What is Cathodic Protection
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What is Cathodic Protection |
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What IS Cathodic Protection? |
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A common form of CP, or cathodic protection, is called impressed current. Impressed current means that a current
is impressed between the buried structure and and an anode. This forces a reversal of the current, and causes the anode to be consumed
rather than the pipe. This current will vary considerably, depending on the surface area of the underground pipe, the soil and other factors. We have sold systems as small as 50 milliamps and as large as 120 amps. A typical gas wellhead is usually in the range of 2 to 6 amps, larger pipelines are usually in the 8 to 30 amp range. Where grid power is readily available, an AC to DC rectifier is usually used. In remote areas, the DC current is commonly supplied by a solar electric (PV) system. |
Another form of CP uses sacrificial anodes.
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For more detailed and specific information on anodes and groundbeds,
LIDA is a good source. |
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The cathodic
protection can be obtained by connecting a noble metal to a less noble. In practice steel is protected by supply of electrons from less
noble metals like Zinc, Aluminum and Magnesium alloys, often called sacrificial anode materials. The anode is sacrificed and eventually
is used up, but the steel is protected. This is often used on boats to keep the metal - including the propeller - from being eaten away.