Correlation between electrochemical impedance measurements and corrosion rate of magnesium investigated by real-time hydrogen measurement and optical imaging. (1st June 2015)

• Record Type: Journal Article
• Authors: Curioni, M.; Scenini, F.; Monetta, T.; Bellucci, F.
• Is Part Of: Electrochimica acta. Volume 166(2015)
• Page Start: 372
• Page End: 384
• Publication Date: 2015-06-01
• Subjects: magnesium -- corrosion -- electrochemical impedance spectroscopy -- hydrogen collection; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2015.03.050
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: The corrosion behaviour of magnesium in chloride-containing aqueous environment was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) performed simultaneously with real-time hydrogen evolution measurements and optical imaging of the corroding surface. The potentiodynamic investigation revealed substantial deviations from linearity in close proximity of the corrosion potential. In particular, differences in the slope of the current/potential curves were observed for small polarizations above or below the corrosion potential. These observations, suggest that the usual method based on the use of the Stern–Geary equation to convert a value of resistance into a value of corrosion current is inadequate. Nonetheless, a very good correlation between values of resistances estimated by EIS and corrosion currents obtained from real-time hydrogen measurement was found. Real-time hydrogen measurement also enabled, for the first time, direct measurement of an 'apparent' Stern–Geary coefficient for magnesium. In order to rationalize the complex behaviours experimentally observed, an electrical model for the corroding magnesium surface is presented.