This paper contains a review of commonly used practices and presents a generalized technique for the calculation of earth potentials for the determination of remoteness of impressed current anode ground beds. The intent is to facilitate proper design and evaluation of anode ground beds of impressed current cathodic protection system for cross-country pipelines.
The performance of titanium mixed metal oxide (MMO-Ti) anodes — provided by five global vendors — targeted for coke breeze backfilled soil impressed current cathodic protection (ICCP) applications, was investigated in this study. The time to failure of the MMO anodes was measured in accordance with NACE TM0-108. Accelerated lifetime testing was performed on MMO anodes to measure sample durability and to adequately meet the current density design requirement (0.06A/cm2). The anodes were immersed in 1M sulfuric acid under varying current densities (1A/cm2, 1.4A/cm2 and 2A/cm2) under controlled temperature, until the samples lost their electro-catalytic properties. The results measured at 1A/cm2 illustrated that time to failure of the tested anodes ranged from 10 days to more than 90 days. While conducting the same test at 1.4A/cm2, time to failure of MMO anodes was reduced to a range of 13 days to a little over 30 days yielding results of anode ranking consistent with those measured at 1A/cm2. Therefore, for the sake of time, the optimum applied accelerated current density was recommended to be 1.4 A/cm2 for Ru/Ta MMO anodes, to push them to their limits at a faster rate in a shorter time.