Which characteristic of a cleaning solvent is critical for penetrant testing?

The critical characteristic of a cleaning solvent used in penetrant testing is that it must not leave any residues. In penetrant testing, a liquid penetrant is applied to the surface to detect discontinuities or defects. For this process to be effective, the surface must be free of contaminants that could interfere with the penetrant's ability to seep into flaws.

If the cleaning solvent leaves any residues on the surface, it can create a barrier, preventing the penetrant from fully entering any cracks or pores. This could lead to false results or missed defects, thus compromising the integrity of the inspection process. Therefore, using a solvent that evaporates cleanly and leaves no residue is essential for ensuring accurate and reliable testing outcomes.

While factors like cost, availability, and biodegradability are relevant in choosing cleaning solvents, they do not directly impact the effectiveness of the penetrant testing process as significantly as the necessity for a residue-free surface does.