Measurement methods and influence factors of coupon off-potential

Coupon instant-disconnect method is an efficient way to evaluate the effectiveness of cathodic protection for buried pipelines. With the increasing measurement demand for pipeline off-potential in the daily management of pipeline cathodic protection, the coupon instant-disconnect method is gradually implemented in China. However, there are still many uncertain factors in the use of the coupon current interruption method, such as the polarization stabilization time and the selection of the coupon size and shape, etc. Through the coupon polarization test on site, the measurement methods and influence factors of the coupon instant-disconnect potential were studied. The results show that the stabilizing instantdisconnect potentials are different after 15-minute polarization for these coupons with different areas, i.e. the smaller the coupon is, the more negative the potential will be. The potential of rectangular coupons is rather more negative than that of circular coupons. The potential of the coupon with deep buried depth is slightly more negative than that of the coupon with shallow depth despite the tiny difference. Finally, some suggestions on the application of coupon instant-disconnect method in engineering were put forward.