Abstract
For the purpose of studying dyeing mechanism of anodic oxide coating of aluminum, ζ-potential, apparent coating resistance, and dyeing affinity of the film were examined.
The results obtained were as follows.
(1) The ζ-potential of sealed anodic coating was nearly constant (at about+30mV). On the other hand, the potential value of unsealed anodic oxide was not constant, but varied with the change of degree of washing and approached to that of the sealed coating with the increase of the degree of washing.
(2) When the unsealed coating was dipped in water, the potential so decreased with time that dyeing affinity also decreased.
(3) The adsorption power decreased owing to the hydration of coating. When the sample was placed in a desiccator to eliminate the influence of hydration, the adsorption power was maintained for a long time.
(4) The ζ-potential shifted toward negative, when the dyeing was carried out in acid dye baths. It would be attributed to the adsorption of anion of the dyestuff. In case of basic dye bath, the potential was kept positive, because the dyestuff was not adsorbed by the coating.
(5) By means of tannic acid treatment, the coating could also be dyed with basic dyestuff, because the ζ-potential of the coating would turn to negative.
