On the electrochemical dealloying of Al-based alloys in a NaCl aqueous solution

The electrochemical dealloying of rapidly solidified Al-based alloys in a 1 M NaCl aqueous solution has been investigated using electrochemical measurements in combination with microstructural analysis. The results show that nanoporous metals (Au, Ag, Pd and Cu) with various morphologies can be fabricated through electrochemical dealloying of the Al-based alloys in the NaCl solution. The electrochemical behaviors of elemental metals (Al, Au, Ag, Pd and Cu) and precursor alloys for dealloying have been studied through open-circuit measurements, potentiodynamic anodic polarization and cyclic voltammetry. The dealloying mechanisms of the precursor alloys and the formation of the nanoporous metals have been analyzed based on cyclic voltammetry curves, chronoamperometry curves obtained at potentials above or below the critical potentials, and microstructural features of the as-dealloyed samples. In addition, a classification for dealloying of a bi-phasic alloy has been proposed according to different dealloying behaviors of coexistent phases in the alloy. It has been found that interactions between coexistent phases prevail during dealloying of the bi-phasic alloy and are in principle dependent on the diffusivity of the more noble element, the curvature-dependent undercritical potential dissolution, and the reaction between the more noble element and chloride ion.