Laser Marking on Magnesium and Zinc Alloys 1

Magnesium and zinc alloys sit in a material class of their own because they are light, reactive and highly reflective, while their main alloys are never pure. Magnesium​ (AZ31B, AZ91D, WE43, AM60) is used for weight saving in automotive, aerospace, electronics housings and portable tools; zinc​ (ZAMAK, Zamak 3/5/7, zinc die-cast, ZA-8/12/27) is used for hardware, locks, handles, enclosures and decorative parts. Both have low melting ranges compared with steel, and both oxidise rapidly once the beam touches them — which is why a fiber laser produces a mark so easily, but also why an inexperienced operator can burn, pit or warp the part. A 1064 nm fiber laser​ is the right tool for the job: it creates a stable oxide layer (dark on Mg, light-to-grey on Zn) without removing metal, so the mark is permanent, corrosion-resistant and readable. On LAMBD equipment — T6 Mini 5–20 W, LM-11-3 20–30 W, LM-1-x MOPA 20–100 W and LM-9-2 50–100 W​ — the beam focuses to a 30–50 µm spot, holds ±0.001 mm repeatability​ and a 0.01 mm minimum line width, which is what allows a 1.5×1.5 mm​ Data Matrix or tiny serial number on a thin-wall magnesium housing. The rule for an English-site buyer is simple: treat Mg and Zn as “oxidising metals that need a cold, controlled recipe,” not as “aluminium with a different name.”

Magnesium is the easier of the two alloys to mark, but only if you respect its low melting point and high oxidation rate. The recommended starting window on a 30 W LAMBD LM-11-3​ is 30–50% power, 40–100 kHz, 300–800 mm/s, 1–2 passes; on a 20 W T6 Mini or LM-1-5, move to the upper part of the speed range and 1 pass, because lower power needs a faster scan to avoid local overheating. The goal is a thin, uniform oxide film — not a deep crater. AZ31B and AZ91D​ (the two most common die-cast and wrought grades) accept this window well and give a dark, high-contrast mark suitable for a serial, QR or logo; WE43 and other rare-earth grades​ may need 5–10% less power because they oxidise even faster. Surface condition matters more than the alloy name: polished magnesium marks darker and more evenly, cast or shot-blasted surfaces are grainy, and parts with oil, cutting fluid or conversion coating must be cleaned first — otherwise the code is blotchy and the coating can trap moisture. For magnesium, never deep-engrave​ in a production recipe: removing material exposes fresh, unprotected Mg and creates a corrosion starter. Use annealing-type marking (oxide only), keep passes to 1–2, and finish with a 30-second sample​ on the actual part before the run. If the part is a thin-wall housing or a component near a seal, reduce power by 10–15% and raise speed; the part must not deform or lose its anodised/coated appearance.

Zinc alloys mark differently because zinc oxide is lighter in colour and the base metal is soft and low-melting. On ZAMAK and zinc die-cast, a plain Q-switched fiber can produce a usable grey code, but the result is often uneven — the mark looks “washed out” at low power and “burned” at high power. This is where MOPA pulse control​ pays for itself: the LM-1-x MOPA​ family (LM-1-5 20–30 W, LM-1-6 50 W) lets you vary pulse width from <10 ns to ~200 ns​ at up to 4000 kHz, so you can tune the thermal dose instead of just turning power up and down. A good starting point for clean, high-contrast marking on zinc is 25–45% power, 60–150 kHz, 400–1000 mm/s, 1 pass, with a preference for shorter pulses and higher frequency when the surface is polished or chrome-plated. For satin or brushed zinc, lower the frequency into the 40–80 kHz​ range and reduce speed slightly to build contrast without pitting. Zinc plating (galvanised steel)​ is a separate case: the coating is thin, so too much energy burns through to the steel and leaves a two-tone mark; keep power at the low end, use 1 pass and test on a real coated panel. Lead-free and decorative zinc parts​ (locks, handles, badges, enclosures) benefit from the same oxide-only approach used on magnesium — no deep engraving, no aggressive cleaning afterwards, and no marking through a grease film. LAMBD recommends saving two recipes per alloy family — “ZAMAK_dark_1.0mm” and “ZAMAK_light_0.5mm” — and switching by part finish rather than by guesswork.

The right machine for Mg/Zn is almost always air-cooled fiber: it is compact, low-power, low-maintenance and does not add the chiller complexity required by 355 nm UV. For prototyping, jewellery, keys, gifts and small batches, choose the T6 Mini 5–20 W​ (draws <0.5 kW​ from 220 V/50 Hz, fits a 6–8 m²​ studio, 100,000-hour​ source). For production of die-cast housings, hardware and serialised parts, choose the LM-11-3 20–30 W​ with a 110×100 mm​ field (optional to 300×300 mm), galvo to 7000 mm/s​ and the same EZCAD + JCZ​ workflow. For color, white and high-contrast work on plated or anodised surfaces, add an LM-1-x MOPA; for high-volume, 24/7 lines, move to the enclosed LM-9-2 50–100 W​ cell with interlock and optional IP54/IP65. Two process points are non-negotiable. First, fume control.​ Magnesium and zinc fumes are fine, irritating and must be captured at the source with a HEPA + activated-carbon extractor​ — LAMBD treats this as mandatory, not optional, because smoke on the F-theta lens changes focus and ruins repeatability. Second, surface preparation.​ Degrease with isopropyl alcohol, remove cutting fluid and let the part dry; do not mark through oil, paint, powder coat or a thick conversion layer unless the recipe was validated for that exact coating. The LM-8-1 CCD​ camera can locate randomly fed Mg/Zn parts and correct position, while the LM-9-2​ cell can verify the code with a camera immediately after marking — both reduce scrap on high-mix lines where part orientation changes constantly.

A good-looking mark is not enough on Mg/Zn: the mark must survive handling, cleaning, salt spray and, for magnesium, the part’s own corrosion protection system. LAMBD recommends a four-step validation. Step 1 — contrast and geometry.​ After marking, check the code to ISO/IEC 15415​ (2D) or ISO/IEC 15416​ (linear): modules must be even, with no burns, bridges or missing cells. Step 2 — first-read rate.​ Scan the code with several readers at different distances and angles; record the result as part of the technical file. Step 3 — environmental test.​ For parts that see outdoor or marine use, run a salt-spray or humidity cycle and re-scan; the oxide mark on magnesium and zinc usually survives well, but a burned or pitted mark will fail first. Step 4 — correlation.​ Every code must link to a database record; LAMBD pulls serial numbers, dates, lots and expiry from Excel via CSV​ into EZCAD, then exports the log to MES/ERP. Two operating rules protect the part. Never use a deep-engraving recipe on Mg/Zn in production​ — oxide-only marking preserves the protective layer. Never clean a marked part with aggressive solvents or abrasive blasting​ afterwards, because both remove the very oxide that makes the code readable. For an English-site buyer the practical conclusion is direct: Mg and Zn are excellent candidates for permanent laser marking, but only when the recipe is built around a thin, controlled oxide layer, the lens is kept clean, fumes are extracted and every code is validated and logged.

Magnesium and zinc alloys​ are marked best by a 1064 nm fiber laser​ working in oxide-only, cold-marking mode — not by deep engraving. Magnesium (AZ31B, AZ91D, WE43, AM60)​ takes a dark, stable mark at 30–50% power, 40–100 kHz, 300–800 mm/s, 1–2 passes; zinc and ZAMAK​ need a lighter touch and benefit from MOPA pulse-width control at 25–45% power, 60–150 kHz, 400–1000 mm/s, 1 pass, with polished surfaces preferring shorter pulses and higher frequency. On LAMBD equipment the result is a 30–50 µm spot, ±0.001 mm repeatability and 0.01 mm line width, enough for a 1.5×1.5 mm​ code on a thin-wall part. The production discipline is the same for both metals: degrease first, mark oxide-only, keep to 1–2 passes, extract fumes with a HEPA + carbon purifier, protect the lens, validate to ISO/IEC 15415, and log every serial number through CSV​ into MES/ERP. Machine choice follows volume — T6 Mini 5–20 W​ for low volume, LM-11-3 20–30 W​ for production, LM-1-x MOPA 20–100 W​ for contrast and color, LM-9-2 50–100 W​ for automated cells — and every model shares EZCAD + JCZ, files and recipes. For an English-site audience the takeaway is clear: treat Mg and Zn as oxidising, low-melting alloys that reward a gentle recipe, and they will deliver a permanent, corrosion-resistant, high-contrast mark without the pitting, warping or coating damage that comes from treating them like steel.