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Aluminum rusting......


Tim240z

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If you have every wiped your hand across a piece of aluminum and come away with a white, chalky powder, that is aluminum oxide. Rust.

 

There are about a thousand different alloys of aluminum. One of the reasons the Mitisubishi Zero fighter was so successful and light was the alloy the Japanese come up with to make the wing spars. It is also the same reason there aren't many WWII zeros flying today. Over the years the aluminum has crystalized to the point where it can be litterally be scooped away with the blade of a screw driver.

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Yup. Despite what most people think, aluminum does corrode. It naturally develops a layer of protection (aluminum oxide) as part of pure aluminum's natural reaction with oxygen. But, that reaction continues and over time aluminum will degrade into a pile of aluminum oxide.

 

Aluminum oxide itself is a very hard material and is used as grit for sandpaper. It also has a melting point 3,700F which is 2,500 degrees above pure aluminum's melting point of 1,200F.

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Please stop calling it rust. It's corrosion like John says. Lots of metal's carrode but we don't call it all RUST. Rust is FeO2 right' date=' not just any oxide.

 

Maybe I'm wrong.[/quote']

 

My 2 cents! I think John stated it by saying; "natural reaction with oxygen." So, I think thats what they refer to as oxidation? Rust is generally associated with iron based materials but, I believe it also applies to other materials as well. All in all its just a process of oxidation.

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Everything oxidizes, even us. That's why we're supposed to eat foods high in antioxidants. Maybe human "rust" causes cancer...

 

Definition of oxidize:

Main Entry: ox·i·dize

Variant: also British ox·i·dise /'äk-s&-"dIz/

Function: verb

Inflected Forms: -dized also British -dised; -diz·ing also British -dis·ing

transitive senses

1 : to combine with oxygen

2 : to dehydrogenate especially by the action of oxygen

3 : to change (a compound) by increasing the proportion of the electronegative part or change (an element or ion) from a lower to a higher positive valence : remove one or more electrons from (an atom, ion, or molecule) intransitive senses

: to become oxidized —ox·i·diz·able /-"dI-z&-b&l/ adjective

 

How antioxidants work.

6. How might antioxidants prevent cancer?

 

Antioxidants neutralize free radicals as the natural by-product of normal cell processes. Free radicals are molecules with incomplete electron shells which make them more chemically reactive than those with complete electron shells. Exposure to various environmental factors, including tobacco smoke and radiation, can also lead to free radical formation. In humans, the most common form of free radicals is oxygen. When an oxygen molecule (O2) becomes electrically charged or "radicalized" it tries to steal electrons from other molecules, causing damage to the DNA and other molecules. Over time, such damage may become irreversible and lead to disease including cancer. Antioxidants are often described as "mopping up" free radicals, meaning they neutralize the electrical charge and prevent the free radical from taking electrons from other molecules.

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Everything oxidizes' date=' even us. That's why we're supposed to eat foods high in antioxidants. Maybe human "rust" causes cancer...

 

Definition of oxidize:

 

 

How antioxidants work.[/quote']

 

Hm, that talk of oxygen getting electrically charged makes me wonder if I should be worried when I retain static electricity (I shock myself a lot at work for some reason).

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I read that site and it said that the aluminum oxide ("rust") is a super-thin but hard substance like saphire or ruby that, once formed, protects the aluminum from degrading further. They said it will not "rust" any more once that initial layer is formed (except when in contact with Mercury, which explains the photo). Very interesting stuff :)

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I read that site and it said that the aluminum oxide ("rust") is a super-thin but hard substance like saphire or ruby that, once formed, protects the aluminum from degrading further. They said it will not "rust" any more once that initial layer is formed

 

Well... assuming a stable environment then what they say is true. But in the real world oxidation continues. Exposure to any type of acidic gas or fluid (acid rain, air pollution) will strip aluminum oxide causing more to form. As aluminum oxides form the part actually loses aluminum. That's why bare aluminum wheels need polishing so often and why aliminum pits. That's also why its critical to shield aluminum with an inert gas while welding. Oxygen has such a strong affinity for aluminum that any oxygen present at the weld pool causes cracking because aluminum oxides are formed inside the weld.

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