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In Situ Investigations of Corrosion via SPM
This publication explores the use of Scanning Probe Microscopy (SPM) for in situ investigations of corrosion processes on metallic surfaces, with examples including stainless steel and aluminum. Corrosion, an interfacial phenomenon beginning at the atomic scale, makes SPM a valuable tool for real-time, high-resolution studies of structural and kinetic aspects under various conditions.
The study demonstrates the dissolution of 304 stainless steel in sodium chloride solution, revealing pitting corrosion mechanisms, and the selective dissolution of aluminum in chloride media. High-force scanning induced localized corrosion on aluminum, highlighting the role of chloride ions in breaking passivating layers. In another example, the stepwise dissolution kinetics of an aluminum thin film in sulfuric acid were captured, emphasizing terrace and defect reactivity.
These findings illustrate SPM’s capabilities for studying corrosion at nanoscale resolution, providing insights into surface interactions, inhibitor effects, and the development of advanced corrosion-resistant materials and coatings.
Oxygen-Free High-Resolution Electrochemical SPM
This publication evaluates the Agilent 5500 AFM’s oxygen-free environmental chamber and its utility in high-resolution in situ electrochemical scanning probe microscopy (EC SPM). The study demonstrates its efficacy through experiments involving reductive desorption of alkanethiol self-assembled monolayers (SAMs) and underpotential deposition (UPD) of copper on gold surfaces.
By purging with nitrogen, the chamber achieves oxygen levels below detection limits, enabling stable cyclic voltammetry measurements and eliminating background currents that interfere with electrochemical processes. This capability was critical in resolving the reductive desorption potentials of C6, C8, C10, and C18 SAMs, which varied from -0.69 V to -0.98 V against an Ag quasi-reference electrode.
The chamber also facilitated atomic-level imaging of transitions between Au (1×1) and sulfate (√3×√3) structures during Cu UPD. These results highlight the chamber’s suitability for oxygen-sensitive EC SPM research, ensuring precision in studying electrochemical reactions and molecular-level transitions.