57 research outputs found
Comportamento eletroquĂmico e susceptibilidade a corrosĂŁo sob tensĂŁo do aço ABNT 1080 utilizado em armaduras de concreto protendido
Estudou-se o comportamento Ă corrosĂŁo e Ă corrosĂŁo-sob-tensĂŁo do aço eutetĂłide empregado em concreto protendido utilizando diversas tĂ©cnicas experimentais, como curvas de polarização, ensaios de tração com velocidades de deformação mĂ©dia, e ensaios fractomecĂąnicos. Utilizou-se como meio, simulando, o que Ă© usualmente encontrado nos poros do concreto, o Ca(OH)2 saturado, contaminado com diversos teores de cloreto e sulfatos. Com fins comparativos, utilizou-se a solução de tiocianato de amĂŽnia padronizada para avaliar a susceptibilidade de aços Ă fragilização por hidrogĂȘnio de aços em concreto. A influĂȘncia de parĂąmetros como potencial, temperatura (entre 0° e 90 ) e temperatura de revenido, entre outros sĂŁo avaliados. O mecanismo de ruptura Ă© avaliado tendo o hidrogĂȘnio uma participação importante neste processo.The corrosion and stress corrosion behaviour of AISI 1080 steel employed in concrete prestressed tendon was studied with different experimental techniques. A simulated solution usually found in concrete with and without contaminants as chlorides and sulphates was used. For comparison purpose the standard ammonium tiocianate solution was employed in some Polarization tests, constant extention rate tests with intermediate velocities and fractomechanic tests. The influence of parameters like potentiall temperature (between 0° and 90°), temper temperature of the steell was studied. The results showed that the fracture mechanism is associated with hydrogen action in the stress corrosion cracking process
2-hydroxyethilammonium oleate protic ionic liquid as corrosion inhibitor for aluminum in neutral medium
Protic ionic liquid (PIL) 2âhydroxyethylammonium oleate (2HEAOl) proved to be a good lubricant for aluminumâforming processes. However, with the aim of keeping the formed component integrity, it is interesting that the same substance employed during forming does not need to be removed and works out as corrosion inhibitor. Then, the aim of this study was to test the performance of 2HEAOl as corrosion inhibitor for aluminum in neutral 0.5 mol/L NaCl medium by electrochemical characterization. Results showed that the concentration of 5 Ă 10â4 mol/L was a suitable concentration to promote corrosion inhibition until 72 h at the high chloride concentration studied. The PIL worked out as mixedâtype organic corrosion inhibitor, as it promoted the diminution of the oxygen reduction reaction rate and, in consequence, the pit initiation by its adsorption on the metal surface
An amino-based protic ionic liquid as a corrosion inhibitor of mild steel in aqueous chloride solutions
Protic ionic liquids (PILs) have shown to be promising substances as corrosion inhibitors (CIs). In line with this, the aim of this study is to study the performance and propose the corrosion inhibition mechanism of Nâmethylâ2â hydroxyethylamine (Mâ2HEAOL) and bisâ2âhidroxyethylamine (BâHEAOL) oleate, for mild steel, in a neutral chloride solution. Electrochemical characterization was conducted under static and hydrodynamic conditions, and it was revealed that Mâ2HEAOL and BâHEAOL worked as mixedâtype CIs with more interference on the anodic reaction. Inhibition efficiency depended on the concentration reaching 97% of inhibition efficiency in 5 mmol/L concentration. Scanning electron microscopy, optical interferometry, Raman spectroscopy, and Fourierâtransform infrared spectroscopy are used to elicit the chemical composition of the surface film and corrosion morphology of steel in the presence of CIs, the adsorption processes of which involved physical and chemical adsorption between metal and different parts of ionic liquids. The results allowed the proposition of a corrosion inhibition mechanism
N-methyl-2-hydroxyethylammonium oleate ionic liquid performance as corrosion inhibitor for mild steel in hydrochloric acid medium
The aim of the present study is to evaluate the performance of Nâmethylâ2â hydroxyethylammonium oleate ([mâ2HEA][Ol]) as a corrosion inhibitor for mild steel in a 0.1âmol/L hydrochloric acid solution and also investigate the role of chloride in the inhibition mechanism. This protic ionic liquid (PIL) has formerly shown a high efficiency as a corrosion inhibitor in a neutral chloride medium. Electrochemical and weight loss measurements, surface contact angle determination, scanning electron microscopy, and Raman spectroscopy were used to understand the factors that influence the response of the studied inhibitor. Results revealed that [mâ2HEA][Ol] behaves as a mixedâtype adsorption inhibitor, by blocking cathodic sites and by modifying the activation energy of the anodic reaction, and it can reach up to 94â97% of inhibition efficiency. PIL adsorption was enhanced by the excess of positive charge of the mild steel. The effect of inhibitor molecule has been discussed to propose a mechanism that explains the inhibitory action of the corrosion inhibitor, pointing out the role of chloride in the inhibition mechanism
MĂ©todo de prevenção da fragilização por hidrogĂȘnio de componentes a partir de revestimentos por aspersĂŁo tĂ©rmica
Universidade Federal do Rio Grande do SulEngenhariaDepositad
TiâCp : eletrochemical behaviour under slurry erosion wear
The tests were performed using a new equipment, built to simulate aqueous erosion and monitor its electrochemical behaviour. This test was called electrochemical slurry erosion wear method. In this equipment, it is possible to measure the efect of simultaneous erosion wear and electrochemical tests on the passive flm behaviour. This kind of test on titanium was not found in the literature review, until now. The aim of this study was to analyse the behaviour of the passive titanium oxide layer, employing polarization curves simultaneously to the slurry erosion wear, unprecedented in the study of titanium passivity under erosive wear, varying the stirring speed and amount of erodent. Therefore, the hydrodynamic shear stress incurred under diferent stirring speed conditions exerts infuence on the corrosion resistance of commercially pure titanium (TiâCp)
Niobium and niobium-iron coatings on API 5LX 70 steel applied with HVOF
The present study aimed to create and characterize niobium and niobium-iron60% coatings applied to steel API 5L X70 using the hypersonic thermal spray process (HVOF). The morphologies of the coatings were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and profilometry, while the coatingsâ hardnesses was evaluated using the Vickers hardness test. The coatingsâ corrosion resistance was evaluated by monitoring their open circuit potential and potentiodynamic polarization and performing electrochemical impedance spectroscopy in a 0.05 M NaCl solution. The results showed that the niobium-iron coating contained minor porosity regions, while such defects occurred over large regions of the niobium coating. In terms of corrosion resistance, the coatings obtained in this work promoted a reduction in the substrateâs corrosion rate, but the presence of discontinuities such as porosity compromised the barrier effects of these coatings
A Genetic Animal Model of Alcoholism for Screening Medications to Treat Addiction
The purpose of this review is to present up-to-date pharmacological, genetic, and behavioral findings from the alcohol-preferring P rat and summarize similar past work. Behaviorally, the focus will be on how the P rat meets criteria put forth for a valid animal model of alcoholism with a highlight on its use as an animal model of polysubstance abuse, including alcohol, nicotine, and psychostimulants. Pharmacologically and genetically, the focus will be on the neurotransmitter and neuropeptide systems that have received the most attention: cholinergic, dopaminergic, GABAergic, glutamatergic, serotonergic, noradrenergic, corticotrophin releasing hormone, opioid, and neuropeptide Y. Herein, we sought to place the P rat's behavioral and neurochemical phenotypes, and to some extent its genotype, in the context of the clinical literature. After reviewing the findings thus far, this chapter discusses future directions for expanding the use of this genetic animal model of alcoholism to identify molecular targets for treating drug addiction in general
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