Which crack detection method should I use?

It depends on the material, defect type and access: MPI for surface cracks in steel, dye penetrant for surface cracks in any non-porous material, eddy current for cracks through paint, and ultrasonic for internal and sub-surface cracks.

What is the difference between MPI and dye penetrant?

MPI detects surface and slightly sub-surface cracks in ferromagnetic (steel) components, while dye penetrant works on any non-porous material but only finds cracks open to the surface.

Can crack detection find internal cracks?

Yes — ultrasonic testing detects internal and sub-surface cracks, whereas MPI, dye penetrant and eddy current are surface methods.

NDT Methods

Crack Detection Methods Compared

MPI, dye penetrant, eddy current or ultrasonic? Here's how to choose the right crack detection method.

2 June 2026 2 min read

Choosing the Right Method

Different crack detection methods suit different materials, defect types and access. Choosing correctly is key to reliable detection.

Method Comparison

A quick guide:

MPI — surface cracks in steel
Dye penetrant — surface cracks in any non-porous material
Eddy current — surface cracks through paint
Ultrasonic — internal and sub-surface cracks

Related Services

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Crack Detection MPI ECT UT

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