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The electrodialysis reversal (EDR) technology was applied as tertiary treatment for final effluent from a Kraft pulp mill industry located in Bahia, Brazil. Two samples were evaluated: first, the f...

The malt bagasse is a solid residue, highly produced in the brewing industry. The presence of high levels of antioxidants in its composition makes this residue an attractive possibility as a corrosion inhibitor, besides being a sustainable and low cost alternative to the inorganic procedures currently used to prevent corrosion. In this sense, this work evaluated the efficiency of the malt bagasse powder as a corrosion inhibitor on the surface of AISI 1020 carbon steel, in different concentrations, in acidic medium 0.5 mol.L-1 HCl. The resistance to corrosion was tested by electrochemical techniques, such as electrochemical impedance spectroscopy (EIS) and anodic and cathodic polarization curves. The efficiency of the corrosion inhibitor was evaluated by weight loss tests. Fourier transform infrared spectroscopy (FTIR) and optical microscope surface image analysis were respectively used as chemical and morphological characterization techniques, respectively. From the EIS results, it can be said that the powder has its efficiency increased once the concentration is higher. On the other hand, the polarization curves shows the malt bagasse powder as an inhibitor presents both anodic and cathodic behavior. The weight loss results confirmed the electrochemical results, showing 92.5% efficiency for the 1.77 g.L-1 concentration. The adsorption isotherm on the steel surface follows Languimir’s Isotherm. The FTIR analysis indicates the presence of heteroatoms such as C, N, O, incorporated in functional groups that could be responsible for the inhibitory properties found in the powder. The images obtained from the optical microscope, showed that the corrosion process, in the presence of the inhibitor in the electrolyte, is retarded. Therefore, the results indicate that the malt bagasse powder has the potential to be a corrosion inhibitor for steel in acidic medium, adding value in the beer production chain.

A estatística descritiva é o ramo da estatística que visa sumarizar e descrever qualquer conjunto de dados, em outras palavras, está preocupado em sintetizar os dados. A presente pesquisa tem como objeto a análise da variabilidade pluviométrica mensal e interanual no município de Canavieiras, localizado no litoral Sul do Estado da Bahia, a partir de série histórica (2005 a 2018) associado com as técnicas de estatística descritiva, com o auxílio do software gratuito BioEstat versão 5.3. Os dados pluviométricos foram extraídos do Portal Hidroweb integrante do Sistema Nacional de Informações sobre Recursos Hídricos (SNIRH), do qual a Agência Nacional de Águas (ANA) é responsável pela coordenação. A precipitação pluviométrica é um fator importante na definição do clima de um município. Seu estudo tem grande importância devido à influência que exerce sobre as condições ambientais e socioeconômicas. Por meio dos resultados, constatou-se grande variabilidade das precipitações no que tange ao desvio em relação à média, com a quadra chuvosa concentrada nos meses de março a julho e em novembro. Foi possível comprovar que o mês de abril destacou por ter a maior variabilidade, com maior desvio padrão e segundo maior coeficiente de variação.

Electrodialysis is a mature technology that exceeded the boundaries of brackish water desalination and continuously shows its adaptability for several applications. Alongside with the evolution of ion-exchange membranes, electrodialysis is currently performed in a variety of arrangements under nonconventional applications and coupled with other technologies in hybrid systems. Throughout this chapter, recent achievements on wastewater treatment and water supply are presented. Novel results comprising the application of conventional electrodialysis, selectrodialysis, bipolar electrodialysis, reverse electrodialysis, electrodeionization, and overlimiting electrodialysis are discussed. The main motivations for ongoing efforts in optimizing electrodialysis systems rely on water supply in remote areas, on saving natural resources, and on reducing industrial costs.

In this work, the wettability of the galvannealed surface pretreated with the hybrid silane APTES/GPTMS film was measured by sessile drop method. The coatings were applied on the substrate from dip-coating method and dried in an oven. The study followed an experimental factorial design, 3³, with contact angle as response. The corrosion resistance was evaluated by electrochemical techniques and the surface morphology was characterized by scanning electron microscopy. The wettability results showed the best condition for galvannealed steel pretreated with the hybrid silane film for 2:1 APTES:GPTMS ratio, 2% silane concentration and 150 min of hydrolysis time, because the result may be related to a higher rate of hydrolysis of the silanes that is influenced by both the functional group present and by the type and number of hydrolyzed groups, resulting consequently in a higher availability of silanol groups in solution, promoting a greater crosslinking of the film on the metallic substrate. Keywords: hybrid silane, corrosion, galvannealed steel, pretreatment, wettability.

The extraction of high added-value compounds employing environmentally acceptable techniques that offer strong selectivity and fast mass transfer rates has attracted interest in various areas of chemistry and engineering. As a result, there are ongoing efforts to develop environmentally friendly processes that employ nonconventional techniques and reagents that are nonhazardous and renewable, which can be used to produce high-quality products, while protecting the environment. Supercritical fluid extraction has advantages that can overcome many of the limitations of conventional extractions, offering an economically viable and green alternative for different industrial sectors. The metal extraction industry is among those engaged in the continuous search for processes that are more efficient. In this sector, due to the gradual depletion of high-grade ores, there has been a focus on efforts to recover metals from complex ores and wastes. Among the different wastes containing metals, waste electrical and electronic equipment (WEEE) can be highlighted due to the large quantity of this material that is now generated. In view of these issues, the purpose of this chapter is to review the application of supercritical CO2 (ScCO2), in the presence of cosolvents and complexing agents, for the recovery of metals from different matrices.

The residue of Ethylene-Vinyl Acetate (EVA) generated in the footwear industry is an economic and environmental problem as it requires large area for storage in landfills and is not biodegradable or capable of transformation into other polymers. Its use as a lightweight aggregate in mortar and concrete results in a material with lower density but with reduced strength. In this paper, piassava fibers (Attalea funifera Martius) were used as reinforcement of lightweight concrete containing 4% and 6% of EVA, with the goal of improving the flexural strength of the material. The determination of density, compressive strength and flexural strength were performed at 28 days of age. The experimental results demonstrate that the addition of EVA decreases the density and flexural strength of the concrete in proportion to the amount of addition, but a recovery resistance is obtained when the piassava fibers are added in amounts of 1 to 2% by volume.

In this work, was performed a comparative analysis of the mechanical properties resulting from the addition of sisal and piassava fibers in lightweight cementitious composites with EVA. The workability, compressive strength, apparent specific mass, tensile strength in bending and deformation capacity were assessed in mixtures and cylindrical and prismatic specimens. EVA reduced apparent specific mass and mechanical properties of the composites. Sisal produced a maximum increase of 49.08% in tensile strength in bending of cementitious matrix with EVA, whereas piassava ensured greater deformation capacity up to rupture, with maximum elongation of 12.693 mm. Ultimately, sisal was more efficient as reinforcement.

RESUMO Silanos são compostos organo funcionais utilizados como agentes de acoplamentos entre interfaces orgânicoinorgânicas, com boas propriedades de adesão. Por esta razão, o uso de silanos como pré-tratamento para aços, vem ganhando espaço já que também são geradores de resíduos de menor toxidade ao meio ambiente e à saúde humana. Para melhorar a barreira de proteção do filme de silano e conferir propriedades de autorreparação, esses filmes podem ser modificados com íons cério. Assim, esse trabalho tem como objetivo avaliar a resistência à corrosão do filme de silanoviniltrimetoxisilano (VTMOS) modificado com íons Ce(III) ou íons Ce(IV) aplicado em aço carbono, utilizando a espectroscopia de impedância eletroquímica (EIE), técnica de varredura por eletrodo vibratório (Scanning Vibrating Electrode Technique -SVET), microscopia eletrônica de varredura (MEV) e transformada de Fourier de espectroscopia na região do infravermelho (Fourier Transform Infrared Spectroscopy -FTIR). Os resultados mostraram que os filmes com adição de íons Ce(IV) apresentaram uma melhor resistência à corrosão se comparados aos filmes com íons Ce(III), isto porque o filme formado com a adição de íons Ce(IV) mostrou um melhor efeito barreira devido à uma maior reticulação do filme. ABSTRACT Silanes are organo functional compounds used as coupling agents between organic-inorganic interfaces, with good adhesion properties. For this reason, the use of silanes as pre-treatment for carbon steel is becoming more and more applicable , since they are also generators of less toxicity residues to the environmental and human health. In order to improve the barrier protection of the silane film and confer self-healing properties, these films can be modified by addition of cerium ions. Thus, these work aims to evaluate the corrosion resistance of vinythrimethoxysilane (VTMOS) film modified with Ce(III) ions or Ce(IV) ions for carbon steel, using the electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that Ce(IV) ions addition improved better corrosion resistance than the films with Ce(III) ions. The higher barrier effect is since the film formed in the presence of Ce(IV) ions is better reticulated.

This study aimed to evaluate the effects on the physical and mechanical properties of the use of crushed sand in a cementitious composite containing EVA (6%) and piassava fibers (2%). Mix A (1:0.5:0.5) and Mix B (1:3:0.6) were used, with four different proportions of replacement of natural sand by crushed sand (0%, 25%, 50% and 100%). In mechanical tests, the Mix A showed no difference with the substitution of aggregates for all evaluated parameters. On the other hand, in the Mix B there was an increase of 54% in compressive strength, 59% in tensile strength in bending, and 79% in the durability test.

Water scarcity has been a cause of concern throughout the world. Brazil, home of the largest freshwater reserve in the world, is no different, as it suffers recurring problems of scarcity and the uneven distribution of water reserves. This research evaluated the Electrodialysis Reversal (EDR) process applied to the treatment of brackish water from the Almada River Basin, southern Bahia, known as the Cocoa Region, in northeast Brazil. In periods of water scarcity, marine intrusion causes high levels of salinity in rivers and freshwater wells. Water collected directly from the Almada River, with high concentrations of sodium and chloride, 661.3 mg/L 1,091.9 mg/L respectively, and electrical conductivity about 2.98 mS/cm, was treated in pilot-scale EDR equipment. The treatment reduced conductivity by 70–80 %, especially removal of sodium and chloride, found in higher concentrations than those found in higher concentrations than those established in regulations for drinking water. After EDR treatment under two different values of applied electric current, the water reached levels suitable for consumption. The system operated at 80 % water recovery rate. The power consumption calculated for each treatment was 1.06 kWh or 2.6 kW/m3 and 0.66 kWh or 1.7 kW/m3. EDR proved to be an efficient alternative to guarantee the supply of drinking water during periods of severe drought.

The increase in dental fluorosis in young people shows that the methods used to tackle the disease are ineffective. Typically, people around the world use groundwater for most activities, and this is the case of people especially in western Bahia, Brazil. In this region, aquifers can contain anomalous concentrations of fluoride. Thus, it is necessary to apply technologies to solve this problem by converting water resources rich in fluorides into drinking water. Consequently, in the present study, electrodialysis reversal (EDR) technology was used for defluoridation of natural water and synthetic solutions, simulating the fluoride concentration of natural water. Laboratory scale tests performed to treat synthetic samples with different fluoride concentrations, 1.5, 6.5, 9.1 and 13.0 mg F−/L, resulted in average fluoride removal of 90%. Additionally, one sample of natural water collected in the region of Cachoeira, city of Santana, Bahia, with an initial fluoride concentration of 7.49 mg F−/L was treated using EDR. Results showed that EDR removed around 80% of the fluoride. The EDR technology reduced fluoride water contamination and adjusted the water to drinkable standards at a feasible cost, showing the viability of EDR for treating water.

We conducted a theoretical study of ion transport through a polar cationic membrane subjected to the action of an electric field. We solved the transport equation without the usual electroneutrality assumption. We investigated the validity of the constant field approximation in the study of ion transport across a membrane and analyzed the case in which the membrane’s charge density is constant. We have shown, by numerical simulations, that the PS model (Sistat and Pourcelly, J Elec Chem 460:53, 1999) does not reproduce the three regimes of polarization curve mode. We also proposed an alternative approach to the problem based on Mean Field approximation. Our approach reproduces qualitatively better the well-known behavior of the polarization curve.

Corrosion represents high losses to the economy, therefore, researches on the minimization of its damages in materials, mainly the metallic ones, are necessary. Among the various alternatives of protection against corrosion, there is the application of corrosion inhibitors that can minimize or even stop the corrosive process of metallic materials. However, at present, substances usually used as corrosion inhibitors present high toxicity, being considered harmful components to the environment and to human health. Therefore, there is an urgent need for studies on viable corrosion inhibitors, by considering not only economic but also environmental costs. The present work studied the use of cocoa bark extract (Theobrama cacao L), for possible replacement of benzotriazole (BTAH) in the corrosion inhibition of ASTM 1020 carbon steel (CS- ASTM 1020) in 18.23 g.L-1 hydrochloric acid media. Weight loss measurements, anodic and cathodic potentiodynamic polarization curves and electrochemical impedance experiments were carried out. The results showed that the addition of the extract to the electrolyte effectively hinder the corrosion process and indicated its adsorption on the electrode surface. In addition, the inhibiting efficiency of the cocoa bark extract was only slightly inferior to BTAH, showing that it can be an environmentally friendly option to toxic inhibitors.

Metallic corrosion can be delayed using corrosion inhibitors. However, several industrial corrosion inhibitors are toxic and harmful to the environment and to the human health. In this context, in the last decades, research has been developed to investigate the performance of low toxicity corrosion inhibitors as green inhibitors obtained from vegetables, which are environmentally acceptable. The present work studied the corrosion inhibition efficiency of peel garlic extract (Allium sativum. L.) for possible replacement of benzotriazole (BTAH) on the corrosion inhibition of ASTM 1020 carbon steel (CS-1020) in 0.5 mol. L−1 hydrochloric acid media. Weight loss measurements, anodic and cathodic potentiodynamic curves and electrochemical impedance (EIS) experiments were carried out. The Fourier transformed infrared spectroscopy (FTIR) was carried out to evaluate the chemical compounds. The morphological characterization was obtained to observe the inhibitor effect in the corrosion products on substrate surface. The results showed that the addition of both inhibitors effectively hinder the corrosion process and indicated their adsorption on the electrode surface. The inhibiting efficiency of the peel garlic extract was only slightly inferior to BTAH showing that the former inhibitor can be an environmentally friendly option to toxic inhibitors. The FTIR analysis showed the presence of chemical compounds which presents antioxidant properties.

This work addresses the use of piassava fibers (PF) as reinforcement for recovered polypropylene (PPr) in the manufacturing of composites. The composites were molded with variable amounts of PF (10, 20 and 30 wt%), with and without maleic anhydride functionalized polypropylene (MAPP) (10 wt%) as compatibilizer. The composites were characterized using mechanical tests (flexural, tensile, impact and hardness), thermal analyses (thermogravimetric analysis and differential scanning calorimetry), along with evaluations of heat deflection temperature, melting flow index, density and morphology. Tensile and flexural strength of composites increased with PF content, but impact strength decreased, since the material became stiffer. The use of MAPP in the formulations yielded superior properties, showing good fiber/matrix interaction. In all, the use of PF as reinforcement in PPr was considered an interesting way of reducing solid waste and to reinforce plastics, being a possible alternative for the substitution of wood in WPC composites.

The aim of this paper was to evaluate the effect of hybridizing glass and curaua fibers on the mechanical properties of their composites. These composites were produced by hot compression molding, with distinct overall fiber volume fraction, being either pure curaua fiber, pure glass fiber or hybrid. The mechanical characterization was performed by tensile, flexural, short beam, Iosipescu and also nondestructive testing. From the obtained results, it was observed that the tensile strength and modulus increased with glass fiber incorporation and for higher overall fiber volume fraction (%Vf). The short beam strength increased up to %Vf of 30 vol.%, evidencing a maximum in terms of overall fiber/matrix interface and composite quality. Hybridization has been successfully applied to vegetable/synthetic fiber reinforced polyester composites in a way that the various properties responded satisfactorily to the incorporation of a third component.

PurposeThe application of coatings on metal substrates can provide an increase in corrosion resistance in the environment where the material is employed. The use of silane causes low environmental impact and may represent an alternative to replace chromates and phosphates applied as a pretreatment prior to surface painting. The objective of this study was to evaluate experimental parameters for the investigation of the formation of a vinyltrimethoxysilane (VTMOS) monolayer on 1010 carbon steel applying electrochemical techniques.Design/methodology/approachA total of 24 types of coated samples were obtained, following three 23 factorial design of experiments (DOE), and one uncoated. The VTMOS monolayer was formed by hand dip process, followed by curing in a stove, using substrates of sanded, pickled and degreased 1010 carbon steel and hydrolyzed silane.FindingsThe results of coated samples were satisfactory as compared to those of uncoated carbon steel, as the former were better protected against corrosion.Originality/valueThis paper shows an evaluation of experimental parameters that influence the formation of a film of silane VTMOS on 1010 carbon steel by means of electrochemical techniques. The results indicated that the silane monolayer VTMOS promotes enhanced properties that prevent corrosion of 1010 carbon steel and the method of film formation directly influences the properties of such protection.

The study of conducting polymeric membranes is decisive in some areas, as in fuel cells and electrodialysis. This work aims the study of membranes using conventional and conductive polymers blends. Two types of polyurethane were used as conventional polymers, commercial thermoplastic polyurethane and polyurethane synthesized from castor oil and 4-4-dicyclohexylmethane isocyanate. Two kinds of conducting polymers were used, polyaniline doped with organic acid and a self doped polyaniline. The polymers and the membranes were characterized by electrical conductivity, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). The synthesis of the membranes produced was proper, featuring a complete reaction, analyzed by FTIR. The membranes also showed good mechanical properties and thermal stability (≈ 220 °C). Among the membranes studied, the polyaniline doped with p-toluenesulphonic acid obtained higher thermal and viscoelastic properties. Thus they can be used in separation techniques using membranes.

In this study, thermal, mechanical and dynamic mechanical analyses of hybrid intralaminate curaua/glass composites were carried out. Distinct curaua/glass fiber content ratio and overall fiber volume fraction (20, 30 and 40 vol.%) were studied. Thermal analysis showed higher thermal stability for the glass reinforcement. Mechanical properties showed, in general, higher impact strength and hardness with glass incorporation. Dynamic mechanical properties showed an increase in storage modulus whereas the glass transition temperature showed no significant trend with glass incorporation. Furthermore, a significant increase in overall properties can be obtained without significantly change the glass transition temperature. Finally, the composites containing more effective reinforcement were more successful in maintaining their properties along the range of temperature studied. Hybridization has been successful and the composite with 30% of curaua fiber replacing the glass fiber displayed similar properties than the pure glass composite.

For nickel and cobalt recovery from spent NiMH batteries by electrowinning, the effect of different electrowinning parameters as boric acid concentration, temperature, current density, and pH were studied using different synthetic solutions. The optimized operational parameters were applied in an electrowinning test with a solution achieved by leaching the electrodes of NiMH batteries. The electrowinning tests were performed galvanostatically in a two-compartment cell separated by an anionic membrane. A platinum/iridium-coated titanium anode and a stainless-steel cathode were used. A sodium sulfate solution served as anolyte. The results demonstrate the technical viability of nickel and cobalt recovery. The chemical composition of the obtained deposit presented high nickel and cobalt concentrations.

Polímeros condutores são uma nova classe de polímeros que tem recebido especial interesse para a produção de membranas e filmes. A polianilina (PANI) destaca-se entre eles por sua elevada estabilidade química, fácil polimerização e baixo custo. O objetivo deste trabalho foi desenvolver uma blenda de polímero convencional (HIPS) com polímero condutor (PANI-CSA) e um filme de polianilina auto-suportado, usando ácido canforsulfônico (CSA) como dopante primário e 4-cloro-3-metil fenol (CMC) como dopante secundário. Estes dois materiais foram empregados como membranas íon-seletivas em um sistema de eletrodiálise para remoção de níquel de soluções. A membrana e o filme foram caracterizados por condutividade elétrica, MEV, espectroscopia FTIR, Raman e TGA. Os resultados obtidos apontam para a possibilidade de aplicação da membrana seletiva para eletrodiálise. A extração de níquel para a membrana sintetizada se mostrou semelhante à extração para a membrana comercial. O filme auto-suportado apesar de exibir boa resistência mecânica no estado sólido apresentou comportamento pouco satisfatório quando colocado em imersão com a solução de trabalho para eletrodiálise, devido ao seu estado quebradiço.

The conventional tannery effluents treatment is not established in order to obtain water in such a quality, that it could be reused in the same process. This study was carried out in order to evaluate the electrochemical treatment of tannery effluents. The photoelectrochemical oxidation and the electrodialysis were applied in these effluents. The obtained results indicated a remarkable removal efficiency of more than 98.5% for all ion species present in effluents. It is noticeable that the effluent treated with combined PEO–ED techniques presents very similar values for the same parameter as the ones presented by normal feed water.

The influence of experimental parameters on the formation of vinyltrimethoxysilane (VTMOS) film to protect 1010 carbon steel against corrosion by electrochemical impedance spectroscopy (EIS) and contact angle measurements was evaluated. Specimens were developed from three 23 factorial designs and an uncoated sample, where the EIS and contact angle were regarded as response variables. The results of coated samples were satisfactory as compared to those of uncoated carbon steel, as the former were better protected against corrosion, besides being more hydrophobic. The optimized specimens showed considerably increased EIS and contact angle values. It is concluded that the design of experiments developed favors to obtain a best finish of VTMOS silane on 1010 carbon steel, according to the EIS and contact angle techniques.

The method PECVD (Plasma Enhanced Chemical Vapor Deposition) enables the growth of hard DLC films, wear-resistant antifriction, with over bonds sp3 and less bonds hydrogen. This paper presents an experimental evaluation process of formation of vanadium carbide layer (VC) by reactive thermodiffusion process for subsequent deposition of DLC. The salt bath is carried out by mixing the reagents: sodium tetraborate decahydrate, vanadium pentoxide and boron carbide. A conical crucible with lid was used, with capacity of 25 grams. The method PECVD used: 200torr vacuum, argon at 1,5sccm, -600V at 0,05torr for 20 minutes, and acetylene at 1sccm, -750V for 40 minutes at 0,07torr and 180°C. It were used the tool steels AISI H13, D2 and O1. The layers of VC were characterized by SEM-EDX/EDS and XRD, and the DLC films were characterized by SEM-EDS, Indentation Test and Raman Spectroscopy. The oxygen proved to be harmful to growth in VC steel substrates by reactive thermodiffusion process. The project of conical crucible with lid reached the goal and contributed to the stabilization of thermodiffusion process, restricting efficiently oxygen environment ensuring complete immersion of the sample, and allowing the growth of VC uniform, homogeneous and efficient for subsequent deposition of DLC films.

The metal-finishing and tannery industries have been under strong pressure to replace their current wastewater treatment based on a physicochemical process. The electrodialysis process is becoming an interesting alternative for wastewater treatment. Electrodialysis is a membrane separation technique, in which ions are transported from one solution to another through ion-exchange membranes, using an electric field as the driving force. Blends of polystyrene and polyaniline were obtained in order to produce membranes for electrodialysis. The produced membranes were applied in the recovery of baths from the metal-finishing and tannery industries. The parameter for electrodialysis evaluation was the percentage of chromium extraction. The results obtained using these membranes were compared to those obtained with the commercial membrane Nafion 450.

Os poliaromáticos são um grupo de polímeros condutores composto por poliaminonaftalenos, poliaminoantracenos, poliaminonaftóis e polinaftoquinonas com a presença de dois ou três anéis aromáticos. Neste trabalho, filmes de poliaminoantraceno (PAA) e 1,5 polidiaminonaftaleno (1,5-PDAN) foram obtidos por eletropolimerização sobre eletrodos de platina, utilizando uma célula de três eletrodos e um único compartimento. Espectroscopia de infravermelho com transformada de Fourier (FTIR) e espectroscopia RAMAN foram usadas para investigar a estrutura do PAA e foi determinada que ela é similar àquela encontrada na polianilina (PAni) e nos poliaminonaftalenos. Estudos do comportamento eletroquímico por voltametria cíclica mostraram que tanto o PAA como o 1,5-PDAN apresentam somente um par redox e que o PAA não tem boa estabilidade à ciclagem repetitiva, ao contrário do 1,5-PDAN. Micrografias obtidas por Microscopia Eletrônica de Varredura mostraram filmes compactos e homogêneos, com estrutura globular para ambos os polímeros. The polyaromatics are a group of polymers composed by polyaminonaphthalenes, polyaminoanthracenes and polynaphthoquinones that have aromatic systems with two or three rings. In this work, films of polyaminoanthracene (PAA) and 1,5 polydiaminonaphthalene (PDAN-1,5) have been electropolymerized on Pt electrodes in a single compartment cell with three electrodes. Fourier transform infra-red (FTIR) and Raman spectroscopies have been used to confirm that the PAA structure is similar to that of polyaniline (PAni). Electrochemical studies have shown that the PAA and the PDAN-1,5 present only one redox pair. However, the PAA did not show a good electrochemical stability, in contrast to PDAN-1,5. The micrographs showed homogeneous and compact films, with globular structure and for both polymers, although PAA showed cracks produced during drying with cold air flow.

Atualmente o aço galvannealed é submetido à fosfatização e/ou cromatização como pré-tratamento superficial; no entanto, por questões econômicas e ambientais, estuda-se a viabilidade de utilizar os silanos como pré-tratamento alternativo. Os silanos são moléculas organofuncionais conhecidas por atuar como agentes de ligação entre superfícies orgânicas e inorgânicas, promotores de adesão em sistemas de pintura e também por fornecerem proteção contra a corrosão. A proteção à corrosão depende principalmente do silano a ser utilizado, das condições de hidrólise e de cura. O objetivo deste trabalho é estudar as condições de hidrólise através de um projeto estatístico de experimentos e o efeito na proteção contra corrosão, de um agente promotor de polimerização redox (íons de cério IV) ou de um inibidor de corrosão (íons de cério III) aplicado aos filmes de silanos (bis-silano funcional: bis-1,2- [(trietoxisilil)propil] tetrasulfeto (BTESPT) e bis-(g-trimetoxysililpropil)amina (BTSPA)) obtidos em 1%, 2% ou 3% de concentração de silano em massa de solução solvente água/etanol (50/50%), nos pHs 4,0, 5,0, 6,5 e 9,0, depositados sobre o aço galvannealed. A natureza porosa natural da superfície desse aço, consequência do tratamento térmico do revestimento de zinco, leva à necessidade de tempos maiores de imersão do metal na solução hidrolizada do silano para que seja completamente molhada levando à formação de um filme compacto e homogêneo. A adição de nanopartículas de sílica também foi estudada variando sua concentração nos filmes. A aplicação dos filmes sobre a superfície metálica foi feita pelo processo de dip-coating. Os filmes foram obtidos em mono e bi-camadas. As condições de cura, em estufa, para a mono camada foram à temperatura de 150ºC por 40 minutos. As condições de cura, em estufa, para a bi-camada foram: primeira camada à temperatura de 150ºC por 20 minutos e segunda camada à temperatura de 150ºC por 40 minutos. Os estudos eletroquímicos foram realizados utilizando medidas de técnica de varredura do eletrodo vibratório (SVET) e de espectroscopia de impedância eletroquímica (EIS), medidas de resistência de polarização linear (Rp) e curva de polarização potenciodinâmicas, obtidas respectivamente, em solução aerada de NaCl 0,05 mo.L-1 e 0,1 mol L-1. A caracterização química dos filmes foi feita através das técnicas de espectroscopia no infravermelho (IR) e micro Raman. A caracterização física das amostras foi analisada por medida da viscosidade cinemática. Foram obtidas medidas de ângulo de contato para caracterizar a hidrofobicidade da superfície do metal recoberto pelo filme de polissilanos modificados. As imagens de microscopias óptica, eletrônica de varredura (MEV) e de força atômica (AFM) foram obtidas para conhecer a morfologia do filme e dispersão (homogeneidade) das nanopartículas de sílica no filme. Os resultados mostraram que tanto para o filme de BTSPA como de BTESPT o pH ideal para a obtenção de um filme mais resistente à corrosão foi o pH 4,0. As análises físico-químicas mostram que a adição de íons Ce (III) ou íons Ce (IV) melhoram as propriedades protetoras e reticulação dos filmes, respectivamente, formando um filme mais homogêneo e compacto. As caracterizações morfológicas mostraram que as nanopartículas de sílica, quando em excesso, formam aglomerados na superfície porosa do galvannealed, promovendo trincas e diminuindo as propriedades anticorrosivas dos filmes. Currently, galvannealed carbon steel has been submitted to phosphatizing and/or chromatizing as surface pre-treatment; however, for economic and environmental issues, the viability to use silanes as an alternative pre-treatment has been studied. The silanes are organofunctionals molecules known for acting as coupling agents, adhesion promoters in paintings as well as for supplying protection against corrosion. The protection against corrosion depends mainly on the silane to be used, cure and hydrolysis conditions. The aim of this work is to study the conditions of the hydrolysis by a statistical project of experiments and the effect on corrosion protection, of either redox polymerization agent(ions of cerium IV) or a corrosion inhibitor (ions of cerium III) added to silane films (bis-functional silane: bis-[trimethoxysililpropyl]amine (BTSPA) and bis-1.2- [triethoxysilylpropyl]tetrasulfide (BTESPT)) obtained at silane concentration of 1%, 2% or 3% in mass of the solvent solution (50/50%) at pHs 4,0, 5,0, 6,5 and 9,0, deposited on galvannealed steel. The natural porous nature of the galvannealed steel surface as a results of thethermal annealing treatment o the zinc coating leads to higher needed immersion times inthe hydrolised silane solution in order to promote a complete wetting of the surface to reach a compact and homogeneous film. The addition of silica nanoparticles was also studied at different concentrationsin the films. The samples of galvannealed steel were immersed in the hydrolysis solution by dip-coating process. The films were obtained in mono and double layers. The cure conditions for the monolayer were obtained at temperature of 150ºC for 40 minutes. The cure conditions for the double layer were obtained: at temperature of 150ºC for 20 minutes for the first layer and at temperature of 150ºC for 40 minutes for the second layer. The electrochemical studies were performed using the scanning vibrate technique (SVET), electrochemical impedance spectroscopy (EIS), linear polarization resistance (Rp) and potenciodinamyc polarization curves, all measurements were obtained in aerated NaCl 0.1mol.L-1or 0.05 mol.L-1solution . The chemical properties of the films were analyzed by infrared (IR) and micro Ramanspectroscopies. The physical characterization of samples was performed by measuring the kinematic viscosity. The contact angle measurements were obtained in order to characterize the hydrophobicity of the silane film coated metal surface. The images from optical y, scanning electron (SEM) and atomic force microscopies (AFM) were performed to characterize the morphology of the film and/or the dispersion of silica nanoparticles in the film. The results showed that for BTSPA as well as for BTESPT the ideal pH to obtain a more corrosion resistant silane film is pH 4.0. The physico-chemical analysis showed that the addition of cerium (III) or cerium (IV) ions increases the cross linking of the film, and the film obtained was more homogeneous, compact and corrosion resistant. The morphological characterization showed that in the porous of galvannealed surface silica nanoparticles agglomerated, consequently promoting cracks and the decrease of anti-corrisive properties of the films.