Thread Sealants and Retaining Compounds Selection Guide

Anaerobic Thread Sealants

Types and Applications

Standard Thread Sealant:

Seals metal pipe threads
Pressurized systems to 10,000 psi
Temperatures to 300°F
General plumbing, hydraulics, pneumatics

High-Temperature Sealant:

Withstands to 450°F
Engine components
Exhaust systems
High-heat industrial applications

Fuel-Resistant Sealant:

Resistant to gasoline, diesel, jet fuel
Fuel lines and fittings
Automotive and aerospace
Chemical processing

Oxygen-Compatible Sealant:

Safe for oxygen systems
Non-petroleum based
Medical and industrial oxygen
Diving equipment

Application Guidelines

Surface Preparation:

Clean threads with solvent
Remove old sealant and debris
Dry completely
Apply to male threads only

Application Method:

Apply to first 2-3 threads
Cover 360 degrees
Avoid excess (can contaminate systems)
Assemble immediately

Cure Time:

Initial seal: 1-2 hours
Full cure: 24 hours
Pressure test after full cure

Retaining Compounds

Types by Strength

Low Strength (Removable):

Slip-fit assemblies
Easy disassembly
Press-fit replacement
Typical shear strength: 1,500-2,000 psi

Medium Strength:

General purpose retaining
Standard press fits
Serviceable assemblies
Typical shear strength: 2,000-2,500 psi

High Strength (Permanent):

Permanent assemblies
Worn component repair
Loose-fitting parts
Typical shear strength: 2,500-3,500 psi

Application Types

Cylindrical Assemblies:

Bearings in housings
Shafts in bearings
Bushings and sleeves
Gear and pulley mounting

Keyed Assemblies:

Keys and keyways
Splined connections
Eliminates backlash
Distributes load evenly

Worn Component Repair:

Rebuild worn housings
Restore shaft diameters
Reduce manufacturing tolerances
Extend component life

Gap-Filling Capability

Standard retaining compounds:

Radial Clearance: 0.002" - 0.015" (0.05-0.4mm)
Maximum Gap: Up to 0.040" (1mm) with special products

Important:

Larger gaps = longer cure time
Optimal clearance: 0.004" - 0.008"
Too loose = reduced strength

Form-in-Place Gaskets

Types

Flange Sealant (Anaerobic):

Metal-to-metal flanges
Gearbox housings
Pump casings
Engine components

RTV Silicone Gaskets:

Flexible flanges
Plastic or composite
Large gaps
General purpose

High-Temperature Gaskets:

Exhaust systems
Engine components
High-heat industrial
To 700°F+

Application Process

Surface Prep: Clean, dry, oil-free
Bead Size: Apply continuous bead
Bead Location: Inside bolt holes
Assembly: Assemble within 5 minutes
Cure Time: 1 hour minimum, 24 hours full

Pipe Dope vs. Thread Sealant

Traditional Pipe Dope (Teflon Tape/Paste)

Advantages:

Familiar to plumbers
Works on dirty threads
Immediate pressure capability
Inexpensive

Disadvantages:

Can shred and contaminate systems
Limited temperature/pressure
Requires proper wrapping technique
Can loosen with vibration

Anaerobic Thread Sealant

Advantages:

Seals all thread clearance
Vibration resistant
No contamination
Consistent application
Higher pressure/temperature

Disadvantages:

Requires clean threads
Cure time before pressure
More expensive
Surface prep critical

Material Compatibility

Metals

Steel/Stainless:

All anaerobic products
Excellent adhesion
Standard cure

Brass/Copper:

Active surfaces
Fast cure
All products compatible

Aluminum:

Active surface
May stain (use aluminum-grade)
Good adhesion

Cast Iron:

Porous surface
May require primer
Good sealing

Plastics

Thermoplastics:

Check compatibility
Some sealants attack plastics
Use plastic-compatible grades

Thermosets:

Generally compatible
Slower cure than metals
May need primer

Temperature and Chemical Resistance

Temperature Ranges

Standard Products:

Continuous: -65°F to 300°F
Intermittent: to 350°F

High-Temperature Products:

Continuous: -65°F to 450°F
Intermittent: to 550°F

Specialty Products:

Continuous: to 500°F+
Cryogenic: to -320°F

Chemical Resistance

Anaerobic sealants resist:

Water and glycols
Hydraulic fluids
Lubricating oils
Most solvents
Mild acids and bases

Not recommended for:

Strong oxidizing agents
Concentrated acids
Certain chlorinated solvents

Industry-Specific Applications

Plumbing/HVAC

Water lines: Standard thread sealant
Gas lines: Fuel-resistant sealant
Hydronic heating: High-temp sealant
Refrigeration: Low-temperature formulas

Hydraulic/Pneumatic

Hydraulic fittings: High-pressure sealant
Air lines: Standard sealant
Vacuum systems: Low-outgassing products
High-pressure: 10,000+ psi rated

Automotive

Engine assembly: High-temp sealants
Transmission: Flange sealants
Differential: Retaining compounds
Fuel systems: Fuel-resistant products

Manufacturing

Gearboxes: Flange sealants
Pumps: Retaining compounds
Compressors: Thread sealants
Machine tools: Precision retaining

Maintenance and Repair

Disassembly

Threaded Connections:

Standard hand tools
Heat (500°F) for stubborn fittings
Break torque typically 2x assembly torque

Retained Components:

Standard pullers/presses
Heat to 500°F breaks bond
Localized heating preferred

Cleanup

Uncured Product:

Wipe with rag
Clean with solvent
Isopropyl alcohol works well

Cured Product:

Mechanical removal
Heat to soften
Soak in solvent

Quality Control

Testing Methods

Torque Testing: Breakaway torque measurement
Pressure Testing: Hydrostatic/pneumatic tests
Leak Detection: Bubble test, dye penetrant
Destructive Testing: Sectioning and examination

Documentation

Batch/lot tracking
Application records
Cure time verification
Pressure test results

Safety Considerations

PPE

Safety glasses
Nitrile gloves
Ventilation for confined spaces
Protective clothing for skin contact

Storage

Cool, dry location
Away from sunlight
40°F - 80°F ideal
Refrigeration extends life

Shelf Life

Unopened: 2-3 years
Opened: 12-24 months
Date-coded for tracking
FIFO inventory rotation

Bulk Purchasing

Benefits:

Volume pricing (cases, gallons)
Consistent supply
Reduced per-unit cost
Custom packaging available

Machrio offers competitive pricing on thread sealants and retaining compounds with volume discounts for industrial users.