Abstract Aluminum alloys are the state-of-art materials for structural components of aircrafts. As they are susceptible to localized corrosion, this kind of damage can become a major threat for its safe use in aircraft components. Therefore, surface protection of aluminum alloys against corrosion is a core issue in these applications. In this work, an alternative eco-friendly cerium-based surface pretreatment was developed and applied on the AA1230 clad of the AA2024-T3 alloy for corrosion protection. The corrosion resistance evaluation of this modified surface was evaluated by several techniques. The results were compared to chromium based conventional treatments and revealed that the coating layer, composed of spherical nodular nanostructures of cerium, obtained with the proposed eco-friendly treatment, improved the corrosion resistance of the alloy. Moreover, it was comparable to the corrosion behavior of chromate-treated alloy, showing that this treatment is a promising alternative to replace chromate based surface treatments.

The construction of gold electrodes using 3 kinds of gold recordable compact discs (CDtrodes) and characterization by electrochemical and spectroscopic techniques are herein reported. Following a surface pretreatment in 0.5 mol L-1 sulfuric acid (H2SO4), the electrochemical experiments were performed in the presence of redox couple ferro/ferricyanide [Fe(CN)6]3-/4-. The immobilization of an oligopeptide bio-inspired by acetylcholinesterase onto the CDtrode was also evaluated. Surface characterization was done by cyclic voltammetry, electrochemical impedance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy and atomic force microscopy. CDtrodes are known to be of low cost, fast and simple construction. They are suitable for immobilizing biological molecules and could be used as disposable transducer for the construction of biosensors.

Austenitic stainless steels, titanium and cobalt alloys are widely used as biomaterials. However, new medical devices require innovative materials with specific properties, depending on their application. The magnetic properties are among the properties of interest for some biomedical applications. However, due to the interaction of magnetic materials with Magnetic Resonance Image equipments they might used only as not fixed implants or for medical devices. The ferromagnetic superalloys, Incoloy MA 956 and PM 2000, produced by mechanical alloying, have similar chemical composition, high corrosion resistance and are used in high temperature applications. In this study, the corrosion resistance of these two ferritic superalloys was compared in a phosphate buffer solution. The electrochemical results showed that both superalloys are passive in this solution and the PM 2000 present a more protective passive film on it associated to higher impedances than the MA 956.

In the present work, the electrochemical behavior of WC-CoCr coatings with 10 (W10), 15 (W15) and 20 (W20) torch passes sprayed by High Velocity Oxygen-Fuel (HVOF) flame on AA7050 aluminum alloy substrate, evaluated in 3.5% NaCl solution, were compared using open-circuit potential (E OC) measurements, electrochemical impedance spectroscopy (EIS) and polarization curves. The coating surfaces and their cross sections were characterized by X ray diffraction and the Rockwell-C hardness test, and also by optical (OM) and scanning electron microscopy (SEM) before and after the corrosion tests. The electrochemical data showed that sample W10 presented higher corrosion resistance than the others in chloride solutions. In some tests, aluminum salts on the coating surface were identified by EDS, indicating the corrosion of the substrate. And using aluminon, aluminum ions were detected and analyzing the surface via stereomicroscopy, hydrogen bubbles were observed, both showing that the electrolyte reached the substrate and galvanic corrosion possibly occurred. The physical characterization showed that sample W10 presented a lower number of cracks and pores, justifying its higher corrosion resistance.

O setor automotivo é um dos mais competitivos e um grande consumidor de materiais ferrosos, que exigem uma eficiente proteção contra a corrosão. Esta proteção é alcançada aplicando revestimentos adequados. Para se aplicar revestimentos se requer uma cuidadosa preparação da superfície que pode ser feita por ataque químico. Neste trabalho, determinou-se a velocidade de reação do aço extra-doce, SAE-AISI 1005, laminado a frio (CFF) utilizando várias soluções ácidas, de baixo custo, baixa agressividade ao meio ambiente e que geram pouco hidrogênio. O estudo cinético foi realizado medindo-se a perda de massa (deltam/mg cm-2) de chapas de aço CFF em função do tempo (s) de reação nas diferentes soluções, com e sem agitação, a 30ºC. Os resultados foram interpretados considerando-se os efeitos de transporte de massa, o efeito oxidante dos íons Me3+ e inibidor dos íons Fe2+. Dentre as várias soluções estudadas a que apresentou maior velocidade de reação foi a solução de H2SO4 2 M + MeCl3 1 M, v = 15,44 x 10-6 g cm-2s-1 para tempos até 1800 s.

The automotive sector is one of the biggest consumers of ferrous materials, which require an efficient protection against corrosion. This protection can be reached applying adequate coatings. A careful surface preparation is required to apply any kind of coatings on surfaces. The surface preparation can be done by a chemical attack. In this work, reaction rates of cold-rolled steel with different acid solutions were determined. The solutions used have low cost, are environmental friendly and some of them generate low quantity of hydrogen. The kinetic study was performed measuring the loss of mass (deltam/mg cm-2) of cold-rolled steel samples with time (s) reaction in the different solutions, with and without solution stirring, at 30 ºC. The results were interpreted considering the mass transfer effect, the Me3+ oxidizing and Fe2+ inhibitor effects on the steel dissolution. Among the different solutions studied, the 2 M H2SO4 + 1 M MeCl3 solution was the one that showed the highest rate, v = 15.44 x 10-6 g cm-2 s-1 for times up to 1800 s.