Published on 30-Mar-2024

Liquid Penetrant Testing Vs Magnetic Particle Inspection: What’s The Difference?

Liquid Penetrant Testing Vs Magnetic Particle Inspection: What’s The Difference?

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When carrying out non-destructive testing, it is important to make sure that you use the most appropriate testing method to identify any flaws or defects. Two of the options that you can use when looking for surface defects are Liquid Penetrant Testing vs magnetic particle testing.

It is a good idea to find out more about them before you choose which would be best for the materials or structure that you want to test. In this article we unpack Liquid Penetrant Testing and Magnetic Particle Inspection, explaining each test, before looking at their similarities and differences.

What is Liquid Penetrant Testing?


Liquid Penetrant Testing (sometimes also known as Dye Penetrant Inspection) is used to detect surface-breaking defects. The penetrant testing definition states that a dye is used to highlight surface cracks and then it is measured under different light sources. Normally, it is used on non-ferromagnetic materials, (these are materials that are non-magnetic and contain no iron).

Liquid Penetrant Testing Procedure

1. The test requires proper preparation of the surface, including cleaning it of contaminants or coatings that may hinder the inspection.

2. The penetrant is applied evenly over the inspected area, either through spraying, brushing, or immersion, depending on the size and shape of the component.

3. Dwell time refers to the duration the penetrant remains on the surface before removal. It's a critical parameter as it determines the effectiveness of the test.

4. Excess penetrant is removed from the surface using a solvent or emulsifier after dwell time to prevent false indications during inspection.

5. After removing excess penetrant, a developer is applied to the surface, acting as a blotter to remove the penetrant from defects and spread it on the surface.

6. The surface is visually inspected under suitable lighting conditions, revealing indications like cracks, pores, or leaks as coloured or fluorescent marks against the background.

7. After inspection, the surface should be cleaned thoroughly to remove any remaining traces of penetrant and developer.

8. The results of the inspection are evaluated based on the type, size, and location of indications observed.

Liquid Penetrant Testing Procedure


Read More, Procedure for Liquid Penetrant Testing

What is Magnetic Particle Testing?