How to Prepare a Surface for Anodising
Preparing aluminium surfaces correctly is a critical step in achieving high-quality, consistent results during the anodising process. Proper surface preparation not only influences the final appearance but also enhances durability, corrosion resistance and adhesion.
Mechanical Finishing: Removing Surface Defects
Anodising does not mask surface imperfections. Scratches, tooling marks and embedded debris introduced during extrusion, machining or handling will remain visible after treatment.
To avoid this, mechanical finishing is required before anodising begins. Techniques such as polishing, linishing, scratch brushing or abrasive blasting help to remove defects and define the desired surface texture.
The roughness of the surface finish plays a major role in the final appearance. A highly polished part will result in a glossy anodised finish, while a rougher surface yields a matt appearance. For applications requiring reflectivity, high-polish finishing is advised, though it is important to note that certain aluminium alloys will still develop a matt look after anodising, regardless of surface preparation.
Chemical Pre-Treatment and Etching
In addition to mechanical finishing, chemical pre-treatment is also used to prepare surfaces for anodising. Etching removes a very thin top layer of material along with the native oxide film, creating a clean and uniform surface.
Depending on the project specifications, chemical pre-treatments can be adjusted to achieve a more matt appearance. However, many facilities do not offer chemical polishing, so all polishing must be completed mechanically beforehand.
For anyone interested in learning more about anodising, check out a specialist such as https://www.poeton.co.uk/surface-treatments/anodising/.
Avoiding Contamination and Damage
Proper packaging is essential once parts are finished, as any damage during handling or transport will show up during anodising. Avoid touching bare aluminium with ungloved hands, as fingerprints can lead to corrosion. Also, never apply sticky tape to finished surfaces; residue is not easily removed during pre-treatment.
In cases where abrasive blasting is used, evenness is key. Uneven blasting can cause visual inconsistencies after anodising. Swarf must also be removed from tapped holes to prevent chemical entrapment.
Preparing aluminium surfaces for anodising is a meticulous but necessary task that directly impacts the quality of the finished product.
