Numerical Analysis and Design Recommendation for Linear Anodes in above Ground Storage Tank Cathodic Protection Systems: Mesh Grid system vs. Concentric Rings

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Abstract
Cathodic protection as a complementary method is one of the most effective ways to prevent corrosion, along with coating and choosing the suitable material. There are different ways to protect the storage tank bottom. Due to the presence of the geo membrane layer and its effective and pivotal role, the use of mixed metal oxide (MMO) anodes is highly recommended. In the current study, the protection process of the above-ground storage tank bottom is simulated using MMO backfilled wire (Concentric Rings) and ribbon anodes (Mesh Grid System). In this regard, several parameters must be considered in reaching the protection criteria. The simulation results show that the effect of the spacing between the anodes, the limiting oxygen current density and the anodic current have the greatest role. Anode depth and soil resistance are also critical factors. Due to the importance of the number of conductor bars and feeding cables, two configurations have been presented for ribbon anodes. These configurations have a direct impact on grid resistance, rectifier size, and related costs. Finally, an economic comparison has been made regarding the use of sacrificial and MMO anodes in the form of ribbon next to wire anodes. The results show that, in the use of ribbon anodes, MMO anodes have better performance than magnesium and zinc sacrificial anodes, and the cost required for MMO linear anodes is far lower than the method of sacrificial ribbon anodes. In the present study, the linear anode system has an estimated cost of approximately 20% less than the ribbon sacrificial anodes made of magnesium and zinc.

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