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The reasons behind the uneven color of the aluminum alloy oxide film


Three possible causes of aluminum profile oxide film color is not uniform:

(1)When the aluminum profile is anodized, there are significant discrepancies in the workpiece area, slot swing range, edge and center position, solution contact, update, and exchange, which lead to uneven color film. Preventive measures include a small swing range while anodizing the aluminum profile and maybe static treatment, although too-low solution temperature can cause map formation or spots, which is not what is intended.

(2) When the aluminum clad parts was under destruction, by cutting off, outer alclad belongs high quality aluminum, enclosed inner layer is miscellaneous aluminum, two aluminum differences, so the oxidation after “benign vitiligo” like spots. The customer often do not quite understand of this phenomenon, manufacturers should do more to explain the work, explain why and how, in order to avoid misunderstanding. 

(3)The issues with process operation

Not all dirt was removed by the local original film and the workpiece's caustic treatment was insufficient;

The surface is still basic after alkali etching since light processing is not applied right away;

the workpiece's interaction during transmission with external material.

When a video exhibits inconsistent color, appropriate action should be done to address the issue from multiple angles.

Fault a reader calls asking the workpiece by after alkali etching conductive oxide film is difficult to obtain the reasons caused by alkaline etching liquid aluminum ion accumulation is too high, after exclusion of many factors and it is difficult to form the conductive oxide film, take into account whether the high aluminum ions alkali etching solution, the other said alkaline corrosion solution is very thick. But the alkali corrosion speed is not fast. Then the author suggests changing alkaline corrosion solution, because after alkaline etching liquid used for too long will aluminum ion accumulation of excess, aluminum ions on the surface of the workpiece is difficult to elution, thus affecting the aluminum surface and the conductive oxide solution contact, thus affecting the formation of oxide film. Another suggestion is that if the unconditional replacement of alkaline etching solution, the workpiece after alkali etching after water rinse immediately after the flow of water rinse, and then a light in a hydrofluoric acid containing concentrated nitric acid, then rinse thoroughly after conducting oxidation treatment. After the readers to telephone said after alkali etching with hot water and the effect is very good. The author is the experience, and in hot water after the hot water and immediately immersed into the water quickly leave, to prevent the workpiece by dry due to oxidation and affect the formation of conductive oxide film.