ST-3® Thread Sealant


ST-3 is a pre-applied process whereby a series of resilient thread sealants are coated onto straight or tapered threaded fasteners. A widely-used automotive industry approved process, ST-3 creates a custom-fit elastic gasket around fastener threads which prevents the passage of most fuels and chemicals, and helps keep joints tight under severe vibration.

How it Works

During the ST-3 pre-application process, ND Industries accurately dispenses a select range of materials onto fasteners, making them self-sealing. The applied sealants act as a partial lubricant, reducing torque tension variation and preventing the galling of metals. They will not harden or cure, allowing fasteners to be adjusted, removed, and replaced, throughout the life of the part if needed. Processed fasteners arrive to the customer dry to the touch, and ready for immediate assembly.


Exceptional Sealing Power

ST-3 creates fasteners which provide an instant seal of over 2000 psi on both straight and tapered threads. Contains PTFE to help with lubricity and sealing.

Offers Multiple Reuses

The materials applied through the ST-3 process are non-hardening with lubricating properties, making fasteners easy to adjust, remove, and reuse.

Resists Vibration

Although ST-3 processed fasteners are primarily for sealing, they also provide a limited amount of resistance to vibrational loosening and thermal shock resistance through a wide range of temperatures.

Environmentally Friendly

Materials used in the ST-3 process are non-hazardous, non-flammable, and will not migrate into fluid systems like paste or tape sealants.

Chemical Resistant

Sealants applied in ST-3 processing are resistant to corrosion from brine, chlorine, acids, and alkalis. They effectively resist natural gas, butane, propane, motor fluids, and other chemicals.

Corrosion Resistance

ST-3 processing inhibits corrosion between mating fasteners which prevents seizing and allows for easy removal.


  • Saves Time: Pre-Applied ST-3 fasteners can be automatically fed through standard feeding devices – speeding up your process and improving productivity.
  • Saves Money: Pre-Applied ST-3 processing is less expensive than hand applying bottled thread sealing compounds or tapes at the point of assembly.
  • Quality Control: Pre-Applied ST-3 fasteners are coated to specification, ensuring consistent performance, unlike the variation from hand applying bottled products.
  • Reliability: Under most operating conditions, Pre-Applied ST-3 fasteners are unaffected by vibration or reversal of stress and greatly reduce the need to re-tighten fasteners.
  • Increased Margins: Add value to your fasteners without adding to inventory by supply customers with self-sealing fasteners.
  • Easy to use: Works on a wide range of material finishes


  • For the ST-3 process, sealants are typically applied one to three threads back from the end of a fastener to assure ease of starting.
  • Indefinite on part life under ideal storage conditions [+40°F (+4°C) to +90°F (+32°C)], but re-certification must occur once a year.

ST-3 Competes With

See technical data table below for full comparison listing


Pipe Plugs, Engine Applications, Head Gasket Application, Under Head Sealant for Torque Tension control, Automotive Hose Fittings, Cooling System, A/C System

Compatible Fasteners

External Threads:Internal Threads:Rivets:
Banjo Bolts, Hex Bolts, Flange Bolts, Wheel Bolts, Machine Screws, Cap Screws, Wood Screws, Sheet Metal Screws, Self Drilling Screws, Shoulder Bolts, Fully Threaded Studs, Double Ended Studs, Singled Ended Studs, Press-In Captive Studs, Carriage Bolts, Lag Bolts, Socket Screws, Set Screws, Eye Bolts, Eye Lags, J-Bolts, U-Bolts, Elevator Bolts, Hangar Bolts, Perforated Base Studs, Through Hole Weld Studs.Flange Nuts, Hex Body Clinch Nuts, Prevailing Torque Nuts, Floating Nuts, Hollow Bolts, Insert Nuts, Lock Nuts, Weld Nuts, Barrel Nuts, Chicago Bolts, Jam Nuts, Wing Nuts, Square Nuts, Self-Locating Projection Weld Nuts (WN/WNS), Spot Weld Nuts, Projection Weld Nuts, Bridge Spot Weld Nuts, Tab Spot Weld Nuts, Square Projection Weld Nuts, Flange Weld Projection Nuts, Stamped Flange Weld Nuts, Spot Weld Cage Nuts.Blind Rivets, Break Stem Open Rivets, Closed-End Rivets, Easy-Entry Rivets, Grip Tite™ Rivets, High-Retention Rivets, High-Strength Rivets, Load Spreading Rivets (lsr), Micro Rivets, Multi-Grip Rivets (mgr), Open-End Rivets, Pull-Thru Rivets, Soft-Set Rivets, Tri-Fold Rivets, Ultra-Grip Rivets, Vgrip® Rivets, Grooved Rivets, Peel Rivets, Steel T Rivets, TVD Rivets, Interlock Rivets, Klik-Lok Rivets, Bulbing Rivets, Domed and Flat Head Solid Rivets, Low-Profile Domed Head Solid Rivets, Countersunk Head Solid Rivets, Mil. Spec Solid Rivets.

Don’t see your parts on this list? We process thousands of different types of fasteners and depending on the quantity will gladly look at whether we can accommodate yours as well.

Technical Data

ProductCompetes WithColorFilm Hardness (ASTM D3363)Thread Friction Coefficient (μth)Temp MaxTemp Min
ST-3-W3M® Fastener Adhesive 4291White5B0.16400°F (205°C)-65°F (-54°C)
ST-3-L33M® Fastener Adhesive 4291White5B0.17400°F (205°C)-65°F (-54°C)
ST-3-L4Nylok® Precote® 5, omniTECHNIK® Precote 5®White350°F (180°C)-65°F (-54°C)
ST-3-L5Loctite® Vibra-Seal® 503WhiteHB0.07350°F (180°C)-65°F (-54°C)
ST-3-L5ALoctite® Vibra-Seal® 503HV
ST-3-L6Loctite® Vibra-Seal® 516Burnt OrangeHB350°F (180°C)-65°F (-54°C)
ST-3-L7Loctite® Vibra-Seal® 517Burnt Orange3H350°F (180°C)-65°F (-54°C)
ST-3-L8Loctite® Vibra-Seal® 503 modWhiteB0.18350°F (180°C)-65°F (-54°C)
ST-3-L8ALoctite® Vibra-Seal® 503HV mod
ST-3-L9Loctite® Vibra-Seal® 516 modBurnt OrangeHB350°F (180°C)-65°F (-54°C)
ST-3-L10Loctite® Vibra-Seal® 517 modBurnt OrangeB0.17350°F (180°C)-65°F (-54°C)
ST-3-L11Loctite® Dri-Seal® 506BlueB350°F (180°C)-65°F (-54°C)
ST-3-L13Loctite® Dri-Seal® 513WhiteB370°F (187°C)-65°F (-54°C)
3M™ is a trademark of 3M Company Corporation, USA.  omniTECHNIK®, Precote®, and Precote 5® are registered trademarks of Omnitechnik, Mikroverkapselungs GMBH LLC, Germany. Nylok®, is a registered trademark of Nylok LLC, USA. Loctite® and Vibra-Seal® are registered trademarks of Henkel Corporation, USA.


Particular formulations of ST-3 meet or exceed the performance requirements of the following specifications and/or standards:

Spec ForSpec NumberND ProcessND Material
Bendix (Allied Signal)BW-317-PST-3ST-3-L5, ST-3-L6
Briggs & StrattonGM TYPE A (9985473)ST-3ST-3-L5, ST-3-L5A
Briggs & StrattonGM TYPE AA (9985490)ST-3ST-3-W
Dana - Boston WeatherheadMS-71ST-3ST-3-W, ST-3-L8, ST-3-L13
Dana - Boston WeatherheadPS-5040ST-3ST-3-W, ST-3-L8, ST-3-L13
Detroit Diesel80K14ST-3ST-3-L10
Detroit Diesel80K15ST-3ST-3-L6
Detroit Diesel9S421ST-3ST-3-L10
Detroit DieselTPS 12635ST-3ST-3-L6, ST-3-L7
Fiat ChryslerMS-CD16ST-3ST-3-W
Fiat ChryslerMS-CD914 TYPE AST-3ST-3-L5, ST-3-L7
Fiat ChryslerMS-CD914 TYPE BST-3ST-3-L5A, ST-3-L6
General Motors9985473ST-3ST-3-L6
General Motors9985490ST-3ST-3-W
General Motors9985490ST-3ST-3 Type 1
Index Sensors & ControlsIndex Item number 4014004ST-3ST-3-L9
John DeereRES 10059ST-3ST-3-L5A, ST-3-L6, ST-3-L5, ST-3-L7
Mack Truck023 GS 17002ST-3ST-3-W
Mack Truck3/6AXS7ST-3ST-3-W
Mack Truck617GS135ST-3ST-3-W
Mack Truck64AMS1ST-3ST-3-W
Meritor (Rockwell)Q-56ST-3ST-3-L6
NavistarCEMS D-31ST-3
Increase product quality while saving time and money with Pre-Applied adhesives and sealants.