1. Color difference and fading are inevitable
The color of black anodizing is mainly achieved through dyeing, and its color is affected by the thickness of the oxide film, the quality of the dye, and the sealing effect. Even with strict control of process parameters, there may still be color differences between batches, especially during large-scale production or replacement of processing equipment.
In addition, surfaces using organic dyes are prone to fading under long-term UV exposure, and even inorganic dyes may experience color fading in outdoor environments, affecting appearance consistency. In addition, if the sealing treatment is insufficient or the oxide layer is too thin, it may also lead to surface fading or even color fading. To achieve optimal light resistance, high-quality dyes need to be selected and fully sealed.
2. Limited machining tolerances
Anodizing will generate a 5-25 μ m thick oxide layer on the surface of aluminum, directly affecting the dimensional accuracy of the parts. For high-precision assembled parts, it is necessary to consider the thickness compensation of the oxide layer in advance during the processing stage, otherwise it may lead to tight fit or poor assembly. Meanwhile, the uneven deposition of oxide film at sharp angles and complex structures further increases the difficulty of size control.
3. Cracking of the oxide layer
In the anodizing process, aluminum parts need to undergo electrolytic reactions, and thin-walled structures are prone to micro deformation under stress concentration. The difference in thermal expansion coefficient between the aluminum substrate and the oxide layer may cause cracks in the black anodized layer.
4. Limited applicability of materials
Black anodizing is not suitable for all metals, only for specific metals such as aluminum, magnesium, and titanium. Moreover, not all aluminum alloys can undergo anodizing treatment, mainly suitable for 5 series, 6 series, and 7 series aluminum alloys, among which 6 series aluminum alloy is the most common and has the best processing effect.