The NDTs - Non-Destructive Testing


Non-destructive testing (NDT) is essential for detecting and evaluating flaws in materials without compromising their structural integrity. These tests identify cracks, pores and inclusions that can affect the strength and safety of materials. 

Metal-Chek is a pioneer in the production of inputs for NDT, with a focus on Liquid Penetrant and Magnetic Particle methods. This ensures maximum quality and reliability for your projects.

The Non-destructive testing is carried out on finished or semi-finished materials to verify the existence (or not) of discontinuities and/or defects, without altering their physical, chemical, mechanical or dimensional characteristics and without interfering with their subsequent use. In other words, tests are carried out to certify the quality of a particular part, without it being damaged or rendered unusable. 

These tests are one of the main quality control tools for materials and products, helping to guarantee quality, reduce costs and prevent accidents. 

They are used in manufacturing, construction, assembly, inspection and maintenance, and are widely applied to welds, castings, forgings, laminates, plastics, concrete, among others, in the Oil & Gas, Power Generation, Petrochemical, Automotive, Aeronautics, Railway, Shipbuilding, Steel, Civil Construction and other sectors.

The The NDTs - Non-Destructive Testing include methods capable of providing information about the defect content of a given product, the technological characteristics of a material, or even the monitoring of degradation in service of components, equipment and structures.

NDT methods are: ACFM (Alternating Current Field Measurement), Vibration Analysis, Calibration and Measurement Reliability, Dimensional Control, Eddy Current, Acoustic Emission, Visual Testing, Leakage, Liquid Penetrant, Electrochemical Potential Measurement, MFL (Magnetic Flux Leakage), Guided Waves, Magnetic Particles , Instrumented Pig, Thermography, Spot Testing, and Ultrasound.

To obtain satisfactory and valid results, the following items must be considered as fundamental elements of these tests:

  • Trained and qualified personnel;
  • Qualified test execution procedure based on standards and perfectly defined acceptance criteria;
  • Duly calibrated equipment.
    Besides the industrial use, the application of NDTs in Agriculture and Civil Construction has grown significantly.

Besides the industrial use, the application of NDTs in Agriculture and Civil Construction has grown significantly.

Learn more: (guide by End Abendi)

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Liquid Penetrant

The Liquid Penetrant Testing is considered one of the best test methods for detecting surface discontinuities in porosity-free materials such as: ferrous and non-ferrous metals, aluminum, metal alloys, ceramics, glass, certain types of plastics or organo-synthetic materials.

Liquid Penetrant is applied with a brush, by spraying with a spray gun or aerosol dispenser, or even by immersing the part in a tank containing the product, and then waiting a certain amount of time for it to infiltrate the discontinuities. This method is based on the phenomenon of capillarity, which is the power of a liquid to flow over extremely small areas due to its low surface tension. 

The penetration power is a very important characteristic since the sensitivity of the test is extremely dependent on it. This penetrant is removed from the surface by washing with water or removing it with solvents. 


The application of a developer (fine white powder with absorption power) must be made in the form of a uniform film that will absorb the penetrant from the discontinuities, showing their location with precision and great simplicity, although its dimensions will be slightly enlarged. 

Discontinuities in cast materials such as cold cracking and stress cracking caused by quenching or tempering processes are easily detected by the Liquid Penetrant method. As well as manufacturing or process discontinuities such as seams, double lamination or material overlap. 

Cracks in Welding and cracks caused by machining, material fatigue or even stress corrosion can also be detected by the Liquid Penetrant


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Magnetic Particles

The test by Magnetic Particles is used to detect surface and subsurface discontinuities in ferromagnetic materials. Defects such as cracks, weld cracks, cold joints, inclusions, cold drop, double lamination, lack of penetration, kinks, segregations, etc. are detected.
The test method is based on the generation of a magnetic field that runs across the entire surface of the ferromagnetic material. 

The magnetic lines of the induced flux in the material deviate from their path when they encounter a surface or subsurface discontinuity, thus creating a region with magnetic polarity highly attractive to Magnetic Particles. At the moment this magnetization is caused, the Magnetic Particles are applied to the part which, in turn, will be attracted to the location of the surface that contains a discontinuity, thus forming a clear indication of a defect.


Some typical examples of applications are castings of ferritic steel, forgings, rolled products, extruded products, weldsThe most common applications are for parts that have undergone machining or heat treatment (nuts and bolts), grinding cracks and many other applications in ferrous materials.
When detecting discontinuities, it is important that they are in such a way that they are "intercepted" or "crossed" by the lines of the induced magnetic flux; consequently, the workpiece must be magnetized in at least two directions offset by 90°.
To carry out this test, electromagnets are used, known as yokes - portable machines - or stationary magnetizing equipment for serial or standardized tests.

Metal-Chek Liquid Penetrant

Dubl-Chek Liquid Penetrant



Auxiliaries for Magnetic Particle Testing

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