Passive Behavior and Passivity Breakdown of AISI 304 in LiBr Solutions through Scanning Electrochemical Microscopy.

The passive behavior and passivity breakdown of AISI 304 stainless steel in LiBr solutions has been investigated by means of scanning electrochemical microscopy (SECM). The sample generation -- tip collection (SG-TC) mode was used to operate the SECM and the tip potential was biased to detect the electroactive species. The evolution of the current at the ultramicroelectrode tip with the applied potential within the passive range was followed at different LiBr concentrations. Results show that the absolute value of the current at the tip increases with the applied potential. Additionally, SECM was also used to detect stable pits formed on the stainless steel surface in a 0.2 M LiBr solution. The results show clear evidence of the presence of high amounts of other reducible species (metal cations) apart from oxygen. Also, the dish-shape morphology of the pits observed using Confocal Laser Scanning Microscopy will be discussed in relation to the kinetics of the reactions observed using SECM. [ABSTRACT FROM AUTHOR]