Why does cast iron not rust?
bud asked:
I noticed in a junk yard that the engine castings, and brake rotors just showed surface rust and can be machined. Sheet metal parts where rusted through. Also I heard that cast iron filings are good for the garden, not steel filings. Is this true?
Thanks
Casting Furnace
I noticed in a junk yard that the engine castings, and brake rotors just showed surface rust and can be machined. Sheet metal parts where rusted through. Also I heard that cast iron filings are good for the garden, not steel filings. Is this true?
Thanks
Casting Furnace
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Tags: 5 Responses to “Why does cast iron not rust?”
cast iron does rust unless galvanized.
It does rust, pretty fast too. Maybe the parts are just thicker and don’t rust all the way through. As it rusts, the oxide is somewhat of a protective barrior to further oxication (?)
They aren’t galvanized
cast iron doesn’t rust because of the high percentage of carbon(3.5-4.5). most steels have less than 1.5% carbon content Cast iron usually exhibits surface rust,whereas steel pits and exfoliates after extended exposure to nature.
The more surface area is open to the air, or oxygen, the faster it rusts. That’s why a sheet, which is pretty much totally exposed, will rust fast, but not thick parts like the engine, etc. Rust, after all, is the product of Iron mixing with Oxygen. Also, steel is a mixture, more specifically a metal alloy, of iron with carbon. Alloys with higher carbon content than this are known as cast iron. Therefore, cast iron rusts slower than sheet metal also because it contains a lot of carbon, rather than being all iron. I don’t know what is better for the garden, but “cast iron” is actually steel, with high amounts of carbon in it.