Metals containing iron, such as most kinds of steel, will rust whenexposed to air and water. Rust is just iron oxide, usually with watermolecules incorporated in it too. It usually takes the form of anorange powder on the surface of the metal. Other metals oxidize or formother compounds in a similar way, although we usually say they corrode.Rusting is a specific kind of corrosion which applies toiron-containing metals.
Rusting has a number of effects on metal objects. It makes themlook orange and rough. It makes them weaker, by replacing the strongiron or steel with flaky powder. Some oxides on some metals such asaluminum form just a thin layer on top which slows down furthercorrosion, but rust can slowly eat away at even the biggest piece ofiron. If a piece of irons strength is important for safety, such as abridge support or a cars brake caliper, it is a good idea to inspectit for rust damage every now and then.
Rust also can cause metal parts that are supposed to slide overone another to become stuck. Just ask someone who has tried to get arusty nut unstuck from a rusty bolt.
Rust can make holes in sheet metal. Rusty car mufflers sometimesdevelop holes in them, and the sheet steel making the outer bodies ofcars will often rust through, making holes.
Rust is a lot less magnetic than iron. An iron magnet will probablystill work almost as well when it has a thin coating of rust on it, butif it has rusted so badly that most of the metal is gone, then it willnot work very well as a magnet.
Rust is an insulator, meaning that it doesnt conduct electricityeasily, unlike iron, which is a metallic conductor. So if someelectrical connection is made with iron, its likely to go bad when theiron surface rusts.
Tom J. (and mike)
(published on 10/22/2007)
