Marking Anodized Aluminum with CO2

The Science

CO2 lasers (10.6μm) don't engrave bare aluminum — the wavelength reflects off polished metal. Anodized aluminum is different: the anodic oxide layer absorbs laser energy and the embedded dye vaporizes, leaving a bright contrasting mark without removing material.

Settings

Typical starting points on a 40W CO2:

• Speed: 400–600mm/s
• Power: 15–25%
• DPI: 300–500
• Passes: 1

Too much power removes the anodic layer and leaves a rough etched surface. Too little power leaves a faded mark. Run a material test — the sweet spot is narrow.

Anodizing Thickness

Type II anodizing (standard, 5–25μm) marks easily. Type III (hard anodizing, 25–150μm) requires more power. If you don't know the type, start with mid-range settings and adjust.

Color and Contrast

Black anodizing marks to bright silver-white. Colored anodizing marks to light grey or silver. High contrast is easiest on dark anodized surfaces.

Cleaning

Wipe with IPA after engraving to remove residue. Marks are permanent — the laser hasn't removed the anodic layer, only the dye within it.