Effect of sol–gel prepared nanoalumina reinforcement content on the corrosion resistances of Al 6061‐Al₂O₃ nanocomposite in 3.5% NaCl solution

Abstract

Sol–gel prepared nanoparticles of pure alpha alumina with 0.5, 1.0, 1.5, 2.0, and 2.5 wt% content were used in the synthesis of Al‐6061 alloy based metal matrix composite via powder metallurgy route. After synthesis, corrosion investigation of the synthesized composite samples were carried out in 3.5% NaCl solution using electrochemical polarization and impedance analysis. A total of 0.5–1 wt% nanoalumina reinforced composite has shown an excellent corrosion resistance of more than an order of magnitude higher as compared to the sintered base alloy. However, a substantial decrease in corrosion resistances of synthesized composite were found after reinforcement of >1.0 wt% nanoalumina and corrosion becomes worse than the sintered base alloy of 2.5 wt% nanoalumina incorporated composite sample. Microstructural examination and relative density measurements of the synthesized composites indicated that increase of porosities and accumulation of nanoparticles in the grain boundary regions conjointly increase the corrosion reaction after exceeding 1.0 wt% nanoalumina reinforcement content.