A. Wantuch, E. Kurgan, P. Gas, “Numerical Analysis on Cathodic Protection of Underground Structures”, 2016 13th Selected Issues of Electrical Engineering and Electronics (WZEE), IEEE Xplore, 2016, art. no. 7800225, [pp. 1-4]. Available at: http://dx.doi.org/10.1109/WZEE.2016.7800225 978-1-5090-1015-8/16/$31.00 ©2016 IEEE Numerical Analysis on Cathodic Protection of Underground Structures Agnieszka Wantuch 1) , Eugeniusz Kurgan 2) , Piotr Gas 3) AGH University of Science and Technology Department of Electrical and Power Engineering al. Mickiewicza 30, 30-059 Krakow, Poland e-mails: 1) awantuch@agh.edu.pl, 2) kurgan@agh.edu.pl, 3) piotr.gas@agh.edu.pl Abstract — The presented paper describes the principles of cathodic protection (CP) of underground tanks using the sacrificial anode as well as method of calculation of the potential, current density and polarization distribution on all sides metallic tanks buried underground. Differential equations with boundary conditions are developed and next solved by FEM in 2D and 3D cases. The main goal of this publication is the computation of such distribution of the external protecting electrodes where protected structure will not corrode and next the calculations in 2D and 3D were compared. The article shows that it is sufficient to use 2D analysis for which the speed of equations solution is significantly larger than in 3D space. Keywords — impressed cathodic protection; corrosion; galvanic protection; finite element method I. INTRODUCTION The term “corrode” is derived from the Latin word “corrodere”, which means “to gnaw to pieces”. Corrosion is a natural process and it can be defined in many ways, for example as a destruction of metals by a chemical or electrochemical interaction with environment that produces a deterioration of the material and its properties. If the steel is e.g. in a dump ground that contains chemicals, the rusting process accelerates. Elements that influence on underground corrosion could be: soil pH value, soil resistivity, wetness, aeration, and other corrosive agents [1]. Corrosion in aqueous solutions proceeds by an electro-chemical process, therefore anodic and cathodic electro-chemical reactions must occur simultaneously. Any metal structures buried in the ground, such as pipelines, tanks are vulnerable to damage caused by the operation located in corrosive soil. From many years the problem of protection against corrosion has been described in many publications. Review of numerical methods applied for corrosion protection issue can be found at [2], [3], [4]. Simulation by adequate partial differential equations by finite element is the major technique used in a analysis of such problems. To accomplish the simulation of the different structures, it is required to have adequate data to serve as boundary condition at the different surface locations of the structure. On corroding surface different electrochemical reactions take place. From numerical simulation point of view, they can be represented by Butler- Volmer equation, which relates current density on surface from overpotential. This relation is highly nonlinear and has to be fulfilled on both anodes and cathodes. This fact causes substantial numerical difficulties by solution adequate partial differential equations with such highly nonlinear boundary conditions. Corrosion is a problem in many areas of life. It appears both in industry, construction, as well as household [5]. The damage caused by corrosion into the millions per year. Corrosion is still a huge problem so continued research is carried out to stop it. II. THE PRINCIPLES OF CATHODIC PROTECTION Metallic piping and propane tanks need cathodic protection to live a long time. Plating, painting or covering the steel tanks by the polyurethane coatings in the factory is the first line of protection against corrosion. But a coating system doesn’t give 100 % efficiency, only 50 to 99 % depending method of installation, upon age. Cathodic protection can be considered as the second line of defense. Importantly, it is one of the most common used electrical methods of corrosion prevention on metallic objects which are in water or soil [6] or there are exposed to other aggressive environment [7]. A. Theoretical Background In the process of corrosion two types of electrochemical reactions, anodic and cathodic, can be identified [8]. The most important cathodic reactions are the evolution of H 2 from acid, neutral or alkaline solution: 2 2 2H O 2e H 2OH       2 2H 2e H      Corrosion always occurs in the anode. The anodic reaction takes place: 2 Fe 2e Fe      The free electrons, which pass to another site on the metal surface, are absorbed by the cathodic reaction. The difference in natural potentials between the steel and the anode causes a positive current to flow from the anode to the steel, which becomes the cathode, because in this case, the total surface of the metal object becomes more negatively charged.