These pre-penetrant etch formulas were developed by jet engine companies for NDT inspection of different metals. They will remove smeared metal from the surface and prepare the part for the subsequent fluorescent penetrant inspection (FPI).

Etchants from GE, Honeywell, and P&W specifications:

  • Class B, for titanium alloys
  • Class C, Schantz reagent, for stainless steel and alloys below:
    • 300- and 400-series stainless steels, precipitation hardening steels, A-286, maraging steels, Rene’ 77, Rene’ 80, Rene’ 95, Rene’ 100, Rene’ 125, Udiment 500, Sel, Sel 15, TD-NiCr, Waspalloy, 17-4 PH, Hastelloy B, C and W.
  • Class E, for carbon steel
  • Class F, for aluminum alloys
  • Class G, for Inco-718

Etchants from CFM specifications:

  • S1093 titanium alloy etchant
  • S1095 carbon steel etchant (equivalent to Class E)
  • S1096 aluminum alloys etchant
  • S1098 stainless steel etchant (equivalent to Class C)


  • Cold ferric chloride local etch solution, Task 70-11-39-100-501 (equivalent to Class G)
  • Sodium hydroxide 15% with corn starch (please call)
  • Rolls-Royce formulas, Class A, ASTM 187 (please call)