Ni element was introduced to aluminum surface by a simple chemical immersion method, and A1-Ni composite anodic films were obtained by following anodizing. The morphology, structure and composition of the A1-Ni anodic films were examined by scanning electron microscopy （SEM）, energy disperse spectroscopy （EDS） and atomic force microscopy（AFM）. The electrochemical behaviors of the films were studied by means of polarization measurement and electrochemical impedance spectroscopy （EIS）. The experimental results show that the A1-Ni composite anodic film is more compact with smaller pore diameters than that of the A1 anodic film. The introduction of nickel increases the impedances of both the barrier layer and the porous layer of the anodic films. In NaC1 solutions, the A1-Ni composite anodic films show higher impedance values and better corrosion resistance.
The elimination of toxic materials in sealing methods for anodic films on 1070 aluminum alloy was studied. The new process uses chemical treatments in cerium solution and an electrochemical treatment in a molybdate solution. Potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) were used to study the influences of sealing methods on the corrosion behavior of anodic films in NaCl solutions. The results show that the Ce-Mo sealing makes the surface structure and morphology of anodic films uniform and compact. Ce and Mo produce a cooperative effect to improve the corrosion resistance of anodic films. Anodic films sealed by Ce-Mo provide high corrosion resistance both in acidic and basic solutions.
