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Polysulfide Sealants

3M™ Aerospace polysulfide sealants for integral fuel tanks, fuselage structures, canopies, and windshields — manganese dioxide cured, solvent-free, and qualified to AMS-S-8802 across every major aircraft platform. From fast-curing brushable Class A fluids to non-chromate low-density Class B pastes, 3M’s AC-Series covers the full sealing lifecycle from assembly through MRO.

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Coast-Line stocks the full 3M™ Aerospace AC-Series polysulfide sealant line — six products covering every sealing zone on the aircraft. All 3M sealants are two-component, manganese dioxide cured, solvent-free polysulfide compounds. They resist aviation gasoline, jet fuel, and petroleum products common throughout the aerospace industry, and are available across multiple work lives (½, 1, 2 hour) to match your assembly or MRO process requirements. Also available in Pre-Mixed Frozen (PMF) format for queue-free shop floor application. 

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Understanding AMS-S-8802 Sealant Classes
Class A
Brushable Liquid
Pourable liquid consistency when mixed. Applied by brush or roller. Used for wet installation of fasteners, faying surface coating, and overcoating fastener heads. Flows into tight spaces and provides uniform coverage across large flat surfaces.
Class B
Thixotropic Paste
Low-sag, non-flowing paste when mixed. Applied by extrusion gun, spatula, or injection kit. Used for fillet sealing, bead sealing, void filling, and caulking joints. Stays in place on vertical or overhead surfaces without sagging before cure.

Class C
Faying Surface
Low viscosity formula designed specifically for faying surface sealing — applied to mating surfaces before assembly so they are sealed as the joint is closed and torqued. Provides the thinnest, most uniform bondline for structural joints.

Fuel Tank
AC-350 — fast-cure, intermediate density, for integral fuel tank and fuselage sealing. Available Class A & B.
Fuselage
AC-730 — corrosion-inhibitive, non-chromate, standard density fuselage sealant for aluminum and dissimilar metal joints.
Low Density
AC-735 & AC-380/AC-770 — 25–33% lighter than traditional sealants. Weight savings for fuselage, fuel tank, and void fill.
Canopy & Windshield
AC-251 — no-craze formulation for acrylic, glass, and polycarbonate aircraft canopies and windshields.
01

Fuel Tank Sealants

Fuel Tank Sealant
3M · Aerospace
3M™ Aerospace Sealant AC-350 — Integral Fuel Tank
The go-to 3M fuel tank sealant — an intermediate density, fast-curing polysulfide family providing outstanding resistance to aviation fuels and petroleum chemicals across integral fuel tank and fuselage sealing applications. Two-component, manganese dioxide cured, solvent-free. Maintains flexibility and bond strength on aluminum, titanium, steel, stainless steel, glass, and many coatings under extremes of temperature, weathering, and stress. Low shrinkage on cure means less rework. Available in Class A (brushable liquid — for fastener overcoating and faying surfaces) and Class B (non-sag thixotropic paste — for fillet sealing, extrusion gun, or spatula). Three work lives for each class match your assembly tempo. Also available PMF (Pre-Mixed Frozen) for mix-error-free application.
AMS-S-8802 AMS-S-3276E Class A · Class B Fast Cure MnO₂ Cured Solvent Free PMF Available
AC-350 Key Data
ChemistryPolysulfide · 2-part MnO₂ cure
Service Temp−65°F to +250°F
ClassesA (liquid) · B (paste)
Work Lives½ hr · 1 hr · 2 hr
DensityIntermediate
Primary SpecAMS-S-8802 · AMS-S-3276E
PMF FormatAvailable
02

Fuselage Sealants

Fuselage Sealant
3M · Aerospace
3M™ Aerospace Sealant AC-730 — Non-Chromate Fuselage
Engineered specifically for fuselage sealing — a standard density, manganese dioxide cured polysulfide sealant formulated for easy tooling with a corrosion-inhibitive system that contains no added chromate. An important advantage for programs pursuing chromate reduction (OSHA and RoHS compliance) without sacrificing corrosion protection between aluminum and dissimilar metal joints. AC-730 provides an effective barrier against galvanic corrosion between dissimilar metals including aluminum-to-titanium and aluminum-to-composite interfaces throughout empennage and fuselage structures. Maintains flexibility and bond strength under extremes of temperature, weathering, and mechanical stress. Highly resistant to jet fuel, chemicals, and petroleum products. Designed for easy tooling — the mixed paste tools out cleanly and holds its shape for fillet sealing.
No Added Chromate Corrosion Inhibitive MnO₂ Cured Dissimilar Metal Joints Easy Tooling Empennage · Fuselage
AC-730 Key Data
ChemistryPolysulfide · 2-part MnO₂ cure
Service Temp−65°F to +250°F
DensityStandard
ChromateNone added — no Cr(VI)
ClassB (thixotropic paste)
Best ForFuselage · dissimilar metal joints
03

Low Density Sealants

Low Density Fuselage
3M · Aerospace
3M™ Aerospace Sealant AC-735 — Lightest Fuselage Sealant
One of the lightest sealants available — a non-chromate, corrosion-inhibitive, fast-cure, low density polysulfide fuselage sealant. At 25% lower density than traditional sealants, AC-735 delivers meaningful aircraft weight reduction at scale, particularly across wide-body programs with thousands of linear feet of fillet and faying surface seals. Manganese dioxide cured, solvent-free. Provides an effective seal on metals, composites, organic coatings, and between dissimilar metals. Highly resistant to jet fuel and chemicals throughout the aerospace industry. Available in both Class A (pourable liquid, brush or roller — ideal for fastener overcoating) and Class B (non-sag paste, extrusion gun or spatula — for fillet sealing). Fast cure for reduced flow times. Provides an alternative to traditional chromate-containing sealants for programs meeting OSHA and environmental requirements.
−25% Density vs. Traditional No Added Chromate Fast Cure Class A · Class B Composites · Metals · Coatings MnO₂ Cured
AC-735 Key Data
Density Saving~25% lighter than traditional
Service Temp−65°F to +250°F
ClassesA (liquid) · B (paste)
Cure RateFast
ChromateNone added
ApplicationFuselage · empennage · composites
Low Density Fuel Tank
3M · Aerospace
3M™ Aerospace Sealant AC-380 — Low Density Fuel Tank
A Class B, low density, fast-cure polysulfide family for fuel tank and fuselage sealing — 33% lighter than conventional fuel tank sealants. Two-component, manganese dioxide cured, solvent-free. Outstanding resistance to aviation gasoline, jet fuel, and petroleum chemicals common to the aircraft industry. The mixed compound is a thixotropic paste applied by extrusion gun or spatula for fillet sealing, bead sealing, and injection sealing. Faster cure and lower density combine to reduce both process time and structural weight.


−33% Density Fast Cure Class B Paste Fuel Tank · Fuselage MnO₂ Cured
Low Density Fuselage
3M · Aerospace
3M™ Aerospace Sealant AC-770 — Fast Cure Low Density
Low density Class B polysulfide sealant for fuselage sealing and void filling — 25% lower density than traditional sealants with fast cure times of just 6 hours (1 hr work life) or 11 hours (2 hr work life). Two-component, manganese dioxide cured, solvent-free. Ideal where both weight reduction and fast process turnaround are priorities. Highly resistant to aviation fuel and chemicals throughout the aerospace industry. Available in 1-hour and 2-hour application life variants.
−25% Density 6 hr or 11 hr Cure 1 hr · 2 hr Work Life Fuselage · Void Fill Class B Paste
04

Canopy & Windshield Sealants

Canopy / Windshield Sealant
3M · Aerospace
3M™ Aerospace Sealant AC-251 — No-Craze Canopy & Windshield
The only sealant in the 3M AC-Series formulated specifically for aircraft transparency sealing — acrylic, glass, and polycarbonate canopies and windshields. Contains no solvents and does not craze — a critical property, as solvent-containing sealants will attack and stress-craze acrylic and polycarbonate aircraft glazing, causing permanent surface damage and structural weakening. AC-251 Black Class B is a two-part, quick-curing polysulfide sealant with a non-sag thixotropic consistency applied by spatula or extrusion gun on vertical or overhead surfaces. Quickly cures to form an excellent seal with outstanding UV and weather resistance — critical for windshield and canopy bond lines exposed to direct sunlight throughout the aircraft service life. Solvent-free formula maintains dimensional stability of the glazing.
No Craze — Acrylic Safe No Solvents UV & Weather Resistant Acrylic · Polycarbonate · Glass Non-Sag Paste Quick Cure
AC-251 Key Data
ChemistryPolysulfide · 2-part · Quick cure
ClassB (thixotropic paste)
SubstratesAcrylic · Polycarbonate · Glass
Solvent ContentNone — no craze risk
ColorBlack
UV ResistanceExcellent
05

Fuel Resistant Coating

Fuel Resistant Coating
3M · Scotch-Weld™
3M™ Scotch-Weld™ Fuel Resistant Coating EC-776 / EC-776SR
A general-purpose, solvent-based adhesive/coating providing outstanding resistance to oils, gasoline, and aromatic fuels — protecting aircraft components in fuel-wetted environments. EC-776 is widely used inside integral fuel tanks and on components adjacent to refuel/defuel fittings, fuel dump valves, drain ports, access panels, system plumbing, and fuel tank vents. Becomes tack-free in approximately 20 minutes and fully cured within 24 hours. Can be applied by brush, flow applicator, or by the fill-and-drain method for aluminum or steel fuel tanks. Excellent adhesion to synthetic rubber, metal, glass, and many plastics. EC-776SR is the identified version — contains a red dye (soluble in fuel) for visual confirmation of proper coverage per MIL-S-4383C. Not recommended for use with alcohol-containing fuels (gasohol) or jet fuel containing microbial organisms.
EC-776: MIL-D-17951E EC-776SR: MIL-S-4383C Tack-Free in ~20 Min Brush · Flow · Fill & Drain EC-776SR — Red Dye ID Rubber · Metal · Glass
EC-776 vs EC-776SR
EC-776 SpecMIL-D-17951E
EC-776SR SpecMIL-S-4383C (+ red dye)
Tack-Free~20 minutes
Full Cure~24 hours
ApplicationBrush · flow · fill & drain
Boeing Spec299-947-107 Ty II Cl 5
3M Aerospace Sealant — Quick Reference Guide
Product Primary Application Type Density Classes Work Lives Chromate
AC-350 Integral fuel tank · fuselage Fuel Tank Intermediate A, B ½ · 1 · 2 hr None
AC-730 Fuselage · dissimilar metal Fuselage Standard B 2 hr None
AC-735 Fuselage · composites · fasteners Low Density −25% vs traditional A, B ½ · 1 · 2 hr None
AC-380 Fuel tank · fuselage Low Density −33% vs traditional B ½ · 2 hr None
AC-770 Fuselage · void filling Low Density −25% vs traditional B 1 · 2 hr None
AC-251 Canopy · windshield transparency Canopy Standard B ½ · 2 hr None

All 3M AC-Series sealants are two-component, manganese dioxide cured, solvent-free polysulfide compounds. Service temperature −65°F to +250°F. Qualified to AMS-S-8802 unless otherwise noted. Available in Semkit™ injection kits, jar kits, pint/quart can kits, and PMF (Pre-Mixed & Frozen) where applicable.

Why Source Tooling Materials from Coast-Line?

3 Leading Manufacturers

Authorized distributor for Airtech, Hexcel, and General Plastics — the three manufacturers covering the full tooling material supply chain in one place.

AS9120 Certified

Full documentation package — C of C, material certifications, and test reports — to satisfy Boeing, Airbus, and OEM program requirements.

Process Knowledge

Our team understands composite tooling processes. We can help you select the right system — prepreg, infusion, or foam board — for your program requirements and temperature targets.

Fast Response

Quote turnaround typically within one business day. Tool schedule slipping? Call us directly — we understand the cost of tooling delays on production programs.