19 Common Types of Welding Defects:Causes & Remedies

In this article, I am going to explain the 19 most common types of welding defects as well as their causes and remedies.


Welding defects generally occur in a welding process due to the inexperienced or unskilled welder or due to fundamental difficulties in the welding operation like arc welding, gas welding, etc.


So without wasting time let's get started.


What is a Welding Defect?

Welding defects arise due to faulty or poor technology used in welding work.


Types of Welding Defects

There are following types of welding defects are found:

  • Undercut
  • Porosity
  • Slag Inclusion
  • Cracks
  • Excessive Penetration
  • Lack of Penetration
  • Spatter
  • Overroll
  • Lack of Fusion
  • Misalignment
  • Underfill
  • Concavity or Convexity
  • Excessive Reinforcement
  • Burn Through
  • Overlap
  • Arc Strikes
  • Arc Crater
  • Waviness of Bead
  • Distortion 

These welding defects we will know in detail one by one with pictures.

See in figure welding defects like undercut, porosity, cracks, etc.

Which are described below in detail.

types of welding defects
Types of Welding Defects


In this defect, some portion remains unfilled near the toe side of the weld metal which is called an undercut.

See in the above figure.

Causes of Undercut

  1. Too much current over-heats the parent metal. 
  2. Not keeping the electrode at the edges for a sufficient time during weaving.   
  3. 'V' being wider.
  4. Shifted of welding centerline.

Remedies of Undercut

  1. Always use low current.
  2. Change the welding technique and stop for some time at the undercut edge.
  3. Decrease the welding speed. 
  4. Use the correct edge preparation.
  5. Cleaning the plate before welding.


If small pores of gas are formed and are spread in the weld metal, then this defect is called 'porosity'.


Causes of Porosity

  1. An overheated electrode.
  2. The wrong electrode for the metal to be welded has excess moisture.

Remedies of Porosity

  1. Use low current.
  2. To avoid porosity always use the correct electrode like weld bright steels, medium carbon steels, and alloy steels with low hydrogen electrodes.
  3. The electrode should be dry, for this; they are kept in a warm and dry place.
  4. Rework by grinding and re-weld wherever needed.


Slag Inclusion

The molten flux adsorbs the oxide from the parent metal surface and floats on the molten weld metal.  


Some of the flux (slag) goes into the molten metal due to which slag is incorporated.


Causes of Slag Inclusion

  1. If the weld pool is not hot enough, the slag solidifies inside the weld.  
  2. This may be due to low current, insufficient heat input, or excessive weaving.
  3. An undercut in the preceding run or too little space between the plates.


Remedies of Slag Inclusion

  1. Increase the current or use narrower weaving. 
  2. Repairs by the grinding and weld again.
  3. Prepare the plates in such a way that there is no blockage in them and the slag can float.



This is a dislocation in the weld metal.  


This may be due to the effect of cooling or stress.

Causes of Cracks

  1. The high strength of joint.
  2. High rate of cooling.
  3. Use of wrong electrodes.
  4. Use of improper welding technique.


Remedies of Cracks

  1. Use joint key pre-heating and/or post heating if necessary.
  2. Cool the welded joint slowly.   
  3. Use another sequence for welding.   
  4. Use weaving motion.  
  5. Use the correct type of electrodes for the type of parent metal to be welded.


Excessive Penetration


In welding of a butt joint, square edge preparation for 3 mm plates and 'V' preparation for thick plates are used.  

This allows for penetration up to full thickness. 

Excessive penetration is not acceptable.


Causes of Excessive Penetration

  1. Running electrodes incorrectly.
  2. Overheating of the weld pool.
  3. Incorrect size and type of electrodes.


Remedies of Excessive Penetration

  1. Use low current.  
  2. Use the correct size and type of electrodes. 
  3. Use the correct dimensioned root face and root gap.


Lack of Penetration   


If the weld metal is not fully penetrated to the root of the joint, it results in a lack of penetration.


Causes of Lack of Penetration

  1. Low ampere current.
  2. Faster travel speed during welding.
  3. Low preheat.  
  4. Inappropriate edge preparation.


Remedies of Lack of Penetration

  1. Use high current.  
  2. Reduce the welding speed.
  3. Use the correct edge preparation according to the thickness of the plates.
See in figure welding defects like spatter, lack of fusion, misalignment, etc.
Which are described below.

defects in welding
Defects in Welding


These are small metal particles that are released during arc welding and settle on the parent metal and the weld surface.


Causes of Spatter

  1. Current being too high.
  2. Longer arc.
  3. Wetting of the electrodes.


Remedies of Spatter

  1. Use low current.  
  2. Use a small arc.  
  3. Use dry electrodes.



Due to the parent metal or pre-welded metal not getting hot enough, the molten weld metal tends to roll over them.

This is called overroll.


Causes of Overroll

  1. Excessive deposition of weld metal.

Remedies of Overroll

  1. Use high welding speed.
  2. Hold the electrode at right angles so as not to deposit too much metal on one side of the weldment.


Lack of Fusion

Weld joints where the deposited weld metal does not form a cohesive bond with the parent metal are known as lack of fusion.


Causes of Lack of Fusion

  1. No mixing of oxides or any other foreign material on the surface of the plates.
  2. The temperature of the parent metal or the preceding run does not rise high enough.

Remedies of Lack of Fusion

  1. Clean the surface thoroughly before welding. 
  2. Adjust the welding parameters to the correct values and use the appropriate welding techniques.



These defects occurred during welding when the weld joint shifted by some distance.


Causes of Misalignment

  1. Due to careless welding fit-up.
  2. Uneven plate thickness welding.

Remedies of Misalignment

  1. Checking straightness of the joint at the time of fit-up or tacking.
  2. Repair through using grinding, and match their nominal thickness to maintain better visually.



This is the incomplete portion of the weld above the base plate that does not maintain the proper bid height, then it is called underfill. 


Causes of Underfill

  1. Improper welding technology.
  2. Increase welding speed.


Remedies of Underfill

  1. Can be stopped by periodically checking the bid height using the weld gauge.  
  2. Wherever there is underfill, the welding will need to be refilled to maintain the proper bid height.


Concavity or Convexity 

This weld is the cavity or dome-like surface of the toe looking into the fillet weld which is known as concavity or convexity. 


Causes of Concavity or Convexity

  1. Occur due to not providing proper current and not maintaining travel speed.  


Remedies of Concavity or Convexity

  1. The repair is to grind the dome-like weld and give proper bid height for flatness, grinding, and mixing the weld with the plate near the plate side weld.


Excessive Reinforcement  

This is the height of the weld deposit over the base metal.  


Standard reinforcement should be 1/16" for the pipe and 1/8" for the plate or structure.  


Causes of Excessive Reinforcement

  1. Slow welding travel speed.
  2. Low ampere.

Remedies of Excessive Reinforcement

  1. Remove excessive reinforcement through grinding.

Now see in figure found defects in welding like burn through, overlap, etc. Which are described below in detail.


most common types of welding defects
Welding Defects


Burn Through 

When an open hole on the sheet is completely melted during welding it is called burn through 


Causes of Burn Through

  1. This is due to excessive heat input. 


Remedies of Burn Through

  1. Make proper V preparation on the molten area and re-weld the burnt weld part with less heat input.



If the face of the weld extends beyond the toe of the weld, it is known as overlap. 


Causes of Overlap

  1. Due to improper welding techniques.
  2. Electrode angle and travel speed.  


Remedies of Overlap

  1. The overlap should be grinded off, and the toe of the weld smoothened.


Arc Strikes 

This is a local weld test prior to welding on the parent metal saw near the weld joint. 


Causes of Arc Strikes

  1. This is due to the negligence of the welder and not using the trial plate with him to start the welding.  


Remedies of Arc Strikes

  1. Wherever arc strikes are found grinding or sanding by sander wheel if found deep, do a die penetration test after grinding. 

Arc Crater

The arc crater is the depression left after the end of the welding run.  


Causes of Arc Crater

  1. Occur due to incorrect welding termination technology. 


Remedies of Arc Crater 

  1. If no crack occurs in the pit, simply fill the hole and start welding.


Waviness of Bead 

Weld metal that is not parallel and does not cover the joint formed by the parent metal.


Causes of Waviness of Bead

  1. Due to the unsteady hand.


Remedies of Waviness of Bead

  1. Improve welding technique.


Contraction of the weld metal during welding forces the base metal to move.


Causes of Distortion

  1. This is occurred due to excessive heat.

Remedies of Distortion

  1. Use a clamp to hold the base metal in position.
  2. Select a low current for the electrode. 
  3. Increase travel speed.  
  4. Weld in small sections and allow to cool between welds.


I hope that I have cleared all your doubts about types of welding defects as well as their causes and remedies.


If you have still any doubts about this topic, you can ask through comments or direct mail me.


FAQ For Welding Defects

What is the most commonly used method of weld inspection?

A variety of methods are used to detect welding defects such as visual inspection, surface crack detection, etc. But most of the two methods of welding inspection are used, which are radiography and ultrasonic because this method examines the internal structure of the welding without destroying any welding part. In a group, these two methods are also called a nondestructive testing method.

Which of the welding defects occur due to incorrect welding techniques?

Cracks in the welding defects occur due to incorrect welding techniques.

What are the causes of excessive penetration in welding?

The main causes of excessive penetration in weldings are an improper selection of electrodes as well as running electrodes incorrectly.

What are the causes of underfill in welding?

Underfill occurred when using improper welding technology as well as increasing welding speed.

What is porosity in welding defects?

Porosity in welding defects is small pores of gas that are formed and spread in the weld metal.

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