Rust
(→What is rust?) |
(→What is rust?) |
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For rust to occur it needs an anode (a piece of metal that gives up electrons), an electrolyte (a liquid that helps transport electrons), and a cathode (a piece of metal that accepts electrons). | For rust to occur it needs an anode (a piece of metal that gives up electrons), an electrolyte (a liquid that helps transport electrons), and a cathode (a piece of metal that accepts electrons). | ||
| − | Rust is an electro-chemical corrosion that occurs in the presence of iron, oxygen, and water. Oxygen and water are available in the open air, and iron is the principal ingredient in steel. | + | Rust is an electro-chemical corrosion that occurs in the presence of iron, oxygen, and water. Oxygen and water are available in the open air, and iron is the principal ingredient in steel. Rust happens more quickly with salt in the air, because salted air is a better electrolyte, speeding up the electro-chemical corrosion of iron. |
Iron, with the chemical symbol of Fe, combines with oxygen, O, to form Fe<sub>2</sub>O<sub>3</sub>, the chemical formula for common reddish-brown rust. In its mineral form, this is known as hematite. | Iron, with the chemical symbol of Fe, combines with oxygen, O, to form Fe<sub>2</sub>O<sub>3</sub>, the chemical formula for common reddish-brown rust. In its mineral form, this is known as hematite. | ||
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There is another iron oxide also known as "rust". It's Fe<sub>3</sub>O<sub>4</sub>. This is also known as "black oxide", or, in mineral form, magnetite. This is the stuff that's left over after using certain products to "convert" rust. Black oxide takes up the same amount of space as iron, so it doesn't bulge it out, like reddish-brown rust, Fe<sub>2</sub>O<sub>3</sub>. Black oxide itself doesn't offer much protection against corrosion, so it's typically covered up (often with [[epoxy primer]]). Black oxide is an example of a conversion coating, a metal coating where part of the surface is converted into the coating itself, by a chemical or electrochemical process. ''(Is this the same thing as blueing?)'' | There is another iron oxide also known as "rust". It's Fe<sub>3</sub>O<sub>4</sub>. This is also known as "black oxide", or, in mineral form, magnetite. This is the stuff that's left over after using certain products to "convert" rust. Black oxide takes up the same amount of space as iron, so it doesn't bulge it out, like reddish-brown rust, Fe<sub>2</sub>O<sub>3</sub>. Black oxide itself doesn't offer much protection against corrosion, so it's typically covered up (often with [[epoxy primer]]). Black oxide is an example of a conversion coating, a metal coating where part of the surface is converted into the coating itself, by a chemical or electrochemical process. ''(Is this the same thing as blueing?)'' | ||
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===Why do older cars rust more than newer cars?=== | ===Why do older cars rust more than newer cars?=== | ||
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