Navegando por Assunto "Corrosion"

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Acesso aberto (Open Access)
Avaliação da influência das águas de poço e industrial tratada na corrosão do cobre
(Universidade Federal do Pará, 2021-02-04) LIMA, Andel Denilson Matos; CARDOSO FILHO, José Carlos de Araújo; http://lattes.cnpq.br/7033790503322903
Efficient corrosion monitoring prevents, in an industry, unplanned downtime for corrective maintenance to exchange parts, pipes, materials, components and equipment made of copper that have contact with raw or treated water and that suffer wear and tear over time. This work monitored through the exposure of well water and treated a cosmetics industry, located in the State of Pará, the level of corrosivity when in contact with corrosion coupons (proof bodies) made of copper. The method of analysis consisted of immersing these coupons in well water and industrial water for 7, 14, 21 and 28 days. In each period, the coupons were removed clean and taken to mass loss tests, corrosion rate, corrosion potential and polarization curves. In addition to physicalchemical and microbiological analyzes of water samples for the calculation of stability, which shows whether the trend is stable, corrosive or fouling. The results showed that well water has low corrosivity and industrial water has moderate corrosivity, even receiving chemical treatment for pH correction and microbiological control. The loss of mass and the corrosion rate of the copper coupon were greater for industrial water and the polarization curves and corrosion potential showed that industrial water has a high degree of corrosion compared to well water.
Acesso aberto (Open Access)
Corrosão em estacas metálicas de torres de energia elétrica
(Rede Latino-Americana de Materiais, 2019-05) VILHENA, Alexandre Evangelista Rodrigues; PINTO, Renata Godinho; COSTA, Rafaela Reis da; PICANÇO, Marcelo de Souza; MACÊDO, Alcebíades Negrão
In order to maintain the quality and continuity of the power supply it is essential to monitor the integrity of the structure of the transmission towers usually executed in steel. This study evaluated soil corrosivity in the Amazon region in the Vila do Conde-Tucuruí stretch, state of Pará. The resistivity, potential soil structure, redox potential, pH, chloride, sulphate and sulfate concentration, besides the Steinrath index and the quantification of the soil corrosivity through the installation of test specimens in the studied soil. The data were collected in the dry and rainy period while the specimens were removed after 12 months of exposure. The soils of the region presented resistivity higher than 20 kΩ.cm, characterizing as few corrosives; the redox potential of 100 to 300 mV indicated mild to moderately corrosive soils; the potential soil structure remained in the range of -0.4 to -0.7 V/ECS being within the range considered normal; the Steinrath index classified the soils into little corrosive to non-corrosive and the corrosion rates of the test specimens indicated high corrosion at 3 meters depth. Based on the results of each evaluation method used it can be verified that the soil corrosivity increases with the depth, besides being favorable to the attack of microbiological corrosion.
Acesso aberto (Open Access)
Estudo da resistência à corrosão de soldas de ferro fundido branco alto cromo na presença de NaOH (30% p.p)
(Universidade Federal do Pará, 2024-10-03) SANTOS, Renata Soraia Guimarães dos; BRAGA, Eduardo de Magalhães; http://lattes.cnpq.br/4783553888547500; https://orcid.org/0000-0003-0739-7592
In the mining industry, specifically in bauxite beneficiation, adverse working conditions are encountered, requiring high mechanical and chemical resistance. For these conditions, it is necessary to choose potentially resistant materials, such as high Cr white cast iron (FFBA-Cr). However, currently, there is no effective recovery of equipment manufactured with FFBA-Cr, mainly due to the difficulty of machinability generated in the repair process. An alternative recovery has been developed by the Laboratory of Characterization of Metallic Materials of UFPA - LCAM, through electric arc welding, using two filler metals, the electric wire ER307L and the wire with high Mn value. In this context, this work proposes to investigate the corrosion resistance of the welded joint, obtained with these two filler metals. The base metal (FFBA-Cr) as a reference and the metals generated by the welded joints, ER307L and with high Mn value, were analyzed. The samples underwent optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and electrochemical tests of corrosion potential, polarization and impedance. It was observed that the samples presented a similar structure of carbide matrix, but with different organization and volumes. However, the electrochemical behavior of corrosion potential, polarization and impedance were similar, with their resulting values very close, variations: 50 V; 3.53 µA; 0.18 ohm, respectively, which was corroborated by the corrosion rate, 0.4 mmpy, and explained by the calculations of Cr and Ni volume, which present inverse values of concentration magnitude between the samples. Raman analyses performed after polarization of the samples indicated the formation of important oxides on this surface and possibly the formation of a passivating layer, which is corroborated by the mass loss analysis that showed the possibility of passivation of the welded joints, despite corrosion processes in the anodic phase of this exposure process over the exposure time.