Field Program on the Use of Coupons to Monitor Cathodic Protection of an Underground Pipeline

Abstract

Abstract This paper presents the results of a four year field program on the use of coupons to monitor the adequacy of the Trans Alaska Pipeline System’s (TAPS) cathodic protection systems. The objective of the program was to evaluate the use of coupons to correct for IR-drop, anode/pipe mixed potentials, and Telluric currents. Coupon monitoring assemblies were designed and installed at over 400 locations in different types of geological strata. Design guidelines, material specifications, and construction and monitoring techniques were developed to efficiently and effectively install and monitor cathodic protection coupon stations. Data evaluation Included, coupons connected to the pipe and cathodic protection system (CP coupon), free corroding coupons (corrosion coupon), coupon “on” and instant-off potentials, polarization potentials, soil resistivity and temperature effects, and surface vs close proximity potentials. As a result of this field and supporting laboratory program, it was concluded that coupons can and will be used to monitor the adequacy of the TAPS cathodic protection systems.