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Previous issue date: 2016-03-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / The present study analyzes the influence of the presence of Ca2+, by the addition of CaCO3 in water saturated with CO2, on the corrosion of SAE 1045 steel tempered and quenched under conditions of 80? C, 15 MPa and 168 hours (7 days) andon the properties of the corrosion scales formed on the steel surface. The corrosion rates of the steel were determined by weight loss tests according to ASTM G1-03 (2010). The techniques of electron scanning microscopy by field emission (FEG/MEV), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and potentiodynamic polarization were used to obtain information about the properties of corrosion scales. Uniform corrosion was observed and the results indicated that by adding calcium carbonate, with concentrations of 10 ppm, 100 ppm, 1000 ppm and 10000 ppm of Ca2+ in solution, the corrosion rates by weight loss and the thicknesses of the corrosion product films decreased. However, the addition of calcium carbonate decreased the corrosion rate for all concentrations, probably due to its property of increasing the pH of the solution. The highest corrosion rate determined by weight loss was observed when corrosion was induced without the presence of calcium carbonate and with concentration of 100 ppm of Ca2+. The corrosion rate did not changed linearly with Ca+ concentrations, the highest corrosion rate was observed for 100 ppm of Ca2+. The EDS analyzes provide information that a mixed carbonate is formed in presence of Ca+2 in solution, probably FexCa1-xCO3, with increasing of Ca incorporation in the crystalline lattice of FeCO3, with increasing of calcium content and a respective reduction of Fe amounts. The XRD analyzes also indicated that the corrosion product films formed in the presence of calcium are composed by FeCO3 enriched with Ca besides oxides and iron hydroxides as goethite - FeO(OH) and Fe3O4 - magnetite. Based on the electrochemical tests, the film that had the more negative potential (Ecorr) and higher corrosion current density (icorr) was the one formed in the presence of 100 ppm Ca2+, and this film showed electrochemical properties very similar to the bare steel. / O presente trabalho analisa a influ?ncia da presen?a de Ca2+, por meio da adi??o de CaCO3 em ?gua saturada com CO2, na corros?o do a?o SAE 1045, temperado e revenido, sob condi??es de 80 ?C, 15 MPa e 168 horas (7 dias) e nas propriedades dos filmes de produtos de corros?o formados na superf?cie do a?o. As taxas de corros?o do a?o foram determinadas por testes de perda de massa segundo ASTM G1-03 (2010). As t?cnicas de microscopia eletr?nica de varredura por emiss?o de campo (FEG/MEV), espectroscopia de energia dispersiva (EDS), difra??o de raios X (DRX) e polariza??o potenciodin?mica foram utilizadas para obter informa??es sobre as propriedades dos filmes de produtos de corros?o. Observou-se corros?o uniforme e os resultados mostraram que ao adicionar carbonato de c?lcio, com concentra??es de 10 ppm, 100 ppm, 1000 ppm e 10000 ppm de Ca2+ na solu??o, as taxas de corros?o por perda de massa e as espessuras dos filmes de produtos de corros?o diminuiram. A adi??o de carbonato de c?lcio reduziu as taxas de corros?o para todas as concentra??es de Ca2+, provavelmente, devido sua propriedade de aumentar o pH da solu??o. A taxa de corros?o n?o variou linearmente com a concentra??o de Ca2+ em solu??o, sendo que a maior taxa de corros?o foi observada para a concentra??o de 100 ppm de Ca2+.As an?lises de EDS indicaram a forma??o de carbonato misto, provavelmente FexCa1-xCO3, com o aumento da incorpara??o de Ca na rede cristalina do FeCO3, visto que com o aumento da adi??o de carbonato de c?lcio observou-se um aumento no teor de Ca e uma respectiva redu??o nos teores de Fe. As an?lises de DRX indicaram que os filmes de produtos de corros?o formados em presen?a de c?lcio s?o compostos de FeCO3 enriquecido com Ca, de ?xidos e hidr?xidos de ferro como goetita - FeO(OH) e Fe3O4 - magnetita. De acordo com os ensaios eletroqu?micos, o filme que apresentou o potencial de corros?o menos nobre (Ecorr) e maior densidade de corrente de corros?o (icorr) foi o formado na presen?a de 100 ppm Ca2+, sendo que este filme apresentou propriedades eletroqu?micas muito similares ao do a?o refer?ncia (sem produto de corros?o na superf?cie).
| Identifer | oai:union.ndltd.org:IBICT/oai:tede2.pucrs.br:tede/6878 |
| Date | 30 March 2016 |
| Creators | Oliveira, Loani Bassani de |
| Contributors | Costa, Eleani Maria da |
| Publisher | Pontif?cia Universidade Cat?lica do Rio Grande do Sul, Programa de P?s-Gradua??o em Engenharia e Tecnologia de Materiais, PUCRS, Brasil, Faculdade de Engenharia |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da PUC_RS, instname:Pontifícia Universidade Católica do Rio Grande do Sul, instacron:PUC_RS |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | -7432719344215120122, 600, 600, 600, 600, -655770572761439785, 4518971056484826825, 2075167498588264571 |
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