In recent decades, the use of coupons has increased dramatically; Because they allow remote monitoring devices to better manage corrosion threats from current interference sources until field interferences are significantly reduced. The purpose of coupons is to show the level of protection or corrosion behavior of coating defects in pipelines. Polarization coupons are also used to simulate an uncovered part of a buried pipe or structure in order to measure the IR lossless potential.

An important cause of error in measuring the potential of buried structures is the error caused by IR loss. There are other factors including the cathodic protection current of the structure itself and stray currents from other sources. Theoretically, a potential measurement without IR loss can be performed by simultaneously cutting off all current sources and measuring the potential at the “off moment”. But it is very difficult to do in practice, so they use polarization coupons instead. These coupons simulate the exposed part of the structure to which they are electrically connected. The measurement is done by momentarily breaking the coupon and recording the potential at the “moment of breaking”. This method obtains the lossless IR potential of the structure at the coupon location with a suitable approximation. Polarization coupons provide the ability to measure without error the potential of the pipe to soil at the “off moment” to detect the level of cathodic polarization on pipelines. They are particularly useful in areas subject to stray currents and in all cathodic protection systems where simultaneous interruption of current sources is impractical or complicated.

The polarization coupon is made of carbon steel with an exposed surface area of 25 cm2 and has an epoxy substrate to seal and protect the connections. Two standard AWG 12 copper wires are provided to connect to the cathodic protection test station.