SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/weld-porosity-poor-shielding

What is the most common cause of porosity when MIG welding?

Poor shielding of the weld pool.

Start playing free

  1. Using a helmet lens that is too dark
  2. Poor shielding of the weld pool ✔
  3. Holding the gun too steady

Why: Porosity means tiny gas holes trapped in the weld. If shielding gas flow is blocked, turbulent or too low, air gets in and makes the holes.

Huh, didn't know that: Wind, spatter built up in the nozzle, or a wrongly set flow meter can all ruin the gas shield.

The dad joke
Porosity is the only time a Swiss cheese weld is bad news.
Like this card?
Play the game

References

Answer: Poor shielding of the weld pool. Porosity means tiny gas holes trapped in the weld. If shielding gas flow is blocked, turbulent or too low, air gets in and makes the holes.

  1. Hobart Brothers, MIG Troubleshooting for Metal-Cored and Solid Wire www.hobartbrothers.com/resources/technical-articles/mig-troubleshooting-for-metal-cored-and-solid-wire
    The most common cause of porosity when MIG welding is poor shielding of the weld pool
    Checked 2026-10-10.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game

Trades & ShopWhich base metal condition can lead to porosity in a weld?Trades & ShopWhich is a common cause of undercut in a MIG weld?Trades & ShopWhat polarity does MIG welding of mild steel use?

That's stuff everyone should know.