How to Fix Porosity in TIG Welding (Step-by-Step)

Porosity is one of the most frustrating defects that can ruin the look and strength of a weld. Even skilled welders face it from time to time, especially when working with stainless steel or aluminum. The good news is that porosity is completely preventable — if you understand its causes and follow the right steps. In this guide, we’ll break down how to fix porosity in TIG welding, step by step.

1. Understand What Causes Porosity

A realistic industrial workshop scene showing a TIG welder working on a slightly rusty and oily metal surface, with visible small pores and bubbles forming on the weld due to contamination and poor gas coverage — Emin Academy

Before fixing porosity, you need to know why it happens. Porosity in TIG welding occurs when gas becomes trapped inside the molten weld pool. The main causes are dirty materials, moisture, oil, rust, or even poor shielding gas coverage. Identifying the root cause is the first step toward clean, solid welds.

2. Clean the Base Metal Thoroughly

A realistic industrial workshop scene showing a welder cleaning a rusty metal surface with a stainless-steel wire brush before TIG welding to remove contaminants and prevent porosity in the weld — Emin Academy

Contamination is the number one reason for porosity. Always clean your metal with a stainless-steel brush or acetone before welding. For aluminum, remove the oxide layer with a dedicated brush. Even fingerprints or dust can trap gas in the weld pool. Remember — in TIG welding, cleanliness equals quality.

3. Check Your Shielding Gas Supply

A realistic industrial workshop scene showing a TIG welder inspecting the argon shielding gas system for leaks at the regulator, hoses, and torch connections; maintaining a steady flow of 20–30 CFH ensures proper gas coverage and prevents porosity — Emin Academy

Use 100% argon for most TIG welding applications. Check the regulator, hoses, and torch connections for leaks. A flow rate between 20-30 CFH (10-15 L/min) is ideal. Too much gas can create turbulence, while too little allows oxygen and nitrogen to enter the puddle — both cause porosity.

4. Inspect the Tungsten and Torch Setup

A realistic industrial workshop scene showing a welder wearing safety gloves and a respirator mask while sharpening a tungsten electrode lengthwise on a grinder; maintaining a clean, properly shaped tungsten tip ensures a stable arc and prevents porosity in TIG welding — Emin Academy

A damaged or contaminated tungsten tip can cause arc instability and poor gas shielding. Sharpen the tungsten lengthwise and keep the tip clean. Ensure the gas nozzle is the correct size for your job and not partially blocked by spatter or dust. A stable arc = fewer gas pockets.

5. Keep Filler Rods Clean and Dry

A realistic industrial workshop scene showing a sturdy metal box filled with neatly arranged TIG welding filler rods labeled ER70S-2, 308L, and 4043, placed on a metal workbench with an argon gas cylinder and blurred industrial equipment in the background — Emin Academy

Filler rods often absorb oil or moisture from your hands or the environment. Store them in a sealed container, and wipe them before use. In TIG welding, even a small amount of contamination on the filler can introduce hydrogen into the weld pool, leading to bubbles and weak joints.

6. Control Heat Input and Arc Length

A realistic industrial workshop scene showing a TIG welder controlling heat precisely with a foot pedal while maintaining a short 3 mm arc length, keeping the weld puddle smooth and stable without overheating — Emin Academy

Too much heat or a long arc can cause the molten metal to absorb more gas. Maintain a short, consistent arc length — around 1/8 inch (3 mm) — and use the foot pedal to manage heat precisely. The goal is to keep the puddle smooth and stable, not boiling or splattering.

7. Ensure Proper Gas Coverage (Back Purging for Stainless)

A TIG welder performing stainless steel pipe welding with argon back purging in an industrial workshop, gas cylinders visible in the background ensuring clean root protection and preventing oxidation — Emin Academy

When welding stainless steel or titanium, use back purging. This process floods the back side of the weld with argon, preventing oxidation. Without it, the root side becomes rough and porous. Back purging is one of the most effective TIG welding techniques for preventing internal porosity.

8. Reweld the Affected Area Carefully

A realistic industrial workshop scene showing a welder grinding out porosity from a stainless steel TIG weld on a pipe using an angle grinder; sparks fly as the welder carefully cleans only the weld bead area before re-welding, with TIG equipment and argon cylinders visible in the background — Emin Academy

If you already have porosity in your weld, grind or cut out the affected area completely. Then, reweld using the corrected settings — clean surface, stable gas flow, and proper heat control. Never try to cover porosity by welding over it; the defect will remain inside.

Reviewed and verified by: A. Emin Ekinci – Metal Fabrication Specialist