Local Electrochemical Methods to Study Corrosion Processes on a Molecular Level

摘要

The corrosion resistance of technical passive alloy is often limited by chemical or structural heterogeneities that might act as potential initiation points for localized corrosion. Micro-and nanoelectrochemical techniques are powerful methods to study the local phenomenas occurring at such heterogeneities. This paper gives a overview of local electrochemical techniques, which are applied to investigate initiation and propagation processes of localized corrosion. A local technique which uses glass microcapillaries as electrochemical microcell is presented. The possibilities and the limitations of the technique are demonstrated. The results of pit initiation studies at sulfur inclusions on 304 stainless steels demonstrate the potential of local corrosion experiments. Corrosion measurements in different scales showed different information. Electrochemical experiments using capillary with a tip diameter in the range of 100 #mu#m allowed evaluating the corrosion behavior of sites that contained a single weak point. Electrochemical measurements using capillary with a tip diameter in the range of 1 #mu#m allowed investigating different spots of single weak point. Hence the corrosion behavior of the weakest zone can be determined.