Porosity is a common welding defect where small cavities or pores form in the weld metal due to trapped gas during solidification. These pores can be visible on the surface or hidden inside the weld (requiring NDT to detect).
Why is Porosity a Serious Issue?
Because it reduces:
✔ Strength – Creates stress points.
✔ Ductility – Makes weld brittle.
✔ Load-Bearing Capacity – Reduces effective area.
✔ Integrity – Can cause cracks & failure.
✔ Pressure Tightness – Not suitable for sealing (e.g., tanks, pipes).
🔍 Main Causes of Porosity
1️⃣ Contamination
Moisture: Damp electrodes, wet base metal, condensation.
Oil, Grease, Paint: Cutting fluids, anti-spatter sprays.
Rust & Dirt: Mill scale or corrosion introduces gas.
2️⃣ Shielding Gas Issues
Inadequate or excessive flow.
Leaks in hoses or fittings.
Wrong gas type or wind blowing gas away.
3️⃣ Welding Technique Errors
Long arc length.
Improper travel speed or torch angle.
4️⃣ Material Problems
Damp or contaminated filler wires.
Base metal with high sulfur.
✅ How to Prevent Porosity
✔ Clean Thoroughly: Remove rust, oil, paint, and dirt before welding.
✔ Store Consumables Properly: Keep electrodes dry in rod ovens.
✔ Ensure Proper Gas Coverage: Correct flow rate (20-25 CFH), no leaks, shield from wind.
✔ Use Correct Technique: Maintain short arc length, proper travel speed, and parameters.
✔ Prepare Joints Well: Ensure good gas access to weld zones.
Quick Tip:
Most porosity issues come from poor cleaning and moisture. 80% of problems can be avoided with proper preparation!
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