Anodizing aluminum is a process that involves applying an oxide coating to the surface of an aluminum part in order to improve its corrosion resistance, wear resistance, and appearance.
1. Direct Anodizing: In this method, parts are directly anodized after they are machined. This is typically done when a matte finish is desired, and the parts have a relatively smooth surface with few imperfections. The surface finish of the parts typically ranges from around Ra 0.8 to 1.6 microns, and the thickness of the anodizing layer is usually between 10-20 microns.
2. Sandblasting: After parts are machined, they may be sandblasted to create a matte finish with a rougher surface. This method is commonly used when the parts have imperfections or uneven surfaces that need to be covered up. The surface finish of the parts after sandblasting typically ranges from around Ra 1.6 to 3.2 microns, and the anodizing layer thickness is usually between 10-20 microns.
3. Polishing: Some parts may be polished to create a smoother, more reflective finish before anodizing. This method is commonly used when a shiny, mirror-like finish is desired. The surface finish of the parts after polishing typically ranges from around Ra 0.2 to 0.4 microns, and the anodizing layer thickness is usually between 5-10 microns.
4. Brushing: In this method, parts are brushed or sanded to create a linear, brushed finish before anodizing. This is often used for decorative purposes in applications such as furniture and automotive trim. The surface finish of the parts after brushing typically ranges from around Ra 0.5 to 1.2 microns, and the anodizing layer thickness is usually between 10-20 microns.
In general, the thickness of the anodizing layer is proportional to the time the parts spend in the anodizing bath. A thick anodizing layer can provide greater corrosion resistance and wear resistance, but may also result in a rougher surface finish. The surface finish of the parts before anodizing also affects the final surface finish after anodizing. Overall, the specific preparation method and desired finish will depend on the application requirements.