Effect of Temperature and Cl- Concentration on the Catalytic Activity of a Stainless-Steel Oxide

Abstract

Galvanic couples between high-strength, noble metal fasteners, such as those made out of titanium or stainless-steel, can cause extensive damage in aluminum alloy airframes. These galvanic couples can drive higher rates of oxidation than would be expected for general corrosion and the corrosion damage can become a stress concentration point for the nucleation of cracks. Understanding the factors that govern the catalytic activity for the oxygen reduction reaction on stainless-steel oxides is important for enabling predictions of the amount of corrosion that can occur for a given set of environmental conditions. We have focused on measurements of the diffusion limited current density for oxygen reduction on UNS S13800 stainless-steel in solutions of varying NaCl concentrations from 0.1 M to 4.6 M and air temperatures ranging from 10oC to 40oC. Estimates of the oxygen diffusion limited current were obtained from potentiodynamic polarization measurements under the various electrolyte concentrations and environmental conditions. The experimental data was then compared with calculated ilim values for the same conditions and assuming a constant diffusion layer thickness. Regression and physics-based models for the effect of environmental conditions on the experimental data have been developed and are used to estimate the effect of the electrolyte on the stainless-steel oxide.The U.S. Naval Research Laboratory sponsored this work under work unit 1L66. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Office of Naval Research, the U.S. Navy, or the U.S. government.