During visual inspection, which defect is most likely to be missed?

• A. Poor surface finish
• B. Lack of penetration
• C. Lack of fusion
• D. Excess penetration

Answer: (C)

The defect most likely to be missed during visual inspection is lack of fusion. This is primarily because lack of fusion refers to the insufficient bonding between the weld metal and the base materials or between layers of weld metal itself. Visually, it can be extremely challenging to detect as the surface may appear intact, and the lack of fusion may only be detected through other methods such as non-destructive testing.

In the context of visual inspection, the inspector often looks for surface discontinuities and overall surface quality. Defects like poor surface finish can be relatively easy to identify since they manifest as visible irregularities. Similarly, lack of penetration and excessive penetration tend to create more apparent anomalies in the weld profile, making them detectable via visual inspection methods. In contrast, lack of fusion may not present any surface-level indicators that would alert the inspector to an underlying issue, thereby making it more likely to be overlooked. This is especially true if there are no external signs such as cracks or blowholes that might suggest a deeper problem.