The Effect of Atmospherically Formed Films on Cu Corrosion Properties using Single Droplet Electrochemistry

Abstract

This study explored the effects of atmospherically formed surface films and surface roughness on Cu corrosion behavior. A comprehensive suite of surface analysis techniques, including X-ray photoelectron spectroscopy, scanning electron microscopy, contact angle measurements, and confocal microscopy, were utilized to characterize the physicochemical properties of the surface films formed over 30 days. Then, both macroscale and droplet electrochemical measurements, such as open circuit potential and linear sweep voltammetry, were performed to explore the films’ effects on the aqueous and atmospheric corrosion behavior of Cu respectively. The results showed that the polarization resistance measured within the droplets was lower than that observed in macroscale experiments, attributable to the varying oxygen diffusion profiles. During atmospheric corrosion, the polarization resistance was dependent on the surface finish due to its impact on the film's composition. Surface characterization revealed the formation of hydroxide and defect oxides that varied between the different surface finishes, resulting in differences in polarization resistances over a 30-day period. However, the films did not affect the polarization resistance measured for samples that underwent aqueous electrochemical corrosion testing, possibly due to their solubility during the open circuit potential period prior to reaching a steady state. This study underscores the importance of surface films on atmospheric corrosion properties and brings skepticism to the need for cathodic cleaning of Cu during aqueous corrosion studies under aerated conditions.