Application of Electrochemical Impedance Spectroscopy and Surface Analysis to the Study of Corrosion Protection of Carbon Steels by Phosphonates

摘要

Surface treatments have been carried out on a carbon steel in solutions containing a monoacid phosphonate (ethyl octodecylphosphonate (EODP)) and a mixture of phosphates (mefhacryloxyethyl-phosphate (MOP)) bearing between one or two acid groups. Corrosion protection afforded by the compounds has been studied by steady-state current-voltage curves and electrochemical impedance measurements using a rotating disk electrode. High protection was obtained by the mixture 1 % MOP and 1 % EODP.Surface analyses (Raman and FTIR spectroscopies, XPS) indicate that the film was essentially the Fe(EODP)_2 complex. MOP plays a significant role at the interface by forming a thin oxide layer which improves the development and the adherence of the layer formed by EODP.