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Why Violent Arcing Occurs When Welding Galvanized Plates & Screws with Capacitor Discharge Spot Welders
Jul 20,2026
Capacitor discharge spot welders produce narrow heat-affected zones, commonly used for galvanized plate & screw welding on home appliance and hardware components. Galvanized materials easily generate arcing, metal spatter, dark welds and surface pits, a frequent mass production quality issue.
I Arcing Phenomena & Hazards
1.Open flame & metal spatter at welding instant, carbon deposition and dark discoloration around nuggets with severe appearance defects.
2.Ablation pits on plates and burn deformation at screw roots, leading to product scrapping.
3.Vaporized zinc adheres to electrodes to form carbon buildup & nodules, triggering continuous arcing in subsequent welds.
4.Unstable welding state alternating between arcing and cold joints with inconsistent weld strength.
5.Flying metal particles risk operator burns and equipment damage.
II Fundamental Cause of Arcing on Galvanized Material
Zinc coating has poor heat resistance. High welding temperature instantaneously vaporizes zinc to form high-pressure gas that bursts through the molten pool and creates spatter. Uneven conductivity of zinc coating plus instantaneous high energy release fails to exhaust zinc vapor fully, causing violent combustion. Oil and oxide residues on workpieces further worsen arcing.
III Main Arcing Triggers
1.Mismatched pressure: insufficient pressure leaves interlayer gaps where discharge creates arcs; excessive pressure crushes coating to extrude molten metal and form spatter.
2.Steep energy waveform: instant full power surge creates violent zinc vaporization and severe arcing.
3.Dirty workpiece surface with oil, fingerprints, dust and oxides causing uneven conduction & local hot spots.
4.Worn, carbonized, nodulated electrodes leading unbalanced force & current transfer.
5.Gaps between contact surfaces: skewed screws, unlevel plates or suspended fixtures create gap discharge.
IV Complete Arcing Elimination Solutions
1 Optimize welding process for slow energy release
1.Adopt slow voltage rise curve to allow gentle zinc vaporization without instantaneous explosion.
2.Set minimal sufficient energy to secure welding without redundant heat input.
3.Implement pre-pressure, constant pressure and post-holding pressure to eliminate gaps and suppress spatter.
2 Workpiece surface pre-treatment
1.Remove oil, dust and contaminants from weld zones before welding.
2.Lightly polish oxidized zinc layers to guarantee uniform conductivity.
3.Deburr screws and clear metal scraps to achieve zero-gap lamination.
3 Electrode & fixture maintenance
1.Grind and clean electrodes before each shift to remove zinc nodules and carbon deposits; replace heavily worn electrodes.
2.Deploy special high-temperature wear-resistant electrodes to reduce zinc adhesion.
3.Install solid backing under weld points to avoid suspended welding; center plates and screws accurately.
4 Standard mass production operation
1.Forbid gap welding and avoid secondary re-welds to prevent pits and arcing.
2.Regularly clean zinc buildup on electrodes during batch production to avoid mass defects.
3.Keep workshop dry to prevent workpiece moisture oxidation and unstable discharge.
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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