Simultaneous pit generation and visualization of pit topography using combined atomic force–scanning electrochemical microscopy

• The operation of combined AFM–SECM for the nucleation of corrosion pits
• Single pit nucleation initiated from the combined effect of acidity and chloride ions
• Dual characteristics of nitrite as corrosion inhibitor and precursor for corrosive attack
• Real time visualization of pit topography during pit nucleation

Combined atomic force microscopy–scanning electrochemical microscopy (AFM–SECM) is for the first time used to generate single corrosion pits on passivating iron surfaces in the micrometer range. The AFM–SECM probe locally generates nitric acid during the oxidation of nitrite ions with the release of protons at selected sites on the surface of the otherwise passive metal. High confinement of passive film breakdown is achieved from the combination of a small probe size and the inhibiting properties of non-reacted nitrite ions on the surrounding passivated surface. Simultaneous visualization of pit nucleation and propagation can be obtained in the same solution without changing the probe by AFM.

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