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HomeShop SuppliesAdhesives, Tapes, & SealantsSealantsSealant Adhesion Promoter3M Aerospace Sealant AC-131 BoeGel EP-II Blue Aerospace Sealant Conversion Coating - 2-Part Kit
3M Aerospace Sealant AC-131 BoeGel EP-II Blue Aerospace Sealant Conversion Coating - 2-Part Kit

3M Aerospace Sealant AC-131 BoeGel EP-II Blue Aerospace Sealant Conversion Coating - 2-Part Kit

AC-131 is a high-performance non-chromated conversion coating for applications on aluminum, nickel, stainless steel, magnesium and titanium alloys. The AC-131 conversion coating is appropriate for parts subsequently finished with epoxy-based and polyurethane-based organic coatings. It is a gradient coating that promoted enhanced adhesion as a result of the checmical interaction at the inorganic metallic interface on one side of the AC-131 coating and the organic primer on the other side. AC-131 provides an excellent environmentally friendly alternative to the high performance requirements for modern coating systems. This process is valid on alloys in the following forms: sheet, plate, foil, forging, and honeycomb core.
Use Instructions
Surface Preparation

AC-131 may be applied after cleaning to a "water-break free" surface. Alkaline cleaning will usually provide a "water-break free" surface. Chemical etching and deoxidizing is generally not required. Manual deoxidation can be accomplished by either Scotch Brite pad abrasion or sanding with #180 grit or finer Aluminum Oxide sandpaper.

Application Process

  • Strip aircraft
  • Alkaline clean to water-based-free surface
  • Apply AC-131 Conversion Coating
  • Prime and paint
  • NOTE: It may be necessary to deoxidize prior to applying AC-131 if a water-break-free surface is not achieved by the cleaning process.

    Application rate is approximately 1 quart of AC-131 for approximately 200 ft-squared of surface to be coated.

    Spray Application

    AC-131 coating solution can be sprayed onto the part surface using a variety of methords including HVLP guns, hand pump sprayers, etc. The solution is applied so as to completely wet the part surface with a mist. Excess solution may run off the part. Larger surface areas may require coating by sections.

    Brush Application

    Apply fresh AC-131 by brushing with a clean natural bristle brush or swabbing with a clean wiper, sheesecloth or gauze. Do not scrub with a brush or application. Apply solution to achieve complete coverage of surface to be treated. Brushes or wipers should not leave streaks on the surface.

    Allow coated part to drain for 3 to 10 minutes. If there is any surplus AC-131 solution that has pooled or collected in crevices, pockets, or other collection areas, including drip edges or fastener holes, use filtered compressed air to blow off excess solution. Do not splatter this excess solution onto adjoining part surfaces. Alternatively a cloth pre-wetted with AC-131 may be used to gently blot, not rub, the surface of pooled solution. Do not blow dry areas of the part that are able to freely drain.

    Dry/Cure of AC-131

    Dry the solution-coated parts under ambient conditions for a minimum of 60 minutes. Minimize contact with the part while drying. Exact drying time will vary depending upon part configuration of the part and ambient conditions. Alternately, after drying at ambient temperature for a minimum of 30 minutes parts may be heated to 140 degress F maximum for an additional 30 minutes minimum to facilitate drying. After drying, coated surfaces should be protected from contamination prior to applying the epoxy-based or polyurethane-based organic coating.

    How It Works

    A Sol-Gel preparation, AC-131 promotes enhanced adhesion as a result of the chemical interaction at the interfaces between the metal and the AC-131 and the AC-131 and the primer.

    Financial Benefits

    Time savings: Reduction in process flow time comparing traditional conversion coatings methods yields a minimum of a 35% reduction in labor-time.

    Enables Lean Manufacturing and Work Cell Manufacturing concepts, reducing cycle times.

    Hazardous materials: Elimination of hazardous chromate materials. Hazardous rinse water and waste water containment systems area eliminated.

    Minimal waste water associated with application of AC-131 as there is no rinsing.

    Environmental Benefits

  • Non-chromated
  • Water-based solution
  • No rinsing, dry in place
  • No fluorides
  • No strong oxidizers
  • No strong mineral acids
  • Health & Safety Precautions

    After using this product, to prevent ingestion, always wash your hands before eating or smoking. Read the Material Safety Data Sheet for more information.


    The shelf life of AC-131 2-part configuration is 12 months from the date of manufacture when stored in the original unopened containers between 40 degrees Fahrenheit and 100 degress Fahrenheit.

  • Superior adhesion of organic coatings to metal substrates.
  • Eliminates chromates from surface treatment process
  • Reduces hazardous materials and waste as compared to other conversion coating products and preparation methods.
  • No scrubbing or rinsing required
  • Versatile application methods; brush, spray, or dip applied
  • Available in kit sizes for specific applications: pints, quarts, gallons, pails and drums
  • Common surface preparation on mixed metal and non-metal substrates. Minimizes masking time
  • Process time savings over conventional conversion coating applications
  • Brightening or deoxidizing step may be eliminated
  • Specifications
    Qualified Specifications

  • BSMS-25-002 (Titanium) - Qualified (4-part clear ONLY)
  • BAC 5663 (Aluminum)
  • BAC 5665 (Titanium, CRES, Nickel)
  • BSPS 07-002 (Titanium)
  • D6-1816 (Aircraft Painting)
  • AAC 1.2 (Aluminum)
  • Testing

    Coatings systems using AC-131 have been tested successfully at the OEM and Depot level.

    The following testing has been performed with passing results:

  • Condensing humidity
  • Rain erosion
  • 3000 hour slat spray
  • Filiform corrosion
  • Wet and dry scribe adhesion
  • Paint softening
  • Acrylic crazing
  • Hydrogen embrittlement
  • Tests were performed using coatings systems (Primer & Topcoat).

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