ABSTRACT This study is aimed at analyzing the mechanical behavior of low-density polyethylene (LDPE) plastic bags exposed for three years to air, immersed in polluted and tap water, buried in soil, and exposed on the soil surface. The pH and conductivity analyses for polluted water resources, clean water and soil extract were performed. Semi-quantitative chemical analysis of soil using X-ray fluorescence spectrometry (XRF) was performed. For the mechanical assay, a 100 kN load cell was used subjected to a traction with obtaining strain curve x deformation. The aqueous soil extract is rich mainly in nitrate, sulfate, and calcium. The polluted water in which the bags were immersed had a high concentration of chlorides, and contained nitrate, sodium, and calcium. Finally, tap water contained mostly sulfate, sodium, calcium, and chloride ions. However, the chloride content of polluted water is ten times the content of tap water. The tensile strength and elongation of degraded samples are lower than the reference, confirming the process of degradation. An exception was the deformation of plastic bag buried in soil which was the highest.

ABSTRACT Inhibitors are one of the oldest methods of mitigating corrosion, which is still a current challenging and costly problem. However, traditional inhibitors are toxic and non-biodegradable, which goes against the principles of Green Chemistry, so named for valuing the use of biodegradable and environmentally friendly products. They can be obtained from plants and their residues that, when subjected to some type of processing, generate extracts or oils with important inhibitory potential. In most cases, green inhibitors are organic compounds classified relating to the mechanism as mixed, having polar functional groups that act as adsorption centers on the metallic surface. This study aimed to carry out a systematic review of the literature on inhibitors from species of Brazilian flora and used in an acid environment to prevent corrosion in carbon steel in a specific medium. Brazil presents a rich biodiversity of flora, with more than 46,200 species cataloged in 2020, which provides a wide field of research in this area. The review included 28 different plant species. The results found were promising, with emphasis on the use of parts of vegetables that are normally discarded and show the potential for development and improvement of green inhibitors for future application on an industrial scale.

RESUMO Os inibidores são um dos métodos mais antigos de combate à corrosão, que ainda hoje é um problema desafiador e caro. Porém, os inibidores tradicionais são tóxicos e não biodegradáveis, o que vai contra os princípios da Química Verde, assim denominada por valorizar o uso de produtos biodegradáveis e ambientalmente amigáveis. Os inibidores podem ser obtidos de plantas e seus resíduos que, quando submetidos a algum tipo de processamento, geram extratos ou óleos com importante potencial inibitório. Na maioria dos casos, os inibidores verdes são compostos orgânicos classificados, quanto ao mecanismo, como mistos, possuindo grupos funcionais polares que atuam como centros de adsorção na superfície metálica. Este estudo teve como objetivo realizar uma revisão sistemática da literatura sobre inibidores de espécies da flora brasileira e utilizados em ambiente ácido para prevenir a corrosão em aço carbono. O Brasil apresenta uma rica biodiversidade de flora, com mais de 46.200 espécies catalogadas em 2020, o que proporciona um amplo campo de pesquisa nesta área. A revisão incluiu 28 espécies de plantas diferentes. Os resultados encontrados foram promissores, com destaque para o uso de partes de vegetais que normalmente são descartadas e mostram o potencial de desenvolvimento e aprimoramento de inibidores verdes para futura aplicação em escala industrial.

In this work, two catalysts, lanthanum manganite strontium-doped perovskite without (LSM) and with (LSMMO) mixed molybdenum oxides, were synthesized by the sol-gel route and deposited by immersion in carbon cloth substrates. Their performance as cathodes in the hydrogen peroxide reduction reaction (HPRR) and oxygen reduction reaction (ORR) was investigated through cyclic voltammetry and electrochemical impedance spectroscopy, the electrocatalytic efficiency of these electrodes in the HPRR was analyzed in KOH and H2O2 medium at 298 K. The performance of the cathodes, in a single compartment, using a nickel plate as an anode was also investigated. The results showed that for the reduction reactions, electrodes developed with LSMMO have more significant catalytic activity than LSM after polarization, resulting in 32% higher current densities, lower electrical resistance after polarization, and a 21% increase in power density.

Abstract The physical and environmental conditions of educational institutions are determining factors for occupant comfort. The Post-Occupancy Evaluation (POE) presents itself as a methodology for verifying environmental aspects in full use, considering the technical criteria and the users' perception. This article discusses the particularities of the ETS-UESC building, in Brazil, applying POE with an emphasis on the environmental comfort of the classrooms. For this, an exploratory research was carried out where the users' perception of ambience was verified, through the application of targeted forms and on-site measurements of the thermal and lighting conditions using a thermohygrometer and a lux meter, and natural ventilation conditions by design analysis, in the light of current regulations. The opinions were compared with the environmental measurements to identify the limitations of the building and to find the dissonant points. About 85% of users are bothered by the thermal conditions where they are exposed to high daily temperatures, above 30 ºC. In spring and summer, room temperatures are above those recommended by NR 17 standard. The quality of natural lighting is questioned by approximately 80% of users, even having illuminance above the recommended limit of 300 lux in the daytime cycle. How thermal and lighting conditions restrict the use of spaces was proven, making it necessary to discuss active or passive technical solutions to mitigate these problems. Therefore, some factors and technical solutions were pointed out that will assist in the suitability of the project in question.

RESUMO O conhecimento das transformações de fase e o papel de diferentes parâmetros no desempenho de sistemas ligados a fosfato são de extrema importância para o campo refratário. Os efeitos do agente de endurecimento, da concentração de ácido fosfórico e dos aditivos no tempo de endurecimento, resistência ao impacto a frio, módulo de ruptura a quente, resistência à abrasão e resistência ao choque térmico dos sistemas refratários quimicamente ligados ao fosfato foram avaliados. O tempo de endurecimento foi menor para misturas contendo cimento (CaO) e uma menor concentração de ácido. Misturas com maior concentração de ácido apresentaram melhor resistência mecânica, à abrasão e ao choque térmico. Apesar de aumentar a resistência mecânica a frio e a abrasão dos materiais, o Budit 6H impactou negativamente as propriedades quentes. Para o aditivo Fabutit761, não houve formação de fase líquida em temperaturas intermediárias e esse aditivo aumentou a resistência mecânica a frio, mas também impactou negativamente a resistência mecânica a quente. As composições contendo cimento como agente endurecedor, ácido fosfórico a 40° Be e aditivo Fabutit761 como fonte extra de fosfato apresentaram um melhor conjunto de propriedades.

ABSTRACT The knowledge of the phase transformations and the role of different parameters in the performance of phosphate-bonded systems are of utmost importance for the refractory field. The effect of the setting agent, phosphoric acid concentration and additives on the setting time, cold crush strength, hot modulus of rupture, abrasion resistance, and thermal shock resistance of the phosphate chemically bonded refractory systems was evaluated. The setting time was shorter for mixtures containing cement (CaO) and a lower acid concentration. Mixtures with a higher acid concentration presented better mechanical, abrasion and thermal shock resistance. In spite of increasing the cold mechanical resistance and abrasion of the materials, the Budit 6H negatively impacted the hot properties. For Fabutit761, there was no liquid phase formation at intermediate temperatures and this additive increased the cold mechanical strength, but it also negatively impacted the hot mechanical strength. Compositions containing cement as a setting agent, 40°Be phosphoric acid and Fabutit761 additive as an extra source of phosphate presented a better set of properties.

Abstract The accelerated artificial aging with ultraviolet radiation, viscosity, density, no-pick-up time, flexibility, and abrasion resistance of lignin-modified road marking paint were evaluated. The addition of lignin did not cause significant changes in the physical chemistry, flexibility and no-pick-time test compared to the precursor paint. The addition of 1.00 wt. % of lignin increased the abrasion resistance by 36%. The Fourier Transform Infrared technique performed before and after exposure to Weather-o-meter aging chamber has shown the cleavage of ester groups that are present in acrylic-based resin. The incorporation of 0.10 wt.%, 0.25 wt.%, and 1.00 wt.% increased the photodegradation resistance of the road marking paint inhibiting the ester group and side-chain scissions, since the C-O and C=O band intensity increased after irradiation. The introduction of lignin delayed the yellowing of the aged samples and improved mechanical and photophysical properties besides being a good strategy for the biomass waste utilization of the paper industry.

RESUMO Este artigo apresenta uma análise de falhas realizada em tubos de um trocador de calor. Trocadores de calor estão entre os equipamentos mais presentes em uma indústria de refino de petróleo, pois a transferência de calor é um dos processos mais importantes e comuns em indústrias químicas e petroquímicas. O equipamento analisado foi o condensador do sistema de topo da torre de regeneração de dietanolamina (DEA) da unidade de hidrotratamento de nafta de uma refinaria de petróleo. O feixe tubular é constituído por 78 tubos na especificação ASTM A213 Grau 316L com 19,05 mm de diâmetro e 1,65 mm de espessura de parede. Os tubos são submetidos ao fluxo aquoso de H2S e dietanolamina na parte externa e água de resfriamento na parte interna. Após uma parada geral programada ocorrida em julho de 2011, após seis anos de operação contínua, foi observada a perda de espessura em vários tubos. O resultado da análise de falha indicou que, através da inspeção visual o processo corrosivo ocorreu de fora para dentro dos tubos. O ensaio de correntes parasitas indicou um processo corrosivo ativo com uma taxa de corrosão de 0,16775 mm/ano. A inspeção ultrassônica realizada através do sistema de inspeção rotativa interna (IRIS) confirmou a perda de espessura e a presença de tubos perfurados, com consequente perda de contenção. A corrosão por amina em presença de H2S foi identificada como o mecanismo básico da falha, agravada pela concentração de DEA superior a 20% em massa. Em outubro de 2019, os tubos deste trocador foram substituídos e a solução proposta para a mitigação do problema foi a diluição da solução com água de lavagem, para a obtenção de concentrações da solução de amina abaixo de 5% em massa nos tubos do feixe deste trocador de calor.

ABSTRACT This paper presents a failure analysis performed on tubes of a heat exchanger. Heat exchangers are among the most common equipment in an oil refining industry, as heat transfer is one of the most important and common processes in chemical and petrochemical industries. The equipment analyzed was the condenser of the top system of the diethanolamine regeneration tower of the naphtha hydrotreating unit of an oil refinery. The tubular bundle consists of 78 tubes in the ASTM A213 Grade 316L specification, with 19.05 mm in diameter and 1.65 mm in wall thickness. The tubes are subjected to the aqueous flow of H2S and diethanolamine on the outside and cooling water on the inside. After a scheduled general shutdown in July 2011, after six years of continuous operation, the loss of thickness in several tubes was observed. The result of the failure analysis indicated that, through visual inspection, the corrosive process occurred from outside to inside the tubes. The eddy current test indicated an active corrosive process with a corrosion rate of 0.16775 mm / year. The ultrasonic inspection performed through the internal rotating inspection system (IRIS) confirmed the loss of thickness and the presence of perforated tubes, with consequent loss of containment. Amine corrosion in the presence of H2S was identified as the basic failure mechanism, aggravated by DEA concentration higher than 20 wt.% in the analyzed equipment. In October 2019, the tubes of this exchanger were replaced and the proposed solution to mitigate the problem was to dilute the solution with washing water, to obtain amine solution concentrations below 5% by mass in the beam tubes of the heat exchanger.

The pitting corrosion of supermartensitic stainless steel (SMSS) was studied in an aqueous solution of 0.1 mol/L NaCl using the scanning vibrating electrode technique (SVET) and cyclic voltammetry. The SMSS showed 0.9% of retained austenite, as verified by Mössbauer spectroscopy. Cuboidal TiN particles were identified on the steel surfaces, by using optical, scanning electron, and transmission microscopy, associated to Mg-Ca-Al rich precipitates. Pit nucleation was slow and only verified after 24 h, associated to TiN/CaO·MgO·Al2O3 complex inclusions, thus on original interdendritic spaces, where lower Cr content and the presence of inclusions are expected.

RESUMO Na indústria de petróleo e gás, o aço inoxidável supermartensítico (Super 13Cr) tem sido utilizado na fabricação de tubos de aço para uso em perfurações de petróleo. O Super 13Cr é uma opção financeiramente mais viável do que o aço super duplex no mercado de óleo e gás. O objetivo deste trabalho é avaliar a influência de variações de pH e da presença de H2S dissolvido no meio na resistência à corrosão do aço super martensítico em solução salina saturada com H2S, simulando assim, as condições de operação no pré-sal da indústria de petróleo. Os testes eletroquímicos utilizados foram a polarização anódica potenciodinâmica e a cíclica. Para a posterior caracterização da superfície, as técnicas utilizadas foram a microscopia ótica e a microscopia eletrônica de varredura (MEV). O efeito da presença de H2S no meio elevou a susceptibilidade à corrosão do aço devido à uma maior desestabilização da camada passiva formada naturalmente, redução do potencial de pite e do potencial de repassivação. O aço super 13Cr também se mostrou menos resistente quando o pH foi variado para valores mais baixos, causando redução no potencial de pite. Com os testes realizados e a análise das micrografias, o aço super 13Cr se mostrou menos resistente frente à corrosão em meios mais ácidos e na presença de sulfeto de hidrogênio no meio. As principais consequências desse aumento de severidade foram a presença de pites em maior quantidade e mais profundos, que podem evoluir em trincas caso haja solicitações mecânicas, potenciais de pite menos nobres e uma grande resistência à repassivação.

ABSTRACT In the oil and gas industry, supermartensitic stainless steel (Super 13Cr) has been used in the manufacture of steel tubes for use in oil drilling. Super 13Cr is a more financially viable option than super duplex steel in the oil and gas market. The objective of this work is to evaluate the influence of pH variations and the presence of H2S dissolved in the medium in the corrosion resistance of super martensitic steel in saline solution saturated with H2S, thus simulating the operating conditions in the industry's pre-salt of oil. The electrochemical tests used were anodic potentiodynamic and cyclic polarization. For the subsequent characterization of the surface, the techniques used were optical microscopy and scanning electron microscopy (SEM). The effect of the presence of H2S in the medium increased the susceptibility to corrosion of the steel due to a greater destabilization of the naturally formed passive layer, reduction of the pitting potential and of the repassivation potential. Super 13Cr steel was also less resistant when the pH was varied to lower values, causing a reduction in pitting potential. With the tests carried out and the analysis of the micrographs, the super 13Cr steel was less resistant to corrosion in more acidic media and in the presence of hydrogen sulfide in the medium. The main consequences of this increase in severity were the presence of larger and deeper pits, which can develop into cracks if there are mechanical stresses, less noble pitting potentials and great resistance to repassivation.

ABSTRACT The neutralization of catalysts with hydrochloric acid is an important step in a biodiesel process which generates steel corrosion due to the decrease in pH, and the addition of chlorides in the medium. Other factor responsible for corrosion and consequently failures is the poor miscibility between biodiesel and acid water generating a heterogeneous coverage of the surface of the pipelines and equipment by biodiesel and acid water, presence of galvanic cells and localized corrosion. In this paper, corrosion failures of AISI 316L and 904L austenitic stainless steels (SS), and of SAF 2205, 2507 duplex SS in a biodiesel plant were identified and studied. The low pH, presence of chlorides, high thermal input in welding, temperature gradient and mainly proximity to the acid injection site play the major roles in corrosion which generate the studied failures. Corrosion failures occurred in pipes transporting biodiesel and acid water, in a spool of acid water injection, in a static biodiesel mixer with acidic water, in a cylindrical decanter vessel, and in heat exchangers.

ABSTRACT This work examined the pitting corrosion resistance of two types of duplex stainless steels: UNS S31803, with molybdenum, and UNS S32304, without molybdenum. Cyclic potentiodynamic polarization and critical pitting temperature (CPT) tests were performed in 3.5 wt% NaCl solution. Scanning electron microscopy (SEM) was used for analysis of the pits on the surface of samples. The two steels studied presented susceptible to pitting corrosion in 3.5 wt% NaCl solution. UNS S31803 steel showed a higher corrosion potential (Ecorr), pitting potential (Epit), and polarization resistance (Rp) compared to UNS S32304 steel. It was also observed that the UNS S31803 steel showed higher capacity to repassivation and CPT than the UNS S32304 steel.

RESUMO Os módulos fotovoltaicos, para serem economicamente viáveis, devem apresentar durabilidade de, no mínimo, 25 anos de operação. A fim de elevar a vida útil dos módulos, é necessário controlar a degradação do encapsulante, o copolímero de etileno acetato de vinila (EVA), pela ação da radiação ultravioleta (UV) e de outros elementos de intemperismo. Esse artigo tem como objetivo avaliar a aplicabilidade de nanocompósitos de EVA e óxido de grafeno (GO) funcionalizado com octadecilamina (ODA) como encapsulantes, caracterizando-os, antes e após terem sido submetidos a processos de envelhecimento acelerado, pelas técnicas analíticas: espectroscopia na região do infravermelho por transformada de Fourier (FTIR-ATR), análise termogravimétrica (TGA) e calorimetria exploratória diferencial (DSC). A fim de adquirir uma melhor dispersão do GO na matriz polimérica do encapsulante EVA, optou-se por sua funcionalização com octadecilamina. Os nanocompósitos preparados foram envelhecidos em câmara UVB, que é usualmente a radiação mais agressiva para polímeros. Os resultados da análise de FTIR-ATR indicam que a presença de GO incrementou a resistência à degradação do material. Foi também observada uma melhora nas propriedades térmicas dos filmes não envelhecidos, o que não foi observado nos envelhecidos. Conclui-se que a adição de GO trouxe benefícios quanto à resistência à degradação do material, embora a sua utilização em nanocompósitos para encapsulantes de célula fotovoltaica dependa do controle do número de folhas de grafeno o que modulará as propriedades ópticas e a transparência do encapsulante. O artigo apresenta uma contribuição para o avanço nas pesquisas referente à degradação, pela radiação UVB, do encapsulante EVA presente nos módulos fotovoltaicos de silício cristalino.

ABSTRACT In order to be economically viable, photovoltaic modules must have durability of at least 25 years of operation. In order to increase the useful life of the modules, it is necessary to control the degradation of the encapsulant, the ethylene vinyl acetate copolymer (EVA), by the action of ultraviolet radiation (UV) and other elements of weathering. This article aims to evaluate the applicability of nanocomposites of EVA and graphene oxide (GO) functionalized with octadecylamine (ODA) as encapsulants, characterizing them, before and after the aging processes, by using the analytical techniques: spectroscopy in infrared region by Fourier transform (ATR-FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). In order to acquire a better dispersion of GO in the polymeric matrix of the EVA encapsulant, we opted for its functionalization with octadecylamine. The prepared nanocomposites were aged in a UVB chamber, which is usually the most aggressive radiation for polymers. The results of the ATR-FTIR analysis indicated that the presence of GO increased the degradation resistance. An improvement in the thermal properties of unaged films was also observed, which was not observed in the aged ones. It is concluded that the addition of GO brought benefits regarding the resistance to material degradation, although its use in nanocomposites for photovoltaic cell encapsulants depends on the control of the number of graphene sheets, which will modulate the optical properties and the transparency of the encapsulant. The article presents a contribution to the advancement of research regarding the degradation, by UVB radiation, of the EVA encapsulant present in crystalline silicon photovoltaic modules.

The effect of the increase in crystalline defects in the structure generated by high-pressure torsion (HPT) on the corrosion behavior of metallic materials is not well understood. This report evaluates the influence of HPT on the corrosion behavior of a solution treated Al-3wt% Mg-0.2wt% Sc alloy in a 3.5 wt./v.% NaCl solution. The electrochemical behavior of the alloy was evaluated using cyclic polarization, electrochemical impedance spectroscopy (EIS), Mott Schottky, X-ray photoelectron spectroscopy, and chronoamperometry testing. The passive current density decreased after HPT processing, indicating a more protective oxide layer was formed on the surface of the HPT-processed alloy. Mott Schottky analysis confirmed the higher protection efficiency of the passive layer on the HPT-processed alloy. The film formed in the solution-treated alloy was a p-type and an n-type semiconductor while the alloy processed by HPT exhibited only an n-type semiconductor behavior. EIS showed that corrosion resistance in a saline medium increased with HPT processing.

ABSTRACT This study aims to investigate the effect of lime addition in cement mortar on corrosion resistance of carbon and galvanized steel reinforcements. Mixed mortars were studied containing three contents of lime (6.7, 13.3, and 26.3 wt.%). The water retention, incorporated air, and compression strength of reinforced mortars were determined. Immersion tests were performed using the reinforced mortars consisting of 12 cycles of immersion in a solution of 3.5% (wt./v) sodium chloride and drying in a stove at 60oC. Electrochemical impedance spectroscopy was used to monitoring reinforcement corrosion after cyclic tests. These measurements were repeated after 36 months of the cyclic immersion testing. After the cyclic immersion tests in a saline solution, the polarization resistance of carbon and galvanized steel reinforcement increased as the lime content in mortar increased, demonstrating the protective effect of lime. After 36 months, the polarization resistance of steels in mixed mortars with the highest lime content was the lowest. For the carbon and galvanized steel in cement and mixed mortars, the polarization resistance increased after 36 months of the cyclic test.