Non-Destructive Testing (NDT) Practice Test

What is a requirement for a penetrant used in inspections?

1. It must evaporate quickly.

2. It must spread easily over the surface of the material.

3. It must change color under UV light.

4. It must be water-soluble.

The correct answer is: It must spread easily over the surface of the material.

A penetrant used in inspections must spread easily over the surface of the material to ensure thorough coverage. This characteristic is crucial because penetrants work by seeping into surface cracks and defects; thus, even and uniform spreading allows for better visibility of flaws when the inspection process is completed. If the penetrant does not spread adequately, it may miss defects, leading to inaccurate inspections and potential undetected failures in the material being examined. The other requirements, such as quick evaporation, changing color under UV light, or being water-soluble, serve different functions but are not universally necessary for all types of penetrant testing. Quick evaporation might be beneficial in certain contexts but could hinder defect visibility if the penetrant dries before inspection. Similarly, while some penetrants exhibit fluorescence under UV light, it's not a requirement for all penetrant tests. The same applies to water solubility, which can limit the types of penetrants available for certain materials or conditions.