Choosing the Right Electrolyte: A Practical Guide to EuMark’s M21, M22, M23, and N11 Formulations

The marking device and stencil are only part of the equation. The electrolyte formulation determines the chemistry of the oxidation reaction, which directly affects the color, depth, contrast, and durability of the finished mark. Using the wrong electrolyte for your metal type produces weak results. Using the right one produces marks that last.

Here’s a practical breakdown of what each EuMark formulation does and when to use it.

M21 — Standard Black Mark on Carbon Steel

M21 is the workhorse formulation for general industrial marking on carbon steel and mild steel. It produces a dense black mark with strong contrast, suitable for part numbers, serial numbers, and logos on tools, structural components, and machinery parts.

Recommended for: carbon steel, mild steel, case-hardened tool steel. Best with: standard film stencils or graphite stamp. Mark appearance: matte black, high contrast.

M22 — Deep Black on Stainless Steel

M22 is formulated specifically for austenitic stainless steels — the grades most commonly used in food processing equipment, medical devices, and precision instruments. It produces a darker, deeper black than general-purpose formulations on these alloys because it’s calibrated to the oxide chemistry of chromium-containing steels.

Recommended for: 304, 316, and other austenitic stainless grades. Best for: medical instruments, food-contact surfaces, chemical plant components. Mark appearance: deep black with sharp edge definition.

M23 — Corrosion-Resistant Mark for Outdoor Use

M23 is designed for environments where the marked part will face ongoing moisture, humidity, or chemical exposure. The formulation produces a mark that is inherently more resistant to corrosion-driven degradation — relevant for outdoor infrastructure, marine hardware, agricultural equipment, and automotive chassis components.

Recommended for: all conductive metals in exposed environments. Best for: parts used outdoors or in wet conditions. Mark appearance: black to grey, with enhanced environmental stability.

N11 — Neutralizing and Anti-Corrosion Treatment

N11 is not a marking electrolyte but a post-marking treatment fluid. Applied after marking, it neutralizes any residual electrolyte chemistry on the surface and provides an initial layer of corrosion protection. Its use is recommended as a standard finishing step in any marking workflow, particularly on carbon steel parts.

N11 works alongside protective oil: N11 neutralizes and protects the immediate post-mark surface chemistry; protective oil then seals the surface for long-term environmental resistance.

Practical Guidance

If you’re unsure which formulation to start with, M21 is the right default for most steel marking applications. If you’re working with stainless steel, start with M22. For any marking in wet or outdoor environments, choose M23 and apply N11 as a finishing step.

All EuMark electrolytes are compatible with the full EuMark product range, including the graphite hand stamp, standard felt pads, and all current marking devices.