Magnetic Particle (MT) Inspection is used on most ferromagnetic material, typically on weld joints. It is effective for detecting surface and near surface discontinuities such as undercut, pinholes, porosity, cold lap, lack of weld fill, lack of fusion, and linear indications.

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There are multiple techniques of Magnetic Particle testing, but the two most utilized are Black and White, and Wet Fluorescent. All techniques utilize iron filing particles being applied to the test piece and then introducing an electromagnetic field via a Yolk or Prod to identify and locate discontinuities.