Non Destructive Testing

An inspection method which does not permanently alter the article

non destructive testing

Non Destructive Testing (NDT) is an inspection method which does not permanently alter the article being inspected, making it a highly-valuable technique that can save both time and money in product evaluation, troubleshooting, and research.


inspection methods Liquid Penetrant Inspection is based upon capillary action, where low surface tension fluid penetrates into a clean and dry surface. Penetrant may be applied to the test component by dipping, spraying, or brushing. After adequate penetration time has been allowed, the excess penetrant is removed, a developer is applied. The developer helps to draw penetrant out of the flaw allowing the indication to becomes visible to the inspector. Inspection is performed under ultraviolet or white light, depending upon the type of dye used.

Magnetic Particle Inspection is used for the detection of surface and sub-surface defects in ferrous materials. An externally applied magnetic field or electric current is applied to the material. The iron oxide particles held in suspension are attracted to the surface field in the area of the defect and hold on to the edges of the defect to reveal it to the inspector. MPI can also be performed with dry particle allowing indications to be inspected under white light.


Temper Etch Inspection is typically performed by chemically etching the components surface with a solution of Nitric Acid in alcohol or water. The etched surface is examined visually to detect detrimental microstructural modifications (e.g. untempered martensite) that result from overheating during improper surface grinding.

Pre-Penetrant Etch uses either acid or caustic solutions to remove 0.0001″ to 0.0002″ of material from the parts surface. This will allow the Penetrant inspector to properly evaluate any surface indications which may have been hidden during the manufacturing process.

Passivation is a final treatment used after FPI or MPI to create a passive layer which is free from all contaminants such as machine metal which may cause corrosion or failure throughout the life of the component.