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Offline uperkurk

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Corrosives
« on: December 08, 2008, 02:42:11 PM »
Hello, I think this is the correct section. I am curios to know what chemicals are corrosive to steel and iron. I know that there are many different types of steal but I mean the general type that is used in houses and small buildings. I think the strongest is sulfuric acid but what other liquids are extremely corrosive to steel and iron. Also I want to know what chemicals when mixed produce the same strength as sulfuric acid. I have know clue about chemistry at all so sorry if this seems like a really straight forward question. Thanks

Offline macman104

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Re: Corrosives
« Reply #1 on: December 08, 2008, 03:28:08 PM »
If you have no experience with chemistry, I wouldn't advise mixing around with concentrated acids.  Can you post a little bit more about what you need the acid for, and maybe someone will be able to help you out better.

Offline uperkurk

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Re: Corrosives
« Reply #2 on: December 09, 2008, 08:17:41 AM »
Well I watched an episode on a tv program called prison break and had two empty tubes of toothpaste and he fill them with some chemicals I dont know which ones. It corroded the steal pipe to the point where you just just snap it off. I wasnted t know if this was a possibility or it was just fake and could never happen. The pipe was like the same sort of steal as a ventaliation system. The big square vents that trun through buildings. I just want to know if sulfuric acid could do this and what chemicals when mixed to do this. Try to explain clearly because I font know anything about this kind of stuff, I'm just curious. Thanks.

**EDIT** I just found this formular that he used but I dont understand what it meams. Any help explaining this...?

 H2SO4 + Ca3(PO4)2 + 6 H2O ↔ 2 H3PO4 + 3 CaSO4.2H2O

It may be hard for you to explain but please try. Thanks

Offline Borek

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Re: Corrosives
« Reply #3 on: December 09, 2008, 08:49:37 AM »
It was a movie chemistry, not the real world chemistry.
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Offline uperkurk

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Re: Corrosives
« Reply #4 on: December 09, 2008, 09:11:50 AM »
So that forumlar means nothin. The chemical symbals are just made up? Well I know that the molecular formula for sulfuric acid is H2SO4 so what do the rest mean? I understand that this is just a program on tv but I also understand that some chemicals when mixed become extremely corrosive. I only wanted to know what chemicals when mixed become very corrosive. If you don't just just say.

Offline Borek

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Re: Corrosives
« Reply #5 on: December 09, 2008, 02:06:46 PM »
The reaction equation is real, but it has nothing to do with iron corrosion. It even doesn't contain iron (Fe).
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Offline P

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Re: Corrosives
« Reply #6 on: December 10, 2008, 04:11:00 AM »
Phosphoric acid can actually be used to reduce rust back into iron - it wont disolve the iron.
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Offline uperkurk

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Re: Corrosives
« Reply #7 on: December 10, 2008, 07:57:44 AM »
Thanks for your replies. I'm not 100% sure but I think sulfuric acid is the most corriosive liquid. I know that if it touches skin it causes very nasty blistering but realistically if I had a 1 inch think plank of steel and I pour some sulfuric acid on it would it start eating away at the steel so after 2 days or so I could just snap it off? Or is there any chemicals that can do this. I know some house hold cleaning liquids contain corrosive chemicals but nothing compared to sulfuric acid.

Offline Borek

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Re: Corrosives
« Reply #8 on: December 10, 2008, 08:00:20 AM »
Phosphoric acid can actually be used to reduce rust back into iron - it wont disolve the iron.

Reduce?
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Offline Borek

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Re: Corrosives
« Reply #9 on: December 10, 2008, 08:05:44 AM »
I'm not 100% sure but I think sulfuric acid is the most corriosive liquid.

As long as you have not defined precisely term "corrosive" and you have not proposed a way of measuring "corrosiveness" such a statement doesn't mean anything. I don't have an example at hand, but I am more then sure that there are alloys that will be very hard to dissolve in sulfuric acid (no matter how concentrated), but will get easily dissolved in even diluted NaOH.
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Offline azmanam

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Re: Corrosives
« Reply #10 on: December 10, 2008, 09:04:39 AM »
This kind of reminds me of an old joke:

Scientist 1: I've done it!  I've invented a universal solvent!  It will dissolve EVERYTHING!
Scientist 2: What are you going to store it in?

If it can 'corrode' prison bars, what are the chances it won't dissolve the toothpaste tube and get all over the prisoner's hand?
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Offline P

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Re: Corrosives
« Reply #11 on: December 11, 2008, 04:19:57 AM »
Phosphoric acid can actually be used to reduce rust back into iron - it wont disolve the iron.

Reduce?

Perhaps I should have said convert.  I figured that the Fe oxidises to form the rust, so it's conversion back to iron (and thus loss of oxygen) would be a reduction, no?

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Offline Borek

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Re: Corrosives
« Reply #12 on: December 11, 2008, 05:30:16 AM »
You will not reduce the iron, you will just convert oxidized iron from the solid oxide to oxidized iron in dissolved iron phosphate.
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Offline uperkurk

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Re: Corrosives
« Reply #13 on: December 11, 2008, 12:39:18 PM »
OK I have no clue what you lot are talking about now lol, I dont mean dissolve to dust I mean like waves hitting a rock will eventually make it weak and it will corrode. I just picture the experiment like having a steel bowl like a cereal bowl and then then pouring some sulfuric acid in it, leave it for a few days then it is weak enough to just hit it with a hammer and it will go through.

Azmanam you said "If it can 'corrode' prison bars, what are the chances it won't dissolve the toothpaste tube and get all over the prisoner's hand?"

The chemicals in the toothpaste tubes only become a corrosive when combined. I wish I could explain abit more lol but I dont know anything about chemistry. The way I see it is regardless or purity or how much it is concentrated or whatever my simple question is, "is there any chemicals that have the strength to corrode, not disolve, but corrode a steel bar 1 inch thick?"

Offline Arkcon

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Re: Corrosives
« Reply #14 on: December 13, 2008, 11:16:30 AM »
If you read the responses carefully, you'll see that the answer is no.  You can't rapidly, or reasonably quickly dissolve steel, with something you can carry in a small tube.

Conc. sulfuric acid will rapidly char organic materials, turning paper, wood, or living tissue into carbon and steam.  But iron would be inert to it -- a different reaction would be needed, we'd want a strong solution, not a concentrated one, and still, it would corrode thin steel, over time, not attack dimensional steel.  Likewise, phosphoric acid is a weak acid, no matter how strong it is, it doesn't hurt iron -- it is , like P: has alluded to, very good at reacting with the coating of rust on the outside of the iron, and making a thin coating of iron phosphate, like Borek: has explained.

We understand that you're new to chemistry, and you're trying to learn.  But we'd like to think that you'd be able to think of things in terms of scale.  Consider: a tube full of some magic juice (not a chemical, given the properties assigned to it,) can soften bars.  What if you had a jar full?  You'd be able to melt vault doors with it.  A shell, of the size the US Air Force can drop would be able to liquefy a half a dozen armored tanks, leaving some badly burned people sitting confused on the ground.  A tanker truck of it, driven into a building, would melt it down.  Yes things like that do happen, but not with a chemical, with lots of heat, and effort to get the attack into place.  Otherwise, we'd never be able to build anything that could hold anyone.  Moderate amounts of acid, like acid rain, would be destroying our structures in a few years, instead of taking centuries.  We wouldn't even have the same sort of culture and civilization we have now, if nothing could endure long enough.

Now, I saw on Mythbusters, they tested the story, that someone in a Mexican prison, broke out by dissolving his bars with the vinegar content of his daily salsa ration, perhaps augmented by oxidation caused by wiring his bars electrically.  Adam and Jamie didn't have the luxury of months of effort, so they weren't very successful.  But I don't doubt the myth strongly, if bars are neglected, if maintenance isn't constantly performed, sure, moderate effort may have result -- I don't know if that was worked into the storyline.  I do know, for some prisoners, there are no bars -- prisoners in the kitchen staff may take a delivery from the back, with no bars -- just 50 yards to the woods, and nothing to stop them.  Just the guard, in a tower, with a rifle.  The person watching them will even tell them, "Feel free to give it a try."  It's just another example, things in this world we live in are designed so that, if you want an extraordinary benefit, you need extraordinary effort.  Many newbs on this forum do not seem to be able to respect that, and want a superlative result, for little effort.

For a shorter explanation along these lines, see this post:
http://www.chemicalforums.com/index.php?topic=27366.0
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

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