structure, the presence of protective coatings, and environmental or operating conditions one system type will be more cost-effective. A list of typical factors deciding which type of system to use is given in Table 2.
Table 2 – CP System Selection Factors
The concepts and application of cathodic protection are now well understood, and the method is a well-proven corrosion control solution. We would recommend that anyone requiring more in-depth advice on the application of CP please contact us where one of our team will be pleased to provide advice and guidance.
There is far more to cathodic protection than these few words and pictures, should you like to discuss cathodic protection further please feel free to contact us or visit the website of AMPP at www.AMPP.org, where additional details, facts, and figures are available
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