CARACTERIZAÇÃO DAS CAMADAS DE Nb2O5 NA AUSÊNCIA OU PRESENÇA DE NANOTUBO DE CARBONO E/OU CARBETO DE SILÍCIO NA SUPERFÍCIE DA LIGA DE ALUMÍNIO AA 3003

Abstract

It is a public knowledge the widespread use of metals in industrial production sectors, some of them addition requiring to the specific characteristics of these material improvements as resistance to corrosion or mechanical, such as hardness, friction, etc. A process for increasing the corrosion resistance and toughness of the metal material, is the chroming, however health problems entailed by their use, because chromium is a carcinogen, has caused the use of this process constraints. Searches are developed to meet the processes that take place in chroming, including NIKASIL®, a process based on nickel and silicon carbide (SiC), also due to problems caused by allergens nickel, has been minimized their industrial application . This work aimed to study and develop a process of metal coating the basis of Nb2O5, carbon nanotubes (NTC) and silicon carbide (SiC), AA 3003 aluminum alloy for replacing the Cr-based treatments 6. This study employed electrochemical techniques and not electrochemical such as: experimental design, anodic potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), X-ray diffraction, thermogravimetry, X-ray fluorescence, X-ray photoelectron spectroscopy, scanning electron microscopy , abrasion and deformation. The experimental results showed that the most effective coating based Nb2O5 obtained by the Pechini method, the conditions were: 5 minutes of immersion and emersion into the polymer resin, a speed of 12 cm min-1, with an initial heat treatment by 60 minute at 100ºC followed by 20 minutes at 450ºC. The sol gel molar ratio was 1:4 (citric acid / ethylene glycol) and acid and niobium ammonium complex of 10:1 (n/n). The morphology of the film formed is homogeneous and comprises organic matter and Nb2O5. Better corrosion resistance is obtained with the proposed Nb2O5 coating, compared to surface treatment Cr+6, suggesting a possible replacement of coating. The addition of SiC NTC and the process of obtaining the Nb2O5 film promotes minimizing the corrosion resistance of the coating, however, increases the hardness and abrasive wear resistance thereof. EIS measurements showed that the film generated Nb2O5 have not the same self-healing of the base film of Cr+6, however, it was observed that for the coated substrate Nb2O5 times until to 96 hours of immersion in the test electrolyte, the strength values were recorded in the order of 105 ohms cm² higher than those of Cr+6 coating, and immersion until to 96 hours for coating scratched Nb2O5 impedance values were higher than those of Cr+6 coating.