New knowledge on localized corrosion obtained from local measuring techniques

• Published in: Electrochimica acta 2001-08, Vol.46 (24), p.3641-3650
• Main Author: de Wit, J.H.W
• Format: Article
• Language: English
• Subjects: AFM; Aluminum alloys; Applied sciences; Corrosion; Corrosion mechanisms; Exact sciences and technology; Filiform; Kelvin; Metals. Metallurgy; Pitting
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/S0013-4686(01)00642-9

Going back in history, corrosion was originally treated as a typical local phenomenon. The theoretical background in those early days was limited and mainly based on thermodynamics. Later, electrochemical theory developed, including reaction kinetics, leading to the mixed potential theory, which elegantly explained uniform corrosion phenomena. In the last decade, many local measuring techniques, with different lateral resolutions, have become available also for application in the electrochemical field. Since then, experimental evidence has been gathered, showing on a submicroscopic scale how in many cases corrosion phenomena can now really be described as local. Quantitative data on local anodic and cathodic potential values have become available. Two examples are given in this paper. The local attack of aluminum alloys, in relation to the microstructure resulting from different heat and quench treatments, was studied with scanning electron microscopy (SEM) and atomic force microscopy (AFM) with combined scanning potential technique. The in situ measured surface potential can explain the observed pitting in detail. Filiform corrosion, a typical example of an oxygen concentration cell, was studied with different techniques including electrochemical impedance spectroscopy (EIS), SEM/EDX and potential measurements with the Kelvin and AFM probes, while polarization curves for typical anolyte and catholyte solutions were related to the local corrosion phenomena in the filiform head.