11 Common Welding Defects and How to Correct Them

Last Updated on May 2022

Welding Defects are the irregularities formed in the weld metal due to incorrect welding patterns, or wrong welding process, etc. The defect might differ from the desired weld bead size, shape, and intended quality.

Welding defects can occur either outside or inside the weld metal. Note, some of the defects might be allowed if the defects occur under permissible limits but other defects such as cracks are never accepted.

Weld Crack

The most serious type of welding defect is a weld crack and it’s not accepted almost by all standards in the industry. It can appear on the surface, in the weld metal, or in the area affected by the intense heat.

There are different types of cracks, depending on the temperature at which they occur:

  • Hot cracks. These can arise as you weld or as the weld joint crystallizes. The temperature at this point rises considerably to over 10,000C.
  • Cold cracks. These are cracks that can appear after you have completed the weld and the temperature of the metal has gone down. The cracks can form hours or even days after the welding process. This type of defect mostly happens when welding steel and can effect the quality of the weld.

The cause of this defect is usually deformities in the structure of steel.

  • Crater cracks. These are cracks that occur at the end of the welding process but before the operator completes a pass on the weld joint. The cracks usually form near the end of the weld. After the weld pool cools and solidifies, it has to have sufficient volume to overcome any shrinkage of the weld metal. Short of this, it will form a crater crack.

Causes of cracks:

  • Use hydrogen when you weld ferrous metals.
  • Residual stress is occasioned by the solidification shrinkage.
  • Base metal contamination.
  • High welding speed but low current.
  • No preheating before starting welding.
  • Poor joint design.
  • High content of carbon and sulfur in the metal.


  • Preheat the metal as required.
  • Provide appropriate cooling of the weld area.
  • Use proper joint design.
  • Remove impurities.
  • Use appropriate metal.
  • Make sure to weld an adequate sectional area.
  • Use the right welding speed and amperage current.
  • To prevent crater cracks ensure the crater is properly filled.
  • Ensure you have a full penetration weld


This welding defect is the groove formation at the weld toe. This reduces the cross-sectional thickness of the base metal. The result is a weakened weld and workpiece.


  • Too high weld current.
  • Too fast weld speed.
  • The use of an incorrect angle. This directs more heat to free edges.
  • The electrode is too large.
  • Incorrect usage of gas shielding.
  • Incorrect filler metal.
  • Poor weld technique.


  • Use proper electrode angle.
  • Reduce the arc length.
  • Reduce the electrode’s travel speed. However, it also shouldn’t be too slow.
  • Choose shielding gas with the right composition for the type of welding you’ll be welding.
  • Use of proper electrode angle and direct more heat towards thicker components.
  • Use proper current, and reduce it when you approach thinner areas and free edges.
  • Choose an appropriate welding technique; one that doesn’t involve excessive weaving.
  • Use the multi-pass technique


This defect can come in the following two forms:

Incomplete Penetration

Incomplete penetration occurs when the groove of the metal is not filled, meaning the weld metal doesn’t fully extend through the joint thickness.


  • There was excess space between the metals you’re welding together.
  • You’re moving the bead too fast thus not allowing enough metal to be deposited in the joint.
  • You’re using a very low amperage setting. This results in the current not being strong enough to adequately melt the metal.
  • Large electrode diameter.
  • Improper joint.


  • Use proper joint geometry.
  • Use a properly sized electrode.
  • Reduce arc travel speed.
  • Choose proper welding current.
  • Check for proper alignment.

Excessive Penetration

Excessive penetration causes burn through. It is the outcome of too much heat in the weld area. You can correct this by:

  • Reducing the wire-feed speed while increasing the speed of travel.
  • Ensuring the root opening and root face is correct.
  • Increasing the stick-out distance when welding and weaving the gun.

Incomplete Fusion

This type of welding anomaly occurs when there’s a lack of good fusion between the weld metal and the base metal. It can also appear between adjoining weld beads. This creates a gap in the joint that is not filled with molten metal.


  • Low heat input.
  • Surface contamination.
  • The electrode angle is incorrect.
  • The electrode diameter is incorrect for the material thickness you’re welding.
  • Travel speed is too fast.
  • The weld pool is too large and it runs ahead of the arc.


  • Use a sufficiently high welding current with the appropriate arc voltage.
  • Before you begin welding, clean the metal.
  • Avoid molten pools from flooding the arc.
  • Use correct electrode diameter and angle.
  • Reduce deposition rate.


Welding Spatter happens when small particles coming from the weld attach themselves to the nearby surface. It’s especially common in gas metal arc welding. This defect can’t be eliminated No matter how hard you try. However, there are a few methods you can keep it to a minimum. For more information on the best anti welding spatter sprays [Read our Full Guide]


  • The running amperage is too high.
  • The voltage setting is too low.
  • The working angle of the electrode is too steep.
  • The surface is contaminated.
  • The arc is too long.
  • Incorrect polarity.
  • Erratic wire feeding.


  • Clean surfaces before welding.
  • Reduce the arc length.
  • Adjust the weld current.
  • Increase the electrode angle.
  • Use proper polarity.
  • Make sure you don’t have any feeding issues.


Porosity comes as a result of weld metal contamination. Trapped gases create a bubble-filled weld that then becomes weak and can collapse with time.

Causes of porosity:

• Inadequate electrode deoxidant.
• Using a longer arc.
• The presence of moisture.
• Improper gas shield.
• Incorrect surface treatment.
• Use of too high gas flow.
• Contaminated surface.
• Presence of rust, grease, oil, or paint.


• Clean the materials before you start welding.
• Use dry electrodes and materials.
• Use correct arc distance.
• Check the gas flow meter and ensure that it is optimized as required with the correct pressure and flow settings.
• Reduce arc travel speed. This will allow the gases to escape.
• Use the right electrodes.
• Use a proper weld technique.

Slag Inclusion

This is one of the welding defects that are easily visible in the weld. For starters, slag is a vitreous material and it occurs as a byproduct of flux-cored arc welding, stick welding, and submerged arc welding. It can occur when the flux, which (the solid shielding material used when welding), melts in the weld or on the actual surface of the weld zone.


  • Improper cleaning.
  • The welding speed is too fast.
  • Not cleaning the weld pass before starting a new one.
  • Incorrect welding angle.
  • The weld pool cools down too fast.
  • The welding current is too low.


  • Increase current density.
  • Reduce rapid cooling.
  • Adjust the electrode angle.
  • Adjust the welding speed.
  • Remove any slag from the previous bead.

Irregular Weld Shape

Irregular welds include the that are too narrow or wide, those that have a very convex or concave surface, plus those having coarse, irregular ripples.

Such characteristics may be caused by:

  • poor torch manipulation,
  • a speed of travel that is too slow,
  • current that is too high or low,
  • improper arc voltage,
  • improper stick out,
  • improper shielding gas.

Simply, avoid the above-mentioned characteristics and avoid irregular weld shapes.


This is formed because of the gas phenomenon in liquid metal.  In such cases, the weld cannot escape as the metal puddles are solidified.

Blowhole can appear:

  • Inside or weld surface
  • Located at the boundary between the base metal and fill metal or
  • Can be distributed, concentrated or discrete in the weld

Remedies of blowhole:

  • Adjust the short arc length, minimize the welding speed of your MIG welding machine
  • After welding, don’t knock the slag immediately to prolong the heat retaining time for the weld
  • Provide sufficient MAG welding / MIG gas, gas shooting distance


This occurs when the weld face goes beyond the weld toe. In this condition, the weld metal rolls forming an angle less than 90 degrees.


  • Improper welding technique.
  • Using large electrodes may lead to this defect
  • High welding current


  • Use a proper technique for welding.
  • Use a small electrode.
  • Less welding current.

Voids And Cracks

These weld defects may be caused by any of the following:

  • Improper fit-up.
  • Improper cooling.
  • Failure to preheat.
  • Concave reinforcement (fillet weld).


You have to ensure you avoid the above-mentioned causes to avoid the possibility of getting voids and cracks on your welds.


So, we have listed the 11 most common welding defects and included their causes and remedies. When detecting them, it’s vital to remove them to forestall the material’s loss of property and strength.

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