As people before have stated, rust is a
iron oxide.
Iron + Oxygen -->
Iron Oxide
4Fe(s) + 3O2(g) --> 2Fe2O3(s)
NOTE: This is a redox reaction. The half-equation for the oxidisation of
Iron is: Fe(s) --> Fe+2(aq) + 2e-
This is mostly correct, but you forgot that
iron in this case needs to be written as Fe(III) not just Fe. This is because
iron is a metal that could have a positive charge of +2 or +3. In the case of rust, the charge is +3, hence the reason it is written Fe(III).
Rewritten it is ==> 2Fe(III)(s)+3O
2(g) --> 2Fe
2O
3(s)
Alright, since I get the feeling only some and not all are adapt at chemistry... he's the jist of what that ment--
You take 2 atoms of
iron with a +3 charge and take 3 molcules of O
2, put them together, and you get 2 molcules of
iron oxide... to be more specific since there are two types of
iron oxide, its
Hematite.
Wolf825
If I recall--the correct formula is actually
Iron + Oxygen + Water or moisture to create rust.. You need to count that third part to create
Iron Oxide. The water or moisture is the medium for allowing the oxidation transfer for electrolytes creating an acid.. I know in a DRY situation (completely free of moisture in the air or surroundings) that rusting occurs MUCH much slower or very little at all...
Been a while since I had chemistry....
kingfisher1 is right, technically, you don't have to have water, it just works a hell of alot faster with water... Here's what that equation would look like ==>
Fe(III)(s)+3H
2O(a) --> Fe
2O
3(s)+3H
2(g)
Ok... and I'm not sure where you guys started talking about acids at... those are another story... Acids have much more complex rules regarding how they bond and what happens when they do. Besides, I doubt ship dumped acid on his screws.
Ship, as far as your brass screws go... It is very possible that A) the rust is that from one of the other steel screws that simply got onto the brass screw... it won't be easy to clean off the brass, but solid brass cannot rust, which brings me to the next seneiro... B) The screw is not solid brass and contains
iron in some form that is exposed. Or, there is alway the last thing I can think of though very unlikely unless those screws have been there for a long long time... C) When 2 metals are touching each other, they act like liquids in really really slow motion in that the property of diffusion applies to them. This means that the brass on the brass screw with start to move over onto the steel screw and the steel will start to move over on the brass... This is normally a very very very slow process, but is speed up by heat. This is why when you change the spark plugs in your car you but anti-seizing stuff on them, because at high tempertures, this process is speed up and after time, the sparkplug with meld with the engine. But my bets goto A and B first.
Another thing about the moisture... Rust is speed up even more when it does to wet or humid and then dry cycles. Example: A plate of
iron that is dipped in water, allowed to dry and then this is repeatly done, will rust faster than a peice of
iron that is left submerged in water... This has to deal with the evaporation of the water and the bonding... Because the electrons are all happily bonded in body of water, but when it evaporates those bonds break.
Anyway, as far as rust being on another peice of metal that is not touching a rusting peice of metal, it is simple. They are both rusting. Rust isn't a virus. It won't jump from one peice to another. Both peices of metal are simply rusting. Rust can start anywhere, anytime where there is
iron and oxygen.
How is it that you can remove rust by way of DC
current, yet batteries that get old tend to rust when the acid leaches
thru the container? How is it that high temperatures tend to rust un-treated metal in an expediated way at times over that of metals that got and stayed moist? This all at times no matter what type of metal or surface treatment is in use.
The reaction is speed up by heat because heat is energy. They extra heat excites the electrons in the
iron. They get excited, and they are more likely to bond with oxygen. And like bahaha said, the electricity splits the Fe
2O
3 molcule and leaves with Fe(III)(s) and O
2 again.. Why you can't do that with AC I'm not sure... maybe you can... I don't know, that's more a weird physics problem...
Does that
clear things up abit? Please, ask questions...
Alrighty, I'm outtie-
-Luke