Electrochemical Dealloying of a Ternary Al67Cu18Sn15 Alloy Compared with that of a Binary Al75Cu25 Alloy

Chemical de-alloying of binary Al₇₅Cu₂₅ (at.%) alloy (consisting of α-Al and Al₂Cu) can be used to prepare bulk nanoporous Cu which shows promise for a number of applications. Chemical de-alloying of ternary Al₆₇Cu₁₈Sn₁₅ alloy (consisting of α-Al(Cu), Al₂Cu and β-Sn(Al,Cu)) can result in nanoporous Cu₃Sn-Cu-Cu₆Sn₅composites where re-alloying between Cu atoms released from de-alloying and Sn atoms in the precursor is involved.  Compared to chemical de-alloying in toxic and expensive solutions, electrochemical de-alloying in neutral salt solution has the advanategs of being pollution-free, inexpensive and readily available.

This paper reports the results obtained from electrochemical dealloying of binary Al₇₅Cu₂₅ alloy and ternary Al₆₇Cu₁₈Sn₁₅ alloy by using potentiodynamic polarization, cyclic voltammetry (CV) and potentiostatic polarization measurements. For electrochemical de-alloying of the binary Al₇₅Cu₂₅, the asynchronous dealloying behaviour and the final size of the porous structure are both potential dependent. For de-alloying of the ternary Al₆₇Cu₁₈Sn₁₅, the concurrence of de-alloying and re-alloying is potential dependent. In addition, when the applied potential (-0.5 V) is below the critical potential of the Al₂Cu phase (-0.41 V), electrochemical de-alloying of Al₇₅Cu₂₅ can be complete leading to nanoporous Cu (52 ± 10 nm). However, complete de-alloying does not occur to the ternary Al₆₇Cu₁₈Sn₁₅ alloy under the same condition due most likely to the existence of β-Sn(Al,Cu) phase.