Laser Coloring vs. Laser Iridescence on Metals: Why Aluminum Differs from Stainless Steel

1. Why Stainless Steel Works for Coloring (Static, Stable Color)

• Temperature Requirement: Laser coloring needs localized heat between 600–1200°C. This heat triggers a controlled oxidation layer to form on stainless steel’s surface; the thickness of this layer determines the final color (e.g., thin layers for gold, thicker ones for blue or purple).
• Melting Point Advantage: Stainless steel has a melting point of 1400–1450°C—well above the 600–1200°C range for coloring. This means the laser can generate the necessary heat for oxidation without melting the base metal, resulting in a durable, static color that doesn’t fade or shift.

2. Why Aluminum Can’t Do Laser Coloring (and What It Can Do Instead)

• The Melting Barrier: To create static laser color, heat would need to reach 600–1200°C—but aluminum melts at 660°C. Any laser energy high enough to approach coloring temperatures would melt or warp the aluminum, ruining the part.
• Aluminum’s Alternative: Laser Iridescence
  For aluminum to get a “colorful” effect, it first needs to be polished to a mirror finish. The laser then etches ultra-fine, microscale textures on this mirror surface.
  • How it works: These micro-textures scatter and reflect light differently at various angles, creating a dynamic, shifting color effect (e.g., blue from the front, green from the side).
  • Key difference from laser coloring: Iridescence is additive in effect (relying on light interaction with textures, not material removal/oxidation) and color changes with viewing angle, while stainless steel’s laser coloring is static and angle-independent.

3. Core Differences: (Stainless Steel) vs. (Aluminum)