A study of dynamic nanoscale corrosion initiation events using HS-AFM

Area of Science:

• Materials Science
• Corrosion Science
• Surface Science

Background:

• Atomic Force Microscopes (AFMs) offer high-resolution surface mapping and property measurement.
• Conventional AFMs have limitations in observing rapid dynamic events.
• High-speed AFM (HS-AFM) operates significantly faster, enabling real-time imaging.

Purpose of the Study:

• To image nanoscale corrosion initiation events in real-time.
• To investigate localized corrosion on thermally sensitized AISI 304 stainless steel.
• To reconstruct local electrochemistry at nanoscale reaction sites.

Main Methods:

• Utilized high-speed atomic force microscopy (HS-AFM) for in situ imaging.
• Combined HS-AFM with Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) milling.
• Performed measurements within a custom liquid cell with electrochemical control.

Main Results:

• Captured multiple frames per second with nanometre lateral and subatomic height resolution.
• Observed and measured dimensions of pits formed at individual reaction sites, like grain boundary carbides.
• Calculated metal reaction volumes, current densities, and ionic fluxes over time.

Conclusions:

• HS-AFM is a powerful tool for studying dynamic nanoscale corrosion processes.
• The study provided a multifaceted picture of localized corrosion initiation.
• Local electrochemistry at nanoscale reaction sites was successfully reconstructed.