Corrosion protective and adhesion properties of a melamine-cured polyester coating applied on steel substrate treated by a nanostructure cerium–lanthanum film

Abstract

The steel surface was treated by a nanostructure cerium–lanthanum conversion coating (Ce–La CC) and its effect on interfacial adhesion and corrosion resistance of a melamine-cured polyester coating (MCPC) was studied. The surface morphology of the samples modified with Ce–La CC was evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) while contact angle measurement was used for surface free energy and work of adhesion determination. The corrosion resistance of MCPC applied on surface-treated samples was examined by electrochemical impedance spectroscopy (EIS) and salt spray analyses, and pull-off test was used to analyze the coating adhesion properties. In addition, the effects of Ce–La CC surface treatment on the cathodic delamination rate of MCPC were studied. Experimental results showed that the adhesion and corrosion resistance of MCPC on the treated sample significantly enhanced as compared to the sample with natural FeO, Fe2O3 and Fe3O4 oxides. Furthermore, computational studies proved that the polyester coating adhered more strongly to conversion layer compared with iron oxide surfaces serving the untreated steel sample.