What two types of indicating mediums are available for magnetic particle inspection?

• A. Iron and ferric oxides
• B. Wet and dry process materials
• C. high retentivity and low permeability
• D. Wet and dry process materials

Answer: (D)

Indicating media in magnetic particle inspection are used to reveal where magnetic flux leaks from defects, and they come in two forms: wet process materials and dry process materials. Wet process materials are fine magnetic particles suspended in a liquid carrier (oil or water-based). When the part is magnetized, the leakage draws the particles to the defect, producing a visible indication. They tend to offer high sensitivity and work well on clean, smooth surfaces, but require cleaning up after the inspection. Dry process materials are dry powders that cling to the surface under the magnetic field. They’re handy for field testing or rough surfaces and don’t involve liquids, though they can be less sensitive than wet methods unless fluorescent powders and UV lighting are used.