Química

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http://repositorio.ufes.br/handle/10/17500
Programa de Pós-Graduação em Química

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Navegando Química por Autor "Agostinho, Silvia Maria Leite"

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    Resistência à corrosão dos aços inoxidáveis em soluções contendo íons cloreto e piridina ou benzimidazol como inibidores de corrosão
    (Universidade Federal do Espírito Santo, 2014-01-01) Soares, Thiago Freitas; Ribeiro, Josimar; Agostinho, Silvia Maria Leite; Barthus, Rosangela Cristina
    The corrosion of stainless steel AISI 304 and AISI 430 was investigated in a solution of NaCl 3.0 % by mass in the absence and presence of inhibitors pyridine or benzimidazole. The electrochemical study was performed using the technique of potentiodynamic and Electrochemical Impedance Spectroscopy (EIS) polarization, the surface morphology of the electrodes was characterized using the techniques: X- ray diffraction (XRD), Atomic Force Microscopy (AFM), Microscopy Scanning Electron (SEM), and the compositions were investigated by analysis of Energy Dispersive X-ray (EDX) and Emission Spectrometry of Laser-Induced Plasma (LIBS). Observed by LIBS and EDX, the difference between the two alloys, the AISI 304 steel which has 10 times more than the nickel steel AISI 430. XRD revealed that the AISI 304 stainless steel there is the existence of two distinct phases, one of iron - nickel and chromium another, as for the AISI 430 there is only one phase chromium. The results obtained by polarization curves show that for a solution of sodium chloride AISI 304 stainless steel is more corrosion resistant than AISI 430 stainless steel. The efficiency of inhibition was evaluated in six different concentrations (5 ppm, 25 ppm, 50 ppm, 100 ppm, 500 ppm and 1000 ppm) for each of the inhibitors at all concentrations and an increase in corrosion potential were observed with an efficacy of inhibition around 80% for the AISI 304 steel and 85% for the AISI 430 steel . The obtained results showed again that impedance at all concentrations of the inhibitors had an increased corrosion potential, which for steel AISI 304 was obtained inhibition efficiency of around 60% and for steel AISI 430 around 85%, as observed in the potentiodynamic polarization. AFM measurements showed that the depth values of pits were at least 4 times smaller than those obtained in the absence of pyridine as an inhibitor for both alloys. In the case of benzimidazole as an inhibitor, the values of depth of pits were at least eight times lower. The results obtained by the weight loss in the presence of inhibitors showed a 2-fold reduction in corrosion rate obtained in the absence of inhibitors. In the potentiodynamic polarization curves of the materials in seawater in the absence and presence of the inhibitor, a decrease of the efficiency of inhibition for both alloys, ranging from 45 % to 60 % was observed, however, it was observed that the organic compounds used are good inhibitors for these materials in solution containing chloride ions.