John Ward John Ward

Tips for Troubleshooting Arc-Welding Defects

December 2, 2020

Weld defects plague even some of the most skilled welders, and usually result from the use of incorrect parameters or welding techniques. They can be frustrating and costly, so follow the tips offered here to help cure and minimize their occurrence.


PorosityPorosity occurs when gas pores become trapped in the solid weld bead. They result from the absorption of gas into the molten weld pool. The gas pores can vary in size, can be distributed uniformly or in a random manner, and can be found on the weld surface or at the center of the bead. 

Weld pores often are caused by the atmospheric gases nitrogen and oxygen contaminating the weld, due to insufficient gas shielding.

To troubleshoot porosity:

  1. Check for sufficient shielding-gas flow. Inspect the gas hoses and welding gun for leaks.
  2. Ensure that the nozzle isn’t clogged and restricting gas flow.
  3. If welding outdoors, avoid windy conditions that can interfere with the shielding gas. 
  4. Verify proper gas flow using the regulator or flow meter. Too little or too much shielding gas can cause porosity. 

Porosity also can originate from hydrogen and oxygen on a contaminated workpiece, such as oxidized metal or moisture on the workpiece. In these cases:

  1. Thoroughly remove any oxide film from the workpiece surface. 
  2. Ensure that the workpiece and welding electrode are completely dry before welding.
  3. Use a filler metal containing deoxidants.

Excess Spatter

Excess spatterWeld spatter—small drops of molten metal sprayed over the workpiece during gas-metal-arc welding (GMAW)—can result from using an incorrect setup or from dirt on the surface of the workpiece. It can damage the workpiece and equipment and increase cleanup time. 

To cure excess spatter:

  1. Adjust the welding parameters. Excess amperage or insufficient voltage can make the arc too cold and result in spatter. Try reducing the wire-feed speed (when using GMAW) or increasing the voltage. 
  2. Check the wire stickout. Excess stickout can cause spatter.
  3. If shielding with straight CO2, try switching to a CO2-Ar mixture.
  4. Ensure that surfaces are clean. Metal covered in paint, oil, rust or dirt can cause spatter. 
  5. Be sure to use the right polarity setting, as the wrong polarity can cause a lot of spatter.

Weld Cracking

Weld crackCracks that form in the weld bead will reduce the strength of the weld. Cracks can be hot or cold.

Hot cracks can occur when the weld metal is just below the solidus (solidifying) temperature—the highest temperature at which an alloy remains solid. A lack of ductility at this temperature can make the metal brittle. Hot cracking usually appears along the weld axis in the middle of the weld.

Cold cracks (or hydrogen cracking) usually occur in high-strength steels where hydrogen is present in the weld metal. Tensile stress on the weld joint also can contribute to cracking.

To help prevent cracking:

  1. Reduce heat input. Lower heat helps the weld metal cool more quickly, so it spends less time near the solidus in a brittle state.
  2. Be sure to use the correct, recommended filler metal. When welding austenitic stainless steels, particularly prone to cracking, use filler metal containing ferrite.
  3. Ensure that there are no sources of hydrogen, such as paint, rust, water, oil, grease or coatings, that might contaminate the weld.

Incomplete Penetration

Incomplete penetration…is when the weld metal does not penetrate the full thickness of the base material. The weld bead should fully penetrate the toe of a fillet weld; shallow fusion can lead to joint failure. The most common causes of incomplete penetration are insufficient weld current and incorrect workpiece alignment. 

To troubleshoot incomplete penetration:

  1. Check the welding current. Increasing amperage will provide more power to melt the filler metal.
  2. Ensure a properly fixtured weld joint, with the proper gap and alignment. 
  3. Reduce travel speed. 


BurnthroughThe opposite of incomplete penetration, burnthrough occurs when the weld metal penetrates all the way through the base material. This occurs most often when welding thin sheet metal (less than 0.25 in. thick).

To address burnthrough:

  1. Reduce the voltage or the wire-feed speed to reduce heat input to the weld. Excess heat is the most common cause of burnthrough.
  2. Increase travel speed. This works particularly well when welding thin aluminum where heat can build up quickly.

Cold Lap/Lack of Fusion

Lack of fusionCold lapping or lack of fusion occurs when the weld metal fails to properly fuse with the base metal. This usually occurs when the weld pool grows too large and overlaps onto the toe of the weld, or if the arc is not properly directed into the weld joint. If the heat of the arc cannot sufficiently melt the base metal, lack of fusion can occur.

To troubleshoot:

  1. Check the welding-gun angle; be sure to hold the gun at an angle between 0 and 15 deg.
  2. Try increasing travel speed and keep the arc on the leading edge of the weld puddle. 
  3. Ensure that the amperage is high enough to properly fuse the metal. Increase the voltage and wire-feed speed where necessary. 
  4. If using the weave technique, try holding the arc on the weld-joint sidewalls for a little longer period of time, to help increase heat input and promote good fusion. MF


John Ward is the editor of the website

Industry-Related Terms: Thickness, Bar Coding, Center, Ductility, Edge, Fillet Weld, Form, Gas Metal Arc Welding GMAW, Penetration, Shielding Gas, Spatter, Surface
View Glossary of Metalforming Terms

Technologies: Welding and Joining


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