In a typical large tank farm at a petroleum refinery, pipeline or distribution terminal, it is very difficult, if not impossible, to measure an IR-drop free potential on aboveground storage tank bottoms. This is because it is difficult to interrupt all of the current sources and also because of the galvanic effects from the many different structures that are bonded together (tanks, pipes, electrical grounding, etc.). Buried coupons have been considered an alternative to measure the true polarized potential (without IR-drop) of pipelines. However, there are many practical as well as theoretical considerations that have to be addressed in order to successfully implement this concept in the field on tank bottoms. These include, among other things, differences in electrolyte adjacent to the tank bottom and coupon and differences in surface conditions of the two cathode materials. Given the growing trend for the use of coupons for
cathodic protection monitoring, and the need for definitive tank bottom CP testing procedures, experiments were done to examine the use of coupons for this purpose. This work presents the methodology and considerations derived from a two-year testing program on an experimental tank bottom mockup.