Method D: Fluorescent Penetrant Post-Emulsifiable, Hydrophilic

Guide to Method D (Post-Emulsifiable, Hydrophilic) processing per ASTM E-1417.

1. Pre Clean The Surface

Use Met-L-Chek® E-59A, R-503, R-504, or MLC 300LF to remove oil, grease and other contaminants from the test surface. The test surface must be clean, dry, and at a temperature of 40-125°F (4.4-52°C) before penetrant is applied.

Products to Use: 

E-59A, R-503, R-504, MLC 300LF:

2. Apply Penetrant

Apply Met-L-Chek® penetrant using spray, immersion, or wipe on. Wait a minimum of 10 minutes; 20 minutes if temperature is between 40-50°F (4.4-10°C) before proceeding to the next step.

Products to Use:

FP-93A(M) – Level 2, FP-95A(M) – Level 3, FP-97A(M) – Level 4:

3. Apply Emulsifier

  • Prior to emulsifier application, pre-rinse part with water. Water temperature: 50-100° F (10-38° C). Water pressure < 275kPa (< 40 psi); only long enough to remove bulk of surface penetrant. This step may be skipped when emulsifier is applied by spray.

Immerse part in gently agitated Met-L-Chek® E-58D emulsifier diluted to 17-20%. for 30 seconds to 2 minutes depending upon part roughness For spray applications emulsifier concentration should be
1-5% and spray contact for less than 2 minutes.

Products to Use:

E-58D:

4. Wash

Wash the part.

  • Water Temperature: 50-100°F (10-38°C).
  • Water pressure: < 40 psi (< 275 kPa).
    • If a hydro-air nozzle is used, limit pressure to < 25 psi (< 172 kPa).
  • Wash Distance: > 12 inches (>30 cm).
  • Wash Time: Only long enough to remove surface fluorescence under UV-A (black light).

For Water-Based Developers go to step 4.A

For Non Water-Based Developers skip to step 4.B

4.A Water Based Developers

Apply Met-L-Chek® D-76B, form “b”, developer or Met-L-Chek® D-78B, form “c”, developer by immersion or spray prior to drying.

  • Dry Time: only long enough to dry surface.
  • Dry Temperature: Not to exceed 160°F (71°C).

Products to Use: 

D-76B, D-78B:

4.B Non-Water Based Developers

Dry the part to be inspected then apply Met-L-Chek® D-72A, a dry powder developer, form “a”, by dusting or apply Met-L-Chek® D-70, a non aqueous developer, form “d”, by by spraying.

  • Dry Time: only long enough to dry surface.
  • Dry Temperature: Not to exceed 160°F (71°C).

Products to Use: 

D-72A, D-70:

5. Inspect

Wait a minimum of 10 minutes before inspection.

  • Maximum wait time is 1 hour for form “d” (non-aqueous) developers.
  • Maximum wait time is 2 hour for form “b” and “c” (aqueous) developers.
  • Maximum wait time is 4 hours for form “a” (dry powder) developers. If times are exceeded, clean the part and reprocess.
  • Use UV-A illumination of > 1000 μW/cm2 at 15 inches (38.1 cm). Inspect parts in a darkened area of < 2 foot candles (< 21 lux).

Other Fluorescent Inspection Methods

Method A: Water Washable

Method B: Post-Emulsifiable, Lipophilic

Method C: Solvent-Removable (Wipe-Off)