ANSI
View official documentation (opens in new tab)ANSI Z136.1, Safe Use of Lasers (applies to all laser cleaning applications)[1]
Ikmanda RoswatiPh.D.Indonesia
Ultrafast photonics and laser-matter interactionPublished
Jul 22, 2026
Weld Heat Tint Laser Cleaning by Color Severity
Crews read weld color on the stainless coupon before they pick a pass, straw tint lifts near 1–2 J/cm² at 1064 nm, but purple-blue Heat-affected area still hides a Cr-depleted layer wire brushing cannot reach. Extraction must cover hex-chrome and iron-oxide fume rows while the beam walks the rainbow band at handheld speed.
Frequently Asked Questions
Does the heat tint color affect how easy it is to laser-clean?
Heat tint color changes how much fluence the strip needs because dark blue and violet weld bands on stainless coupons carry roughly 100 nm oxide stacks through thin-film interference, far thinner than mill scale. Kumar tested pulse durations from 20 to 1020 ns and found the effective fluence threshold for complete tint removal rises as pulse length lengthens. (CXP heat tint guide; cxp-heat-tint-guide)
Does laser cleaning restore stainless steel passivation?
Laser cleaning does not restore stainless passivation on the MAG and TIG welds tested in the DIVA thesis, visible tint lifts but critical pitting temperature and passivity did not return, and the same coupon literature puts 304L surface melting at 0.36 J/cm² according to Carvalho, so stay above oxide cleaning but below that melt floor on thin beads. (Carvalho EPJ Nucl. 2017; Carvalho 2017)
Can laser cleaning remove titanium weld discoloration the same way as stainless?
Titanium weld discoloration is alpha-case and oxygen diffusion into hot metal, not the chromium-rich interference oxide that forms on austenitic stainless GTAW beads. The same 1064 nm screening band from stainless heat-tint coupons does not transfer to cp-Ti or Ti-6Al-4V without a relabeled alloy coupon and a separate fluence bracket.
Sources(3 references)
- Heat tint oxide thickness by interference color cxp-solutions.com (opens in new tab) — ~100 nm oxide at dark blue/violet heat tint
- Laser weld oxide removal and corrosion resistance restoration diva-portal.org (opens in new tab) — laser ablation did not restore corrosion resistance on tested alloys
- Laser decontamination of 304L stainless surface oxide epj-n.org (opens in new tab) — Fm = 0.36 J/cm² minimum fluence causing 304L surface melting
Laser enclosure rules on weld tint strip lines
Post-weld oxide removal still runs under national laser-safety zoning regardless of whether the part is 304, 316L, or duplex stainless, beam enclosure, eyewear, and controlled work areas per ANSI Z136.1 apply before the handheld head crosses the rainbow band.
Sources(1 reference)
- ANSI Z136.1 — Safe Use of Lasers webstore.ansi.org (opens in new tab) — national laser safety standard for all laser cleaning applications
Match weld color to energy before the next weld pass
1Disqualify wire brush and pickling paste first
- Purple-blue weld tint will not restore passivation unless the pulsed pass clears oxide without reheating the bead, wire brushing leaves the Cr-depleted layer beneath the rainbow film and cannot satisfy 29 CFR 1910.1026 monitoring if hex-chrome action level hits 2.5 µg/m³ without capture.
- Pickling paste with nitric and hydrofluoric acids cannot be scoped as zero-wastewater when the job still generates acid effluent, laser strip eliminates paste handling but not particulate capture.
2Bracket fluence to color severity on the coupon
- Straw gold on 304L coupons clears in the lowest 0.5–2.0 J/cm² band cited for heat-tint cleaning, do not transplant a mill-scale window onto nm oxide. (JLA heat tint 2022)
- Hold fluence below Carvalho's 0.36 J/cm² melt reference on thin-gauge bead profiles until bare metal reads under shop lighting.
3Walk interpass tint at handheld throughput
- Handheld post-weld systems report 1–1.5 m/min on stainless oxide, fast enough to track common TIG travel between passes on the same joint coupon.
- Keep HEPA source capture active for the full pass; Cr-rich oxide dust continues through the strip even after visible color lifts.
Sources(2 references)
- Handheld weld oxide removal throughput p-laser.com (opens in new tab) — 1–1.5 m/min cleaning speed on stainless weld oxide
- Laser-assisted removal of weld heat tints from stainless steel pubs.aip.org (opens in new tab) — 0.5–2.0 J/cm² heat-tint ablation window on stainless coupons
Stainless grade sets the heat-tint strip margin on weld test pieces
Weld heat tint always forms on stainless steel, the variation is alloy grade and color severity, not substrate family. Straw gold on 304L coupons sits in the lowest published cleaning band; purple-blue oxide on a 316L weld coupon still needs fluence below the melt floor on thin-gauge bead profiles.
| Substrate | Ablation threshold (J/cm²) | Substrate damage (J/cm²) | Process window | Regime |
|---|---|---|---|---|
| Stainless steel 304 / 316 (weld heat tint) | 0.5–1.5 | 5–12 | 3.3–24×Moderate — nm oxide clears before bulk stainless damage on labeled coupons | sublimation-ablation |
Sources(2 references)
- Laser-assisted removal of weld heat tints from stainless steel pubs.aip.org (opens in new tab) — weld-heat-tint-stainless row — 0.5–1.5 J/cm² F_th per ablation-thresholds.json
- Laser-assisted removal of weld heat tints from stainless steel surface, Journal of Laser Applications, 2022 doi:10.2351/7.0000561 (opens in new tab) — Stainless Steel: 5–12 J/cm²
Color, thickness, and passivation limits from test-piece literature
Weld tint severity, oxide thickness, cleaning band, and post-laser passivation outcomes, each row is a different planning decision on stainless weld coupons.
| Parameter | Value |
|---|---|
| Color maps to corrosion risk | Straw to black bands warn of deepening Cr depletion beneath the oxide |
| Oxide film thickness | 30–500 nm — far thinner than mill scale on the same alloy family |
| 1064 nm ablation band | 0.5–2.0 J/cm² on stainless heat tint — strongest ns use case in JLA 2022 |
| Passivation after laser | Laser ablation alone did not restore CPT on tested MAG/TIG welds |
| Interpass handheld speed | 1–1.5 m/min — matches common welding travel for tint between passes |
Sources(1 reference)
- TWI — heat tint color and corrosion severity twi-global.com (opens in new tab) — heat tint color warns of underlying metallurgical damage severity
Pulse energy — Weld Heat Tint Laser Cleaning
Working fluence ~0.75 J/cm² on Stainless steel 304 / 316 (weld heat tint) (window 0.50–5.00 J/cm²). Bars: datasheet max pulse energy; color: process status.
- Wuhan Sintec STPL-V-i1600: 250 mJ — In process window
- Laserax LXQ-UHP 3000W: 150 mJ — In process window
- Laserax LXQ-UHP 2000W: 150 mJ — In process window
- Narran ROD 2000: 100 mJ — In process window
- Narran ROD 2000 Bright+: 100 mJ — In process window
- P-Laser QF-2000: 100 mJ — In process window
- Laserax LXQ-UHP Series (500W–3kW): 100 mJ — In process window
- 4JET JETLASER M1000: 100 mJ — In process window
- Laserax LXQ-UHP 1000W: 100 mJ — In process window
- Narran ROD 1000 Bright+: 100 mJ — In process window
- P-Laser QF-1000: 100 mJ — In process window
- 4JET JETLASER M500: 100 mJ — In process window
- Laserax LXQ-UHP 500W: 100 mJ — In process window
- Narran ROD 500 Bright+: 100 mJ — In process window
- Netalux Jango®: 100 mJ — In process window
- Narran ROD 1000: 50 mJ — In process window
- Narran ROD 500: 50 mJ — In process window
- P-Laser QF-500: 50 mJ — In process window
- Netalux Kamino 300: 50 mJ — In process window
- cleanLASER CL 500: 25 mJ — In process window
- SenFeng SF1000HC: 50 mJ — In process window
- SenFeng SF500HC: 50 mJ — In process window
- Powerlase Vulcan 500c: 40 mJ — In process window
- Narran ROD 300 Air: 15 mJ — In process window
- cleanLASER CL1000iF: 10 mJ — In process window
- 4JET JETLASER M200: 10 mJ — In process window
- Powerlase FL-C100C: 5.0 mJ — In process window
- Narran ROD 100 Air: 1.5 mJ — In process window
- PULSAR Laser SHARK P CL 1000A: 1.5 mJ — In process window
- P-Laser ECO-C 500: 1.5 mJ — In process window
- PULSAR Laser SHARK P CL 500A: 1.5 mJ — In process window
- PULSAR Laser SHARK P CL 300M: 1.5 mJ — In process window
- Han's Laser HC-PD 200W: 1.5 mJ — In process window
- PULSAR Laser SHARK P CL 200M: 1.5 mJ — In process window
- Han's Laser HC-PD: 1.5 mJ — In process window
- Han's Laser HC-PD 100W: 1.5 mJ — In process window
- PULSAR Laser SHARK P CL 100M: 1.5 mJ — In process window
- Han's Laser HC-PD 50W: 1.1 mJ — In process window
- P-Laser QFC-300: 1.0 mJ — In process window
- P-Laser ECO-C 200: 1.0 mJ — In process window
- In window
- Below threshold
- Near damage
- Damage risk