There is renewed interest in the use of corrosion coupons for monitoring catholically protected pipelines. The resurgence in interest was prompted by the need to determine.the -850 mV (Cu/CuSO4) polarized potential recommended by NACE International RP0169-96 where traditional methods (e.g., current intemuption) may not be feasible or practical. A variety of coupon sizes, shapes, orientations, and means of measurement have been developed over the years, with many in use today around the world. The results from a field study on operating pipelines using coupons of two different sizes (49 and 4.2 cm2) in two widely different soil environments are presented, and correlations between the cathodic protection parameters of on-potential, instant-off potential, IR drop, and polarization on the coupons and pipes are discussed. Factors controlling the relationships are analyzed and some limitations in the use of coupons are considered.
Key Words: Coupons, cathodic protection, pipeline, field study.