Effect of a Magnetic Field on Electrolytic Coloring of Anodic Oxidation Coatings on Aluminum

Abstract

The influence of a 700G magnetic field was investigated using baths containing cobalt sulfate, nickel sulfate or a mixture of the two for electrolytic coloring of the anodic oxidation coatings on aluminum formed in baths of H₂SO₄ or NaOH-H₂O₂. By measuring, in the presence of a magnetic field, the reflection absorption spectra of electrolytic colored film formed in nickel bath, it was possible to observe a high reflection absorbance at longer wavelengths.
Magnetic hysteresis curves showed a higher residual magnetic flux density and coercive force than in the case of nonmagnetic fields. In DC and AC electrolysis at constant voltage, the electrolytic current was increased by the effect of a magnetic field. It is considered that electrolytic current was induced by the magnetic force, and acted to enhance the electrolytic reduction of metallic ions in the bath. These results indicate that electrolytic deposition of metal in the pores was affected by the Lorentz's force and enhanced in the presence of a 700G magnetic field.