What is the most common finish used for aluminum in the sheet-metal shop?

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

Answer: (A)

In sheet-metal work, the default surface you get from rolling aluminum is the mill finish—the as-rolled surface produced by the rolling mill. It’s the most common because it’s inexpensive and requires no extra processing, yet it’s perfectly suitable for many parts that will be bent, formed, riveted, or further treated later if needed. Finishes like anodizing, painting, or polishing are added only when specific properties are required: anodizing for corrosion resistance and color, painting for appearance and protection, and polishing for a bright cosmetic look. Since most jobs don’t need those extra steps, the mill finish remains the typical choice.