Stress-Affected Oxygen Reduction Reaction Rates on UNS S13800 Stainless Steel.

Carlos M Hangarter,Steven A Policastro,Rachel M Anderson

doi:10.3389/fchem.2022.820379

Carlos M Hangarter, Steven A Policastro + Show 1 more

Open Access

https://doi.org/10.3389/fchem.2022.820379

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Abstract

This work investigates the previously unexplored impact of tensile stress on oxygen reduction reaction (ORR) kinetics of a precipitation-hardened, stainless-steel fastener material, UNS S13800. ORR is known to drive localized and galvanic corrosion in aircraft assemblies and greater understanding of this reaction on structural alloys is important in forecasting component lifetime and service requirements. The mechano-electrochemical behavior of UNSS13800 was examined using amperometry to measure the reduction current response to tensile stress. Mechanical load cycles within the elastic regime demonstrated reversible electrochemical current shifts under chloride electrolyte droplets that exhibited a clear potential dependence. Strain ramping produced current peaks with a strain rate dependence, which was distinct from the chronoamperometric shifts during static tensile load conditions. Finally, mechanistic insight into the dynamic and static responses was obtained by deoxygenation, which demonstrated ORR contributions that were distinct from other reductive processes.

Highlights

Mechanical stress and strain effects on reaction kinetics are well recognized for noble metal electrocatalyst materials (Amakawa et al, 2013; Du et al, 2015; Yan et al, 2016)
These NaCl concentrations are of interest in atmospheric corrosion as they correspond to sea water and the equilibrium NaCl droplet concentrations at 25°C/80% RH, respectively (Tang et al, 1997)
In both cases onset of the hydrogen evolution reaction (HER) from water reduction occurs negative of the oxygen reduction reaction (ORR) limiting current, −1.0 VSCE in 0.6 M NaCl and −0.9 VSCE in the 4.6 M NaCl

Summary

INTRODUCTION

Mechanical stress and strain effects on reaction kinetics are well recognized for noble metal electrocatalyst materials (Amakawa et al, 2013; Du et al, 2015; Yan et al, 2016). This discrepancy was attributed to adsorption differences in the supporting electrolyte (KNO3 vs KSO4) as well as chemical and electronic structure differences of the passive film Qualitative agreement with the latter was observed for acid treated UNS S30200 stainless steel springs under tensile stress, but the magnitude was greater, essentially doubling the kinetic constant. Recent work in dilute chloride electrolytes has demonstrated that chloride ions decreased passivity due to hindered enrichment of Cr3+, Mo4+ and Mo6+ content, while increasing hydroxylation in the passive film outer layer (Wang et al, 2020) This suggests the range of chloride concentrations experienced during galvanic atmospheric corrosion likely has an impact on passive film structure and charge transport. Two different experimental cell configurations were used for complementary oxygenated and deoxygenated experiments that enabled further analysis of the amperometric results

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