REJANE MARIA PEREIRA DA SILVA

REJANE MARIA PEREIRA DA SILVA

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Naphthenic corrosion using electrochemical and analytical techniques
2022 - SIMOES, A.M.P.; SILVA, R.M.P.; SUFFREDINI, H.B.; SANTOS, L.F.; BASTOS, I.N.
Naphthenic acid corrosion of steel was studied in a stagnant, biphasic oil/aqueous phase system, by means of electrochemical measurements and surface analysis. Corrosion was restricted to the region of the aqueous phase, as crater-shaped pits that eventually coalesced, generating a nearly uniform attack in the vicinity of the oil phase. In-situ electrochemical impedance spectroscopy (EIS) reveals the processes occurring at the aqueous phase, which nevertheless increase with the fraction of oil phase and with degree of acidity of the oil.
Naphthenic acid corrosion of API 5L X70 steel in aqueous/oil environment using electrochemical surface-resolved and analytical techniques
2022 - SILVA, REJANE M.P.; SUFFREDINI, HUGO B.; BASTOS, IVAN N.; SANTOS, LUIS F.; SIMOES, ALDA M.P.
Naphthenic acid corrosion of steel is studied in crude oil/aqueous phase system at ambient temperature, using a biphasic stagnant liquid without emulsification, by means of electrochemical measurements and surface analysis. The in-situ electrochemical impedance is assigned to the processes occurring at the aqueous phase. Corrosion occurred only in the region of the aqueous phase, as crater-shaped pits that eventually coalesced, generating a nearly uniform attack in the vicinity of the oil phase. The impedance values, normalized to the aqueous region only, reveal corrosion rate increasing with the ratio of crude oil/water. Despite the localized character of the anodic oxidation, the iron naphthenate corrosion products became partitioned between the two phases. Surface-resolved electrochemical techniques in aqueous solution revealed enhanced activity of the regions pre-exposed to oil.
O processo de anodização do alumínio e suas ligas
2021 - ARAUJO, JOAO V. de S.; SILVA, REJANE M.P. da; KLUMPP, RAFAEL E.; COSTA, ISOLDA
Al and its alloys are found in several industrial applications. However, like most metals, this material is not immune to corrosion, being necessary to be protected against corrosion. One of the methods most commonly employed to improve the corrosion resistance of Al alloys is the anodizing process, which consists of thickening of the natural oxide (Al2O3) presents in Al through anodic oxidation. The anodizing process is accomplished by immersion of the Al alloy into an acid bath and passing an electric current through it. This process produces two layers: a barrier layer thicker than the natural oxide and a layer with regular arrangement of nanopores (porous layer). This duplex structure forms the anodized layer with a large specific surface area. With the advent of nanotechnology, this layer has been applied in other areas due to its low cost, stability, absence of toxicity, and biocompatibility. In this context, this paper addresses a historical and electrochemical review of the anodizing process of Al and its alloys, presenting the main events that culminated in the development of the current processes and the understanding of the relationship between the chemical reactions and the mechanisms that occur during nucleation and development of the oxide layer.
Structural characterization, global and local electrochemical activity of electroless Ni–P-multiwalled carbon nanotube composite coatings on pipeline steel
2021 - OLIVEIRA, MARA C.L. de; CORREA, OLANDIR V.; SILVA, REJANE M.P. da; LIMA, NELSON B. de; OLIVEIRA, JEFFERSON T.D. de; OLIVEIRA, LEANDRO A. de; ANTUNES, RENATO A.
In this work, composite Ni–P-multiwalled carbon nanotube films were produced by electroless deposition. The main goal was to investigate the influence of multiwalled carbon nanotube loading on the local electrochemical behavior of the composite films, as probed by scanning electrochemical microscopy (SECM). The coatings were also characterized with respect to their crystalline structure, surface, and cross-section morphologies. Adhesion strength was examined by scratch tests. The global electrochemical behavior was evaluated by potentiodynamic polarization. The local electrochemical activity was investigated by probing the Fe2+ oxidation in the surface generation/tip collection mode of the SECM. The results revealed that multiwalled carbon nanotubes increased the adhesion strength and reduced the electrochemical activity on the surface of the coated samples.
Corrosion protection of the AA2198-T8 alloy by environmentally friendly organic-inorganic sol-gel coating based on bis-1,2-(triethoxysilyl) ethane
2021 - KLUMPP, RAFAEL E.; DONATUS, UYIME; SILVA, REJANE M.P. da; ANTUNES, RENATO A.; MACHADO, CARULINE de S.C.; MILAGRE, MARIANA X.; ARAUJO, JOAO V. de S.; VIVEIROS, BARBARA V.G. de; COSTA, ISOLDA
In this work, a surface coating composed of organic‐inorganic hybrid sol‐gel based on bis‐1,2‐(triethoxysilyl) (BTSE) ethane was applied on AA2198‐T8 samples, and its effect on corrosion resistance was investigated and compared with that of a chromate layer formed in a solution with hexavalent chromium ions. The corrosion resistance of BTSE coated samples was evaluated by immersion tests in sodium chloride solution (0.005 mol/L NaCl) and monitored by global electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and local electrochemical techniques such as scanning vibrating electrode technique (SVET) and scanning electrochemical microscopy (SECM). The formed coating layers were characterized by X‐ray photoelectron spectroscopy (XPS). The results pointed out that the BTSE is an effective alternative coating for corrosion protection of new generation Al‐Cu‐Li alloys and could replace chromates obtained in toxic and carcinogenic CrVI containing solutions leading to improved corrosion protection.
Surface analysis, microstructural characterization and local corrosion processes in decarburized SAE 9254 spring steel
2019 - SANTANA, JESSICA C.C. de C.; SILVA, REJANE M.P. da; ANTUNES, RENATO A.; SANTOS, SYDNEY F.
The aim of the present work was to study the surface chemistry, microstructure and local corrosion processes at the decarburized layer of the SAE 9254 automotive spring steel. The samples were austenitized at 850 and 900 °C, and oil quenched. The microstructure was investigated using confocal laser scanning microscopy and scanning electron microscopy. The surface chemistry was analyzed by X-ray photoelectron spectroscopy. Electrochemical impedance spectroscopy and potentiodynamic polarization were employed to assess the global corrosion behavior of the decarburized samples. Scanning electrochemical microscopy (SECM) was used to evaluate the influence of decarburization on the local corrosion activity. Microstructural characterization and XPS analysis indicate a dependence of the local electrochemical processes with the steel microconstituents and Si oxides in the decarburized layer.
Structural, adhesion and electrochemical characterization of electroless plated Ni-P-carbon black composite films on API 5L X80 steel
2019 - OLIVEIRA, MARA C.L. de; CORREA, OLANDIR V.; SILVA, REJANE M.P. da; LIMA, NELSON B. de; OLIVEIRA, JEFFERSON T.D. de; OLIVEIRA, LEANDRO A. de; ANTUNES, RENATO A.
In this work, composite Ni-P-carbon black coatings were obtained by electroless deposition on API 5L X80 substrates. The effect of carbon black on structural, adhesion and electrochemical properties of the plated samples was evaluated. Scanning electron microscopy analyses were carried out to examine the top surface and cross section of the films. Scratch tests were employed to evaluate coating adhesion properties. Potentiodynamic polarization tests were carried out to investigate the global electrochemical behavior of the deposited layers. Scanning electrochemical microscopy (SECM) was employed to measure local electrochemical activity over the coated surfaces. The carbon black concentration markedly affects the morphology, adhesion and electrochemical properties of the Ni-P-carbon black layers. The results point to an optimum carbon black content to achieve the best performance against corrosion. The coatings obtained at a carbon black concentration of 0.25 g L21 provided the best protection ability. The results are discussed with respect to coating morphology, adhesion and electrochemical activity.