Research On The Potential Distribution On The Ship Hull Under Cathodic Protection

With the application and development of the computer and the modern numerical methods, finite difference method (FDM), the finite element method (FEM) and the boundary element method (BEM) have been applied to corrosion problems of the ship hull under cathodic protection. These methods have solved many complicated models of the cathodic protection problems successfully. But the numerical methods also have limitations. It is time consuming and costly for factories (such as shipyards) to estimate potential and current density distribution by using numerical methods. Therefore it is significant to find a simple method to describe the distribution of potential and current density under the cathodic protection.For the purpose of this research, the analytic method of electromagnetism theory, such as the method of separation of variables, Fourier method of integral transform, Hankel method of integral transform and the method of conformal transform are used to derive a series of analytic solutions of potential and current density for some typical calculation models for ship hull under cathodic protection. Comparing with the BEM, it shows that the feasibility of using those formulas to map the electric field under cathodic protection is convincible. Meanwhile, the guide ruler for arranging the sacrificial anodes and designing the insulating shielding reasonably is proposed in this thesis.Neural network method is also used to build the relationship between the analytic results and the BEM results. The position parameters and the analytic values of potential (or current density) are taken as the input parameters. And the BEM results are taken as the output parameters. Through the training performance, the initial weights and thresholds of the relationship between the results are obtained by using the gradient descent with momentum algorithms. At last, a simple method to calculate the values of potential and current density on the ship hull under cathodic protection which meets the precision requirement in engineering is realized.