Fundamentals and Control of CO2 and H2S Corrossion

This course will start with a background to the electrochemical nature of corrosion setting the scene as to the energetic driving force for corrosion and the electromotive force produced by galvanic cells. EMF voltages can be affected by both temperature and concentration, i.e. the Nernst Equation. Pourbaix developed the Nernst equation into a corrosion potential map, which we use to highlight when corrosion is possible or not possible.

However, the thermodynamic potential of corrosion occurs at zero current, and does not take into account the effect of constant current on voltages. For corrosion we need to understand the kinetics of electrode processes, best explained by constructing Evans diagrams. This finally allows us to thee the true complexity of corrosion and the difficulty in prediction. This is a significant amount of extremely complex chemistry, but without it we cannot understand the causes of corrosion.

The course will then look at sweet and sour corrosion, looking at how the corrosion product can affect corrosion rates, particularly the large surface area cathode effect. We look at the different types of corrosion modelling
software packages and discuss predictive corrosion modelling approaches.

Following that we tackle the complexities of sour corrosion, the causes of cracking and the toxicity of H2S, as well as corrosion mitigation strategies, starting off with coatings and pipelines, coating assessment, field joints and so on.

Finally we will complete the course with a discussion of cathodic protection, inhibitors, materials selection.