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A traditional use of cerium was in the pyrophoric ferrocerium alloy used for lighter flints. Because of the high affinity of cerium to sulfur and oxygen, cerium itself or as mischmetal is used in various aluminum alloys, and iron alloys. In steels, cerium degasifies and can help reduce sulfides and oxides, and it is a precipitation hardening agent in stainless steel. Adding cerium to cast irons opposes graphitization and produces a malleable iron. Addition of 3–4% of cerium to magnesium alloys, along with 0.2–0.6% zirconium, helps refine the grain and give sound casting of complex shapes. It also adds heat resistance to magnesium castings. Cerium metal is sometimes added to aluminum to improve aluminum's corrosion resistance. Cerium alloys are used in permanent magnets, and in tungsten electrodes for gas tungsten arc welding. Cerium is used in carbon-arc lighting, especially in the motion picture industry.

Another important use of cerium oxide is in a hydrocarbon catalyst in self cleaning ovens, incorporated into oven walls and as a petroleum cracking catalyst in petroleum refining. Major automotive applications for cerium (III) oxide are as a catalytic converter for the oxidation of CO and NOx emissions in the exhaust gases from motor vehicles.