How to Use Magnaflux Dye Penetrant

Written by alec chapman
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How to Use Magnaflux Dye Penetrant
Any ferrous or non-ferrous metallic component is suitable for dye penetrant inspection. (gear device image by Pali A from

Magnaflux dye penetrant is a non-destructive test method for determining if a metallic component has any number of surface flaws. It can be used to check for fine surface cracks that are otherwise invisible to the naked eye, as well as porosity, cold shuts, hot tears and other casting defects. The primary advantage of dye penetrant inspection is that it can be accomplished without the use of large and expensive specialised machines that are typically required for the other varieties of non-destructive testing.

Skill level:
Moderately Easy

Things you need

  • Dye penetrant spray
  • Developer spray
  • No-residue degreasing solvent
  • Clean rags or terry-cloth towels
  • Stiff bristle brush
  • Safety Glasses
  • Gloves

Show MoreHide


  1. 1

    Clean the part to be inspected thoroughly using a degreasing solvent. Force dirt and grime out of hard-to-reach areas using a stiff-bristled brush that is softer than the part. Use a steel wire brush on ferrous components and a natural or synthetic fibre brush on aluminium and magnesium components. Use a clean rag to dry the part as much as possible. Allow the remaining solvent to evaporate in an open area free from sources of ignition and check for any remaining surface contamination. Repeat this step if any debris remains. Remove any protective paint or sealer from the part as this will also affect the results of the test.

  2. 2

    Use the spray can of penetrant dye to completely cover the surface of the part. Repeat the cleaning procedure if the dye does not adhere to certain areas of the part that may still have an oil or grease film. Let the penetrant infiltrate into the surface of the part for up to 30 minutes. If the penetrant dries completely, an additional light spray coat will be required before proceeding to the next step.

  3. 3

    Wipe the penetrant off the surface using another dry clean towel. Spray solvent sparingly onto the towel to slightly moisten it to help to remove any stubborn dried penetrant. Ensure that the towel is not too wet, as this can wash penetrant out of any potential cracks or defects. The towel should not leave any residue or trace of solvent immediately after it has passed over a surface.

  4. 4

    Shake the spray can of developer vigorously for up to 60 seconds. Hold the spray can 8 to 12 inches away from the part and try to cover only small areas at a time. Spray the developer lightly over the surface of the part until a thin, uniform, pale white film is produced over the entire surface. Watch the part as the developer dries.

  5. 5

    Inspect the developed part surfaces. Defects will appear as bright red lines or dots. Larger and brighter spots that continue to grow over time indicate more extensive or deep defects below. Parts without any defects can now be reused. Clean all parts to be reused with solvent and a rag.

Tips and warnings

  • More time should be spent cleaning the part than performing the inspection, as the results of a well-cleaned part will be much clearer.
  • Always use proper personal protective equipment when using solvents and spray chemicals. Take extra precautions to ensure these chemicals stay away from your eyes, face and skin.
  • Used mechanical components are often sharp, and proper handling techniques should be used to prevent lacerations.

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