Abstract Bovine infectious mastitis is largely resistant to antibacterial treatment, mainly due to mechanisms of bacterial resistance in the biofilms formed by Staphylococcus aureus. Melaleuca (MEO) and citronella essential oils (CEO) are promising agents for reducing or eliminating biofilms. Free melaleuca oil presented a medium Minimum Inhibitory Concentration (MIC) of 0.625% and a Minimum Bactericidal Concentration (MBC) of 1.250%, while free citronella oil showed medium MIC and MBC of 0.313%. Thus, free CEO and MEO demonstrate bacteriostatic and bactericidal potential. We generated polymeric nanocapsules containing MEO or CEO and evaluated their efficacy at reducing biofilms formed by S. aureus. Glass and polypropylene spheres were used as test surfaces. To compare the responses of free and encapsulated oils, strains were submitted to 10 different procedures, using free and nanoencapsulated essential oils (EOs) in vitro. We observed no biofilm reduction by MEO, free or nanoencapsulated. However, CEO nanocapsules reduced biofilm formation on glass (p=0.03) and showed a tendency to diminish biofilms on polypropylene (p=0.051). Despite nanoencapsulated CEO reducing biofilms in vitro, the formulation could be improved to modify the CEO component polarity and, including MEO, to obtain more interactions with surfaces and the biofilm matrix.

Biodiesel is a renewable fuel produced from vegetable oils and animal fats transesterification. However, due to its chemical characteristics, it is susceptible to oxidation causing losses to its manufacturers and users. In this work a series of salicylates were synthesized and employed as secondary antioxidants in biodiesel B100. The accelerated oxidation tests were carried out against copper and iron. The biodiesel oxidation degree was followed by the acidity index. Among the synthesized compounds, isopropyl salicylate was able to inhibit the oxidation process by 55% when induced by copper and 52% when it was induced by iron after 8 hours exposure. The commercial antioxidant TBHQ was used as a positive control presenting lower inhibition values than isopropyl salicylate. It should be noted that salicylates are accessible molecules in just one reaction step, high yields and low cost, these being desirable characteristics for the biodiesel industry.

RESUMO Os incentivos às políticas energéticas e as atuais exigências ambientais motivam a busca por fontes de energia alternativa, como o gás hidrogênio. Este trabalho tem como objetivo a produção do gás hidrogênio via eletrólise do ácido fórmico, utilizando eletrodos de aço carbono 1008 e ferro Armco. Os ensaios foram feitos mediante planejamento experimental, e empregaram-se as técnicas de microscopia óptica, polarização potenciodinâmica catódica, potencial de circuito aberto e cronoamperometria. Os resultados mostraram que o tratamento da superfície dos eletrodos com lixa de carbeto silício (SiC) #320 é eficiente quando comparada aos outros tratamentos testados, para o desprendimento de H2. O ferro Armco, apresentou maior produção de hidrogênio, em média 70% a mais quando comparado com a platina em ambos os meios estudados, entretanto sua vida útil é menor.

ABSTRACT Incentives for energy policies and current environmental requirements motivate the search for alternative energy sources such as hydrogen gas. This paper aims at the production of hydrogen gas via electrolysis of formic acid using electrodes of 1008 carbon steel and Armco iron. Samples were done by experimental design, and employed the techniques of optical microscopy, cathodic potentiodynamic polarization, open circuit potential and chronoamperometry. The results showed that the surface treatment of the electrodes with #320 grit SiC abrasive paper is effective when compared to the other treatments tested for the evolution of H2. The Armco iron, showed higher hydrogen production, on average 70% increased when compared with platinum in both studied media, however its lifetime is shorter.

A adsorção das substâncias orgânicas nos metais, em diferentes meios, tem sido atribuída a diferentes efeitos, tais como: tamanho da cadeia carbônica, tipo ou número de heteroátomo presente na estrutura da molécula, reatividade, efeito estérico, entre outros. O objetivo desse trabalho é estudar o comportamento eletroquímico do Indol (C8H7N), para o aço inoxidável AISI 430, quando se muda o meio de estudo de H2SO4 1 mol L-1 para HCl 1 mol L-1. Experimentalmente foram empregadas as técnicas seguintes: medida de potencial de circuito aberto, curvas de polarização potenciodinâmica anódica e catódica, espectroscopia de impedância eletroquímica, microscopia óptica e eletrônica de varredura. Esses resultados sugerem que a adsorção do indol, em presença de SO4-2, é menor em relação ao meio que contem íons Cl-, fato justificado pela ação do indol como ácido fraco, pois o mesmo possui apenas um único par de elétrons, o qual é deslocado e participa do sistema π-elétron aromático. Dessa forma, a primeira etapa da reação do indol, em meio ácido, é a protonação e a geração de um indol cátion.

The adsorption of organic substances in metals and in different media has been attributed to different effects, such as the carbon chain size, type or number of heteroatom in the molecule structure, reactivity, the steric effect, among others. The objective of this work is to study the electrochemical indole behavior for AISI 430 stainless steel (SS), when changing the study media from H2SO4 1 mol L-1 to HCl 1 mol L-1. The experimental techniques used are as follows: the open-circuit potential, anodic and cathodic potentiodinamic polarization, electrochemical impedance spectroscopy, optical microscopy and scanning electron microscopy. These results suggest that the adsorption of indole in the presence of SO4-2 is lower than in the medium containing Cl-, which is justified by the indole action as a weak acid, because it has only a single pair of electrons, which is displaced and takes part in the π-electron aromatic system; thus the first step of the indole reaction in acid media is the protonation and generation of an indole cation.

As moléculas auto-organizáveis (SAM - Self Assembly Monolayer) são inibidoras de corrosão, devido à capacidade de se organizarem sobre superfícies formando filmes finos. A SAM apresenta elevada afinidade pelo óxido formado sobre o alumínio, porém as interações entre a camada de óxido e as SAM nem sempre são satisfatórias, pois o óxido formado na superfície apresenta heterogeneidades, que interferem na formação do filme de SAM. O objetivo desse trabalho foi estudar a proteção à corrosão do alumínio AA 2024-T3 associada ao SAM, após tratamento com desengraxante alcalino. A caracterização eletroquímica foi realizada por espectroscopia de impedância eletroquímica e polarização potenciodinâmica anódica em meio de Na2SO4 0,5 mol. L-1 em pH 4,0. A morfologia superficial foi investigada por microscopia óptica. Os resultados mostraram que as SAM promoveram maior proteção do alumínio, quando este foi pré-tratado com o desengraxante.

Self-assembly molecules (SAM - Self Assembly Monolayer) are corrosion inhibitors, due to their capacity to organize on surfaces, forming thin films. SAM presents a high affinity to aluminum oxide. However, the interactions between the oxide layer and SAM are not always satisfactory; therefore the oxide formed on the surface presents heterogeneities that hinder SAM film formation. The aim of this work was to study the corrosion protection of aluminum AA 2024-T3 associated with SAM, after treatment with alkaline degreasing. The electrochemical characterization was carried out by electrochemical impedance spectroscopy and anodic potentiodynamic polarization in Na2SO4 0,5 mol.L-1 in pH 4,0. The superficial morphology was investigated by optic microscopy. The results showed that SAM promoted greater aluminum protection when this was pretreated with degreasing.

As distribuidoras de combustíveis utilizam containers de aço inoxidável para o armazenamento de biocombustíveis, entretanto, na literatura, há poucos relatos sobre os aspectos corrosivos desse aço em biodiesel. O objetivo desse trabalho é estudar o comportamento corrosivo do aço inoxidável austenítico 304 na presença de biodiesel, não lavado e lavado com soluções aquosas de ácido cítrico, oxálico, acético e ascórbico 0,01 mol L-1e comparar com os resultados obtidos para o cobre (ASTM D130). Empregaram-se técnicas como: espectrometria de absorção atômica (EAA) e microscopia óptica (MO). Os resultados de EAA mostraram uma baixa taxa de corrosão para o aço inoxidável, os elementos de liga estudados foram Cr, Ni e Fe, a maior taxa observada foi para o cromo, 1,78 ppm/dia em biodiesel não lavado ou lavado. As MO do aço 304, quando comparados com as do cobre, comprovaram a baixa taxa de corrosão para o sistema aço 304/biodiesel, entretanto comprovaram que, tanto o aço 304, quanto o cobre, sofrem corrosão em amostras de biodiesel.

Fuel distribution uses 304 stainless steel containers for the storage of biofuels, however, there are few reports in the literature about the corrosive aspects this steel in biodiesel. The objective of this research is to study the corrosive behavior of 304 austenitic stainless steel in the presence of biodiesel, unwashed and washed, with aqueous solutions of citric, oxalic, acetic and ascorbic acids 0,01 mol L-1, and compare with results obtained for the copper (ASTM D130). The employedtechniques were: atomic absorption spectrometry (AAS) and optical microscopy (OM). The results of EAA showed a low rate of corrosion for the stainless steel, the alloys elements studied were Cr, Ni and Fe, the highest rate was observed for the chrome, 1.78 ppm / day in biodiesel with or without washing. The OM of the 304 steel, when compared with that of copper, has a low corrosion rate in the 304 steel/biodiesel system. Not with standing, this demonstrates that not only the 304 steel, but also the copper, corrodes in biodiesel.