There is a difference between "magnaflux" (liquid penetration inspection)
and a magnetic particle inspection.
Magnaflux is the name of the company that developed the modern processes of "liquid penetration inspection"
www.cnde.iastate.edu/ncce/PT_CC/Sec.1.1/Sec.1.1.html"Liquid Penetrant Testing (PT) - Test objects are coated with visible or fluorescent dye solution. Excess dye is then removed from the surface, and a developer is applied. The developer acts as blotter, drawing trapped penetrant out of imperfections open to the surface. With visible dyes, vivid color contrasts between the penetrant and developer make "bleedout" easy to see. With fluorescent dyes, ultraviolet light is used to make the bleedout fluoresce brightly, thus allowing imperfections to be readily seen."
A magnetic particle inspection involves running a current of electricy through the part to magnatize it.
"The magnetic particle inspection method is one of the oldest and most widely utilized forms of nondestructive testing currently in use today. Magnetic particle testing uses magnetic fields and small magnetic particles, such as iron filings to detect flaws in components. In theory, it is a relatively simple concept. When a bar magnetis broken in the center of its length, two complete bar magnets with magnetic poles on each end of each magnet will result. If the magnet were cracked but not broken completely in two, a north and south pole will form at each edge of the crack, just as though the break had been completed. If iron particles were then sprinkled on this cracked magnet, these particles will be attracted not only to the ends of the magnets poles but also to the edges of the crack."
www.cnde.iastate.edu/ncce/MT_CC/Principles.html