Corrosion Electrochemistry at Micro/Nano-Scale

Abstract

A fundamental understanding of corrosion mechanisms is the key to developing suitable corrosion protection approaches for metallic structures and new corrosion resistant alloys for emerging technologies. However, corrosion testing methods such as mass loss and conventional electrochemical testing average over large areas and thus often mask the underlying mechanisms, due to either low sensitivity, low resolution, and/or a lack of element-resolved information. Recent advances in electron microscopy have led to development of liquid-cell transmission electron microscopy (LC-TEM) that allows in-situ monitoring of morphological and even compositional evolution in materials at high spatial resolution during interactions of surfaces with aqueous environments. However, electrochemical testing in such restricted volume with a very thin (~ 500 nm) electrolyte layer places stringent demands not only for a reference electrode, but also for a comprehensive understanding of the factors affecting electrochemical kinetics at the nano-scale1.In order to solve the need for a micro-reference electrode, we recently proposed the concept of metallic Luggin-Haber probe2. The metallic Luggin-Haber probe is a metal wire that serves as a bridge between the test solution and the reference electrode that was in a physically-distinct container. In standard-scale electrochemical cells, it was found that the metal bridge (MB) provides a means of making potential measurements that are identical to those made using a direct reference electrode or using a salt bridge.The MB is shown to be compatible with a wide range of electrochemical techniques including cyclic potentiodynamic polarization and electrochemical impedance spectroscopy. The present work explores the compatibility of the MB for electrochemistry in LC-TEM using Pt as working electrode. The work includes the effect of radiolysis of electrolyte, electrolyte flow rate, pH and potential scan rate on electrochemical kinetics when using LC-TEM, in a detailed comparison with results obtained using a standard-scale electrochemical cell. Present work is a discrete effort towards developing advanced methodologies for electrochemical measurement in situations involving restricted electrolyte volume including thin electrolyte layers, droplets, localized corrosion sites, batteries and fuel cells. References A. Kosari, H. Zandbergen, F. Tichelaar, P. Visser, H. Terryn, and A. Mol, Corrosion, 76, 4–17 (2020).S. Choudhary, K. Marusak, T. Eldred, and R. G. Kelly, J. Electrochem. Soc., 169, 111505 (2022).