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Properties of Penetrant Materials (Surface Energy (To effectively wet out…
Properties of Penetrant Materials
Surface Energy
To effectively wet out a surface of material, the surface energy of the penetrant must be lower than the surface energy of the material.
Wetting occurs when the adhesive forces of the penetrant molecules are stronger than the cohesive forces
Density/ Specific Gravity
Affects the penetration speed
Viscosity
Resistance to flow
Affect surface wetting and crack penetration
Ultraviolet and Thermal Stability of Penetrant Indications
Exposure to a period of high intensity UV light decreases brightness
Experience heat degradation at an elevated temperature
Removability
must be removed effectively from the part surface to maintain the contrast between the indication and the background
Techniques of removal
Water washable
Post-Emulsifiable, Lipophilic (oil-based)
Solvent wipe
Post- Emuldifiable, Hydrophilic (water based)
Types of penetrant
Fluorescent Penetrants
fluoresce when exposed to ultraviolet radiation
brightness contrast
Visible Penetrants
provides high contrast against the white developer background
Colour contrast
H'ng Zi Xian 134314
Law Chun Yen 134317