What kind of particle suspension is often used in MPI?

In Magnetic Particle Inspection (MPI), the particle suspension commonly used is either aqueous or solvent-based. This versatility allows MPI technicians to select a suspension that best suits the specific material and environmental conditions of the inspection process. Aqueous suspensions typically consist of minute magnetic particles suspended in water, often with additives to improve wetting and stability, making them easier to work with and safer for the environment. On the other hand, solvent-based suspensions use organic compounds as a carrier fluid, which can provide better penetration into smaller defects and are typically used with non-aqueous systems.

Water-based suspensions, while common, do not encompass the entire range of options available in MPI. Similarly, oil-based suspensions are a type of solvent-based system, but restricting to solely oil-based options limits the versatility and applicability to various inspection scenarios. Gas-based suspensions are not used in MPI, as the magnetic particles need to be in a fluid medium to effectively carry and group around defects in the material being inspected. Thus, the broad classification of both aqueous and solvent-based suspensions captures the primary types used in practice while offering flexibility for different materials and conditions during inspections.