IMPROVING THE FORMATION AND PROTECTIVE PROPERTIESOF SILANE FILMS BY THE COMBINED USEOF ELECTRODEPOSITION ANDNANOPARTICLES INCORPORATION

摘要

Silane coupling agents could improve the adhesion and protective properties of paints andrnorganic coatings on metals, and have been widely applied as an environmental compliant anti-corrosivernpretreatment of metals, aiming to alternating highly toxic chromating process. Recently, a novel technique,rnnamely electrodeposition, has been used to prepare silane films. Investigations indicated that thernelectrodeposited silane films performed higher corrosion resistance. Almost at the same time, it has beenrnreported that silica nanoparticles incorporations could also enhance the protectiveness of silane films. Inrnthis paper, these two novel techniques were used together to prepare protective organic-inorganicrnlong-chained dodecyltrimethoxysilane (DTMS)/SiO2 composite films on aluminum substrates. The resultsrnshowed that both the two techniques can improve the films formation and thereby their protectiveness. Therninfluences of the deposition potential and the silica content were investigated by electrochemicalrnimpedance spectroscopy (EIS) and scanning electron microscopy (SEM). As the deposition potential shiftsrnnegative or the silica content in the silane solution increases, the corrosion resistance of the prepared filmrnfirst increases to a certain value and then decreases. “Critical conditions”,I.e. a “critical depositionrnpotential” and a “critical silica content” were observed, respectively, under which the prepared silane filmsrnhad the highest corrosion resistance. The enhancement in film thickness has been detected in the case ofrnSiO2 incorporation and (or) cathodic electrodeposition from the depth profiles of the relevant atoms ofrnsilane films as measured by secondary-ion mass spectroscopy (SIMS), probably suggesting that the silicarnparticles participate in the film deposition.