Case Study for Upgrading the Design of Impressed Current Cathodic Protection for Tank Bottoms as an External Corrosion Control Method

Engineering design calculations for tank bottom sections, including direct current requirements and voltage calculations, followed by additional structures, such as electrical grounding systems, have already been successfully implemented and controlled in field conditions. Furthermore, the effect of soil resistivity in layers, oxygen content and the pH value of the soil against the disproportionate IR-Drop voltage, including its effect on potential distribution, have been already successfully observed. Other influences, such as the depth and location of the anode groundbed determination along with the establishment of impressed current cathodic protection related to the main tools and equipment, such as external corrosion control methods, have been defined as the most effective ways in order to control potential distribution against the additional structures. Persuant to the verification results from the site located at Marangkayu, East Borneo, it has been determined that high soil resistivity could cause error readings in accordance with the accumulation results of the true readings and the IR-Drop voltage, since under real conditions, the tank structure would have received less current flow from an anode compared to a lower result. Naturally, a low pH value from the soil would decrease soil resistivity and enhance potential distribution from the anodes to the tank structures. The results show that the cathodic protection required 10 additional anodes, (each one is of a tubular mixed metal oxide) with a DC supply at minimum amperage of 154 Amps and a minimum voltage supply of 32 Volts. During the research, it was identified that high soil resistivity above 3000 ohm-cm would cause error readings. Naturally, acidic soil is in the region of pH 5-7 value, which would decrease soil resistivity and enhance the potential distribution from the anode to the tank structure.

Aboveground storage tank, Engineering design, Impressed current cathodic protection, Potential mapping, Voltage drop

Atkins, C.P., Lambert, P., Coull, Z.L., 2002. Cathodic Protection of Steel Framed Heritage Structures. In: Proceedings of the 9th International Conference on Durability Building Materials Components, Australia, pp.11–15

Fontana, M., 2005. Corrosion Engineering. McGraw Hill Book Company, Inc., Hoboken, New Jersey, USA

Jones Deny, A., 2005. Principles and Prevention of Corrosion. McGraw Hill Book Company, Inc., Hoboken, New Jersey, USA

Kroon, D.H., 2005. Cathodic Protection of Aboveground Storage Tank Bottoms. Materials Performance ,Volume 33, pp.26–30

Lambert, P., Mangat, P.S., Flaherty, F.J., Wu, Y.Y., 2008. Influence of Resistivity on Current and Potential Distribution of Cathodic Protection Systems for Steel-framed Masonry Structures. Corr Eng Sci Tech, Volume 43, pp.16–22

Peabody, A.W., 2007. Control of Pipeline Corrosion. NACE International The Corrosion Society, John Wiley & Sons, Inc., Hoboken, New Jersey, USA

Riemer, D.P., Orazem, M.E., 2005. A Mathematical Model for the Cathodic Protection of Tank Bottoms. Journal of Corrosion Science, Volume 47, pp. 849–868

Telles, J., Wrobel, W., Mansur, J., 2000. Boundary Elements for Cathodic Protection Problems. Boundary Elements VII, Volume 1, pp. 63–71