Editing Magnetic particle inspection (section)

== Magnetic particle powder ==
A common particle used to detect cracks is [[iron oxide]], for both dry and wet systems.

*Wet system particle range in size from less than 0.5 micrometers to 10 micrometers for use with water or oil carriers. Particles used in wet systems have pigments applied that fluoresce at 365 [[Nanometer|nm]] ([[ultraviolet]] A) requiring 1000&nbsp;μW/cm<sup>2</sup> (10 W/m<sup>2</sup>) at the surface of the part for proper inspection. If the particles do not have the correct light applied in a [[darkroom]] the particles cannot be detected/seen. It is industry practice to use UV goggles/glasses to filter the UV light and amplify the visible light spectrum (normally green and yellow) created by the fluorescing particles. Green and yellow fluorescence was chosen because the human eye reacts best to these colors.

[[File:US Navy 101220-N-7981E-121 Aviation Structural Mechanic 1st Class Charles Martens, a non-destructive inspection (NDI) technician.jpg|thumb|After applying wet magnetic particles, a U.S. navy technician examines a bolt for cracks under ultraviolet light.]]

*Dry particle powders range in size from 5 to 170 micrometers, designed to be seen in white light conditions. The particles are not designed to be used in wet environments. Dry powders are normally applied using hand-operated air powder applicators.
*Aerosol applied particles are similar to wet systems, sold in premixed aerosol cans similar to hair spray.

===Magnetic particle carriers===
It is common industry practice to use specifically designed oil and water-based carriers for magnetic particles. Deodorized kerosene and [[mineral spirits]] have not been commonly used in the industry for 40 years.{{when|date=April 2021}} It is dangerous to use kerosene or mineral spirits as a carrier due to the risk of fire.{{cn|date=May 2025}}