What Is Anti-Seize?

Anti-seize compound is a high-temperature lubricant paste containing metallic or ceramic particles suspended in a grease carrier. Applied to threaded fasteners, it prevents galling, seizing, and corrosion between mating metal surfaces — especially in high-heat, high-corrosion, or dissimilar-metal joints.

Why It Matters

A seized bolt is more than an inconvenience. In maintenance-heavy industries — petrochemical, power generation, automotive, aerospace — a single seized fastener can mean cutting, drilling, and retapping. That turns a 10-minute job into a 4-hour nightmare. Anti-seize prevents this for pennies per fastener.

Types of Anti-Seize

Copper-Based

The most common general-purpose anti-seize. Fine copper flake in a petroleum or synthetic carrier.

  • Temperature range: -65°F to 1800°F
  • Best for: Steel-on-steel, stainless-on-stainless, exhaust manifolds, spark plugs, pipe fittings
  • Avoid: Ammonia environments (attacks copper), copper-sensitive alloys
  • K-factor: ~0.13–0.15

Nickel-Based

For extreme temperatures and environments where copper is prohibited (nuclear, food processing, certain chemical plants).

  • Temperature range: -65°F to 2400°F
  • Best for: Stainless steel flanges, turbine bolts, nuclear applications
  • K-factor: ~0.14–0.16

Aluminum-Based

Contains aluminum particles. Good for preventing galvanic corrosion between dissimilar metals.

  • Temperature range: -60°F to 1600°F
  • Best for: Aluminum-to-steel joints, electrical connections, outdoor/marine fasteners
  • K-factor: ~0.14–0.16

Molybdenum Disulfide (Moly)

A dry-film lubricant, often combined with other anti-seize types. Excellent for extreme pressure but lower temperature limit than metal-based compounds.

  • Temperature range: -65°F to 750°F
  • Best for: High-load bolted joints, press fits, slow-moving assemblies
  • K-factor: ~0.12–0.14

Ceramic-Based

Non-metallic particles for applications where metal contamination is unacceptable.

  • Temperature range: up to 2700°F
  • Best for: Oxygen service, food processing, pharmaceutical, nuclear
  • Note: Will not cause galvanic corrosion

Torque Adjustment — The Most Important Section

Every engineer and mechanic needs to understand this: Torque specs in manuals, standards, and engineering tables almost always assume dry, unlubricated threads. Anti-seize dramatically changes the torque-tension relationship.

The Physics

When you tighten a bolt, only about 10–15% of the applied torque actually stretches the bolt (creating clamping force). The other 85–90% is lost to friction — roughly 50% under the bolt head and 35–40% in the threads.

Anti-seize reduces thread and bearing friction by 20–40%. That means:

  • Same torque = 20–40% more clamping force
  • Same clamping force = 20–30% less torque needed

If you apply dry torque specs to lubricated bolts, you WILL over-stress the joint.

How to Adjust

Use the nut factor (K-factor) method:

T = K × D × F

  • T = Torque (in-lbs or ft-lbs)
  • K = Nut factor (friction coefficient, dimensionless)
  • D = Nominal bolt diameter (inches)
  • F = Desired preload/clamp force (lbs)

Common K-factors:

Condition K-Factor Torque Reduction from Dry
Dry (as-received, plain steel) 0.20 Baseline
Zinc plated, dry 0.17–0.19 ~10%
Oil/light grease 0.15–0.18 10–25%
Copper anti-seize 0.13–0.15 25–35%
Moly anti-seize 0.12–0.14 30–40%
Cadmium plated, waxed 0.12–0.14 30–40%
PTFE/Teflon paste 0.12–0.13 35–40%

Example: A 1/2″-13 Grade 8 bolt spec’d at 90 ft-lbs dry. With copper anti-seize (K=0.14 vs dry K=0.20), the adjusted torque is: 90 × (0.14/0.20) = 63 ft-lbs. Applying the full 90 ft-lbs with anti-seize would overshoot the target preload by 43%.

Application Best Practices

  • Apply sparingly — A thin film on the threads is sufficient. Glob it on and you change the effective K-factor unpredictably.
  • Coat both male and female threads when possible, plus the bearing surface under the bolt head
  • Hand-start threaded fasteners — Anti-seize masks cross-threading until it’s too late
  • Don’t use anti-seize as a substitute for proper thread repair — Damaged threads need inserts, not lubricant
  • Keep it off the thread locker — Anti-seize and Loctite are opposites. Never use both on the same fastener.
  • Store properly — Metal-based anti-seize separates over time. Stir before use.

When NOT to Use Anti-Seize

  • Where thread-locking compound is specified — Anti-seize prevents adhesion
  • On fasteners torqued to yield (TTY) — These are designed for dry installation and are one-time-use
  • Oxygen service — Only use ceramic-based anti-seize (metal-based compounds can be fuel sources)
  • Where specified otherwise — Some OEM procedures explicitly require dry torque; follow the spec

Bottom Line

Anti-seize is essential insurance for stainless, aluminum, and high-temperature fasteners. But it demands torque discipline. Apply it correctly, reduce your torque values accordingly, and you’ll never deal with a seized bolt again. Ignore the torque reduction and you’ll trade seized bolts for broken ones.