Which finish is most commonly used for aluminum in the sheet-metal shop?

• A. Anodized
• B. Painted
• C. Polished
• D. Mill

Answer: (D)

Aluminum sheet stock in most sheet-metal shops starts with mill finish—the natural surface produced by the rolling mill. This finish is the default because it’s the cheapest and quickest way to start a job: no extra processing, ready for forming, cutting, and assembling as needed. Finishes like anodizing, painting, or polishing are added only when the design calls for specific appearance or corrosion resistance, which adds cost, steps, and time. So for everyday fabrication, mill finish is the most common starting point.