Serial Number Marking on Steel: Electrochemical vs. Dot Peen vs. Laser

A serial number on a steel part is only useful if it can still be read when the part comes back for service years later. Most shops choose between three methods: electrochemical marking, dot peen and laser. Each one will mark stainless or tool steel. The differences are in what the method does to the part, what it costs, and how it fits your volume. Here is how they compare when you are the one who has to pick.

Electrochemical marking

You lay a stencil with the serial number on the part, press an electrolyte-soaked pad on top, and a low-voltage current passes through the open areas of the stencil. In one mode you get a dark oxide mark on the surface. In the other, the characters are etched into the metal.

Strengths:

• No heat, no impact. Hardness, dimensions and the surface around the mark stay as they were.
• Any conductive metal, including hardened tool steel, marks with the same settings.
• Crisp, high-contrast characters, logos and 2D codes. The stencil sets the resolution.
• Low upfront cost, and the unit is portable.

The limitation: each new serial number needs its own stencil. A thermal stencil printer makes that a quick step at the bench, but on a fully automated line running thousands of unique numbers per shift, a laser will be faster.

Dot peen

A carbide or hardened stylus hits the surface repeatedly and builds each character out of small dents. The result is deep and stays legible under paint or on rough castings.

The cost is mechanical stress. Each dot is a small plastic deformation, and some drawings and customer specifications prohibit impact marking on thin-walled, hardened or fatigue-critical parts. Check the requirements on your print first. Dot peen also needs solid fixturing, and it is noisy.

Laser marking

A fiber laser marks with heat: it ablates material, or on stainless steel it discolors the surface layer (annealing). It is fast, fully programmable and uses no consumables, so it is the default for high-volume automated production.

The trade-offs are heat and price. On stainless, the heat affects the passive layer at the mark, and many medical and food-equipment manufacturers validate their laser settings for corrosion resistance for that reason. The equipment costs many times more than an electrochemical system, and an open laser station needs an enclosure or other laser safety controls.

Comparison at a glance

	Electrochemical	Dot peen	Fiber laser
Heat	None	None	Local heating
Mechanical stress	None	At every dot	None
Mark	Dark oxide or etched	Dot indentations	Annealed color or engraved
New serial number	New stencil	Software	Software
Consumables	Electrolyte, felt, stencil tape	Stylus wear	None
Upfront cost	Low	Medium	High
Portable	Yes	Handheld units available	Usually fixed
Best for	Low to medium volume, sensitive or hardened parts, logos	Rough or painted surfaces, deep marks	High-volume automated lines

If your part falls under a marking standard such as MIL-STD-130 for US defense items, the method and mark quality the drawing or contract specifies always take precedence over general comparisons like this one.

Marking a serial number, step by step

1. Enter the serial number, or a whole run of numbers, in the stencil software.
2. Print the stencil on the thermal stencil printer.
3. Clean the area, lay the stencil down and hold the electrolyte pad on it for a few seconds.
4. Wipe the mark with neutralizer.

With our Super Set 04, one mark takes 2 to 5 seconds and the full cycle per part is about 10 seconds. Marking mode gives a mark depth of approx. 0.001 in (0.025 mm); deep etch mode goes deeper as you increase the marking time.

Equipment for serial numbers

Serial numbering needs a printer that turns out a fresh stencil for each number. Both systems with our CD410 printer do this, QR codes and barcodes included:

• EUmark Set 07: compact dark-marking unit with the CD410 printer, for parts where a dark, high-contrast serial number is all you need.
• EUmark Super Set 04: full unit with AC and DC modes, dark marking and deep etch, the CD410 printer and the full electrolyte set.

Marking parts for aircraft maintenance? See our guide on reviewing an etch marking electrolyte against SOPM 20-50-10.

Quick answers

Can I put a different serial number on every part? Yes. Every number gets its own stencil, printed in your shop from the software.

What about hardened steel? Hardness doesn’t change the process. Hardened tool steel marks just like mild steel.

How permanent is the mark? It is part of the metal surface. It won’t wipe off, and it holds up to wear, cleaning and solvents.

Have a specific part in mind? Email eumark@eu-mark.com with the material and the mark size, and we’ll tell you which setup fits.