Effect of plating mode and complexing agent on morphology of pigmented anodic alumina coatings

• Published in: Transactions of the Institute of Metal Finishing Vol. 86; no. 2; pp. 109 - 114
• Main Authors: Zemanová, M., Chovancová, M., Blaho, P., Ušák, E., Valtýni, J.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 01.03.2008
• Subjects: ALTERNATING CURRENT; ALUMINIUM ANODIC OXIDATION; MORPHOLOGY; PERIODIC REVERSE CURRENT; PIGMENTATION
• ISSN: 0020-2967; 1745-9192
• DOI: 10.1179/174591908X272933

The influence of periodic reverse current and complexing agents (citrate acid, 5-sulphoisophthalic acid) on the morphology of stripped pigmented aluminium finishes has been studied. Pigmentation was realised by electrolytic colouring with usage of alternating and periodic reverse current. The applied pigmentation electrolytes, based on nickel, were prepared with and without usage of a complexing agent. Parameters of colour space were measured by spectrocolorimetry. Stripping was carried out in chromic phosphorous acid to remove the coating of aluminium oxide prepared by anodic oxidation on aluminium. The thickness and mass of the stripped coating were tested and related to stripping time. The content of nickel on the stripped surface was determined by energy dispersive X-ray analysis and morphology of the stripped surface by SEM. In the complexing agent free electrolyte, the use of periodic reverse current improved deposit morphology. The presence of complexing agents generally improved deposit quality over that obtained in complexing agent free electrolytes by alternating current electrolytic pigmentation. Under the test conditions of PRC electrolytic colouring with citric acid, the complexing agent electrolyte negatively influences the colouring of anodic alumina. Periodic reverse current pigmentation was found to yield macroscopically and microscopically highly arranged deposit morphology on the stripped aluminium finishes.