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The effect of a minor amount of Ni on local corrosion behavior was investigated using Al-Cu-Mg amorphous alloys. Cyclic polarization studies revealed that the addition of a small amount of Ni can enhance both pitting and repassivation potentials significantly, in both the amorphous and devitrified crystalline state. The pit growth kinetics were also ennobled and slowed by the minor solute Ni. Electron microscopy analysis revealed a porous layer depleted with Al and Mg in pits, indicating preferential dissolution. The porous layer was finer in the presence of Ni. A new mechanism of corrosion is discussed. The possible roles of Ni are also discussed.

The effect of Ni as a minor alloying element on the anodic dissolution behavior of solute rich Al-Cu-Mg-based amorphous alloys ((Al 75 Cu 17 Mg 8 ) 97 Ni 3 and Al 70 Cu 18 Mg 12 ) was studied. A small addition of Ni enhances both the pitting potential in 0.6 M NaCl, and resistance to dealloying 1 M HCl, and 5 M HCl þ 5 M LiCl solutions. A crystalline, Cu-rich nanoporous structure forms in pits as a result of selective dissolution of Al and Mg in both alloys, with the finest structure present in the Ni containing alloy. The increase in potential drop during pit stabilization due to the greater Ohmic resistance through the finer porous layer is one of the reasons that the pitting potential is ennobled. Ni in solid solution also hinders anodic dissolution in artificial pits which is speculatively linked to an increase the energy barrier for the dissolution of Al around Ni by forming stronger bonds. The Ni alloying also reduces the probability of finding Al-Al bonds. These result in a reduction in the dissolution kinetics which in turn ennobles the pit stabilization potential. Technological implications for corrosion resistant conventional Al-Cu-Mg alloy design and alternatively a new route to the creation of nanoporous Cu are discussed.

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