Hybrid films with (trimethoxysilylpropyl) methacrylate (TMSM), poly (methyl methacrylate) PMMA and tetraethoxysilane (TEOS) applied on tinplate

Abstract

The tetraethoxysilane (TEOS) influences morphological and electrochemical properties of hybrid films by function of concentration. Moreover, the use of acetic acid as a catalyst in the sol enables a more complete hydrolysis of the silane precursors due to the fact that the acetic acid goes through a more complete ionization when in aqueous solution. The aim of this paper is to study the effect of the concentration of tetraethoxysilane (TEOS) on the protective properties of the film on tinplate substrate. The tinplate was coated with a hybrid film obtained from a sol-gel method constituted of the following alkoxide precursors: 3 - (trimetoxisililpropil) methacrylate (TMSM) and poly(methyl methacrylate) PMMA. The effect of tetraethoxysilane (TEOS) concentration has also been evaluated. The films hydrolysis was performed at a pH value of 3. 0 using acetic acid as a catalyst. The films were obtained by dip-coating process, cured for 3 hours at 160 ºC. The film morphology was evaluated by SEM and profilometry. The electrochemical behavior of the films was evaluated by open circuit potential monitoring, potentiodynamic polarization and electrochemical impedance spectroscopy. The film hydrophobicity was determined by contact angle measurements. The studied films have shown good performance as to corrosion resistance on tinplate. The hybrid film which was obtained through the addition of an excessive amount of TEOS (T3A3) showed increased thickness. Nevertheless, due to an intense densification of the film, promoted by the addition of TEOS, a formation of cracks was registered, thereby compromising the corrosion resistance.