Microscale chemical imaging to characterize and quantify corrosion processes at the metal-electrolyte interface

TL;DR

This paper presents a novel microscale imaging setup combining optical microscopy and synchrotron techniques to study corrosion processes at metal-electrolyte interfaces with high spatial resolution, enabling in-situ analysis of corrosion mechanisms.

Contribution

The study introduces a new experimental capillary setup that allows real-time, in-situ chemical imaging and quantification of corrosion processes at the microscale.

Findings

Corrosion rates can be quantified in situ using X-ray transmission.

Oxygen and iron diffusion control ferrihydrite precipitation and transformation.

The setup reveals detailed corrosion mechanisms at the metal-electrolyte interface.

Abstract

We introduce an experimental setup to chemically image corrosion processes at metal-electrolyte interfaces under stagnant, confined conditions relevant in a wide range of situations. The setup is based on a glass capillary, in which precipitation of corrosion products in the interfacial aqueous phase can be monitored over time with optical microscopy, and chemically and structurally characterized with microscopic synchrotron-based techniques (X-ray fluorescence, X-ray diffraction, and X-ray absorption spectroscopy). Moreover, quantification of precipitates through X-ray transmission measurements provides in-situ corrosion rates. We illustrate this setup for iron corrosion in a pH 8 electrolyte, revealing the critical role of O2 and iron diffusion in governing the precipitation of ferrihydrite and its transformation to goethite. Corrosion and coupled reactive transport processes can thus be monitored and fundamentally investigated at the metal-electrolyte interface, with micrometer-scale resolution. This capillary setup has potential applications for in-situ corrosion studies of various metals and environments.