What distinguishes penetrants from sealants?

The distinction between penetrants and sealants is fundamentally rooted in their intended purposes and applications in materials testing and maintenance. Penetrants are specifically designed for defect detection; they work by seeping into any surface discontinuities such as cracks or voids in a material. When excess penetrant is removed and the surface is treated with a developer, any trapped penetrant will cause a visible indication of defects to appear, allowing inspectors to identify flaws in the material that need to be addressed.

On the other hand, sealants are utilized to prevent leakage by filling gaps or spaces between materials. Their primary function is to create a barrier that can inhibit fluid penetration or airflow, ensuring that joints or connections remain sealed and functional. This key differentiation in function—where penetrants are geared towards revealing defects while sealants focus on prevention—underscores why the answer that identifies penetrants as tools for defect detection and sealants as materials for preventing leakage is accurate.