The Effects of 2wt% Cu Addition on the Corrosion Behavior of Heat Treated Al-6Si-0.5Mg-2Ni Alloy

Authors: A. Hossain, M. A. Gafur, F. Gulshan, A. S. W. Kurny

Abstract:

Al-Si-Mg-Ni(-Cu) alloys are widely used in the automotive industry. They have the advantage of low weight associated with low coefficient of thermal expansion and excellent mechanical properties – mainly at high temperatures. The corrosion resistance of these alloys in coastal area, particularly sea water, however is not yet known. In this investigation, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization have been used to evaluate the corrosion resistance of Al-6Si-0.5Mg-2Ni (-2Cu) alloys in simulated sea water environments. The potentiodynamic polarization curves reveal that 2 wt% Cu content alloy (Alloy-2) is more prone to corrosion than the Cu free alloy (Alloy-1). But the EIS test results showed that corrosion resistance or charge transfer resistance (Rct) increases with the addition of Cu. Due to addition of Cu and thermal treatment, the magnitude of open circuit potential (OCP), corrosion potential (Ecorr) and pitting corrosion potential (Epit) of Al-6Si-0.5Mg-2Ni alloy in NaCl solution were shifted to the more noble direction.

Keywords: Al-Si alloy, potentiodynamic polarization, EIS, SEM.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1094703

References:

[1] J. T. Staley, and D. J. Lege, "Advances in aluminium alloy products for structural applications in transportation’, J Physique IV, Colloque C7, supplément au Journal de Physique III , vol.3, 1993, pp.179-190.
[2] S. Anand, T .S. Srivatsan, Y. Wu, and E. J. Lavernia, "Processing, microstructure and fracture behavior of a spray atomized and deposited aluminium-silicon alloy”, Journal of Materials Science, vol.32, 1997, pp.2835-2848.
[3] S. Zor, M. Zeren, H. Ozkazance, and E. Karakulak, "Effect of Cu content on the corrosion of Al-Si eutectic alloys in acidic solution”, Anti-Corrosion Methods and Materials, vol.57(4), 2010, pp.185-191.
[4] M. J. Robinson, "Mathematical modeling of exfoliation corrosion in high strength aluminum alloys”, Corros. Sci., vol. 22(8), 1982, pp.775-790.
[5] G. Svenningsen, J. E. Lein, A. Bjorgum, J.H. Nordlien, and K. Nisancioglu, "Effect of high temperature heat treatment on intergranular corrosion of Al-Mg-Si(Cu) model alloy’, Corros. Sci., vol.48, 2006, pp. 258–272.
[6] G. Svenningsen, and M. H. Larsen, "Effect of artificial aging on intergranular corrosion of extruded Al-Mg-Si alloy with small Cu content”, Corros. Sci., vol.48, 2006, pp.1528–1543.
[7] G. Svenningsen, and M. H. Larsen, "Effect of thermomechanical history on intergranular corrosion of extruded AlMgSi(Cu) model alloy”, Corros. Sci., vol.48, 2006, pp.3969–3987.
[8] G. Svenningsen, J. E. Lein, A. Bjorgum, J.H. Nordlien, and K. Nisancioglu, "Effect of low copper content and heat treatment on intergranular corrosion of model AlMgSi alloys”, Corros. Sci., vol.48, 2006, pp. 226-242.
[9] M. H. Larsen, and J. C. Walmsley, "Significance of low copper content on grain boundary nanostructure and intergranular corrosion of AlMgSi(Cu) model alloys”, Mater. Sci. Forum, vol.519-521, 2006, pp. 667-671.
[10] Z. Asghar, G. Requena, and F. Kubel, "The role of Ni and Fe aluminides on the elevated temperature strength of an AlSi12 alloy”, Mater. Sci. and Eng. A, vol.527, 2010, pp.5691-5698.
[11] F. Stadlerl, H. Antrekowitsch, W. Fragner, H. Kaufmann, and P. J. Uggowitzer, "The effect of Ni on the high-temperature strength of Al-Si cast alloys”, Mater. Sci. Forum, vol.690, 2011, pp.274-277.
[12] F. Stadlerl, H. Antrekowitsch, W. Fragner, H. Kaufmann, and P. J. Uggowitzer, "Effect of main alloying elements on the strength of Al-Si cast alloys at elevated temperatures”, International Journal of Cast Metals Research, vol.25(4), 2012, pp.215-224.
[13] H. Zhan, J. M. C. Mo, F. Hannour, L. Zhuang, H. Terryn, and J. H. W. de Wit, "The influence of copper content on intergranular corrosion of model AlMgSi(Cu) alloys”, Materials and Corrosion, vol. 59, 2008,pp.670–675.
[14] M. Abdulwahab, I. A. Madugu1, S. A. Yaro, and A. P. I. Popoola, "Degradation Behavior of High Chromium Sodium-Modified A356.0-Type Al-Si-Mg Alloy in Simulated Seawater Environment”, Journal of Minerals & Materials Characterization & Engineering, vol.10(6), 2011, pp.535-551.