The Real Electrochemical Boundary Conditions Based on the Polarization Process

To solve the problem of the boundary condition of the electrochemical field for a cathodic protection system of a steel offshore platform jacket, a new concept for the real electrochemical boundary condition was first proposed. The new idea considers that different points on the steel surface have different surface states and different polarization processes. The new method involved using sixteen sets of measurement equipment and a small test jacket to obtain different polarization processes at different points. A new test device was designed to obtain the relationship curves of potential/current density at different points. The polarization processes at different points were obtained. We first found that all polarization processes had four stages: rapid polarization, data jumping, polarization with middle speed, and slow polarization. At the end of the measurement, the current density interval exhibited a convergence phenomenon. The fitting curve based on the endpoint of the fourth stage of each relationship curve was regarded as the real boundary condition. The boundary condition was verified by the small test jacket and the real jacket. The comparison between the calculation and the measurement proved that the boundary condition was correct. The real boundary condition based on the new method reflected the real state and polarization process of the jacket and provided the correct incoming data for electrochemical field.