Cathodic Protection

The science of cathodic protection (CP) was born in 1824, when Sir Humphrey Davy made a presentation to the Royal Society of London: "The rapid decay of the copper sheeting on His Majesty's ships of war, and the uncertainty of the time of its duration, have long attracted the attention of those persons most concerned in the naval interest of the count. ... I entered into an experimental investigation upon copper. In pursuing this investigation, I have ascertained many facts ... to illustrate some obscure parts of electrochemical science... seem to offer important application." Davy succeeded in protecting copper against corrosion from seawater by the use of iron anodes.
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From that beginning, CP has grown to have many uses in marine and underground structures, water storage tanks, gas pipelines, oil platform supports, and many other facilities exposed to a corrosive environment (see Corrosion Costs Study findings). Recently, it is proving to be an effective method for protecting reinforcing steel from chloride-induced corrosion. (reference)
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The basic principle of CP is simple. A metal dissolution is reduced through the application of a cathodic current. Cathodic protection is often applied to coated structures, with the coating providing the primary form of corrosion protection. The CP current requirements tend to be excessive for uncoated systems. The first application of CP dates back to 1824, long before its theoretical foundation was established. Cathodic protection has probably become the most widely used method for preventing the corrosion deterioration of metallic structures in contact with any forms of electrolytically conducting environments, i.e. environments containing enough ions to conduct electricity such as soils, seawater and basically all natural waters. Cathodic protection basically reduces the corrosion rate of a metallic structure by reducing its corrosion potential, bringing the metal closer to an immune state.
Cathodic Protection 101 (709 KB)
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Corrosion Costs and Preventive Strategies Study
The cost of cathodic protection of metallic structures subject to corrosion can be divided into the cost of materials and the cost of installation and operation. Industry data have provided estimates for the 1998 sales of various hardware components totaling $146 million. The largest share of the cathodic protection market is taken up by sacrificial anodes at $60 million, of which magnesium has the greatest market share. Major markets for sacrificial anodes are the water heater market and the underground storage tank market.
The costs of installation of the various cathodic protection (CP) components for underground structures vary significantly depending on the location and the specific details of the construction. For 1998, the average total cost for installing CP systems was estimated at $0.98 billion (range: $0.73 billion to $1.22 billion). The total cost for replacing sacrificial anodes in water heaters and the cost for corrosion-related replacement of water heaters was estimated at $1.24 billion per year; therefore, the total estimated cost for cathodic and anodic protection is $2.22 billion per year. (reference)
Information Module
Sacrificial anodes
Impressed current
Groundbed design
Backfill materials

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At CPM we specialize in corrosion control for metallic structures which are buried in soils, submerged in water or imbedded in concrete.We solve corrosion related problems for buried and submerged pipeline facilities, underground and aboveground storage tanks, docks and piers, rapid transit systems, bridges, parking structures, electric power generation and transmission facilities as well as steel reinforced structural elements and process equipment.

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