No abstract

No abstract

No abstract

In the present study we compared the beneficial effect on the incorporation of modified silane nanocoating and conducting polymer additive to the adhesion and protection of aluminium surface with epoxy coating. Results proved that the protection imparted by the silane coating, suitably modified with phosphonic groups, showed an excellent adhesion to the metallic substrate as well as good adherence with the epoxy outer layer, which result in an improved corrosion resistance. The incorporation of 1% of poly (3-methyl thiophene acetate) (P3TMA) also improved the adhesion force of the epoxy paint adhered to the aluminium surface. However, the adhesion force decreased with the increase of the immersion time in NaCl 3.5% solution. In conclusion, both bilayer systems [vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) and VTMS/TEOS/ ethylenediaminetetra(methylene phosphonic acid) (EDTPO)] and also the employment of P3TMA in the epoxy coating showed better results in accelerated corrosion assays, i.e. very low blistering formation was observed, compared with control samples based in a monolayer coating directly adhered to the aluminium surface.

Polypyrrole films doped with oxalic acid and tungstate were potentiostatically electropolymerized on aluminum alloy 1100. Two statistical factorial designs (fractional and complete) were used to study the influence of the synthesis variables on the film performance against corrosion. Corrosion protection of the polypyrrole films doped with oxalate and tungstate anions (PPy/OXA/W) on the aluminum alloy was evaluated by potentiometric and electrochemical impedance spectroscopy (EIS) measurements in a 0.05 mol L -1 NaCl solution. The results obtained showed that the best performance against corrosion was detected with the PPy/OXA/W film synthesized at 1.0 V, 1.5 C in 0.2 mol L -1 pyrrole, 0.1 mol L -1 oxalic acid and 0.05 mol L -1 sodium tungstate solutions provide a protective effect against corrosion.

Sol-gel films were prepared using different ratios of two silica precursors, vinyltrimethoxysilane (VTMS) and tetraethylorthosilicate (TEOS), targeting the anticorrosion treatment of aluminum alloy 2024-T3. The electrochemical behavior of the alloy coated with such films, which was studied in a 0.05 mol L -1 NaCl solution, revealed that the VTMS/TEOS ratio drastically affects the anticorrosion performance. Electrochemical impedance spectroscopy (EIS) results provided evidences that the best anticorrosive response occurs with the films prepared from 50% v/v ethanol, 46% v/v water, 3% v/v VTMS and 1% v/v TEOS. Moreover, the effects of the addition of ethylenediamine tetra(methylene phosphonic acid) (EDTPO) to a hybrid sol-gel matrix were examined. The corrosion resistance was considerably improved when the concentration of added phosphonic acid was 3.7510 -5 mol·L -1 . Scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses revealed that EDTPO-containing films provide a more uniform coverage. Results evidenced the formation of Si-O-Al linkages in the VTMS/TEOS and VTMS/TEOS/EDTPO systems and that the VTMS/TEOS/EDTPO system contained P-O-Al linkages. The P-O-Al bonds, combined with the silica network action, may be responsible for the good anticorrosive behavior of the VTMS/TEOS/EDTPO films.

No abstract

No abstract