Microelectrodes for studies of localized corrosion processes

Electrochemical techniques using microcapillaries as electrochemical cells allow the study of local processes on passive metal surfaces. Due to the enhanced current resolution down to pA and fA, processes in the micro- and nanometer range can be studied. The results obtained on high-molybdenum containing stainless steel indicate that pit initiation is caused by active MnS inclusions. Molybdenum as alloying element has only a minor effect on the initiation process. The superior corrosion resistance of the high-molybdenum containing alloy has to be attributed to a considerably improved repassivation tendency. Noise measurements revealed that the current noise is largely caused by the dissolution of small inclusions. Furthermore microelectrochemical noise measurements allow evaluation of the experimental data with respect to their statistical relevance.