Liquid penetrant tests are widely used in the industry and are especially helpful, easy and rapid for application on parts. The test, a nondestructive means of locating and determining the severity of surface defects or surface defects with surface openings in materials, IS based upon capillarity( l '21. So, capillarity or capillarity attraction is one of the three basic physical phenomena, which are wetting-contact angle, capillarity reaction and spriting. The materials, processes and procedures are designed to facilitate capillarity through the surface discontinuities for sensitive application of liquid penetrant testing.
The first step in the penetrant inspection process is to clean the surface and existing surface flaws of contami-nants that might interfere with penetrant performance. After preparation of parts which is required prior to liquid penetrant testing, the liquid penetrant is applied to the surface of the part, and sufficient 'penetration time' is allowed for penetration into surface discontinuities12' 31
After the penetration time, the excess penetrant will be removed with a lint-free cloth, water, and occasionally with an approved solvent based excess penetrant remover, This removal process permits the penetrant in the dis-continuities to remain, dried and application of the solvent-based developer.
The test sensitivity depends upon the type of materials that are used in the test stages and the characteristics of defects and test materials. Capillary action is important in those processes ill For example; the penetration time