Benefits and drawbacks of pourbaix diagram

Although Pourbaix diagrams are one of the most elegant and probably the least labour intensive ways of modelling the corrosion processes, there is no comprehensive review of benefits and drawbacks of this method. Pourbaix approach is extremely useful for visualisation of materials behaviour in corrosive environments. This method is applicable to alloys as well as pure metals, and can help in the analysis of complex environments with multiple ionic species present. The diagrams conveniently summarise thermodynamics of the corrosion process (pressure, temperature, pH, electrochemical potential, phase stability) and readily propose the remedy (cathodic/anodic protection options). However, this method is limited to wet corrosion where varying pH is involved. In addition, Pourbaix diagrams fail to account for localised nature of corrosion and provide only general prediction for uniform corrosion. Although it is possible to build the diagrams for alloys, such atlases do not reflect on the particular compositions. Finally, one of the most crucial drawbacks of this simple yet powerful method is that it shall not be used for evaluation of the kinetics of the process. This paper discusses each of these issues in detail and provides recommendations and guidelines for the effective use of Pourbaix diagrams in various situations.