Ferrocerium

Spark trails from a cigarette lighter

Ferrocerium is a synthetic pyrophoric alloy of “mischmetal” (cerium, lanthanum, neodymium, other trace lanthanides and some iron – about 95% lanthanides and 5% iron) hardened by blending in oxides of iron and / or magnesium. When struck with a harder material, the mixture produces hot sparks that can reach temperatures of 3,000 °C (5,430 °F) when rapidly oxidized by the process of striking the rod: Striking both scrapes fragments off, exposing them to the oxygen in the air, and easily ignites them by friction heat, due to cerium's remarkably low ignition temperature ~170 °C (338 °F).

Its easy flammability gives ferrocerium many commercial applications, such as the ignition source for lighters (where it is often misleadingly called “flint”), strikers for gas welding and cutting torches, deoxidization in metallurgy, and ferrocerium rods. Due to ferrocerium's ability to ignite in adverse conditions, rods of ferrocerium are commonly used as an emergency fire making device in survival kits.

Discovery and composition

Main articles: Mischmetal and Carl Auer von Welsbach

Ferrocerium alloy was invented in 1903 by the Austrian chemist Carl Auer. It takes its name from its two primary components: iron (from Template:Lang-la), and the rare-earth element cerium, which is the most prevalent of the lanthanides in the mixture. With the exception of the extra iron oxide added to harden it, the mixture is approximately the combination found naturally in tailings from thorium mining which Auer was investigating. The pyrophoric effect is dependent on the brittleness of the alloy and its low autoignition temperature.

It is also known in Europe as Auermetall after its inventor Baron Carl Auer, baron von Welsbach. Three different Auermetalls were developed: The first was iron and cerium, the second also included lanthanum to produce brighter sparks, and the third added other heavy metals. In Auer's first alloy, 30% iron (ferrum) was added to purified cerium, hence the name "ferro-cerium".

A modern ferrocerium firesteel product is composed of an alloy of rare-earth metals called mischmetal (containing approximately 20.8% iron, 41.8% cerium, about 4.4% each of praseodymium, neodymium, and magnesium, plus 24.2% lanthanum.) A variety of other components are added to modify the spark and processing characteristics. Most contemporary flints are hardened with iron oxide and magnesium oxide.

Element	Cerium	Iron	Neodymium	Praseodymium	Magnesium	Lanthanum
Proportion	41.8%	20.8%	4.4%	4.4%	4.4%	24.2%

Use

A “flint” spark lighter in action

Small sphere of burnt ferrocerium oxides from lighter

While ferrocerium-and-steels function in a similar way to natural flint-and-steel in fire starting, ferrocerium takes on the role that steel played in traditional methods: When small shavings of it are removed quickly enough, the heat generated by friction is enough to ignite the shavings, converting the metal to the oxide – the sparks are tiny flecks of burning metal. The sparking is due to cerium's low ignition temperature between 150 and 180 °C (302 and 356 °F). About 700 tons were produced in 2000.

Comparison with natural flint

Ferrocerium bears no chemical relationship to the mineral named flint. The similarity lies in the fact that both materials have historically been used to generate sparks to ignite fires. In traditional flint-and-steel fire-starting systems that use natural flint, the hard flint rock strikes tiny iron particles from the steel, which then ignite due to frictional heating. This is essentially the mechanical opposite of the operation of a ferrocerium “flint” in a modern lighter, where the hardened steel wheel strikes particles of ferrocerium off of the “flint”; in both cases, however, the friction of the strike ignites flakes of metal, the difference is which metal is ignited. In a classic flint and steel system, it is the steel that burns, while in a ferrocerium system, it is the ferrocerium.

Flint spark lighter

This Mora knife has a ferrocerium rod that can be stored in the handle.

A flint spark lighter (sometimes just called a spark lighter, striker, or flint lighter) is a type of lighter used in many applications to safely light a gaseous fuel to start a flame. It is most commonly used for Bunsen burners, and for propane grills, and oxyacetylene welding torches.

A “flint” spark lighter works by rapidly rubbing a small piece of ferrocerium upon the sharp edge of any substance that is harder than the ferrocerium rod. Carbon steel works better than most other materials in much the same way flint and steel are used. This manual rubbing action, done by squeezing the handle, creates a spark, which ignites the gaseous fuel.

As tinder-igniting campfire starter rods it is sold for survivalists and bushcraft hobbyists under such trade names as “Blastmatch”, “Fire Steel”, and “Metal-Match”. Some manufacturers and resellers incorrectly call them “magnesium” rods, other manufacturers combine a strip of ferrocerium along with a strip of magnesium in the same item. The combined ferrocerium-magnesium rod is used by first using a knife to scrape magnesium flakes onto the tinder, and then striking the ferrocerium close to the magnesium flakes. The sparks from the ferrocerium will ignite the magnesium, which will burn even hotter and better ignite the tinder.

See also

• Firelighting

External links

• Jorgenson, John D.; Corathers, Lisa A.; Gambogi, Joseph; Kuck, Peter H.; Magyar, Michael J.; Papp, John F.; Shedd, Kim B. (2006). "Minerals Yearbook 2006: Ferroalloys" (PDF). United States Geological Survey. Retrieved 2009-04-24.