Welding Defects

Cold Lap

Cold Lap is a condition where the weld filler metal does not properly with the base metal or the previous weld pass material (inter-pass cold lap). The arc does not melt the base metal sufficiently and causes the slightly molten puddle to flow into the base material without bonding


Porosity is the result of “gas entrapment” in the solidifying metal. Porosity can take many shapes on a radio-graph but often appears as dark round or irregular spots or specks appearing singularly, in clusters, or in rows. Sometimes, porosity is elongated and may appear to have a tail. This is the result of gas attempting to escape while the metal is still in a liquid state and is called “wormhole porosity” All porosity is a void in the material and it will have a higher radio-graphic density than the surrounding area.

Cluster Porosity

Cluster Porosity is caused when flux coated electrodes are contaminated with moisture. The moisture turns into gas when heated and becomes trapped in the weld during the welding process. Cluster porosity appears just like regular porosity in the radio-graph but he indications will be grouped close together.

Slag Inclusion

Slag inclusions are non metallic solid material entrapped in weld metal or between weld and base metal. In a radio-graph, dark, jagged asymmetrical shapes within the weld or along the weld joints areas are indicative of slag inclusions.

Incomplete Penetration (IP) or lack of penetration (LOP)

Incomplete Penetration (IP) or lack of penetration (LOP) occurs when the weld metal fails to penetrate the joint. It is one of the most objectionable weld discontinuities. Lack of penetration allows a natural stress riser from which a crack may propagate. The appearance on a radio-graph is a dark area with well defined, straight edges that follows the land or root face down the center of the weldment.

 Incomplete fusion

Incomplete fusion is a condition where the weld filler metal does not properly fuse with the base metal. Appearance on radio-graph is usually appears as a dark line or lines oriented in the direction of the weld seam along the weld preparation or joining area.


Internal Concavity or Suck Back

Internal concavity or suck back is a condition where the weld metal has contracted as it cools and has been drawn up into the root of the weld. On a radiograph it looks similar to a lack of penetration but the line has irregular edges and it is often quite wide in the center of the weld image.

Internal or Root Undercut

External or Crown Undercut

Offset or Mismatch

Inadequate Weld Reinforcement

Excess Weld Reinforcement


Tungsten Inclusion

Oxide Inclusion

Discontinuities in TIG Welds

Burn Through

Common Mistakes to Avoid in Pipe Welding

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