Protective properties of cataphoretic epoxy coating on aluminium alloy \AA6060\ modified with electrodeposited Ce-based coatings: Effect of post-treatment

By Ljiljana S.
Published in Progress in Organic Coatings NULL 2015

Abstract

Ce-based conversion coatings (CeCCs) are a promising alternative to toxic chromate coatings on the metal substrates. In this work the CeCCs were electrodeposited on aluminium alloy \AA6060\ from aqueous solution of Ce(NO3)3 at different potentials (?0.95 V, ?1.2 V and ?1.4 V). Effect of deposition potential and post-treatment in the phosphate solution on morphology and protective properties of CeCCs with top cataphoretic epoxy coating was studied. To assess the differences between the protective systems, originating from the different CeCCs pre-treatments, electrochemical impedance spectroscopy (EIS), polarization measurements, \AFM\ and SEM/EDS analysis were used. The \EIS\ study was undertaken to follow the evolution of corrosion behaviour of epoxy coating/CeCCs protective systems over prolonged time of exposure to the chloride environment (3 wt.% NaCl). Results suggest significantly improved corrosion stability of epoxy coating on \AA6060\ with as-deposited CeCCs sub-layers with respect to the same epoxy coatings with phosphate post-treated CeCCs. The far best protective properties, i.e., the greatest value of pore resistance and the lowest value of corrosion current density were provided by the epoxy coating/CeCC protective system with CeCC deposited at ?1.2 V and without post-treatment.

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