Corrosion behaviour of an AlZnSnSrGa alloy in aqueous solutions of NaCl and Na<inf>2</inf>SO<inf>4</inf>

Abstract

The alloy composed of Al(95.53%), Zn(2.85%), Sn(0.515%), Ga(0.1%) and Sr(0.009%), with the weight percents in the parentheses, was prepared by melting, using Al(99.84%), a product of the Aluminium Plant-Podgorica, as the base material. The corrosion behaviour of this alloy was tested in relation to the behaviour of the base metals, by both open curcuit potential and polarization resistance methods, in aqueous solutions of both NaCl and Na2SO4, the concentration of which varied within the range 0.00051-0.51 mol dm-3. Over the whole salt concentration ranges, the corrosion parameters indicate that the corrosion rate of the alloy is significantly higher than the rate of the base material. For instance, for the concentration range 0.00051-0.51 mol dm-3, the stationary open circuit potentials, related to SCE, in NaCl solutions were -1.200 to -1.460 V for the alloy and -0.693 to -0.920 V for Al, while in Na2SO4 solutions, the stationary open circuit potentials were - 1.190 to -1.465 V for the alloy and -0.780 to -0.860 V for Al. At the same time, the corrosion current density in NaCl solutions varied within 11-89 μA cm-2 for the alloy and 0.35-0.80 for Al, while in Na2SO4 solutions it amounted to 5.7-52 μA cm-2 for the alloy and 0.28 - 0.88 μ cm-2 for Al.