This study aims to develop a quantitative understanding of the effect of cathodic kinetics on IGC propagation at open circuit conditions. A new experimental setup using a sintered Ag/AgCl electrode as a combined reference and counter electrode was used to measure cathodic kinetics in thin films. This setup avoided the counter electrode products usually associated with a platinum electrode (H+ or OH-) and maintained uniform current density by placing the electrode right above and parallel to the sample.
Preliminary results indicate that under open circuit conditions (as experienced during service), the cathodic kinetics govern the IGC behavior under droplets/thin films. Different oxidizers like ozone (introduced in the gas phase) and potassium persulfate (introduced in solution) were used to increase cathodic kinetics. AA5083 samples were also coupled to carbon steel, which acted effectively as a galvanostat by suppling the cathodic current required to sustain the anodic activity on AA5083.
Initial thin film electrochemical results agree well with the existing corrosion framework for IGC in full immersion. An understanding of IGC in thin films/atmospheric exposures will provide a basis for developing a framework for IGC in service conditions.