The effect of pretreatments with siloxanes on the corrosion resistance of aluminium in NaCl solution

The inhibitory action of different pretreatments with metacryloxypropylmeth oxysilane (MAOS) on the corrosion of aluminium in NaCl aqueous 3.5% solutio ns has been examined. Free corrosion and electrochemical tests (potentiodynamic polarisation and electrochemical impedance spectroscopy) were performed to characterise the resistance to general and localised corrosion of pretreated specimens. The surfaces of uncorroded pretreated samples were characterised by SEM and AFM . Their surfaces were also examined with XPS technique before and after cor rosion attack. It was found that the inhibitory action of MAOS against general and localis ed corrosion depends on the nature of the solvent in which it is dispersed. The siloxane polymeric film formed by MAOS aqueous dispersion acts as a go od corrosion inhibitor in the whole exposure time range, whereas the inhibi tory power of the polymeric film formed by MAOS methanol solutions decrease s with increasing immersion time. (C) 1999 Elsevier Science S.A. All rights reserved.