Early Stages of Film Formation and Surface Growth on Tin Electrodes at Bicarbonate Medium: a Modelistic Approach

Abstract

Abstract A modelistic approach of the early stages of film formation and surface growth on tin electrodes at bicarbonate medium under dynamic conditions is presented. The modelistic treatment was applied to both anodic and cathodic processes. In order to organise the paper, the potential interval of interest was divided into two potential windows, each one involving one of the anodic peaks and their corresponding cathodic counterparts. The Müller–Calandra model (also known as the layer-pore resistance model) was considered suitable to interpret the film growth processes occurring during the positive scan. A derivation of the former, developed by Devilliers et al., which take into account the conductive electrical nature of the surface compound, was applied to explain the reduction of the film formed within the first potential window. On the other hand, it was verified that the use of a simple model to interpret the cathodic process occurring at the second potential window was not possible due to the complex nature of the process. In this case, a mixed control kinetics was proposed and the current was considered as the sum of two contributions. In order to complement the description and specially to determine the role of diffusion and mass transport in film formation, rotating disk measurements were also carried out.