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How to Reduce Zinc Burn-Off & Spatter When Welding Galvanized Plates with Weld Screws on MF Spot Welders
Jul 29,2026
Medium frequency spot welders support mass welding of galvanized plates and weld screws with stable performance and high precision. However, zinc coating has a low melting and boiling point, so common defects including zinc ablation, dark/light weld nuggets, spatter and porosity easily occur during production.
I Root Causes of Zinc Burn-Off & Spatter
Zinc’s boiling point is far lower than steel. During welding, zinc vaporizes ahead of steel; zinc vapor cannot escape in time and breaks through the molten pool, causing spatter, arcing and zinc peeling & discoloration. Main triggers:
1.Direct high-temperature welding without preheating: zinc vaporizes violently instantly, generating massive spatter and wide burnt areas.
2.Excessive welding heat: surplus heat only aggravates zinc oxidation & spatter without improving joint strength.
3.Mismatched pressure: insufficient pressure creates gaps and gap arcing; overpressure crushes surrounding zinc coating.
4.Heavy oil, dust and contaminants on weld spots: they generate extra gas at high temperature and worsen porosity & spatter together with zinc vapor.
5.Worn, eccentric or zinc/carbon-deposited electrodes: uneven current distribution causes local overheating and zinc loss.
6.Pressure released too fast after welding: molten pool not fully solidified when lifting the gun, triggering secondary spatter and nugget collapse.
II Practical Optimized Processes
1.Three-stage welding sequence: low-current preheating to exhaust zinc gas smoothly and eliminate gaps; moderate current main welding for nugget formation; hold pressure for slow cooling to reduce spatter and zinc layer tearing.
2.Stable pressure welding: sufficient pre-pressure to tightly attach screws and plates without suspended gaps to eliminate arcing at source; adopt moderate welding pressure to avoid crushing surrounding zinc.
3.Gentle temperature control to cut thermal damage: lower peak heat input, adopt steady uniform heating to realize even zinc vaporization, balancing weld strength with low zinc loss and minimal spatter.
4.Clean workstations before welding: remove oil and dust on weld contact surfaces.
5.Standard electrode maintenance: use spherical electrodes to disperse heat; grind and clean zinc/carbon buildup regularly to keep flat end faces; guarantee unobstructed machine water cooling to prevent electrode thermal deformation.
6.Regulate production rhythm: avoid continuous dense welding; adopt skip welding with cooling intervals to prevent heat accumulation on workpieces and electrodes.
III Common Process Misconceptions
1.Higher current equals stronger joints: high current only intensifies zinc burning and spatter without improving tensile strength.
2.Galvanized welding inevitably creates spatter: segmented temperature control enables stable mass production with minimal zinc ablation.
3.Skipping preheating leads to batch arcing and large-area zinc peeling.
4.Random pressure adjustment: both excessive and insufficient pressure cause cold joints and zinc loss plus spatter.
IV Quick Remedies for Defects
1.Zinc whitening around nuggets: insufficient preheating & fast temperature rise; optimize preheating and slow heat input.
2.Fine scattered spatter: inadequate pre-pressure & zinc buildup on electrodes; extend pre-pressure time and grind electrodes.
3.Nugget collapse & skewed screws: excessive pressure & electrode misalignment; fine-tune pressure and calibrate welding head coaxiality.
4.Unstable strength & occasional cold joints: dirty electrodes & loose circuit connections; clean electrodes and fasten wiring terminals.
V Daily Equipment Maintenance
Tighten conductive joints and grind oxidized contact surfaces regularly for stable discharge. Calibrate electrode alignment daily. Workpieces must be fully supported without suspended welding to avoid gap arcing, spatter and zinc ablation caused by uneven force.
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Wuxi HAIFEI Intelligent Equipment Co., Ltd.
Wuxi HAIFEI Welding Equipment Co., Ltd.
Add: 28 Shuiyun Road, Yuecheng, Jiangyin, Jiangsu Province, China. (Postal Code: 214404)
Mobile: +86 18915302352
Email: wushijie@jshaifei.com