Cathodic Protection of Underground Structures Cathodic protection is widely used to prevent corrosion of underground structures including pipelines and storage tanks. Cathodic protection is often used to supplement coatings which have been applied to these structures. In cathodic protection, a very small electrical current flows from an anode to the structure. This current will cause the electric potential of the structure to shift in the negative direction. As this shift occurs, the corrosion reaction slows down and eventually stops. Cathodic protection can prevent corrosion from occurring in the first place and it can stop the corrosion process if it has already begun. Cathodic protection cannot, however, reverse corrosion damage which has already occurred. Electrochemical Devices, Inc. Products Electrochemical Devices, Inc. manufactures reference electrodes, impressed current anodes and constant current rectifiers which are used for corrosion prevention by the cathodic protection process. To see an overview of our product line, click on Product Line Guide. Reference electrodes and cathodic protection coupons designed for underground applications comprise our U Series. EDI also designs and manufactures custom corrosion monitoring and prevention products for use in underground applications. Click on the U Series Selection Guide for a further description of these products. Featured Product: Cathodic Protection Coupon Potential measurements of underground structures made with portable reference electrodes placed on the surface or buried permanent reference electrodes often contain an error known as IR Drop error. IR Drop error results from the interaction of the cathodic protection current with the soil resistance. One way of accounting for this error is to momentarily interrupt the cathodic protection current and measure the potential immediately after interruption. This so-called instant-off potential can be substantially free of IR Drop error. It is often impossible to interrupt cathodic protection current on structures protected with sacrificial anodes. Even in cases where current interruption is possible, there may be other sources of current at that location such as those from nearby cathodic protection systems, stray currents or telluric currents. Cathodic protection coupons, sometimes called instant off sensors, have been developed as a means to make instant off potential measurements under virtually all conditions. A cathodic protection coupon is a piece of metal which is electrically bonded to the structure through an interruptible connection at a test station. The coupon is usually the same type of metal as the structure but is located very close to the reference electrode. Normal measurements are made with the coupon electrically bonded to the structure. When instant-off or IR drop free measurements are required, the potential of the coupon is monitored as the electrical bond is interrupted. The proximity of the coupon to the reference electrode minimizes the IR drop error in this measurement. Coupons are available as separate pieces of metal, attached to a test station, or attached to a permanent reference electrode. Coupons supplied by EDI are attached to our reference electrodes. This gives the corrosion engineer the greatest amount of design flexibility in locating the coupon while ensuring that it remains sufficiently close to the reference electrode to minimize any IR drop error. Both our standard LongLife reference electrode, Model UL, and the reduced diameter SlimLine reference electrode, Model US, can be ordered with coupons attached.

	Electrochemical Devices, Inc.
Sales Office:	P.O. Box 355, Belmont, MA 02178
	Phone: (617) 484-9085, Fax: (617) 484-3923
Main Office:	P.O. Box 31, Albion, RI 02802-0031
	Phone: (401) 333-6112, Fax: (401) 333-9724
	e-mail: info@edi-cp.com

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