magnetic inspection oil

magnetic inspection oil

[mag′ned·ik in′spek·shən ‚ȯil]
(metallurgy)
A light petroleum oil, such as kerosine or naphtha, to which has been added fine ferromagnetic particles (usually colored black or red for contrast) to form an inspection penetrant; when the penetrant is applied to a metal surface being inspected, the ferrous particles accumulate in any surface cracks by magnetic attraction, thereby permitting the cracks to be discernible.