Effect of alumina nano-particle size and weight content on the corrosion resistance of AA1070 aluminum in chloride/sulphate solution

Abstract

The effect of specific alumina (Al2O3) nano-particle sizes (500 nm and 80 nm) and weight content (5% and 10%) on the electrochemical characteristics and corrosion resistance of AA1070 monolithic aluminum alloy (1070AL) in 0.1 M H2SO4, 1.78% NaCl and 0.1 M H2SO4/1.78% NaCl solutions was evaluated by potentiodynamic polarization test, open circuit potential measurement and optical microscopy analysis. The composite specimens at 80 nm particle size generally had lower corrosion rates than their composite counterparts. Results showed the combined sulphate/chloride solution severely deteriorated the surface properties of 1070AL and the alumina aluminum matrix composites (1070AL/Al2O3) coupled with having the highest corrosion rate values. The extent of surface deterioration was relatively smaller for 1070AL/Al2O3 specimens. Corrosion pits and intergranular cracks were observed on the surface morphology of 1070AL and 1070AL/Al2O3 specimens in NaCl solution despite having the lowest corrosion rate values. Significant passivation behavior was observed the specimens during potential scanning despite their highly electronegative corrosion potentials. SO42− anions in H2SO4 solution did not cause any significant change on morphology of the aluminum specimens with respect to the corrosion rate values being the second highest by comparison. 1070AL/Al2O3 at 80 nm and 10% weight content had the lowest corrosion rate among the composites which was comparable to 1070AL in 0.1 M H2SO4 and 1.78% NaCl solution.