List of some common weld defects:

• Incomplete fusion
• Porosity
• Cracks
• Lack of penetration
• Undercut
• Slag inclusions
• Tungsten inclusions
• Misalignment
• Weld bead irregularity
• Weld bead concavity
• Weld bead convexity
• Weld bead spatter
• Weld bead undercut
• Weld bead overlap
• Weld bead contamination
• Weld bead reinforcement
• Weld bead lack of fusion
• Weld bead lack of penetration
• Weld bead lack of sidewall fusion
• Weld bead lack of throat
• Weld bead lack of width
• Weld bead cold lap
• Weld bead hot lap
• Weld bead root cracks
• Weld bead root porosity
• Weld bead root penetration
• Weld bead root undercut
• Weld bead root reinforcement
• Weld bead root concavity
• Weld bead root convexity
• Weld bead toe cracks
• Weld bead toe porosity
• Weld bead toe penetration
• Weld bead toe undercut
• Weld bead toe reinforcement
• Weld bead toe concavity
• Weld bead toe convexity
• Weld bead face cracks
• Weld bead face porosity
• Weld bead face penetration
• Weld bead face undercut
• Weld bead face reinforcement
• Weld bead face concavity
• Weld bead face convexity

This is not an exhaustive list, as there may be other types of weld defects that are not listed here.