The mechanical behavior of the API 5L X80 steel exposed to the produced water by the petroleum industry, besides being dependent on the intrinsic properties of the steel, is influenced by the corrosivity characteristics of the electrolyte that may be associated with the presence of microorganisms. The objective of this work was to investigate the plastic deformation of API 5L X80 steel exposed to produced water. The tests were conducted in static systems (abiotic and biotic) containing produced water after 360 days. The process of corrosion of the coupons were evaluated by topographic 3D analysis and roughness, and the mechanical behavior by tensile test and fracture analysis by scanning electron microscopy. Surface topography and roughness were modified by the interaction of the consortium of microorganisms with the substrate associated with the corrosion process. The results indicate that microorganisms induced the formation of pits which caused the coupons to lose plasticity.

Corrosion of pipelines can be significantly affected by the activity of microorganisms present in the environment. The objective of this work was to investigate the influence microbial in the corrosion behavior of API 5L X80 steel in produced water by open circuit potential, polarization curves and electrochemical impedance spectroscopy measurements. Physical-chemical and microbiological analyzes were performed in the produced water and the tests were conducted in biotic and abiotic systems. The films and corrosion morphology developed in the steel over time were characterized by scanning electron microscopy. The results confirm that the activity of the consortium of microorganisms in the formed biofilm accelerated the dissolution of the iron, causing pitting corrosion in the steel exposed to the biotic system. Through the adjustment of the equivalent electrochemical circuit, the impedance results allowed to interpret the interactions between electrode, film and electrolyte.

Corrosion of buried pipelines is a matter of concern to the oil and gas industry since the time when carbon steel began to be widely used in these pipelines for the transportation of fluids. The microbial communities associated with biofilms promote modification in the surrounding environment and may accentuate the degradation of oil and gas pipelines causing leaks or even accidents. This work aimed to evaluate corrosion and biofilm formation in carbon steel API 5LX60 coupons buried in clayey soil from an industrial region in north-eastern Brazil. The average corrosion rates were determined by gravimetric test and the quantification of bacteria and fungi were using the Most Probable Number (MPN) and Colony Forming Units (CFU) techniques respectively. The results showed a great influence of clayey soil on corrosion rates and time of adherence for microorganisms on metal surfaces.

High-strength low-alloy steel is used in pipelines, which transport oil/gas and also produced water in the process of the secondary recovery of oil. This paper investigates the corrosion of X80 steel after immersion in static systems (biotic and abiotic). The corrosion rate, the corrosion morphology and the hardness of the coupons were investigated. The corrosion products were determined by SEM/EDS and XRD. The corrosion rates of the coupons in the biotic system were moderate and had an agressive pit morphology, while those of the coupons in the abiotic system were low with less aggressive pit. The hardness of the coupons after exposure to the systems of produced water was not changed compared with that of the control coupons. The corrosion products formed in the biotic system were Fe(OH)3, Fe(OH)2, FeOOH, Fe3O4, FeS2, FeCl3, and in the abiotic system, NaCl, CaCl2 and SrSO4. BaSO4 and CaCO3 were identified in both systems.

Co-Ni/SiC nanocomposite coatings were obtained by codeposition of SiC nanoparticles in a bath with nickel and cobalt, using API 5L X80 as the substrate. The influence of cathodic current density on deposit properties was investigated. Measurements of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) were performed in 3.5 wt% NaCl solution to investigate a corrosion performance. The morphology and chemical analysis of the surfaces were analyzed by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and related with micro-hardness and X-ray diffraction (XRD). The results indicate which composite coatings have acicular morphology, with higher micro-hardness values than those found for the carbon steel substrate. The Co-Ni/SiC coating increased the corrosion potential and the resistance to polarization, which resulted in lower corrosion rates than those obtained without uncoated steel.

Galvanized steel has been widely applied in different applications and the industry significantly increased its production in recent years. Some galvanized structures can be completely or partially buried, such as transmission tower footings. The corrosion of these metallic structures is related to the soil chemical and physicochemical properties, which define the aggressiveness of the environment. To assess the effect of the soil moisture on galvanized steel corrosion, a comparative study was carried out. Carbon steel coupons, with or without galvanization, were buried in clay soil collected from an industrial region in the northeast of Brazil. The chemical, physicochemical and microbiological characteristics of the soil were determined. The thickness of the galvanized coating was measured by scanning electron microscopy (SEM). Corrosion tests were conducted in different soil moisture conditions using the following techniques: potentiodynamic polarization curves and gravimetric tests. The results showed the influence of soil moisture on corrosion rates. The electroplating decreased corrosion rates, especially when the coupons were exposed to low moisture soil.

Samples of LDPE/modified starch blends 80/20 m/m before and after exposure to gamma rays were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. The effect of gamma radiation is clearly seen in the samples irradiated at a dose of 25 kGy. The main alteration in the polymeric material after exposure at the radiation range was a decrease in the mechanical properties, alterations in the chemical structure of the blend with an increase in the carbonyl and vinyl indices and the appearance of new crystalline symmetry generating a crystalline domain not existing before in the blend.

Nesse trabalho foi realizado um estudo sobre diferentes tipos de amido quanto ao crescimento, e a atividade amilolítica de culturas mistas e isoladas dos fungos Phanerochaete chrysosporium e Talaromyces wortmannii. Avaliaram-se também as propriedades térmicas e mecânicas das blendas de polietileno/amido anfótero (na proporção 80/20 (m/m)) antes e apos a inoculação das culturas mistas desses fungos.O amido regular Amidex 3 e o amido modificado Fox5901 foram os que se destacaram quanto ao crescimento celular e produção da enzima amilase. Apesar do pouco tempo de exposição dos filmes com os fungos, pode-se concluir que os microrganismos promovem mudanças físicas e químicas na estrutura da blenda, modificando suas propriedades térmicas e mecânicas. A alteração do grau de cristalinidade e das propriedades mecânicas das blendas podem ser indícios da modificação provocada pelo processo de biodegradação.

This study evaluated in relation the growth, and the amylolytic activity of mixed and isolated cultures of Phanerochaete chrysosporium and Talaromyces wortmanni on different types of starch. The thermal and mechanical properties in polyethylene/starch blends (proportion: 80/20 (w/w) before and after inoculation of the mixed cultures were evaluated. The regular starch Amidex 3 and the modified starch Fox5901 stood out in relation to the cellular growth and production of the amylase enzyme. In spite of the short time that the blends were exposed to the fungi, the microorganisms promoted physical and chemical changes in the structure of the blend, modifying its thermal and mechanical properties. The alteration of the degree of crystallinity and mechanical properties of the blends could be indications of the modification caused by the biodegradation process.

This work deals with the biodegradation of blends of poly(beta-hydroxybutyrate)/starch and poly(beta-hydroxybutyrate-co-hydroxyvalerate)/starch. The blends were obtained by evaporation of the solvent in the mixture of the polymers in chloroform. Tests were carried out in presence of micro-organisms which acted as biodegradation agents. The blends were consumed as carbon substrate and the production of CO2 was evaluated in the process. In addition, the polyesters' mechanical properties were reduced by the incorporation of starch in its structure. (¹H) NMR and infrared spectroscopy detected some characteristic polyester degradation groups in the polyesters' chemical structure, thus confirming the alteration suffered by it.