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An electrochemical study of the corrosion of polymer coated iron
Author(s) -
Feser Ralf,
Stratmann Martin
Publication year - 1990
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199000383
Subject(s) - corrosion , tafel equation , coating , electrochemistry , electrolyte , materials science , metal , chemistry , electrode , polymer , metallurgy , composite material , analytical chemistry (journal) , chromatography
In this study unconventional electrochemical techniques are introduced, which allow analysis of the corrosion of polymer‐coated metal surfaces. Due to the high ohmic resistance of polymer films conventional electrochemical techniques like impedance spectroscopy frequently provide no information about the corrosion reaction at the phase boundary metal/organic coating. Therefore, in this study, a second reference electrode positioned below the polymer film is used, which allows to measure or control the electrode potential of the interface metal/coating directly. Using this reference electrode dc‐ and ac‐measurements were performed. The diffusion coefficient of O 2 in an adherent coating is determined using well known transport equations. Furthermore, the corrosion kinetics of iron below the coating is elucidated. Whereas a Tafel‐slope of the iron dissolution of about 60 mV/decade is observed, the rate constant has to be much lower than for uncoated metals. Combining the results of dc‐ and ac‐measurements, the corrosion rate of coated iron in O 2 ‐saturated electrolyte is calculated, which is mainly controlled by the transport of oxygen through the coating.