Investigating corrosion using high-speed AFM

The unpredictable nature of stress corrosion cracking (SCC) calls for further research into the mechanisms under which it and other forms of destructive corrosion occur. Observation of crack initiation at the nanoscale could give valuable insight into the processes that take place within metals during SCC. The high-speed atomic force microscope (HS-AFM) we have developed operates at speeds orders of magnitude faster than conventional atomic force microscopes (AFMs), and is capable of capturing multiple frames per second, allowing for dynamic events to be observed directly in real-time, with nanometre lateral resolution and subatomic height resolution [1]. Furthermore, HS-AFM is a valuable tool for studying solid-liquid interfaces and as such has the potential for in situ corrosion studies [1]. The applications for HS-AFMs are still relatively unexplored, and advances in HS-AFM technology are ongoing. In this paper, corrosion mechanisms were investigated using our contact mode HS-AFM. Hardness induced topographic maps of the surface of sensitised austenitic stainless steels have been produced, in which chromium carbide precipitation can be clearly seen by means of proper surface preparation [2]. Furthermore, a micro strain rig was custom built such that samples could be imaged under stress, alongside corrosive conditions, for investigations into SCC initiation. Laferrere et al. have previously demonstrated the use of HS-AFM to image nanoscale corrosion events, with parallel electrochemical control [3]. The research presented here builds upon this previous investigation, further substantiating the capability and potential of HS-AFM for applications in materials and corrosion science.