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MaterialsModule 3.6~4 min read

Coated Metals

A CO2 can't mark bare metal on its own, but it removes powder coat and most paints cleanly, and with a marking spray like CerMark it can leave a permanent black mark on the metal underneath. Combine with a rotary for tumblers.

Powder-coated tumbler

Speed400-500 mm/s
Power25-40%
Line interval0.1 mm
Air assistLow

Goal: ablate the coating cleanly to reveal the metal underneath, without melting paint into a halo. Test on the bottom of the tumbler first.

Cleaning powder-coat residue after engraving
Even with clean settings, ablated powder coat leaves a faint chalky / burnt residue at the engrave edges that IPA alone won't fully remove. Enduramark BLU Powder Coating Residue Cleaner is the community-standard solution, wipe on, wait 30 seconds, wipe off, and the engrave reveal is crisp instead of hazy. Critical for premium-finish tumbler work.

Marking spray on bare metal (CerMark LMM-14)

A CO2 beam bounces off bare metal instead of marking it. Marking spray gets around that: you coat the metal, the beam fuses the coating to the surface, and a rinse leaves a permanent black mark. The standard product is CerMark LMM-14, a 6 oz aerosol made for metal; Brilliance Laser Inks is the other brand you'll see most often. LMM-14 bonds to bare stainless steel, brass, aluminum, titanium, copper, nickel and tin. It will not bond over lacquer or a clear coat, so engrave or strip any coating off the area first.

1. COATthin, even coatbare, clean metalSpray clean bare metal, then letit dry to a light gray powder.2. FUSEbeam travelscoating fused into the surfaceWherever the beam passes, thecoating bonds to the surface.3. RINSEpermanent black markbare metal everywhere elseWater washes the rest away.Only the fused mark stays.
How a marking spray gets a CO2 beam to mark bare metal: the coating absorbs the energy the metal would reflect, and fuses where the beam passes.

1. Prep and spray

  1. Degrease the metal. Oil and fingerprints stop the bond. Wipe with isopropyl alcohol and let it flash off.
  2. Shake the can for a full two minutes once the mixing ball rattles. A short shake is what makes the can spit and clog. Ferro, the maker, says it sprays best with the can between 70 and 90°F.
  3. Spray from 8 to 12 inches away in two light passes, starting off the part and sweeping past it, for a thin, even coat.
  4. Let it dry. It air-dries to a light gray powder in about two minutes, and a heat gun or hair dryer gets it there in seconds. Don't handle the coated area, and mark it soon after.
The most common mistake: spraying too thick
A heavy coat soaks up the beam, so it needs more power to bond, and past a point it won't bond at all. Too thin, and there isn't enough pigment for a solid mark. Two light passes, not one wet one.

2. Mark it: high power, slow speed

Ferro's starting points for LMM-14 hold power at 100% and change only the speed as tube wattage changes. Softer metals need slower passes, and Ferro recommends at least a 50W tube for brass and aluminum.

CO2 tubeStainless steelAluminumBrass
25W10% speed4% speed2% speed
35W15% speed7% speed4% speed
50W20-30% speed10% speed6% speed

Every row: 100% power, 500 DPI. On tubes over 75W, 90% power is fine. Source: Ferro's LMM-14 Aerosol technical data sheet.

Those speeds are a percentage of the machine's top speed. On a Ruida machine in LightBurn, where speed is in mm/s, read them as "very slow" and find your own number with a LightBurn Material Test: power fixed, a row of speeds side by side.

3. Rinse and scrub-test

Wash the unbonded coating off with water and a wet sponge or towel. Most of it comes off right away, and a little scrubbing takes the rest. Then scrub each test mark with a medium-duty Scotch-Brite pad, the durability check Ferro recommends: a mark that survives the scrub is bonded. Pick the setting that passes cleanly and write it down.

When you're done, turn the can upside down and spray for 3 to 5 seconds to clear the nozzle, then wipe the tip. Store the can upside down and below 120°F so the solids don't settle over the intake.

Two-tone tumbler: silver and black in one job

Put both techniques on one powder-coated tumbler: engrave through the coating to reveal silver stainless, then spray and re-mark only part of the design so it turns black. Grant from Thunder Laser USA walks through the whole job in How to Mark Stainless Steel on a CO2 Laser With Marking Spray. (I'm a Thunder Laser USA ambassador.)

  1. Use a chuck rotary. The tumbler stays clamped for both passes, and the rotary has to return to the same start point or the black won't land on the silver. Rotary setup is in Straight-Wall Tumblers & Bottles.
  2. Pass 1: through the powder coat. Engrave the full design. Grant's settings on a Bolt Pro 36 were 750 mm/s, 60% power and a 0.07 mm line interval, which he called a first guess on a new machine.
  3. Spray without unclamping. Cover the rotary with paper, spray the engraved area, and dry it with a heat gun. Overspray lands inside the machine, so run the exhaust while you spray.
  4. Pass 2: only the parts that go black. Select just those shapes, such as the lettering or a border. Grant slowed down and used 400 DPI at the same power.
  5. Rinse and clean up. Wash off the loose coating, then take any leftover haze off the silver areas with a melamine sponge (Magic Eraser). Grant kept it away from the black areas to be safe.