In flux-core welding, porosity is most often caused by which condition?

• A. Moisture
• B. Incorrect shielding gas
• C. Too fast travel speed
• D. Overheating of base metal

Answer: (A)

Moisture in the flux is the primary cause of porosity in flux-core welding. When the flux absorbs water, heating during welding releases hydrogen from that moisture. Hydrogen easily gets trapped in the molten metal and forms gas pockets as the weld cools, resulting in porosity. Keeping flux dry and properly stored reduces this risk, and welding practices should also minimize moisture exposure around the weld area. While shielding gas issues, travel speed, or overheating can contribute to weld defects in some cases, they are not as consistently responsible for porosity in FCAW as moisture in the flux.