Oxygen reduction reaction (ORR) is an important cathodic reaction that often drives galvanic corrosion. In atmospheric environments, this reaction is responsible for accelerated corrosion from enhanced transport associated with discontinuous electrolytes. In load bearing structures, galvanic couples are subject to mechanical stresses that often necessitates these dissimilar metal unions. Greater understanding of mechanical stress effects on fundamental reactions of galvanic corrosion, such as ORR, is important from a forecasting perspective for improved prediction of component lifetimes and service requirements. Furthermore, extension of this behavior to confined, concentrated electrolytes is important to understand stress effects in atmospheric environments.

This work reports the impact of tensile stress upon oxygen reduction reaction (ORR) for stainless steel fastener materials. Chronoamperometry was used to observe and quantify the influence of tensile stress profiles on ORR under NaCl droplet electrolytes. NaCl was utilized as a seawater proxy at concentrations of 0.6 M NaCl and 4.6 M NaCl, the latter corresponding to 80% relative humidity, which is near the deliquescence point for NaCl. The ORR current was shown to increase with tensile stress and displayed reversible behavior with simple stress profiles. Deoxygenated experiments were performed to isolate ORR contributions from oxide dynamics. Details of current transients during strain ramping are used to demonstrate these features are distinct from the ORR current shift observed during static tensile stress. Polarization experiments were performed during static tensile holds in the elastic and plastic regime for greater insight of stress effects on reduction kinetics. EIS and Mott-Schottky experiments were conducted to gain insight into the oxide behavior.