Loctite 242 Blue Medium-Strength Threadlocker

Product Name

Loctite 242 Multi-Purpose Medium Threadlocker

Brief Description

Loctite 242 is a blue, medium-strength, thixotropic, anaerobic adhesive designed for locking and sealing threaded metal fasteners. It prevents loosening from vibration and protects against leaks, rust, and corrosion. This multi-purpose threadlocker is suitable for fasteners ranging from 1/4 inch (6 mm) to 3/4 inch (19 mm) in diameter and allows for normal disassembly with standard hand tools.

Popular Applications & Uses

• Locking and sealing threaded metal fasteners (6mm to 19mm / 1/4" to 3/4" diameter).
• Preventing loosening of metal fasteners caused by vibration and shock.
• Protecting threads from leaks, rust, and corrosion.
• Automotive applications such as valve covers, water pumps, alternators, and oil pans.
• Maintenance of light machinery, light conveyors, door hardware, and tow motors.
• Home applications including lawn mowers, grills, locksets, bicycles, and furniture.
• Securing pump or motor mounting bolts, engine rocker nuts, and equipment housing screws.
• Ideal for fasteners that require normal disassembly with standard hand tools for servicing.

Industries that Commonly Use It

• Aerospace/Defense: The Loctite brand is used in demanding applications, including military-grade products.
• Automotive Service/Repair: For various engine and vehicle component fasteners.
• Construction/Building Services: For securing door hardware and other fasteners where disassembly might be needed.
• Energy: Used for pump and motor mounting bolts in energy-related equipment.
• General Manufacturing: For light machinery, conveyors, and general industrial fastening needs.
• Industrial Supply: A common product sold through industrial supply channels.
• Marine: For fasteners in marine environments where vibration and corrosion prevention are critical.
• Metal Fabrication: For locking and sealing threaded metal assemblies.
• Prosumer: For home repairs, lawn equipment, bicycles, and furniture assembly.
• Transportation/Specialty Vehicle: For bicycles and general vehicle maintenance where removable fasteners are used.
• Distributers & Resellers: As a widely distributed industrial and consumer product.

Special and Unique Features

• Medium Strength: Allows for disassembly with standard hand tools, making it ideal for parts requiring occasional servicing.
• Anaerobic Curing: Cures in the absence of air when confined between close-fitting metal surfaces.
• Thixotropic: Prevents the liquid product from migrating or dripping after application to the substrate.
• Corrosion and Rust Protection: Effectively seals threads to prevent rust and corrosion.
• Vibration and Shock Resistance: Prevents fasteners from loosening due to operational vibrations and shocks.
• Fast Fixture Time: Sets in approximately 10 minutes on active metals (like steel), with a range of 5-20 minutes depending on the substrate.
• Controlled Lubricity: Provides accurate clamp loads during assembly.

Key Properties

• Chemical Type/Base: Dimethacrylate ester / Methacrylate.
• Color: Blue.
• Strength: Medium.
• Viscosity: Medium, 800-1600 cP (mPa·s) at 25°C.
• Fixture Time: 5-20 minutes (10 minutes on active metals).
• Full Cure Time: 24 hours.
• Temperature Range (after cure): -65°F to 300°F (-50°C to 150°C).
• Specific Gravity: Approximately 1.10.
• Flash Point: >212°F (>100°C).
• VOC Content: 0.56% by weight / 6.17 g/l.

Surface Compatibility

• Recommended for: Metal fasteners, including steel, brass, stainless steel, and plated surfaces.
• Not recommended for: Plastic parts, particularly thermoplastic materials where stress cracking could result.
• Limitations: Not for use in pure oxygen and/or oxygen-rich systems, or as a sealant for chlorine or other strong oxidizing materials. Not suitable for applications requiring “food safe” locking and sealing of fasteners.
• Preparation: For best performance, surfaces should be clean and free of grease. A primer (e.g., Loctite SF 7649) may be needed for inactive metals or low temperatures to accelerate cure.

Known backups / known substitutes

• Lockfast T42 Nutlock
• LK242 (equivalent of Henkel Loctite 242)
• 3M TL42
• Bondloc B242
• Hernon 423
• Loxeal 54-03
• Permabond A115
• General medium-strength threadlockers from brands like Permatex and Threebond.
• Vibratite (as a general threadlocker alternative).
• Non-chemical alternatives (less effective for critical applications): White plumbers thread tape, nail polish, beeswax.

Comparison Note

• Loctite 243: Often considered an upgraded, more general-purpose version of Loctite 242. It offers improved oil tolerance, allowing it to cure on as-received fasteners with minor oil contamination without prior cleaning. It also provides primerless performance on both inactive and active metals and has upgraded temperature resistance (up to 360°F / 182°C). While still medium strength, it has slightly lower shear strength, potentially making disassembly easier.
• Loctite 222 (Purple): This is a low-strength threadlocker, designed for very small fasteners that require frequent adjustment or easy removal with minimal torque.
• Loctite Red (e.g., 271): Represents high-strength, permanent threadlockers. These are used for applications where fasteners should not be removed easily and typically require localized heat (around 500°F / 250°C) for disassembly.
• Loctite Green (e.g., 290): A high-strength wicking grade threadlocker, often used for preassembled fasteners like set screws. It also requires heat and/or special chemicals for disassembly.