The use of coupons has significantly increased the last decades because remote monitoring devices allow better managing of the corrosion threats caused by interference sources while significantly reducing field interventions. It is the aim of coupons to represent as good as possible the protection level or corrosion behavior of a coating defect on the pipeline. Cathodic protection (CP) coupons is used to simulate an exposed section of buried pipe or structure for the purpose of conducting IR drop free potential measurements.

IR drop errors are a significant source of inaccuracy in potential measurements on underground structures. There are a number of sources of them including the structure's own cathodic protection current and stray currents from other sources. In theory, IR drop free potential measurements can be made by interrupting all current sources simultaneously and making an "instant off" potential measurement. In practice, this is very difficult so CP coupons are used instead. CP coupons simulate an uncoated part of the structure to which they are electrically bonded. Measurements are made by momentarily disconnecting the coupon and recording the "instant disconnect" potential. This reading approximates an IR-drop free potential on the structure at the location of the coupon. CP coupons provide the ability to measure an error-free ‘instant-OFF’ pipe to soil potential, to prove the level of cathodic polarisation achieved on the pipeline. They are particularly useful in areas subject to stray currents and on all cathodic protection systems where the synchronised interruption of current supplies is complex or impractical.

CP coupon is made from carbon steel with an exposed area of 25cm² and has an epoxy base to seal and protect the wire connections. Two 12 AWG stranded copper leads are provided for connection to a CP test station.