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Effect of Equal-Channel Angular Pressing on Pitting Corrosion of Pure Aluminum

DOI: 10.1155/2012/450854

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The effect of equal-channel angular pressing (ECAP) on the pitting corrosion of pure Al was investigated using electrochemical techniques in solutions containing 0.1?m?mol·dm?3 of Na2SO4 and 8.46?mol·dm?3 of NaCl (300?ppm?Cl?) and followed by surface analysis. The potential for pitting corrosion of pure Al was clearly shifted in the noble direction by the ECAP process indicating that this process improves resistance to pitting corrosion. The time dependence of corrosion potential and the anodic potential at 1?A·m?2 revealed that the rate of formation of Al oxide films increased due to a decrease in the grain size of the Al after ECAP. Since there exists a negligible amount of impurity precipitates in pure Al, the improvement in pitting corrosion resistance of pure Al by ECAP appears to be attributable to an increase in the rate of formation of Al oxide films. 1. Introduction Although aluminum is inherently an active metal, it shows excellent corrosion resistance over a neutral pH range of 4–8 due to its superficial oxide film. In solutions containing Cl?, however, pitting corrosion occurs locally where the oxide film is attacked by Cl? [1–7]. On the other hand, reducing the grain size of metallic materials to the submicron range or even the nanometer range using equal-channel angular pressing (ECAP), high pressure torsion (HPT), or severe torsion straining processing (STSP) is increasingly being studied with the aim of improving mechanical properties such as strength and ductility [8–13]. Although the literature is reasonably scarce with investigations reporting the effects of severe plastic deformation upon the pitting and general corrosion behaviour [14–20] of Al-based alloys, mainly AA1100 and AA5052 (Al-Mg), those reported their majority suggests that corrosion resistance decreases with decreasing the grain size [14, 15]. It should also be remarked that chloride content, pH and other characteristics and nature of solution significantly affect the corrosion behaviour. Considering the ECAP, it has been reported both increase and decrease on the corrosion resistance [15, 17, 18]. Ralston et al. [15] recently reported that finer grains of commercially pure (c.p.) grade Al samples provide significant gains into the corrosion resistance in acidic and alkaline sodium chloride media whilst having lesser, but noticeable, impact in near neutral electrolytes [15]. It was also reported [15] that ECAP has provided low corrosion rates by using a single cast ingot of ultrahigh purity Al. Precipitate compounds of Fe-Al and Si were found around the pitting area.


[1]  H. H. Uhlig, Corrosion and Corrosion Control, Sangyo Tosho, Tokyo, Japan, 1968.
[2]  G. Ito, Corrosion Science and Engineering, Corona, Tokyo, Japan, 1973.
[3]  Z. Szklarska-Smialowska, “Pitting corrosion of aluminum,” Corrosion Science, vol. 41, no. 9, pp. 1743–1767, 1999.
[4]  L. Fedrizzi, F. Deflorian, S. Rossi, and P. L. Bonora, “Study of aluminium filiform corrosion by using electrochemical techniques,” Materials Science Forum, vol. 289–292, no. 1, pp. 485–498, 1998.
[5]  S. Y. Yu, W. E. O'Grady, D. E. Ramaker, and P. M. Natishan, “Chloride ingress into aluminum prior to pitting corrosion. An investigation by XANES and XPS,” Journal of the Electrochemical Society, vol. 147, no. 8, pp. 2952–2958, 2000.
[6]  M. Shao, Y. Fu, R. Hu, and C. Lin, “A study on pitting corrosion of aluminum alloy 2024—T3 by scanning microreference electrode technique,” Materials Science and Engineering A, vol. 344, no. 1-2, pp. 323–327, 2003.
[7]  G. Bereket and A. Yurt, “The inhibition effect of amino acids and hydroxy carboxylic acids on pitting corrosion of aluminum alloy 7075,” Corrosion Science, vol. 43, no. 6, pp. 1179–1195, 2001.
[8]  R. Z. Valiev, N. A. Krasilnikov, and N. K. Tsenev, “Plastic deformation of alloys with submicron-grained structure,” Materials Science and Engineering A, vol. 137, no. C, pp. 35–40, 1991.
[9]  R. Z. Valiev, R. K. Islamgaliev, and I. V. Alexandrov, “Bulk nanostructured materials from severe plastic deformation,” Progress in Materials Science, vol. 45, no. 2, pp. 103–189, 2000.
[10]  J. J. Park and D. H. Shin, in Ultrafine Grained Materials II, The Minerals, Metals & Materials Society, Warrendale, Pa, USA, 2008.
[11]  Z. Horita, M. Furukawa, M. Nemoto, and T. G. Langdon, “Development of fine grained structures using severe plastic deformation,” Materials Science and Technology, vol. 16, no. 11-12, pp. 1239–1245, 2000.
[12]  J. Horita, “Production of ultrafine-grianed structures using equal-channel angular pressing,” Journal of the Japan Welding Society, vol. 74, p. 88, 2005.
[13]  Z. Horita, “Nano—structural control using severe plastic deformation,” Materia Japan, vol. 41, p. 422, 2002.
[14]  W. R. Osório, C. M. Freire, and A. Garcia, “The role of macrostructural morphology and grain size on the corrosion resistance of Zn and Al castings,” Materials Science and Engineering A, vol. 402, no. 1-2, pp. 22–32, 2005.
[15]  K. D. Ralston, D. Fabijanic, and N. Birbilis, “Effect of grain size on corrosion of high purity aluminium,” Electrochimica Acta, vol. 56, no. 4, pp. 1729–1736, 2011.
[16]  W. R. Osório, J. E. Spinelli, I. L. Ferreira, and A. Garcia, “The roles of macrosegregation and of dendritic array spacings on the electrochemical behavior of an Al-4.5 wt.% Cu alloy,” Electrochimica Acta, vol. 52, no. 9, pp. 3265–3273, 2007.
[17]  D. Song, A. Ma, J. Jiang, P. Lin, D. Yang, and J. Fan, “Corrosion behavior of equal-channel-angular-pressed pure magnesium in NaCl aqueous solution,” Corrosion Science, vol. 52, p. 481, 2010.
[18]  N. Birbilis, K. D. Ralston, S. Virtanen, H. L. Fraser, and C. H. J. Davies, “Grain character influences on corrosion of ECAPed pure magnesium,” Corrosion Engineering Science and Technology, vol. 45, no. 3, pp. 224–230, 2010.
[19]  W. R. Osório, J. E. Spinelli, C. R. M. Afonso, L. C. Peixoto, and A. Garcia, “Microstructure, corrosion behaviour and microhardness of a directionally solidified Sn-Cu solder alloy,” Electrochimica Acta, vol. 56, no. 24, pp. 8891–8899, 2011.
[20]  I. J. Son, H. Nakano, S. Oue, S. Kobayashi, H. Fukushima, and Z. Horita, “Pitting corrosion resistance of ultrafine-grained aluminum processed by severe plastic deformation,” Materials Transactions, vol. 47, no. 4, pp. 1163–1169, 2006.
[21]  Z. Horita, T. Fujinami, M. Nemoto, and T. G. Langdon, “Equal-channel angular pressing of commercial aluminum alloys: grain refinement, thermal stability and tensile properties,” Metallurgical and Materials Transactions A, vol. 31, no. 3, pp. 691–701, 2000.
[22]  N. Baba, Denkaiho Niyoru Sankahimaku, Maki Shoten, Tokyo, Japan, 1996.
[23]  H. Takahashi, K. Kasahara, K. Fujiwara, and M. Seo, “The cathodic polarization of aluminum covered with anodic oxide films in a neutral borate solution-I. The mechanism of rectification,” Corrosion Science, vol. 36, no. 4, pp. 677–683, 1994.
[24]  B. Zaid, D. Saidi, A. Benzaid, and S. Hadji, “Effects of pH and chloride concentration on pitting corrosion of AA6061 aluminum alloy,” Corrosion Science, vol. 50, no. 7, pp. 1841–1847, 2008.
[25]  W. R. Osório, L. C. Peixoto, M. V. Canté, and A. Garcia, “Electrochemical corrosion characterization of Al-Ni alloys in a dilute sodium chloride solution,” Electrochimica Acta, vol. 55, no. 13, pp. 4078–4085, 2010.
[26]  N. Birbilis and R. G. Buchheit, “Electrochemical characteristics of intermetallic phases in aluminum alloys : an experimental survey and discussion,” Journal of the Electrochemical Society, vol. 152, no. 4, pp. B140–B151, 2005.
[27]  W. R. Osório, L. C. Peixoto, P. R. Goulart, and A. Garcia, “Electrochemical corrosion parameters of as-cast Al-Fe alloys in a NaCl solution,” Corrosion Science, vol. 52, no. 9, pp. 2979–2993, 2010.
[28]  R. Ambat, A. J. Davenport, G. M. Scamans, and A. Afseth, “Effect of iron-containing intermetallic particles on the corrosion behaviour of aluminium,” Corrosion Science, vol. 48, no. 11, pp. 3455–3471, 2006.


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