Machining anodized and painted extrusions: plan the finish

Define both the incoming and the delivered condition

A request for “black aluminum” leaves important questions open. Identify the incoming condition—mill finish, anodized or painted—and attach the project finish specification or approved reference. State whether the machining order includes any subsequent finishing or only work on stock supplied in its existing finish.

Anodizing, powder coating and wet painting are different treatments. Hydro describes anodizing as conversion of the aluminum surface into an oxide layer. Finish choice and processing can affect appearance and other surface properties, so the required system should be identified rather than selected from colour alone.

Source context: Hydro — aluminum surface treatment

Choose the sequence for the actual part

There is no single sequence for every architectural profile. Some parts are fabricated and then finished; some systems use long lengths finished before cutting or other fabrication. Hydro identifies prefinishing long lengths as an option with certain mechanically joined designs.

For this order, identify each step and who owns it: stock supply, machining, cleaning or preparation, finishing, inspection and packing. Resolve whether the final dimensions are checked before or after finishing. If a supplier proposes changing the sequence, confirm the effect on visible surfaces and acceptance before authorizing the change.

Source context: Hydro — machining and fabrication · Aluminum Extruders Council — finishing extrusions

Resolve cut ends and newly machined surfaces

Machining through an existing finish exposes material at the cut or feature. Identify whether those surfaces are concealed, visible, mating or subject to a project-specific treatment. The drawing and finish scope should say what the buyer expects at delivery.

Do not assume a general touch-up instruction satisfies the project finish requirement. Identify the authorized method and who performs it where treatment is required. If surfaces or features must remain bare, define the boundary and coordinate the method with the finisher. Keep sealant, gasket and electrical-contact requirements with the responsible designer’s specifications.

Mark visible faces and agree the appearance reference

Mark the surfaces visible in the completed assembly. Include the accepted sample or appearance criteria where the order requires one. A single colour name does not fully define texture, gloss or the effect of preparation on an anodized surface.

The Aluminum Anodizers Council explains that mechanical texture and defects remain evident through anodizing. Finishing is not a reliable way to hide machining or handling damage. Flag surfaces where tooling contact, burrs or marks would be unacceptable, and agree the handling plan before the batch enters production.

Source context: Aluminum Anodizers Council — specifying anodized aluminum · Aluminum Anodizers Council — finish designation system

Carry the project specification through the purchase order

For organic coatings, AAMA 2603, 2604 and 2605 describe different performance requirements. FGIA published updated 2026 editions of this series. The process name or colour does not establish which performance specification the project requires.

Carry the exact specified finish, edition and approved product information into the order, along with any required documentation. Do not silently substitute a newer edition or a different finish system. If the design documents conflict, have the project’s authorized team resolve the requirement before procurement or finishing proceeds.

Source context: FGIA — 2026 updates to AAMA 2603, 2604 and 2605

Protect the part through receiving

Agree separators, wrap or film, bundle sizes and label locations around the finished surfaces. Keep labels and packing instructions consistent with the receiving team’s assembly sequence. Check that the packaging protects the part without obscuring its identity.

Manufacturer handling guidance stresses supported movement and dry storage; wet packaging can stain finishes. At receiving, check quantities, identification and condition before the parts are mixed into production. Record damage with the affected part or bundle details so the teams can distinguish incoming damage from subsequent handling.

Source context: YKK AP — YHC 300 SSG installation manual (PDF)