How long would steel last underground until it was no longer recognisable?

Discussion in 'Science' started by Foliage, Feb 8, 2015.

  1. Foliage

    Foliage Member

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    If you buried a plane in the ground that gets fairly typical rainfall each year, how many years would it take before it was corroded beyond a state that was not recognisable.

    If you went digging 1000 years later would you still find enough metal to know it was a plane?
     
  2. kesawi

    kesawi Member

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    Planes are predominantly aluminium alloys due to their lighter weight, although newer commercial airlines are now being made from carbon reinforced plastic.

    Do you want to know specifically about steel or planes?
     
  3. OP
    OP
    Foliage

    Foliage Member

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    Either or.
     
  4. RnR

    RnR Member

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    Given that they are pulling viking swords out of the ground which are more than a 1000 years old, yeah I would suspect a plane would last a 1000 years. Whether or not it would be recognisable as a plane would depend strongly on the ground conditions.
     
  5. oculi

    oculi Member

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    out of the ground or out of oxygen depleted bogs and so on? there are actually more surviving bronze age tools than iron age as they don't corrode like iron.

    (answering for aluminium as they don't make steel planes) I'd guess 2-300 years given the state of found WW2 planes i've seen on the telly, but even then there would be bits of glass, plastic, airline food lying around, and there would be high levels of aluminium oxide and other stuff indicating that there was a plane there once.

    Why do you ask?
     
  6. Recharge

    Recharge Member

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    I would imagine it would depend entirely of the medium in which it was burred, level of acidity, oxygen content, other minerals and level of moisture.
     
  7. RobRoySyd

    RobRoySyd Member

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    Also depends on it being pure metal or not. Some alloys of iron such as Hastelloy are very corrosion resistant. Same goes for aluminium which is rarely used in its pure form.
     
  8. kesawi

    kesawi Member

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    There is a standard which is used for estimating corrosion rates of steel. An extract can be found at http://www.steelconstruction.info/Corrosion_of_structural_steel#Chlorides. It is still highly variable even within each exposure classification. Assuming the upper end of a C2 environment the average corrosion rate is 25 microns per year. The steel will have two sides, and will corrode from bother of them, therefore the overall corrosion rate will be 50 microns per year. If the steel is 1mm thick (1000 microns), it will have fully corroded in approximately 20 years. This is only an estimate as environmental factors will ultimately determine how long it takes.

    Aluminium is a little more difficult to estimate as it corrodes at a logarithmic, rather than linear, rate. It initially corrodes rather quickly as it is highly reactive with oxygen however the aluminium oxide which forms on the surface acts as a protective coating. As more oxide develops the rate of corrosion slows. The rate of corrosion for aluminium is dependent on pH of the environment with a slightly acidic environment providing the lowest corrosion rates. I've see aircraft wrecks in PNG that are around 70 years old, both buried, exposed and in the sea which are still in reasonably good condition (some have even been recovered and fully restored). The thickness of the skins on some of these would have been no more than that of a soft drink can.
     
  9. power

    power Member

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    does this help?

     
  10. Ravennoir

    Ravennoir Member

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    The other side of it is, even if all the metal corroded away, the way the dirt would compact would leave behind a plane shaped hole. It could also change the composition of the dirt and perhaps leave colourisation
     
  11. power

    power Member

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    corrosion is simply a chemical reaction, so the oxide as you note will be left behind and if there are not air gaps etc it should retain some sort of shape.
     
  12. kombiman

    kombiman Dis-Member

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    I'm always amazed watching Time Team and that even if some metal, crap by todays standards, corrodes it still leaves enough marks in the ground to identify.
     
  13. OP
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    Foliage

    Foliage Member

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    Interesting vid!
     
  14. ikonz0r

    ikonz0r Member

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    Also how deep are you talking? If there is enough pressure it might just fossilise ;)
     
  15. newynut

    newynut Member

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    Airline food would be totally unchanged even after a few millenia.
     
  16. ThankDog

    ThankDog (Banned or Deleted)

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    As a tangent, I read the other day that something about the altitude, oxygen mixture or pressure in flight affected taste buds so that even the tastiest butter-poached Maine bug would taste like cardboard.
     
  17. broox

    broox Member

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    until you add a shirt ton of salt.
     

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