Which of the following electrodes will NOT leave a good appearance in the weld bead?

The E6010 electrode is primarily known for its deep penetration and is used for making root passes in pipe welding. While it excels in producing high-quality welds in terms of strength, its slag properties and the way it produces the weld bead can lead to a less visually appealing finish as compared to other electrodes.

E6012, E7018, and E7024 electrodes are designed with features that promote better surface finishes. E7018, for instance, is known for producing smooth, aesthetically pleasing welds, and is often used in structural applications where appearance is important. Similarly, E7024 is designed for flat and horizontal welding, and it tends to leave a clean and attractive bead as well.

Therefore, the nature of the E6010's capabilities and its results in terms of appearance make it less effective at leaving a good visual quality in the weld bead compared to the other electrodes mentioned. This is why E6010 is identified as the electrode that will not leave a good appearance in the weld bead.