What is Magnetic Particle Testing (MT)? A Guide for NDT Firms

Magnetic particle testing (MT) is a non-destructive testing method that detects surface and near-surface discontinuities in ferromagnetic materials. It is widely used for weld inspection, casting control, and structural steel component examination. Because it is fast to apply and its results are visually interpretable, MT is a preferred method in field conditions.

How does MT work?

In MT, the material is magnetized and iron oxide particles (wet or dry) are applied to its surface. Where a discontinuity exists at or near the surface, the magnetic field is disrupted at that point; particles accumulate at the disruption and form a visible indication.

The basic steps are:

1. Surface preparation: Paint, oil, and dirt are removed.
2. Magnetization: Applied using a yoke, prod, or contact method.
3. Particle application: Wet fluorescent or dry colored particles are used.
4. Examination: The surface is inspected under UV-A or white light.
5. Demagnetization: Where required, the material's residual magnetic field is removed.
6. Recording: Indication size, orientation, and location are reported.

Which materials is MT used on?

MT can only be applied to ferromagnetic materials — iron, steel, nickel, and cobalt alloys. It does not work on non-magnetizable materials such as aluminum, austenitic stainless steel, or titanium.

Preferred applications:

• Weld seams and heat-affected zones (HAZ)
• Cast and forged components
• Structural steel profiles and connection points
• Pipe and vessel welds (as a complement to PE inspection)

Standards used in MT inspection

• ISO 17638 — Magnetic particle testing of welds
• ASTM E709 — Standard guide for magnetic particle testing
• EN ISO 9934-1 / 9934-2 — General principles and methods
• ASME Section V, Article 7 — Pressure vessel and pipeline applications

MT personnel qualification

Under EN ISO 9712, MT personnel are certified at Level 1, 2, and 3. The certificate scope (e.g., welds or castings) must match the inspection type. In firms where multiple technicians work with different certificate scopes, manually tracking this match is error-prone.

How NDT software organizes MT documentation

Information that must be captured during an MT inspection includes: equipment calibration, particle batch number, light intensity measurements, ambient temperature, and indication sketches. Collecting this on paper and then re-entering it into a computer is both a time loss and a source of archive inconsistencies.

Good NDT management software provides:

• Digital recording of method, standard, particle type, and equipment details on the MT work order
• Automatic check that technician certificate scope matches work order requirements
• Digital MT report template with indication recording and sketch fields
• UV meter and light measurement value logging
• Filterable MT inspection archive ready for TÜRKAK audits

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