CARACTERIZAÇÃO ELETROQUÍMICA E MORFOLÓGICA DE LIGAS Ni-Fe OBTIDAS EM SOLUÇÕES DE SULFATO
ELECTROCHEMICAL AND MORPHOLOGICAL CHARACTERIZATION OF Ni-Fe ALLOYS OBTAINED FROM SULFATE SOLUTIONS
Santana, Ana Isabel de C.; Díaz, Susana Losada; Barcia, Oswaldo Esteves; Mattos, Oscar Rosa
http://dx.doi.org/10.4322/tmm.2012.007
Tecnol. Metal. Mater. Min., vol.9, n1, p.42-47, 2012
Resumo
O comportamento de ligas NiFe é objeto de intensa investigação devido ao grande número de aplicações desses materiais no meio industrial. A eletrodeposição é um dos processos mais utilizados para produção dessas ligas devido ao seu baixo custo e sua capacidade de recobrir geometrias complexas. Variáveis do processo, como pH, densidade de corrente e composição do banho, podem afetar a cinética de deposição da liga bem como a morfologia e a estrutura dos depósitos obtidos. O objetivo do presente trabalho é estudar o efeito do pH sobre a cinética de deposição, composição e morfologia dos filmes. Os resultados das curvas de polarização e análise química mostram duas regiões: a primeira refletindo a redução de H+. Com aumento da polarização a corrente passa a variar fortemente com o potencial e a redução metálica ocorre com boa eficiência. A morfologia dos filmes varia com o pH da solução. Em pH 5, os depósitos são homogêneos e compactos. Para menores valores de pH (pH 1), são observadas trincas ao longo da superfície.
Palavras-chave
Ligas níquel-ferro, Efeito do pH, Eletrodeposição
Abstract
The behavior of NiFe alloys has been the object of intense research due to its wide industrial application. Electrodeposition is one of the most used processes for producing these alloy films owing to its low cost and capability to recover complex geometries. Parameters of the process such as pH, current density, and bath composition can affect the kinetic of deposition as well as the morphology and structure of the resulting deposits. The aim of the present work is to study the effect of pH solution on the deposition kinetics, composition and morphology of the films. The polarization curves and chemical analysis show two major regions. The first one reflects the H+ reduction. Increasing polarization makes the current to vary sharply with potential. High efficiency on metal electrodeposition is observed in this part of the curves. The morphology of the films changes according to the pH solution. At pH 5 the deposits are smooth and compact. At lower pH (pH 1) cracks are observed throughout the surface.
Keywords
NiFe alloys, pH effect, Electrodeposition.
Referências
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11 DÍAZ, S. L. et al. ZnFe anomalous electrodeposition: stationeries and local pH measurements. Electrochimica Acta, v. 47, n. 25, p. 4091-100, Sept. 2002. http://dx.doi.org/10.1016/S0013-4686(02)00416-4
2 BENTO, F. R.; MASCARO, L. H. Electrocrystallisation of Fe-Ni alloys from chloride electrolytes. Surface & Coatings Technology, v. 201, n. 3-4, p. 1752-6, Oct. 2006. http://dx.doi.org/10.1016/j.surfcoat.2006.02.055
3 BALACHANDRAN, R. et al. Effects of ultrasonic field in pulse electrodeposition on NiFe film on Cu substrate. Journal of Alloys and Compounds, v. 481, n. 1-2, p. 336-9, July 2009. http://dx.doi.org/10.1016/j.jallcom.2009.02.129
4 GANGASINGH, D.; TALBOT, J.B. Anomalous electrodeposition of nickel-iron. Journal of the Electrochemical Society, v. 138, n.12, p. 3605-11, Dec. 1991. http://dx.doi.org/10.1149/1.2085466
5 KIELING, V.C. Parameters influencing the electrodeposition of Ni-Fe alloys. Surface and Coatings Technology, v. 96, n. 2-3, p. 135-139, Nov. 1997. http://dx.doi.org/10.1016/S0257-8972(97)00078-9
6 BRENNER, A. Electrodeposition of alloys: principles and practice. New York: Academic Press, 1963. 2v.
7 DAHMS, H.; CROLL, I. M. The anomalous codeposition of iron-nickel alloys. Journal of the Electrochemical Society, v. 112, n. 8, p. 771-5, Ago. 1965.
8 MATLOSZ, M. Competitive adsorption effects in the electrodeposition of Fe-Ni alloys. Journal of the Electrochemical Society, v. 140, n. 8, p. 2272-9, Ago. 1993.
9 SANTANA, A.I.C. et al. A kinetic study on nickel electrodeposition from sulfate acid solutions. I. Experimental results and reaction path. Journal of the Electrochemical Society, v. 156, n. 8, p. D326-30, June 2009. http://dx.doi. org/10.1149/1.3147263
10 DÍAZ, S. L. et al. Electrodeposition of iron in sulphate solutions. Electrochimica Acta, v. 53, n. 25, p. 7426-35, Oct. 2008. http://dx.doi.org/10.1016/j.electacta.2008.01.015
11 DÍAZ, S. L. et al. ZnFe anomalous electrodeposition: stationeries and local pH measurements. Electrochimica Acta, v. 47, n. 25, p. 4091-100, Sept. 2002. http://dx.doi.org/10.1016/S0013-4686(02)00416-4
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