RESUMO
We studied atmospheric corrosion on Rapa Nui Island, using galvanized and non-galvanized SAE 1020 steel samples exposed on racks. We also added Charpy samples of both materials to directly determine the effect of corrosion rate on these materials' impact toughness. The results indicated a correlation between corrosion rate and toughness loss in the studied materials. In the corrosion study, we could also demonstrate the effect from increased insular population growth on contaminants which aid atmospheric corrosivity. Results showed that atmospheric SO2 has tripled compared with similar corrosion studies done 20 years ago (Mapa Iberoamericano de Corrosión, MICAT), increasing corrosion rates. Our results show how human factors can influence changes in environmental variables that strengthen corrosion.
RESUMO
In this work, the production of a novel methodology for the application of natural corrosion inhibitors on steel, using an autoclave is presented. Tests were carried out using Artemisia vulgaris. The inhibitor was produced with a simple soxhlet extraction process using 15 g of Artemisia vulgaris and 260 mL of Ether. Once the inhibitor was produced, the steel was immersed in it, to form a coating that protects the material against corrosion. Thermogravimetry analyzes (TGA) were performed on the inhibitor, to determine the degradation temperature; it was observed that, at 321 °C, the loss of organic mass begins. After applying the inhibitor to the steel, the Fourier Transform Infrared Spectroscopy (FTIR) technique was used to determine the vibrational bands and the difference between the spectra for the steels before and after the coating was applied. For the evaluation of the method efficiency, Electrochemical Impedance Spectroscopy (EIS) and polarization resistance tests were performed, where Nyquist diagrams and Tafel curves were obtained, for steels with and without treatment. In this case, an increase of 93% in the corrosion resistance, and an 88% decrease in the corrosion rate were observed, proving that this methodology can be used to protect steel against corrosion and extend the steel's useful life.
RESUMO
In this study, an experimental and statistic investigation approach based on analysis of variance (ANOVA) and response surface methodology (RSM) techniques was performed to find the significant main effects and two-factor interaction effects and to determine how the controllable factors such as cutting speed, feed rate, depth of cut (DOC), tool nose radius, substrate and coating method of cutting tools influence surface quality in turning of AISI 1045 steel. The first optimal or near-optimal conditions for the quality of the generated surface and the second ones, including maximum material removal rate, were established using the proposed regression equations. The group mean roughness of the turned workpieces was lower from using chemical vapor deposition (CVD)-coated carbide inserts than the group means of other types of inserts; however they could not achieve the specific lowest roughness. The physical vapor deposition (PVD)-coated carbide and cermet inserts achieved the best surface quality when the specific combinations within the range interval of controllable factors were used in the experiment, showing that they may be applied to finish turning processes or even to particular high material removal rate conditions associated with the lowest roughness.
RESUMO
Abstract The electrochemical corrosion inhibition properties of the combined admixture of 1,3-diphenyl-2-thiourea and 4-hydroxy-3-methoxybenzaldehyde on mild steel in 1 M H;SO4 and HC1 acid media were studied through weight loss analysis, potentiodynamic polarization method, optical microscopy and IR spectroscopy. Results showed that the organic mixture effectively inhibited the corrosion of mild steel in both solutions with an optimal inhibition efficiency of 97.4% and 97.47% in H2SO4 from weight loss and potentiodynamic polarization test, while the corresponding values in HC1 were 94 71% and 89.73% respectively. Thermodynamic calculations showed that the compound chemisorbed onto the steel surface blocking the diffusion of corrosive anions Observations from micro-analytical images confirmed the effective inhibition property of the compound and its presence on the surface topography of the steel Infrared spectra revealed the presence of the functional groups of the organic compound responsible for corrosion inhibition The adsorption of the compound was deduced to obey the Langmuir, Frumkin and Freundlich adsorption isotherm.
Resumen Se estudiaron las propiedades de inhibición de la corrosión electroquímica de la mezcla combinada de 1,3-difenil-2-tiourea y 4-hidroxi-3-metoxibenzaldehido sobre acero dulce en medios de H2SO4 y HC1 1 M mediante análisis de pérdida de peso, método de polarización potenciodinámica, microscopia óptica y espectroscopia IR. Los resultados mostraron que la mezcla inhibe eficazmente la corrosión del acero dulce en ambas soluciones con una eficacia de inhibición óptima de 97,4% y 97,47% en H2SO4, mientras que los valores correspondientes al HC1 son 94,71% y 89,73%. Los cálculos termodinámicos demostraron que el compuesto quimiosorbido sobre la superficie de acero bloquea la difusión de aniones corrosivos Las imágenes micro-anal ticas confirmaron la efectiva propiedad de inhibición del compuesto y su presencia en la topografía superficial del acero. Los espectros infrarrojos revelaron la presencia de los grupos funcionales del compuesto orgánico responsable de la inhibición de la corrosión La adsorción del compuesto se dedujo siguiendo las isotermas de adsorción de Langmuir, Frumkin y Freundlich.
Resumo Estudaram-se as propriedades de inibição da corrosão eletroquímica da mistura combinada de 1,3-difenil-2-tioureia e 4-hidroxi-3-metoxibenzaldeido em aço macio em meios de H2SO4 e HC1 1 M através de análise de perda de peso, método de polarização potenciodinâmica, microscopia óptica e espectroscopia de IV. Os resultados mostram que a mistura inibiu eficazmente a corrosão de aço macio em ambas as soluções com uma eficiência de inibição óptima de 97,4% e 97,47% em H2SO4, enquanto os valores correspondentes ao HC1 são respectivamente 94,71% e 89,73%. Os cálculos termodinâmicos mostram que o composto quimisorvido sobre a superfície de aço bloquea a difusão de aniões corrosivos As imagens micro-analíticas confirmam a propriedade de inibição do composto e sua presença na topografia superficial do aço. Os espectros de infravermelho revelaram a presença dos grupos funcionais do composto orgânico responsáveis pela inibição da corrosão. A adsorção do composto foi deduzida seguindo às isotermas de adsorção de Langmuir, Frumkin e Freundlich.