Linear sweep voltammetry (LSV) test parameters in alkaline medium were optimized by Doehlert matrix design in order to quantify the deleterious phases in a superduplex stainless steel UNS S32750. The microstructural analysis was performed, in several heat treated specimens, by Light Optical (LOM) and Scanning Electron (SEM) Microscopies and correlated with the electrochemical tests. In these tests, optimized parameters were obtained for tests in aqueous solutions of KOH. The concentration of 3.55 mol l −1 , scan rate of 3.42 mV s −1 and initial potential of −0.818 V, showed a good correlation between the deleterious phases precipitated and charge density values. Differently from LOM characterization, chi and sigma deleterious phases can be distinguished by LSV optimized test. Finally, this test can be a non-destructive powerful tool of quality control to detect embrittlement and corrosion resistance decay that commonly affected this stainless steel as consequence of inadequate fabrication processes.
Rev. Virtual Quim. |Vol 11| |No. 5| |1521-1539| 1521 Artigo Estudo da Eficiência do Extrato da Alga Prasiola crispa como Inibidor de Corrosão em HCl 1 mol L -1 Souza, G. G. P.; Sampaio, M. T. G.; Furtado, A. B.; Buzzetti, P. H. M.; Ramos, C. J. B.; Teixeira, V. L.; Velasco, J. A. C.; Damasceno, R. N.; Ponzio, E. A.* Rev. Virtual Quim., 2019, 11 (5), 1521-1539. Data de publicação na Web: 1 de novembro de 2019Abstract: The algae Prasiola crispa extract was investigated as a possible corrosion eco-inhibitor for carbon steel in HCl 1 mol L -1 medium. The techniques used for the evaluation were the gravimetric tests, electrochemical polarization and electrochemical impedance spectrometry. The analysis showed that the extract has a great corrosion efficiency, reaching 95.9 % efficiency in the concentration of 0.800 g L -1 . The mechanism of inhibition is based on the adsorption of molecules on the steel surface generating a protective barrier. The study of the adsorption isotherms showed that the Langmuir model is the most appropriate and that the adsorption process is spontaneous presenting a ΔG ads of -27.9 kJ mol -1 which constitutes an intermediate behavior between a physical and chemical adsorption.
ResumoO extrato da alga Prasiola crispa foi investigado como possível eco-inibidor de corrosão para aço carbono em meio de HCl 1 mol L -1 . As técnicas utilizadas para a avaliação foram os ensaios gravimétricos, de polarização eletroquímica e de espectrometria de impedância eletroquímica. As análises mostraram que o extrato possui ótima eficiência anticorrosiva, chegando a 95,9 % de eficiência em concentração de 0,800 g L -1 . O mecanismo de inibição se baseia na adsorção das moléculas na superfície do aço gerando uma barreira protetora. O estudo das isotermas de adsorção mostrou que o modelo de Langmuir é o mais apropriado e que o processo de adsorção é espontâneo apresentando um ΔG ads de -27,9 kJ mol -1 , o que configura um comportamento intermediário entre uma adsorção física e química Palavras-chave: Eco-Inibidor; Prasiola crispa; aço carbono A36; ensaio gravimétrico; polarização eletroquímica; espectroscopia de impedância eletroquímica.
An optimised electrochemical technique, linear sweep voltammetry (LSV) in KOH solution (LSV-KOH) was confronted with the double loop electrochemical Potentiokinetic reactivation (DL-EPR) to verify which is the best technique to quantify deleterious phases (DP) in a UNS S32750 super duplex stainless steel. DL-EPR presented an error in determination of deleterious phases in the range of 6.9-100%. LSV-KOH show a better accuracy in quantification of deleterious phases volume fractions, the error range for LSV-KOH was 2.4-26.2%. When the morphology of sigma changes from lamellar to divorced, was observed modifications on LSV-KOH voltammograms. In specimens where lamellar morphology is present, the voltammograms show two peaks curve. Meanwhile, in specimens where occurred also divorced precipitation of sigma the voltammograms changes to a 3 peaks curve. This feature is due to the dissolution of sigma phase boundaries which has different compositions according to the form of sigma precipitation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.