2. Marking Process Types on Stainless Steel
Annealing (Oxide Marking)
What happens: The laser heats the surface to 400–800°C without removing material. A thin oxide layer forms, creating a dark mark. The surface remains smooth.
When to use: Medical devices, food-grade equipment, any application where corrosion resistance must be preserved.
Advantages:
- No material removal — surface integrity maintained
- Marks survive passivation and sterilization
- Smooth surface — no crevices for bacterial contamination
- High contrast on polished surfaces
Disadvantages:
- Mark can be removed by aggressive abrasion
- Limited color range (dark brown to black)
- Less durable than deep engraving for outdoor/abrasive environments
Engraving (Material Removal)
What happens: The laser vaporizes material, creating a physical groove. Depth depends on power, speed, and number of passes.
When to use: Tooling, nameplates, parts exposed to abrasion, any application needing tactile marks.
Advantages:
- Deepest, most permanent marks
- Survives painting, coating, and severe abrasion
- Tactile — can be felt by touch
- Can be color-filled for additional contrast
Disadvantages:
- Removes material — creates crevices
- May compromise corrosion resistance if too deep
- Slower than annealing
- Rougher surface finish
Color Marking (MOPA Required)
What happens: Precisely controlled laser pulses create oxide layers of varying thickness, which interfere with light to produce different colors. Requires a MOPA fiber laser with adjustable pulse width.
When to use: Branding, decorative applications, consumer products, anti-counterfeiting.
Advantages:
- Produces vivid, permanent colors without inks or dyes
- Excellent for branding and aesthetics
- Colors are inherent to the oxide layer — won’t fade or peel
Disadvantages:
- Requires MOPA fiber laser (more expensive than standard Q-switched)
- Colors vary with viewing angle and lighting
- Parameter development is time-intensive
- Surface finish sensitivity is high
