Caracterização de superfícies de aços galvanizados utilizando a técnica de espectroscopia de impedância eletroquímica

• Ano de defesa: 2013
• Autor(a) principal: Kenia Barros Batista
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Engenharia Química; Análise espectral; Engenharia quimica; Aço galvanizado
• Link de acesso: http://hdl.handle.net/1843/BUOS-986HZV

One of the biggest changes in recent years regarding the application of steel as a structural element was the use of steel coated with zinc for situations that require superior corrosion resistance. A wide range of galvanized steel products is available from production lines of continuous strips, technologically advanced (electroplating and hot dip galvanizing) coating specifications offering special requirements of the automotive industry (surface quality, formability, weldability and thickness control layer, etc.). Given this scenario the objective of this study was therefore to evaluate the performance against corrosion of Fe-Zn phases of commercial galvannealed steel manufactured by the domestic industry. The phases were obtained by anodic dissolution of steel surface "galvannealed". Besides this, we evaluated the corrosion behavior in three galvanized steels produced by the same domestic industry, the steel electrogalvanized (EG), hot-dip galvanized without thermal treatment of the zinc layer (GI) and galvanized hot with heat treatment layer zinc (GA). The technique used was electrochemical impedance spectroscopy which provides information on the corrosion resistance of steel in a corrosive medium and data on the mechanism of the corrosion process. The electrolytes used were 0.1 HCl mol/L NaOH 0.1 mol/L NaCl, 0.35 mol/L NaCl and 3.42 mol/L + ZnSO4.7H2O 0.35 mol/L. It was observed that the most aggressive electrolyte for galvanized steels were solution of sodium chloride and zinc sulfate heptahydrate. It was also observed that most of the resistance polarization phase was alkaline range, compared to other Fe-Zn do. This phase contains the higher iron content relative to zinc, and iron passive pH above 9. Also in alkaline steel galvannealed (GA) had the highest polarization resistance compared to steel eletrogalvanizado (EG) and hot-dip galvanized without thermal treatment of the zinc layer (GI). In acidic medium, the zeta and delta phases, with higher zinc content showed higher polarization resistance for stage range.