In situ electrochemical scanning probe microscopy corrosion studies on duplex stainless steel in aqueous NaCl solutions

Electrochemical scanning tunnelling microscopy and atomic force microscopy have been used to observe, in situ and in real time, the early stages of corrosion on duplex stainless steel in aqueous NaCl solution. With the specimens polarised in the transpassive region, the in situ techniques monitored clearly a process involving first a progressive etching of the damage layer, second the appearance of austenite and ferrite phases, and finally the formation of corrosion pits. A summary of these results is presented and the advantages and disadvantages of such in situ approaches are illustrated by comparing these observations with those obtained by ex situ examinations of the corroded specimen surfaces. (C) 1996 The Institute of Materials.