Papers by Merlin C.E. Bandeira
Editora Científica Digital eBooks, 2022
Flow accelerated corrosion (FAC) is a steel degradation that occurs in heat recovery steam genera... more Flow accelerated corrosion (FAC) is a steel degradation that occurs in heat recovery steam generators in the power industry. The mechanism of this corrosion comprises an electrochemical dissolution of the semi-protective magnetite layer (Fe3O4) that is formed within the pipes employed in the boilers. The FAC is influenced by different factors such as fluid velocity, pH and dissolved oxygen concentration. In this context, Rotating Cage tests were used to evaluate the influence of pH and dissolved oxygen content on FAC of A210, P11 and P22 steels. General corrosion was lower for P11 and P22 steels, an effect consistent with the presence of chromium in their compositions. General corrosion was most critical at pH 8.5. The corrosion intensity decreased for the three steels when the dissolved oxygen concentration increased, at 2 m/s. This behavior is coherent considering the most effective precipitation of Fe2O3 inside the pores of the Fe3O4 layer in a more oxidizing environment. For 3 m/s, the corrosion intensity increased for both materials when oxygen increased, showing the shear stress effect. These behaviors were more significant at pH 8.5. About pitting corrosion, the analyzes show localized attack in most coupons, however with very low number of pits.
ABM Proceedings, Oct 1, 2018
Resumo O aço carbono é um material amplamente empregado na indústria petrolífera devido sua eleva... more Resumo O aço carbono é um material amplamente empregado na indústria petrolífera devido sua elevada resistência mecânica e baixo custo. Entretanto, este material não possui boa resistência à corrosão. Neste contexto a predição da taxa de corrosão é de extrema importância para estimar a durabilidade desses materiais. Atualmente isto é feito com base em dados de ensaios de perda de massa em um único tempo de imersão, estimando-se a taxa de corrosão. Contudo, para converter os dados de perda de massa em taxas de corrosão é imprescindível que os ensaios sejam conduzidos em diferentes tempos de imersão e que haja linearidade entre perda de massa e tempo. Neste trabalho a corrosão do aço carbono em meios saturados com CO2 foi investigada através de ensaios de perda de massa em três tempos de imersão diferentes, com o objetivo de avaliar essa linearidade. Dos quatro meios corrosivos estudados, um não apresentou linearidade entre PM e tempo de imersão, sendo portanto incorreto extrapolar os dados para taxa de corrosão. Os resultados comprovaram que a extrapolação de dados de PM para taxas de corrosão não pode ser aplicada sem uma prévia verificação da linearidade entre perda de massa e tempo de imersão. Palavras-chave: Corrosão; CO2; Perda de massa; Taxa de corrosão.
Journal of Solid State Electrochemistry, May 3, 1999
The present study focuses on the electronic and electrochemical features of a copolymer electroch... more The present study focuses on the electronic and electrochemical features of a copolymer electrochemically grown from pyrrole and trans-[RuCl2(pmp)4] monomers, where pmp = 3-(pyrrol-1-ylmethyl)pyridine. The results from electrochemical impedance spectroscopy analyses revealed the redox behavior of the poly{pyrrole-trans-[RuCl2(pmp)4]} compound as well as the non-homogeneous nature of the extremely thin polymeric layers. An equivalent circuit is proposed for an optimized film produced under the scope of the work.
Materials Research
Flow accelerated corrosion (FAC) is a steel degradation that occurs in heat recovery steam genera... more Flow accelerated corrosion (FAC) is a steel degradation that occurs in heat recovery steam generators in the power industry. The mechanism of this corrosion comprises an electrochemical dissolution of the semi-protective magnetite layer (Fe 3 O 4) that is formed within the pipes employed in the boilers. The FAC is influenced by different factors such as fluid velocity, pH and dissolved oxygen concentration. In this context, Rotating Cage tests were used to evaluate the influence of pH and dissolved oxygen content on FAC of A210, P11 and P22 steels. General corrosion was lower for P11 and P22 steels, an effect consistent with the presence of chromium in their compositions. General corrosion was most critical at pH 8.5. The corrosion intensity decreased for the three steels when the dissolved oxygen concentration increased, at 2 m/s. This behavior is coherent considering the most effective precipitation of Fe 2 O 3 inside the pores of the Fe 3 O 4 layer in a more oxidizing environment. For 3 m/s, the corrosion intensity increased for both materials when oxygen increased, showing the shear stress effect. These behaviors were more significant at pH 8.5. About pitting corrosion, the analyzes show localized attack in the majority of coupons, however with very low number of pits.
The standard Rotating Cage (RC) is a very useful comparative method for screening materials, crud... more The standard Rotating Cage (RC) is a very useful comparative method for screening materials, crude oils and corrosion inhibitors. Thinking of reduce costs and time expended in laboratory tests, mainly to evaluate inhibitors by RC and electrochemical techniques tests; we developed an Electrochemical Rotating Cage Autoclave assembly (ERCA). Herein we present the ERCA system and the electrochemical response validation using a well-known redox system. Additionally, we compared the impedance diagrams of bare carbon steel in a 0.16% NaCl brine at 500 RPM with 1 and 100 bar of CO2. Preliminary results of inhibitors electrochemical evaluation during the RC test showed the film formation and growth. With ERCA is possible to use electrochemical techniques to monitor the corrosion process or inhibitor action during the RC laboratory test. Electrochemical results can be compared with standard weight loss performed after the test using the standard RC samples tested in the same batch. The aim is...
Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico
A comparative study on the corrosion protection of Nd-Fe-B magnetic alloys using polypyrrolic or ... more A comparative study on the corrosion protection of Nd-Fe-B magnetic alloys using polypyrrolic or poly {trans-[ R~C l~(v p y)~] f coatings M.C.E. ~andeira', F .D. ~rochnow', I. costa ' , C.V. ~r a n c o ' ' LEC-Depto. de Quimica-CSliversidade Federal de Santa Catarina-, Brasil.
Corrosion Science, 2021
Abstract Guanine inhibition of copper corrosion in 0.1 M HCl was characterized by electrochemical... more Abstract Guanine inhibition of copper corrosion in 0.1 M HCl was characterized by electrochemical and weight loss experiments under hydrodynamic conditions as well as by Surface-enhanced Raman spectroscopy (SERS). Cyclic voltammetry and polarization measurements revealed that Guanine adsorption modifies copper surface, thus inhibiting its corrosion. Weight loss and electrochemical impedance experiments showed that Guanine has an inhibition efficiency (ξ) of ∼87 % and that its protection is maintained up to 333 K. SERS measurements revealed that neutral Guanine adsorbs on copper at a wide potential range, forming a Cu(I)Guanine complex at greater immersion times.
Journal of Raman Spectroscopy, 2019
Surface enhanced raman scattering (SERS) spectra of 4‐methylimidazole (4‐MeImid) are shown for th... more Surface enhanced raman scattering (SERS) spectra of 4‐methylimidazole (4‐MeImid) are shown for the first time on a copper electrode and in the presence of chloride. The potential dependence on the spectra reveals that the N1H tautomer is majority close to the open circuit, but the N3H tautomer predominates at more cathodic polarizations. At these latter conditions, 4‐MeImid orientation changes from tilted to perpendicular, and such a behavior is similar to the one of Imid at natural pH. Interesting issues are observed at pH = 2.0: (a) 4‐MeImidH+ is not identified on the metal surface for the whole applied potential range and must be either adsorbed as an ion pair with chloride or in the bulk solution; (b) at open circuit and anodic polarization, its neutral form is the unique azole species present, in contrast to the ImidH+ behavior, which is easily observed in the surface spectra.
Journal of The Electrochemical Society, 2018
Corrosion Science, 2018
This discussion presents an analysis of the recent paper by Kahyarian, Brown and Nesic published ... more This discussion presents an analysis of the recent paper by Kahyarian, Brown and Nesic published in this Journal Kahyarian et al. (2017). Indeed, the paper claims an anodic participation of CO 2 in the iron dissolution mechanism, not detected by our work also published in this same journal Almeida et al. (2017). The anodic role was, however, only limited to the analysis of Tafel slopes behaviour. This is what was typically done in the early works of iron dissolution in acid media during the 1960′s, so that a discussion about this methodology based on the progress of the electrochemistry that has been developed since the 1980′s is absolutely necessary.
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Papers by Merlin C.E. Bandeira