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Penetrant testing, PT

Testing method for materials that utilize a penetrant and then a developer to identify any cracks in the surface of the material.

Illustration of Penetrant testing, PT

The process

A. The material to be tested must first be cleaned to remove any impurities.

B. A penetrant is sprayed on the surface of the material and allowed to penetrate any cracks, which usually requires about 5-30 minutes.

C. The penetrant is wiped with a clean, dry cloth until the cloth is no longer stained by the agent.

D. A - developer is applied to the surface and the penetrant is extracted from any cracks present. This process usually requires about 10-60 minutes. After extraction, the cracks will be surrounded by the penetrant which, thanks to the color contrast between the two, makes it easy to detect the presence of cracks.

Advantages and disadvantages
In comparison with alternative methods
Very sensitive method, able to find extremely small defects
Can be used on magnetic materials
Can be used on non-magnetic materials
Can be used in some plastics, can be used on some glass materials
small objects with complex shapes can be examined
Power supply is not required
Easy to understand
Requires only a little experience
Batch survey of small items possible
Large surfaces can be inspected quickly
Can only detect surface defects
Time consuming procedure and can rarely be performed faster than 30 minutes
The method usually can not be applied to painted products
Messy process
Interpretation of the results can sometimes be difficult
The material's surface finish can affect the sensitivity of the inspection