Is it true that solar flux is preferred for multi-pass welds because it only needs to be applied once?

The assertion that solar flux is preferred for multi-pass welds because it only needs to be applied once is not accurate. Solar flux, or flux in general, is typically used in welding processes to protect the weld joint from contamination by atmospheric elements, particularly during the welding process. In multi-pass welding, each pass may require its own application of flux to ensure that the surface is clean and free of oxides or other contaminants that could compromise the integrity of the weld.

Using solar flux only once may not provide adequate protection for subsequent passes, especially in environments where oxidation can occur quickly. Therefore, it is essential to apply flux as needed for each pass to maintain the quality and strength of the weld.

The other options touch on varying conditions and specific instances, but the core reasoning lies in the fundamental requirements of the welding process. Multi-pass welds require careful attention to the condition of the joint prior to each pass to ensure optimal outcomes.