3M™ Aerospace Sealant AC-251

  • Options available
  • | Select product options for IDs.

Maintains flexibility and bond strength for reliable performance on aircraft transparencies

Contains no added solvents to prevent crazing on transparent surfaces

Formulated to resist UV degradation

View more details
Frequently viewed resources
Tech Data Sheet (PDF, 94KB)Safety Data Sheet (PDF, 0B)
Find a Distributor


  • Maintains flexibility and bond strength for reliable performance on aircraft transparencies
  • Contains no added solvents to prevent crazing on transparent surfaces
  • Formulated to resist UV degradation
  • Black color provides clean exterior mold lines
  • Non-sag formula is easy to mix and apply by injection dispenser or spatula for fast application time
  • Qualified to multiple aerospace material specifications

3M™ Aerospace Sealant AC-251 is our two-part, manganese dioxide cured, polysulfide based sealant for aircraft windshields, canopies and windows. This quick curing product is easy to tool, and the non-sag formula holds its shape on vertical and horizontal surfaces. AC-251 is effective for acrylic, glass, and polycarbonate aircraft transparencies and exterior mold line applications.


Single airline passenger window seat
Fast-curing window and canopy sealant AC-251 is formulated to resist UV degradation in service
Clearly Effective
3M™ Aerospace Sealant AC-251 is designed to create an aesthetically pleasing and highly effective seal. Its formulation prevents crazing on adjacent transparent surfaces, making our black, non-sagging product look as good as it performs. AC-251 is designed for optimal performance when used with 3M™ Adhesion Promoter AC-137.

When mixed, 3M Aerospace Sealant AC-251 is a thixotropic paste formulated for easy application by injection gun or spatula. AC-251 provides superb tooling properties and quick cure times to help meet a wide range of production process needs. It is available as a two-part product in both kit and bulk-packaging forms, to meet a variety of application requirements. AC-251 is ideal for sealing out moisture and corrosive elements. It is available in 1/2, 1 and 2 hour work lives and typical cure times of 4, 7 and 9 hours, respectively.

See 3M™ Mix & Dispense Equipment
Product Class Application Life* Typical Tack Free Time* Typical Cure Time*
(30 Shore A Hardness)
Specific Gravity Applications
3M Aerospace Sealent AC-251 B-1/2 1/2 hour 4 Hours 4 Hours 1.59 Window & Canopy
B-1 1 hour 5 hours 7 hours
B-2 2 hours 8 hours 9 hours
*Measured at Standard Conditions (77°F / 25°C and 50% Relative humidity )

Smart Sealants, Robust Results
When you use 3M Sealants, you're applying science, ingenuity, aerospace expertise and cost saving solutions. They have outstanding resistance to aviation fuel and petroleum products common to the aircraft industry. 3M™ Aerospace Sealant AC-251 is carefully formulated for customers in the aerospace industry. Always read the SDS and Tech Data Sheet along with your internal governing documents prior to use.

Our Best for Your Best
3M is proud to partner with organizations across the spectrum of aerospace and related industries. Enabling efficiencies, reducing process times and lowering aircraft weight is how we execute our never-ending mission to offer best-in-class adhesives, sealants, surface protection products and composite resins that effectively reduce costs on multiple fronts. Professionals across the industry know the numerous advantages of 3M Aerospace. Our brand is widely recognized for the highest standards of quality and performance, adding value to the final results. By engineering reliability, longevity and value into all of our products, we have a history of saving money by reducing waste, rework and time.


Aerospace specifciation portal
Find what you need in our aerospace specification portal.

3M maintaints partnerships with every major aircraft OEM in the world. Find your spec today.


Typical properties


Contact a Sales Rep

  • All fields are required unless indicated optional

  • 3M takes your privacy seriously. 3M and its authorized third parties will use the information you provided in accordance with our Privacy Policy to send you communications which may include promotions, product information and service offers. Please be aware that this information may be stored on a server located in the U.S. If you do not consent to this use of your personal information, please do not use this system.

  • Submit

Our apologies...

An error has occurred while submitting. Please try again later...

Thank you!

Your form was submitted successfully. A member of our team will be in touch.