Effects of Anodic Electrodeposition Coating on the Structure of Three-Step Coloring Films on Aluminum

• Published in: Japanese Journal of Applied Physics Vol. 39; no. 12R; p. 6700
• Main Authors: Yamamuro, Masaaki, Morisaki, Shigeyoshi
• Format: Journal Article
• Language: English
• Published: 01.12.2000
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.39.6700

Three-step electrolytic coloring of aluminum was carried out by applying sulfuric acid, low-voltage AC anodic oxidization between DC anodic oxidization and electrolytic coloring. The films produced by this three-step electrolytic coloring method were observed using a transmission electron microscope (TEM) and a scanning electron microscope (SEM) to study the influence of anodic electrodeposition (ED) coating on the film structure. AC electrolysis following DC anodic oxidization showed the current recovery phenomenon, and an AC anodizing layer was generated under the DC anodizing layer with the barrier layer remaining. In addition, the thickness of the barrier layer of the AC anodizing layer indicated the simultaneous progress of the metal compound deposit reaction and the formation reaction of the barrier layer for electrolytic coloring. The ED coating did not affect the structure of each anodizing layer greatly, nor did it affect the metal compound deposited in the AC anodizing layer, but the metal compound that was previously deposited unevenly in the DC anodizing layer could no longer be observed using a TEM. The discoloration of the electrolytic colored film with ED coating may not be attributable to a change in the interference distance due to elution of the deposits in the AC anodizing layer or to a change in the thickness of the barrier layer, but rather to a change in the conditions of the metal compound deposited in the DC anodizing layer.