GMAW Welding Level 2 Practice Test 2026 - Free Practice Questions and Study Guide

Gas porosity happens when gas becomes trapped in the molten weld metal as it solidifies. The shielding gas is there to protect the weld puddle from the atmosphere, so if the shielding gas isn’t flowing properly (or leaks, or the wrong gas is used), air can enter and form pores. Cleanliness also matters—oil, grease, dirt, rust, or moisture on the workpiece can release gases or contaminate the weld and lead to porosity at the surface. The current setting mainly changes how much heat is put into the weld and how well it fuses; if the current is too low, you’ll get poor fusion or a cold weld, not porosity from gas entrapment. So claiming surface porosity is caused by insufficient current isn’t correct; shielding gas flow issues and surface cleanliness are the real culprits.