Results 1 - 10 of 1766
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[en] The inhibition of corrosion of corrosion of the aluminium sheet (commercial) in solutions of sodium hydroxide was studied by weight loss methods and the variation of pH value of the corrosion solution was detected. At constant alkali concentration the inhibitor efficiency increased with increase in the concentration of the inhibitor. (When the inhibitor concentration was 0.5% and above.) But at low concentrations of the inhibitors (0.1% and below) the efficiency decreased to minus values. At 2.0% concentrations of inhibitors, the inhibitive efficiencies of the inhibitors increased in the order, p-am-inophenol (85.6%) < p-cresol < hydroquinone < phenol < p-nitrophenol < p-chlorophenol (98.6%) At constant inhibitor concentration the efficiency decreased with increase in alkali concentration. An increase in exposure period or temperature did not appear to have any marked effect on inhibitive efficiency. The variation of pH values in the solution had also a small effect. As for the effect of substituent groups, when an equal number of molecules of each of the compounds was present in the alkaline solution the efficiency of different para-compounds increased in the order: p-aminophenol (77.8%) < phenol < hydroquinone < p-chlorophenol < p-cresol < p-nitrophenol (96.1%)
[en] Corrosion is one of the main problems of degradation in components, tooling, equipment and even in structural applications, examples of this are the carbon steels. In the present work, the capacity of corrosion inhibition of a biodegradable organic extract from the Nopal plant (Opuntia ficus-indica), for the protection of carbon steel type AISI 1018 was studied adding 50% v/v of the Nopal extract (EN) in a solution of H2SO4 (0.6 mol.l-1). Polarization Resistance (LPR) and Electrochemical Impedance Spectroscopy (EIS) techniques were used for the electrochemical evaluation at room temperature for 24 h in order to obtain corrosion rates (Vcorr) and inhibition efficiency (IE). Metallographic examination was also carried out to register the surface damage by corrosion. The results showed a reduction of the Vcorr with a maximum IE value of about 84% by adding the organic- liquid extracted from Nopal.
[es]La corrosión es uno de los principales problemas del deterioro en componentes, herramentales, equipos e inclusive a nivel estructural, ejemplo de esto son los aceros al carbono. En el presente trabajo se estudió la capacidad de inhibición a la corrosión de un extracto orgánico biodegradable proveniente de la planta del Nopal (Opuntia ficus-indica) para la protección del acero al carbono tipo AISI 1018, al agregar el 50% v/v del extracto de Nopal (EN) en una solución de H2SO4 (0,6 mol.l-1). Se utilizaron las técnicas de Resistencia a la Polarización (LPR) y Espectroscopía de Impedancia Electroquímica (EIS) para determinar la eficiencia de inhibición (IE) a temperatura ambiente durante 24 h y obtener las velocidades de corrosión (Vcorr), posteriormente se llevó a cabo la evaluación metalográfica para registrar el daño superficial. Los resultados mostraron una reducción de la Vcorr con una IE máxima del 84% al adicionar el inhibidor orgánico EN.
[en] The influence of H2S on the corrosion of iron and the corrosion prevention mechanism of an inhibitor was investigated with a differential capacitance measurement and a weight loss measurement method. The results show that H2S accelerates both the anodic iron dissolution and the cathodic hydrogen evolution in most cases. However, H2S acts as an inhibitor of the corrosion of iron under certain special conditions. An EIS method is proposed to explain the ability of inhibitors
[en] Despite the big influence of the microstructure and chemical composition of plain carbon steels and low alloy steels on corrosion in saline mediums with CO2, the results found in the literature are contradictory. An aspect that is less studied is the effect of these variables on the formation and characteristics of the films as products of corrosion and on the efficiency of the inhibitors used in oil production. Previous works have shown that the efficiency of the inhibitors is affected by the microstructure and that this effect depends on the inhibitor's molecular structure. This work aims to further define the relationship between the films of corrosion products, the steel microstructure and the efficiency of the inhibitors. A plain carbon steel was studied with two different microstructures in a 5% NaCl deoxygenated solution at 40oC, pH 6, saturated with CO2 under laminar flow conditions. The efficiency of an imidazoline-based commercial inhibitor commonly used in oil production was characterized. The inhibitor was added after different periods of pre-corrosion: 24, 48 and 72 hours. The characteristics of the surface films were analyzed by SEM. Electrochemical tests were carried out (electrochemical impedance, resistance to lineal polarization every 24 h.) and the corrosion potentials were also recorded. The results show that the properties of the surface films and the inhibitor's efficiency depend on the microstructure with higher values for the quenched and tempered samples than for the annealed samples. While the inhibitor's efficiency diminishes in all cases along with the degree of pre-corrosion, the amount of this decrease is different for each microstructural condition (CW)
[en] The inhibitive performance of Sapindus on the acidic corrosion of Aluminium was studied using myriad experimental and computational techniques. Sapindus showed 98% of inhibition efficiency at 2000 ppm. Inhibition efficiency of Sapindus was found to be directly proportional to its concentration in the acidic medium. Effect of temperature was also studied and it played a corrosive role by increasing the corrosion rate and decreasing the inhibition efficiency of Sapindus. Thermodynamic parameters of adsorption were derived to enunciate the findings. Mechanism of adsorption was also explored using electrochemical impedance spectroscopy and potentiodynamic polarization (Tafel) studies which displayed a profound physisorption mechanism. (paper)
[en] Self-healing coatings inspired by biological systems possess the ability to repair physical damage or recover functional performance with minimal or no intervention. This article provides a comprehensive and updated review on the advantages and limitations associated with common autonomous and non-autonomous self-healing mechanisms in protective organic coatings used for anti-corrosion purposes. The autonomous healing mechanisms are often enabled by embedding polymerizable healing agents or corrosion inhibitors in the coating matrices. For non-autonomous mechanisms, the healing effects are induced by external heat or light stimuli, which trigger the chemical reactions or physical transitions necessary for bond formation or molecular chain movement.
[en] Electroless depositions of nickel were conducted in different bath conditions to find optimum conditions of electroless nickel plating at low operating temperature and pH. The effect of complexing reagent on stability of plating solution was investigated. Sodium citrate complexed plating solution is more stable than sodium pyrophosphate complexed solution. The effects of nickel salt concentration, reducing agent, complexing agent and inhibitor on deposition rate was investigated. The effects of pH on deposition rate and content of phosphorous in deposited nickel were also analyzed. Electroless deposited nickel become crystallized with increasing pH due to lower phosphorous content. In optimum operating bath condition, deposition rate was 7 μm/hr at 60 .deg. C and pH 10.0 without stabilizer. The rate was decreased with stabilizer concentration
[en] Both the organic and inorganic compounds commonly used in the industry to inhibit the corrosion process of metals and its alloys are mostly composed by highly toxic chemicals, in addition to being more expensive. In this research sugar-components derived from the Morinda Citrifolia (MC) leaves have been extracted in aqueous solution to perform a natural inhibitor capable to control de corrosion damage, which can replace the traditional inhibitors, being environmentally friendly. The experimental results indicate that this compound has shown excellent performance as corrosion inhibitor, reaching inhibition efficiency (EI), values up to 90% at inhibitor concentrations ranging 0.8 to 2 g·L−1 and immersion times of about 1 to 4 h. It has been found that the inhibition process takes place by the adsorption of the molecules on the surface of the metal (AISI 1045), by a physisorption mechanism.
[es]Los compuestos tanto orgánicos como inorgánicos empleados en la industria para inhibir el proceso de corrosión de los metales y sus aleaciones son en su mayoría sustancias químicas altamente tóxicas, además de ser costosas. En este trabajo se han extraído en medio acuoso componentes azucarados derivados de la planta Morinda Citrifolia (MC) para obtener un inhibidor natural capaz de controlar el daño por corrosión, el cual puede sustituir a los inhibidores tradicionales, siendo amigable con el medio ambiente. Los resultados indican, que este compuesto ha demostrado un excelente comportamiento como inhibidor de la corrosión, alcanzando valores de inhibición hasta el 90% para concentraciones de inhibidor de entre 0,8 y 2 g·L-1 y tiempos de inmersión 1 a 4 h. Se ha comprobado experimentalmente que el proceso de inhibición tiene lugar por la adsorción de las moléculas orgánicas naturales sobre la superficie del metal (AISI 1045), por un proceso de fisisorción.
[en] Kinetics of oxidation of lactose by (Cu(bipy)2)2+ in alkaline medium using Ru(III) as an inhibitor has been studied spectrophotometrically at 40 °C. The studies show that the rate of the reaction is zero order with respect to (Cu(bipy)2)2+ and first order with respect to (lactose). The order of reaction is found to be two at low concentrations of OH- (from 1.48×105 to 3.47×105 M) and less than two at its high concentrations (from 4.27×105 to 6.31×105 M). There is a substantial decrease in the pseudo-zero order rate constant with increase in the concentration of Ru(III) chloride, indicating the role of Ru(III) chloride as an inhibitor. Decrease in the rate with increase in dielectric constant of the medium is observed, while ionic strength of the medium and bipyridyl concentration has no influence on the rate. Based on kinetic data and spectrophotometric evidences, a suitable mechanism is proposed for the studied reaction. (author)