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Making rust

  1. Jun 22, 2004 #1

    mrjeffy321

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    Hello, I want to make some rust (iron oxide, Fe2O3), and I know there are many ways of going about this, but I would like to be able to get a significant quantity and be able to use it within a short period of time.

    Here are the 4 methods I have tried:
    -electrolysis, putting a peice of iron on the annode and letting it corrode, but this takes a long time to get it out of the water and it isnt very pure
    -the old fashion was of putting an iron nail in salt water, but this takes a while to get any usefull amount
    -next I tried putting some very thin steel wool into water (with and without salt), I am most pleased with this method because it seems to rust rather quickly and I dont need that much water to do it with, it wont take as long to evaporate off the water and get the rust, but it still takes too long to do that

    -I know that if you "burn" steel wool, you are oxidizing the iron and making rust, well this is fast, and it should produce lots of rust, but when I trie it, it does produce a rather entertaining show with some sparks, but when it is over, all I have is a darker, more britter version of what I started with, I dont "see" any rust, but isnt that what it is suppose to produce?
    if I could get this method to work, it would be my most preferable, it is the fastest and easiest in producing the most rust, but I cant seem to get the rust I am making, how can I do this? is it becase that even though the iron is reacting to make the rust, the other elements in the "Steel" wool are keeping it from being gotten some how?

    any other fast mean of making the rust would work to, but I would still like to learn what the problem is with the steel wool method aswell.

    thanks
     
  2. jcsd
  3. Jun 22, 2004 #2

    chroot

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    The fastest and easiest method to make rust is to put some steel wool in a dish full of vinegar, then add a little bleach. It'll turn to rust nearly instantly. WARNING: THE PROBLEM WITH THIS METHOD IS THAT THE SOLUTION EVOLVES CHLORINE GAS, WHICH IS HIGHLY TOXIC, HARMFUL TO THE EYES AND RESPIRATORY TRACT, AND CAN KILL YOU. IF you attempt to use this method, do it outdoors, hold you breath when adding the reagents, and don't go anywhere near the dish for at least a few minutes after combining them. Please be extremely, extremely careful with this method.

    - Warren
     
  4. Jun 22, 2004 #3

    mrjeffy321

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    wow, you are so helpful.

    I am well aware of the dangers of chlorine, and will be carefull while doing this.
     
  5. Jun 23, 2004 #4

    Gokul43201

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    I think peroxide would work as well (if not better)...but it is easier to find bleach.
     
  6. Jun 23, 2004 #5

    mrjeffy321

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    well, I am still trying to find out what the problem is with the burning of the steel wool.

    I am also trying to know exactly what is going on with the bleach + vinegar reaction, what is the reaction formula for that?

    bleach is NaClO right?
    Fe(s) + C2H3O2(aq) + NaClO(aq) ---> F2O3(s) + Cl2(g) + ......

    does it make sodium hydroxide, and then the hydroxide make the rust, is CO2 produced too?
     
  7. Jun 23, 2004 #6

    chroot

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    Well, you probably don't have nearly a large enough temperature to actually burn iron with a standard lighter. All you're doing is depositing carbon soot on it.

    Also, I mixed up my reagents -- you need a 2:1 ratio of bleach to vinegar, so you're better off immersing the steel wool in bleach and adding some vinegar, not the other way around.

    I'm not quite sure about the full chemical equation for the reaction, but I'll work on it a bit and see if I can figure it out. Keep in mind as well that rust is typically anhydrous, Fe203 * 5H20 or something...

    - Warren
     
  8. Jun 23, 2004 #7

    mrjeffy321

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    well, im not totaly certain, but I have seen my idea of the steel wool "rusting" confirmed from various other sources, also when I do burn it (by means of a 9 volt battery or flame, long after I take the heat source away, the reaction continues, it does look like something besides just soot is happening. It is like it is burning in slow motion, the steel wool nearest the heat turns red/orage and throws off sparks and smoke and this continues upward untill all of the availible wool is used up and after it is done you can tell that something has happened and you cannot react that same peice again.

    when this [the reaction] is over, I want to collect this rust, without if possible, also collecting the remnents of the reaction that I did to make it, will this be possible. for example, when I rust somehting with salt water, in order for me to collect the rust, I decant and then evaporate all the water I can, but this leaves the salt behind which mixes with the rust, what will be left behind from the bleach and vinegar reaction?

    how does this reaction look, could this be close, it is unballenced of course

    Fe(s) + C2H3O2(aq) + NaClO(aq) -> Fe(s) + Co2(g) + Cl2(g) + NaOH(aq)

    the iron does nothing in the first reaction, but the acedic acid and bleach make chlorine gas and carbon dioxide, and they bubble away and are out of the reaction, that leaves the iron and the sodium hydroxide

    Fe(s) + NaOH(aq) -> Fe(s) + Na+(aq) + OH-(aq) -> Fe2O3(s) + H2O + Na+

    then the sodium hydroxide breaks up into ions and the hydroxide ion goes and splits up to make the Iron(III) oxide and more water, leaving just the sodium ion behind, but this last part seems wrong to me, possible there is stil some chloring hanging around from the first reaction to make sodium chloride, but that doesnt seem quiet right either

    or even better yet, how about this one, but it doesnt produce chlorine gas:
    2Fe(s)+ 2C2H3O2(aq) + 7NaClO(aq) -> Fe2O3(s) + 3H2(g) + 4CO2(g) + 7NaCl
     
  9. Jun 23, 2004 #8

    mrjeffy321

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    you know what, none of those formulas that I gave above is correct, because I forgot the extra hydrogen on acitate to make it acetic acid, so all of those are wron, and if you just mentally add in an extra hydrogen, then I dont thnink it will work, the hydroxied would perhaps combine with it and make water, and then leave out the sodium again.
     
  10. Jun 23, 2004 #9

    Gokul43201

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    Actually, I believe it's the following :

    Bleaching action is simply oxidation by nascent (atomic) oxygen released from the bleach :
    3NaOCl + 2Fe -> 3NaCl + Fe2O3

    The other reaction that simultaneously occurs (even in the absence of iron - yes, this is what makes bleach smell of chlorine gas) is :

    2NaOCl + 2H(+) (from vinegar) + 2e(-) -> 2NaOH + Cl2
     
  11. Jun 23, 2004 #10

    mrjeffy321

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    ok, so basicaly the vinegar is just speeding up the reaction, it isnt necesary.

    and the bleach only reaction, amkes the rust, along with plain old salt water, sow I just need a wa to seperate the rust from the salt.
     
  12. Jun 23, 2004 #11
    The heating of the steel wool is interesting. If I am understanding you correctly there is something left over when the burning stops. Everything doesn't convert to smoke.

    If what is left is black, and very brittle so that you can crumble it easily, it is probably Fe3O4. This is magnetic oxide of iron or Magnetite. If you can attract it with a magnet, I'll bet that's what you've made. If you can't, then it is something else.

    I wonder about the smoke. It could be that the manufacturers coat the steel wool with some very light oil so stave off rusting. Just a guess. This might account for why it burns by itself.

    There is another possibility, which is that in the heating, somehow, ferrous oxide (FeO) is first formed. FeO has the property that it burns spontaneously upon contact with oxygen in the air. This might account for why it continues to burn by itself. Again just a guess.

    If you put something like a dinnerplate in the freezer untill it is cold you may be able to get the smoke from this burning to condense on it. If it is soot, you may be able to measure its resistence with a meter. That would indicate an oil coating on the steel wool. If it won't conduct, it may be one of the iron oxides.

    I made a whole bunch of rust a couple years ago with old nails and vinegar water. I can't for the life of me remember what I wanted it for. Anyway, I put the nails and vinegar water in one of those cheap little rock tumblers so that the rust would continually be scraped off the nails as it formed. Once in a while I poured the liquid out through a coffee filter, added more to the tumbler and set it going again. You can wash the rust as many times as you think you need to and get rid of most of the water with the coffee filter method, which is cheap. Each time you do it you lose some of the rust to the filter, though, can't scrap it all out.

    -Zooby
     
    Last edited: Jun 23, 2004
  13. Jun 23, 2004 #12

    Gokul43201

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    Salt is soluble in water; rust isn't.
     
  14. Jun 23, 2004 #13

    mrjeffy321

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    the material that is left over after burning the steel wool appears[to a color blind person] to be more blueish and darker than the original steel wool, it feels more brittle and flakes more easily. I think the resulting material is magnetic, but the magnet could just be attracting to the unreacted particles of the original steel wool that excaped burning, which was magnetic to start with. when I soak the resulting steel wool in water, it appears to do the same thing as the normal steel wool, nothing at first, but slowly the water turns brown as it gets filled with rust.

    I have seen places online that claim that burning the steel wool does infact make Fe2O3, but I cannot find any right now. perhaps it does, but the extra heat of the reaction makes a second reaction to turn the Fe2O3 into the magnetic Fe3O4.
     
  15. Jun 23, 2004 #14

    Gokul43201

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    That probably is Fe3O4 (my guess) you are seeing. It is often refered to as mill-scale in the heat treatment of wrought steels and is generally described as black in color. You may have seen blue from the HAZ (heat affected zone -like near a weld joint).

    The oxidation state of Fe in Fe3O4 is +2.67. When this is dropped into the bleach solution, it gets further oxidized to the +3 state (in Fe2O3). Also, this will make much less salt (NaCl) than if you just used the plain steel wool.

    Another thing you could do, if you had a sensitive balance, is weigh the steel wool before and after burning. If you measure more than a 65% increase in weight, you definitely have Fe2O3 in there.
     
  16. Jun 23, 2004 #15

    BobG

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    I can vouch for MrJeffy's claim that steel wool does indeed burn.

    Wrapping some steel wool around one end of a pencil, igniting it, and setting the other end in a centrifuge gets quite a reaction from the other students (not that I've ever tried this ... at least not more than once).

    From a functional stand point, steel wool is a great compliment to a steel/flint firestarter kit. It can take hours to actually get wood shavings to ignite from the sparks given off by flint and steel unless you're really good at it. Mashing your wood shavings into a pad of steel wool and then refluffing it allows you to get your fire started a lot quicker. The steel wool ignites just about the first time any spark hits it. It burns quickly, so you want the wood shavings intermeshed in the steel wool. They burn a little longer and give you enough time to start adding more wood.

    If you sort your laundry and wash cotton separately, the lint from the lint screen in the dryer works nearly as well as steel wool (maybe that's why the dryer manual says to clean the lint screen before every load).
     
  17. Jun 23, 2004 #16

    mrjeffy321

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    will non magnetic Fe2O3 naturaly turn into Fe3O4 on its own, just by using the energy from its surroundings?
    because when making the rust, it starts out redish brown and appears to be non magnetic, but now the older stuff that has been floating around in the water the logest has turned much darker, and the stuff that I have dried out, alot of it is attracted by a magnet. so that is why I am thinking I am getting alot of this magnetic dark stuff, the Fe2O3 is slowly changing to Fe3O4 on its own, I though you had to apply a lot more heat to get it to change.
     
  18. Jun 23, 2004 #17

    chroot

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    Have you tried bleach + vinegar yet? :smile:

    - Warren
     
  19. Jun 23, 2004 #18

    mrjeffy321

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    yes, I basicaly have 2 batches of rust right now; the stuff I made early on with salt water which I have dried out about half of it, and I also have the bleach and vinegar batch which is still very wet, that will probably take another day or two to dry depending on the weather. but even the stuff I just made today with bleach and vinegar shows signs of turning dark and there is a "skin" developing on the water, and some of it is magnetic.
     
  20. Jun 23, 2004 #19

    chroot

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    You seem to be very concerned about the purity of your rust -- may we ask what the rust is for, and why its purity is so essential?

    - Warren
     
  21. Jun 24, 2004 #20

    mrjeffy321

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    yes, I guess it might seem like I am very concerned about the rust purity, I think that is just is the way I am, I like to have things pure unless I intend to mix them, but I dont think I absolutely need pure Fe2O3 rust.

    I was intending to make the rust for a little thirmite reaction I wanted to try by burning Aluminum powder with the rust to make pure Iron and Aluminum Oxide, plus alot of excess energy :smile:
    but I dont think the purity of the rust will be all that important to this reaction
     
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