Electrochemical impedance spectroscopy and linear polarization applied to evaluation of porosity of phosphate conversion coatings on electrogalvanized steels |
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| Authors: | Vanessa de Freitas Cunha Lins Geraldo Francisco de Andrade Reis Carlos Roberto de Araujo |
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| Institution: | a Corrosion and Surface Engineering Laboratory, Chemical Engineering Department, Federal University of Minas Gerais, Rua Espirito Santo 35, 6th floor, Belo Horizonte 30160-030, Brazil
b Chemical Department, Federal University of Minas Gerais, AV. Antonio Carlos, 6627-Pampulha, Belo Horizonte 31270-901, Brazil |
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| Abstract: | In this work, electrochemical impedance spectroscopy and linear polarization are used in determining porosity of zinc phosphates, and of nickel and manganese modified zinc phosphates on electrogalvanized steel. The porosity of the phosphate layers ranges from 0.1% for the manganese-modified hopeite to 8% for hopeite, using the linear polarization and the electrochemical impedance spectroscopy techniques. The porosity values measured using the two techniques were in agreement. All impedance spectra of coated samples showed two steps, with two capacitive arcs and an inductive looping. |
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| Keywords: | Phosphate conversion coatings Electrochemical impedance spectroscopy Porosity Linear polarization |
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