What is a desirable property of magnetic particles used for the inspection medium?

A desirable property of magnetic particles used in magnetic particle inspection is that they should have all the characteristics mentioned, including being non-toxic, possessing high permeability, and having low retentivity.

Being non-toxic is essential for safety, particularly in environments where operators may have prolonged exposure. Non-toxic materials ensure that the inspection process does not pose health risks to personnel or contaminate the components being inspected.

High permeability is a crucial property for magnetic particles. It allows them to easily become magnetized in the presence of an applied magnetic field, ensuring that any potential defects in the material can be effectively detected. High permeability enhances the sensitivity of the inspection process.

Low retentivity is also important. Low retentivity means that the particles do not retain significant magnetism once the applied magnetic field is removed. This characteristic is beneficial because it ensures that the particles will not interfere with subsequent inspections or applications as they return to a non-magnetic state easily.

In summary, incorporating all these characteristics into the magnetic particles ensures an efficient, safe, and effective inspection process, making option D the most comprehensive and desirable answer.