What is a Spark plug made of?
What is a Spark plug made of?
A ceramic insulator carrying a centre electrode of nickel, platinum or iridium inside a steel shell.
A plug's "heat range" is not about how hot a spark it makes but about how fast it conducts heat away, set by the length of the insulator nose. Too cold and the tip fouls with carbon; too hot and it becomes a glow plug and pre-ignites the mixture, which can destroy a piston. Iridium and platinum plugs last far longer, sometimes over 150,000 km, because the fine centre wire erodes slowly — the ordinary nickel plug wears its gap open and the ignition system eventually cannot bridge it. Torque matters more than most people expect: overtightening distorts the shell and changes the heat path, and the manufacturer's figure always takes priority over a generic chart.
Component by component
| Part | Material | Why that material |
|---|---|---|
| insulator | sintered aluminium oxide ceramic | It has to insulate against 20,000-40,000 volts while conducting combustion heat away and surviving 900 °C — almost nothing else does all three. |
| centre electrode | nickel alloy with a copper core, tipped with platinum or iridium in long-life plugs | Copper conducts heat out of the tip; iridium melts near 2450 °C and erodes slowly, so a very fine tip can survive and it needs less voltage to fire. |
| ground electrode | nickel alloy welded to the shell | It must hold its position within tenths of a millimetre while glowing hot, because the gap sets the required firing voltage. |
| shell | plated steel with a rolled thread and a sealing washer or taper seat | The shell carries the earth path and the clamping load, and must seal a combustion chamber at 100 bar. |
| internal resistor | a carbon or glass resistive seal, typically 5 kΩ | It suppresses the radio interference the spark generates, which is why fitting a non-resistor plug can upset the engine electronics. |
Other cars and driving objects
- Car tire Several different rubber compounds reinforced with steel and textile cord — closer to a composite than to rubber.
- Car battery Lead and lead dioxide plates in dilute sulfuric acid, in a polypropylene case — mostly lead, by weight.
- Airbag A coated nylon bag inflated by a small solid-propellant gas generator in about thirty milliseconds.
- Brake pad A friction compound of fibres, fillers and resin, moulded and bonded onto a steel backing plate.
- Windshield (windscreen) Two sheets of ordinary glass laminated to a tough plastic interlayer, which is what stops it falling out.
- Seatbelt Woven polyester webbing designed to stretch a controlled amount, plus a locking retractor and a pyrotechnic pretensioner.
Common questions
- What is a Spark plug made of?
- A ceramic insulator carrying a centre electrode of nickel, platinum or iridium inside a steel shell.
- What is the insulator of a Spark plug made of?
- Sintered aluminium oxide ceramic. It has to insulate against 20,000-40,000 volts while conducting combustion heat away and surviving 900 °C — almost nothing else does all three.
- What is the centre electrode of a Spark plug made of?
- Nickel alloy with a copper core, tipped with platinum or iridium in long-life plugs. Copper conducts heat out of the tip; iridium melts near 2450 °C and erodes slowly, so a very fine tip can survive and it needs less voltage to fire.
Related pages
- Car tire Several different rubber compounds reinforced with steel and textile cord — closer to a composite than to rubber.
- Car battery Lead and lead dioxide plates in dilute sulfuric acid, in a polypropylene case — mostly lead, by weight.
- Airbag A coated nylon bag inflated by a small solid-propellant gas generator in about thirty milliseconds.
- Brake pad A friction compound of fibres, fillers and resin, moulded and bonded onto a steel backing plate.
- Windshield (windscreen) Two sheets of ordinary glass laminated to a tough plastic interlayer, which is what stops it falling out.
- Seatbelt Woven polyester webbing designed to stretch a controlled amount, plus a locking retractor and a pyrotechnic pretensioner.
- Pencil Stationery and paper
- Tennis ball Sport and games
- Banknote Around the house
- Golf ball Sport and games
- Paper Stationery and paper
- Glass Building materials
Sources
- Official vendor product documentation — At One Place