Nickel Electrochemical Deposition onto the Surface of Anodized Aluminum

Abstract

The use of ordered anodic aluminum oxide for nickel electrochemical deposition is studied. The conditions for aluminum anodization in a bath based on oxalic acid, thinning of the barrier oxide layer, and nickel electrochemical deposition from a sulfamate bath are described. The deposited nickel has a lattice constant of 3.51 Å and a texture in which the (100) grain planes are parallel to the surface. The surface morphologies of the anodic oxide layer and the upper and lower parts of the deposited nickel layers are examined using electron microscopy. The mean size of the oxide pores is 50 nm, the mean interpore diameter is 102 nm, and the oxide porosity is 21.5%. The surface topography of the bottom of the deposited nickel layer features a nanoscopic pattern formed by rods, which is identical in pore size and morphology to the oxide surface. The rod length is defined by the thickness of the anodic oxide layer formed on the aluminum-substrate surface. This feature is due to the homogeneous filling of oxide pores during nickel electrodeposition. We find that thinning of the anodic oxide layer to below 10 nm may impair adhesion of the oxide layer to the aluminum substrate and thus lead to nickel deposition on both sides of the oxide layer. The formation of dendrites is noted, and the possible causes of this as well as conditions favoring their growth are discussed.