Finite element calculation of the polarisation behaviour of a metal in an aqueous solution using the dilute solution model

This article describes the calculation of the polarisation behaviour of a metal in an aqueous environment using a computational electrochemistry code based on finite elements. The corrosion system consisted of three parallel reactions (oxygen reduction, hydrogen evolution and metal dissolution), taking place in the centre at the surface of the rotating disc electrode (RDE). The selected problem is simple enough to be solved analytically, which allows verification of the finite element calculation. Simultaneously, the example is rich enough to demonstrate the potential and the advantages of finite element simulation for corrosion science and engineering. The analytical and finite element calculations were in excellent agreement. The influence of the speed of the RDE, of the bulk concentration of dissolved oxygen and of the bulk hydrogen ion concentration on the polarisation behaviour have been determined. The use of finite elements had the following specific advantages. Firstly, no prior assumption on the diffusion layer thickness had to be made. Secondly, transport by diffusion, convection and electro-migration were taken into account. Thirdly, the finite element approach is general and flexible enough to tackle more complex systems. The calculations presented here are a first step towards the finite element simulation of stress corrosion cracking of stainless steel in an aqueous nuclear environment.