This paper investigates the behavior of paper strips containing iron-gall inks prepared with tannins from different sources, subjected to natural and thermally-induced aging. Results indicate that inks containing initial concentrations of ferrous sulphate ranging from 0.2 to 10.0 g are amenable to treatment with calcium phytate, and thata good correlation exists between the recovery of excess iron and the initial concentration. Infrared spectra showed an absorption band at 1,750 cm−1, typical of esther, solely in the samples prepared with a condensed tannin. The condensed nature of this tannin produced a different oxidation pattern, with iron removal inferior to those observed from inks produced with hydrolisable tannins. When tannic acid was used ferrous iron removals ranged from 0.050 to 1.800 g, decreasing to 0.5 g in the presence of copper; the same behavior was observed for the remaining hydrolisable tannins, with a lower recovery from the condensed tannin. The adopted natural aging procedure released a higher amount of ferrous iron compared to ASTM thermal aging. This was probably due to the marked effect of humidity, not considered in the thermal procedure. A series of archaeometric possibilities were used to help elucidate the degradation of cellulose strips impregnated with iron-gall inks.
Corrosion inhibitors are widely used to guarantee asset integrity from oil exploration and production stages (e.g. drilling equipment and metal piping in producing wells) to refinery, as well as during transportation of produced fluids and finished by-products. The major forms of corrosion found among the oil and gas industry include chemical, electrochemical, mechanical, and microbiologically induced. Corrosion inhibition by organic compounds is applied mostly in electrochemical corrosion due to acidic gases (H2S and CO2), from which CO2 corrosion is considered one of the major threats in oil and gas producing assets. According to the literature, amide and amine/diamine are the main classes of corrosion inhibitors used to combat sweet corrosion (CO2) in oilfields. However, the constant need to overcome new challenges makes it possible to create novel chemicals or to identify well-known molecules that can be improved in order to meet both the market demands and technical requirements, for example: guaranteed inhibitory capacity under several conditions, low emulsion and foaming tendency. In the present work, evaluations of different alkoxylation degrees and types of diamines were carried out in order to analyze the influence on the corrosion behavior of a carbon steel surface (SAE 1020 and API 5L X65), as well as emulsion and foaming tendencies. For these studies, the corrosion measurements were either performed by linear polarization resistance (LPR) or by weight loss measurements. The data revealed that their corrosion protection of carbon steel depended critically on the alkoxylation type and degree. Therefore, a suitable choice of molecule can create a tailor-made product to achieve specific requirements. The chemicals developed have shown good corrosion inhibiton performance and have satisfied defined pratical requirements to avoid emulsion and foaming tendencies.
ResumoO desenvolvimento da indústria metal-mecânica nos últimos anos tem levado à demanda de materiais com propriedades mecânicas e de resistência à corrosão cada vez melhores, com o objetivo de suportar severas condições de uso e assim garantir melhor desempenho para equipamentos e estruturas que utilizam os componentes fabricados com estes materiais. Neste contexto, é de fundamental importância conhecer bem a microestrutura destes materiais, que influencia consideravelmente suas propriedades. O propósito deste trabalho é realizar uma caracterização preliminar de ligas não ferrosas (de alumínio e de cobre) utilizadas na fabricação de componentes antifricção. Com esta finalidade, técnicas como microscopia ótica, microscopia eletrônica de varredura (MEV), envolvendo análises de EDS e de EBSD, assim como ensaios de microdureza foram utilizadas para caracterizar a microestrutura do material (liga Al-Sn-Si-Cu). Os resultados obtidos neste estudo permitiram a identificação das fases presentes neste material. Palavras-chave: Caracterização microestrutural; Alumínio; Fricção. MICROSTRUCTURAL CHARACTERIZATION OF ALUMINUM ALLOY FOR ANTIFRICTION COMPONENTS AbstractIn the last years the development of the mechanical and metallurgical industry has led to the search for materials with even better mechanical properties and corrosion resistance, with the purpose of withstanding severe conditions of use and thus assesses better performance for equipments and structures that use components fabricated with such materials. In this context it is very important to know in detail the microstructure of these materials that influence considerably their properties. The purpose of this work is to achieve an initial characterization of non ferrous alloys (aluminum and copper based alloys) used in the fabrication of antifriction components. With focus on this aim, techniques such as optical microscopy, scanning electron microscopy (SEM), comprising EDS and EBSD analysis procedures were used to characterization the microstructure of the alloy (Al-Sn-SiCu). The results obtained in this study allowed the identification of the phases present in this material.
The present work evaluated the structure and heterogeneities, surface chemistry, hydrophobicity level, and corrosion protection in a saline environment of electrodeposited sol-gel superhydrophobic coatings on carbon steel, using microscopy techniques, energy dispersive X-ray spectroscopy (EDX), water contact angle measurements, and electrochemical impedance spectroscopy (EIS). Furthermore, the effect of silane precursor concentration on the aforementioned response variables was tested. Regarding the structure, results point out rough deposits composed of two layers with different properties and thicknesses, and preferential deposition on the top area of the carbon steel coupon. Elemental mapping proved the chemical stability of the film in NaCl 3.5%wt., while increasing the amounts of silane precursor up to 40 mmol showed also increased results for water contact angle (157 o ), impedance modulus at 0.01 Hz (10 7 Ohm.cm 2 ), and film thickness (70 µm). However, the addition of greater amounts resulted in miscibility issues in the hydrolysis solution.
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