The same laser can leave a crisp black logo on stainless steel, a bright white mark on a black anodized plate, and nothing at all on a polished copper part. The machine did not change. The metal and its surface did.
Laser engraving metal works by changing the surface color, removing metal, or removing a coating. Bare metal needs a fiber laser marking machine. Painted, powder-coated and anodized parts can be marked by removing the coating, but the exposed metal may need protection.
This page covers what a laser does to metal, which machine suits each metal and surface, how to mark painted and coated parts, whether the mark will rust, and how to stay safe with fumes.
Have a part in mind? Send us the metal and its finish and we will suggest a machine and a method.
A note on bias: I work for HeatSign, and we build laser marking machines. Facts about coatings, corrosion and fumes come from standards, research papers and public maker guides. We do not link to other machine makers.
What does a laser actually do to metal?
A laser does one of three things to metal. It anneals the surface to change its color, it vaporizes metal to engrave a groove, or it burns off paint or anodizing to show the metal below. Some coatings can also change color without breaking through.
What the laser does | What you see | Typical metals | Watch out for |
|---|---|---|---|
Annealing: heats the surface so it changes color | Black or colored mark, smooth to the touch | Stainless steel, titanium, other iron alloys | Fades above about 200 °C; can lower corrosion resistance |
Engraving: vaporizes (boils off) metal | A groove you can feel | Steel, aluminum, brass, tool steel | About 0.01–0.02 mm per pass in our experience, so depth takes many passes |
Coating removal: burns off paint, powder coat or anodizing | Bright metal showing through the coating | Painted steel, powder-coated parts, anodized aluminum | The exposed metal has lost its protection |
Color change in the coating | Darker or lighter mark, coating stays closed | Some firearm and industrial coatings | Works only on coatings made for it; test first |
Four terms used on this page
- Annealing mark
- A color mark made by heat. Nothing is removed, so the surface stays smooth.
- Anodizing
- A hard oxide layer grown on aluminum, often dyed black, blue or red.
- MOPA
- A fiber laser source with an adjustable pulse length. It can make black marks on anodized aluminum and colors on stainless steel.
- Passivation
- An acid treatment that restores the corrosion-resistant film on stainless steel.
The difference between etching and engraving is mostly depth. For a closer look, see laser etching vs laser engraving on metal.
Which laser works on each metal and surface?
Use a fiber laser marking machine for bare steel, stainless, aluminum, brass and titanium. Use MOPA for black marks on anodized aluminum and colors on stainless. A CO2 laser marking machine can remove paint or anodizing, but it cannot mark the bare metal underneath.
Metal and surface | What the laser does | Machine to use | Watch out for |
|---|---|---|---|
Carbon steel and tool steel | Engraves or darkens | Fiber laser marking machine | Bare steel can rust at the mark |
Stainless steel | Anneals black or color, or engraves | Fiber; MOPA for colors | Corrosion resistance at annealed marks |
Bare aluminum | Engraves; marks are light grey | Fiber laser marking machine | Low contrast on polished parts |
Anodized aluminum | Removes the dye for a white mark, or darkens it black | Fiber for white; MOPA for black | White marks expose bare aluminum |
Brass and copper | Engraves; copper can turn black or white | Fiber with short pulses, or MOPA | Most of the light reflects |
Titanium | Anneals to black or color | Fiber or MOPA | Color depends on heat; test settings |
Chrome- or nickel-plated parts | Darkens or removes the plating | Fiber laser marking machine | Do not break through the plating |
Galvanized (zinc-coated) steel | Removes or darkens the zinc | Fiber laser marking machine | Zinc oxide fumes; lost zinc protection |
Painted steel | Burns off the paint to show metal | Fiber; CO2 removes paint only | Exposed steel can rust |
Powder-coated parts | Burns off the coating | Fiber laser marking machine | Thick coating needs more passes |
E-coated (electrocoat-painted) parts | Burns off the thin coating | Fiber laser marking machine | Or mark before e-coating |
Fiber laser marking machines handle almost every bare metal. CO2 laser marking machines do not: their beam is not absorbed well by bare metal. They can burn off paint or anodizing, but not mark the metal itself without a marking paste.
The stainless steel logo in the photo is a dark surface mark. For more on stainless, see our stainless steel laser engraving machines. To compare laser types across 17 materials, see fiber vs CO2 vs UV laser marking.
How do you laser engrave metal, step by step?
Identify the metal and its finish, then clean off oil and dust. Fix the part at the right focus and test settings on a scrap piece with the same finish. Mark the part, check the result, and protect any bare metal you exposed.
- Identify the metal and finish. Bare, painted, powder-coated, anodized or plated? The table above tells you what the laser will do.
- Clean the surface. Oil and dust change how much light the surface absorbs, so marks come out uneven.
- Fix the part and set the focus. A part that moves or sits off focus gives blurred or uneven marks.
- Test on a scrap piece with the same finish. Paint, powder coat and anodizing vary by supplier, so settings from one batch may not suit the next.
- Mark the part. For depth, add passes rather than pushing power to the limit.
- Check the result. Look at contrast, edges and, for barcodes, the scan grade.
- Protect exposed metal. If you burned through paint or plating, treat the mark before the part goes out. More on this below.
How do you laser engrave painted or powder-coated metal?
Painted or powder-coated metal can be marked three ways: burn off the coating to show bright metal, change the coating’s color without breaking through, or mark the part before it is coated. Coatings are usually only 20–100 µm thick, so passes must be controlled.
Coating | Typical thickness | What it means for marking |
|---|---|---|
Liquid paint, powder coat | Powder coat often 60–80 µm | A few passes remove it; more passes start engraving the metal |
E-coat | Often 18–28 µm | Very thin; one pass may break through |
Anodizing, decorative (Type II) | About 2.5–25 µm | White mark with fiber; black with MOPA |
Hard anodizing (Type III) | About 12.5–100 µm | Needs more energy; test first |
For scale, a sheet of office paper is about 100 µm thick. Thickness ranges come from US military anodizing specs and coating industry data.
Option 1: burn off the coating to show metal
This gives the strongest contrast: bright metal against a dark or colored coating. The fiber laser marking machine removes the paint in the shape of the text or logo and stops at the metal.
The photo shows a logo marked this way on a grey painted steel panel. The trade-off is that the metal under the mark is now bare.
Option 2: change the coating’s color without breaking through
Some coatings are made to darken or lighten under a laser while staying closed. One firearm coating maker, for example, uses 20–60 W fiber lasers to change the coating’s tone without removing it. Ordinary paints rarely behave this way, so ask the coating supplier and test.
Option 3: mark before the part is coated
If the part will be e-coated, you can mark it first and let the mark show through. A Data Matrix code is a small square barcode, a bit like a QR code. One laser maker’s tests found its cells needed to be larger than 0.75 mm to read after e-coating. Cells of 1.25 mm worked best.
For galvanizing and thick paint, see how deep to mark before painting or galvanizing.
Marking painted or coated parts?
Send us a coated sample or the coating type and thickness. We will tell you which of the three options fits.
Will laser-engraved metal rust or corrode?
It can. Removing paint, powder coat or anodizing leaves bare metal that may corrode at the mark. Annealed marks on stainless can also lose corrosion resistance. Protect exposed steel, agree the protection with your customer, and match passivation to the marking process.
Mark | Risk | What to do |
|---|---|---|
Paint or powder coat burned off steel | Bare steel can rust at the mark | Apply a rust-preventive liquid right after marking; for outdoor parts, agree a clear coat or touch-up with your customer |
White mark on anodized aluminum | Bare aluminum is exposed and may corrode, blurring the mark | Use MOPA black marks, which darken the layer instead of removing it, or seal the mark |
Annealed black mark on stainless | More heat means lower corrosion resistance at the mark | Use the lowest heat that gives contrast; match passivation to the mark |
Chrome or nickel plating | Breaking through opens a path for corrosion | Darken the plating without burning through it |
Zinc coating (galvanizing) | Removing zinc removes its protection | Mark before galvanizing, or keep the mark shallow and protect it |
Our practice: when a mark burns through paint, powder coat or plating to bare steel, we wipe on a rust-preventive liquid straight after marking. It is a cheap step that stops the mark from turning brown in storage.
For anything that ships, the protection is a customer decision. A coating expert’s advice is to agree it with your customer, even an internal one, and prove it with a salt spray test, which sprays salt mist on sample parts to speed up rusting.
Stainless steel and passivation
Research on stainless steel shows heat input is the main factor in how much a laser mark lowers corrosion resistance. Pulse width and frequency matter less.
Passivation can also fade annealed marks. In one study, marks that failed had about 15% less chromium, the element that keeps stainless from rusting. Citric acid passivation was gentler on marks than nitric acid, which shortened mark life through autoclave (steam sterilizing) cycles. Choose the method under ASTM A967, the US standard for passivation.
When marking and passivation are matched, laser marks have lasted at least 500 sterilization cycles plus strong alkaline (pH 14) cleaning in published medical device work.
How do you engrave reflective metals like brass and copper?
Copper absorbs only about 1–5% of a fiber laser’s 1 µm light, so most bounces off. Use short pulses with high peak power (a lot of energy packed into each burst), or a MOPA machine. Brass marks well with fiber. Copper can be marked black by annealing or white by etching.
Those absorption figures come from welding research, but the physics is the same for marking. Green light at 532 nm is absorbed far better, around 40–45%, which is why some copper processing uses green lasers.
For marking, a fiber laser marking machine with short pulses is usually enough. Brass, as in the photo, takes fine marks and deep engraving well. A MOPA source gives more control on bright copper. See MOPA vs Q-switched fiber laser sources.
Is it safe to laser engrave painted, plated or galvanized metal?
Lasering paint, plating or zinc gives off harmful fumes. Zinc oxide fumes cause metal fume fever, chromium plating can release hexavalent chromium, and PVC-type coatings release hydrogen chloride. Use fume extraction on every job, and an enclosed machine in shared rooms.
Surface | Fume of concern | US limit (OSHA) |
|---|---|---|
Galvanized (zinc) steel | Zinc oxide fume; causes metal fume fever, a flu-like illness | 5 mg/m³ |
Chrome-plated or chromium-bearing parts | Hexavalent chromium, a cause of cancer | 5 µg/m³ |
PVC-type coatings | Hydrogen chloride, which also corrodes equipment | Avoid, or use chemical filters |
Stainless steel | Dust containing chromium and nickel | Extract at the source |
The OSHA technical manual calls these laser-generated air contaminants and asks for enough ventilation to keep them below exposure limits. In practice, that means a fume extractor at the marking head on every job.
Open laser markers also need eye protection. For safety classes and enclosures, see laser classes for marking machines.
Which laser engraving machine fits your metal parts?
For most metal parts, a 20–30 W fiber laser marking machine handles bare and painted surfaces. Add MOPA for black or color marks. Use a handheld fiber marker for large painted parts, and an enclosed machine where people work nearby.
Most metal parts: desktop fiber laser marking machine20–60 W. Bare metal, paint removal, barcodes and logos. $1,950–5,000.See the desktop fiber laser marker → 
Large or installed parts: handheld fiber laser markerTake the marker to the part. $1,950–3,800.See portable laser markers → 
Shared rooms and fumes: enclosed fiber laser marking machineClosed, interlocked cabinet; pair it with a fume extractor. $3,500–7,000.See the enclosed machine →For black marks on anodized aluminum or colors on stainless, see the MOPA laser engraver. For deep work, see the deep laser engraver for metal. To choose power and lens size, see our desktop laser marking machine guide.
Laser Engraving Metal FAQ
Can a CO2 laser engrave metal?
Not bare metal. A CO2 laser marking machine can burn off paint or anodizing from metal, or mark bare metal with a special marking paste. For direct marks on steel, stainless, aluminum or brass, use a fiber laser marking machine.
Can you laser engrave painted metal without removing the paint?
Only with coatings made for it. Some firearm and industrial coatings change tone under a fiber laser marker while staying closed. Most ordinary paints are simply burned off, so test on a sample with the same paint.
Does laser engraving remove anodizing?
A standard fiber or CO2 laser marking machine removes the dyed layer and leaves a white mark showing bare aluminum. A MOPA laser marking machine can darken anodized aluminum to black without removing the layer.
Does laser marking affect stainless steel corrosion resistance?
It can. Heat input is the main factor, so use the lowest heat that gives contrast. Passivation can restore protection but may fade marks. Choose the method under ASTM A967; citric acid is gentler on marks.
What wattage do I need to laser engrave metal?
For surface marks, barcodes and paint removal, 20–30 W is enough. For deep engraving or faster cycles, choose 50–60 W. See our desktop laser marking machine guide for more.
How deep can a laser engrave metal?
Each pass removes about 0.01–0.02 mm in our experience, so depth comes from many passes. For marks deeper than about 0.1 mm, see laser vs dot peen vs stamping.
Look at the surface before you look at the machine. Bare metal needs a fiber laser marking machine. Coated metal can be marked by removing the coating, but then the bare metal needs protection, even if that is just a coat of rust-preventive liquid.
Sources
- OSHA Technical Manual, laser hazards
- US 29 CFR 1910.1026, chromium (VI) exposure limit
- ASTM A967, Chemical passivation treatments for stainless steel parts
- MIL-A-8625, Anodic coatings for aluminum
- Published research on corrosion of laser-marked stainless steel; coating and laser maker application notes. We do not link to other companies’ sites.
