Surface Cleaning or Pre cleaning: The test surface is cleaned to remove any dirt, paint, oil, grease or any loose scale that could either keep penetrant out of a defect, or cause irrelevant or false indications. Cleaning methods may include solvents, alkaline cleaning steps, vapor de-greasing, or media blasting. Purpose of cleaning to remove dirt from defect open to surface.
Application of Penetrant: The penetrant is then applied to the surface of the item being tested. The penetrant is usually a contrast coloured mobile fluid with high wetting capability. The penetrant is allowed “dwell time” to soak into any flaws (generally 5 to 30 minutes). The dwell time mainly depends upon the type of penetrant being used, material being tested and the type & size of flaws.
Removal of Penetrant: First of all clean he surface with dry lint free cloth as best as possible. Take moist or damped cloth with solvent & clean entire surface until it no sign of penetrant on cleaning cloth. Important not spray the solvent on the test surface directly, because this can remove the penetrant from the flaws. If excess penetrant is not properly removed, once the developer is applied, it may leave a background in the developed area that can mask indications or defects. In addition, this may also produce false indications severely hindering the ability to do a proper inspection. Also, the removal of excessive penetrant is done towards one direction either vertically or horizontally as the case may be.
Application of developer: After excess penetrant has been removed, a white developer is applied to the sample.Apply Non aqueous developer over entire surface of item under examination.