Copper (metal flake)

Copper (CAS 7440-50-8) in anti-seize compounds appears as fine metal flake — particles ranging from a few microns to tens of microns in diameter, suspended in a petroleum-grease carrier. The copper flake provides the core function of anti-seize: at the thread interface under load and heat, the copper particles deform plastically and fill microscopic surface irregularities, creating a lubricating barrier that prevents metal-to-metal contact (galling) and maintains the ability to disassemble fasteners cleanly after years of thermal cycling.

Copper anti-seize is the most widely used formulation in automotive service because copper withstands temperatures up to approximately 1800°F (982°C) without breaking down — covering spark plug threads, exhaust manifold studs, brake-caliper hardware, and most passenger-vehicle exhaust applications. The limitation is compatibility with stainless steel at sustained high heat: copper can cause stress-corrosion cracking on stainless steel fasteners exposed to prolonged thermal cycling above approximately 400°F (204°C), making nickel-based anti-seize the correct choice for stainless exhaust applications.

The primary environmental concern with copper metal flake is aquatic toxicity. Copper ions in water are acutely toxic to aquatic invertebrates (NOEC for Daphnia magna: <0.01 mg/L) and fish at ppb-level concentrations. This toxicity is the basis for copper's UN 3082 marine-pollutant transport classification and for its inclusion in virtually every copper anti-seize product's aquatic-toxicity deduction under environmental scoring.