AWSCWI.COM inspection of weld porosity to uphold AWS D1.1 Code welding requirements.

Porosity in Welding | 5 Amazing Ways to Prevent it

In Porosity in Welding by Matthew BehlenLeave a Comment

What Causes Porosity in Welding?

Porosity in welding is typically caused by Nitrogen and Oxygen absorption into the weld puddle from lack of adequate shielding gas. Hydrogen and oxygen molecules in the form of contaminants may also convert to gas and become trapped in the weld metal. These porous gas bubbles can weaken the weld and make it more susceptible to corrosion and loss of structural properties. There are a number of factors that can cause porosity, including:

  • Improper welding technique
  • Contaminated welding material
  • Inadequate shielding gas
  • High welding temperature
  • Moisture in the weld metal

How to Prevent Porosity in Welding

Prevent porosity in welding by following these few simple rules:

  • Using the correct welding technique for the material being welded
  • Using clean welding material
  • Providing adequate shielding gas
  • Controlling the welding temperature
  • Drying the weld metal before welding

If porosity does occur, it can be repaired by grinding or chipping out the defective weld metal and re-welding the area.

Porosity can have a significant impact on the strength and durability of a weld. It is important to take steps to prevent porosity in order to ensure that the welds are strong and reliable.

AWSCWI.COM inspection of weld porosity to uphold AWS D1.1 Code welding requirements.

AWSCWI.COM’s meticulous inspection for weld porosity in action.

Cluster Porosity in Welding

Cluster porosity in welding refers to a concentration of small gas pores or cavities formed within the weld metal. These clusters can significantly impair the mechanical properties and appearance of the weld. Here’s an overview covering its appearance, reasons for occurrence, prevention methods, and repair techniques:

What Does Cluster Porosity Look Like?

  • Appearance: A group of small, spherical voids or holes visible on the surface or inside the weld bead.
  • Pattern: Typically appears as a localized cluster within a specific area of the weld, rather than being evenly distributed.
  • Surface Indication: May be visible on the weld surface by a good welding inspection professional or detected through non-destructive testing methods if below the surface.

Reasons for Cluster Porosity Occurrence

  • Contaminated Base Metal or Filler Material: Presence of oil, grease, moisture, or rust can introduce hydrogen or other gases into the weld pool.
  • Improper Shielding Gas: Use of incorrect type, insufficient flow, or contamination of shielding gas can lead to gas entrapment.
  • High Welding Speed: Too rapid welding speeds can trap gas in the solidifying metal.
  • Poor Welding Technique: Incorrect technique or electrode manipulation can contribute to gas being trapped and weld slag inclusion.
  • Material Thickness: Thicker materials require proper preheating to avoid rapid cooling, which can trap gas.

How to Prevent Cluster Porosity

  • Clean Welding Surfaces: Ensure base and filler materials are clean and free of contaminants before welding.
  • Proper Shielding Gas Use: Select the appropriate shielding gas and ensure a consistent flow rate to protect the weld pool.
  • Optimize Welding Parameters: Adjust welding speed, voltage, and current to appropriate levels for the material and welding position.
  • Adequate Preheating: Preheat thicker materials to the recommended temperature to slow the cooling rate.
  • Use Low-Hydrogen Processes and Consumables: Opt for welding processes and consumables that minimize hydrogen in the weld area.
  • Use a rod oven for Low-Hydrogen Consumables to bake the moisture from the flux coating.

How to Fix Cluster Porosity

  • Grinding Out and Re-welding: Remove the affected area by grinding or gouging, then clean the area thoroughly before re-welding.
  • Preheat Before Re-welding: Apply preheat (if applicable) to reduce the cooling rate and minimize the risk of porosity on subsequent passes.
  • Adjust Welding Technique: Modify technique or parameters based on the analysis of what caused the porosity to prevent recurrence in the repair weld.


Preventing and repairing cluster porosity requires attention to detail in preparation, execution, and post-weld inspection to ensure the structural integrity and aesthetic quality of the weld. 

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