About Cola and rusting

[Sigmarus]

So im sure many of you guys know that Cola can remove rust,but im curious how does it remove it(The process).I heard its something to do with ions and how acid and alkali work?

[DrP]

I think it is over hyped how effective it can be. In theory the phosphoric acid can reduce the iron in the iron oxide back to iron I suppose, but it never seems to be as effective as you see in these you-tube vids of demonstrations of it.

[Sigmarus]

But ermm do you know how the process of acids and alkalis work in this removal of rust?

[DrP]

By reducing the oxide back to the metal as I said above. It is a reduction reaction. Look up REDOX reactions and start from there.

[Manticore]

It works very nicely in some circumstances. I had a wing fuel tank drain valve seize up once. Dumping it in a glass of Coke freed it up quite quickly. The acid may be fairly weak, but the effervescence helps to get it into places where a plain liquid would probably not go (so it has to be fresh Coke, not that flat stuff left over from last night!).

[DrP]

Maybe so Manti - but I am just a little sceptical of these you-tube vids you see of a totally rusted bumper becoming gleaming again after a can of coke has simply been poured over it. Those types of vids are also sometimes used to suggest that coke is bad for you by the anti chem folks- "look what it does to rust! what's it doing to your gut!?!?!" - (I am pretty sure this emoticon used to have a different name... one we can't use anymore on the forum - lol).

[Sigmarus]

is there any equation to show the reduction effect between coca-cola and rust?Thanks!

[Manticore]

Maybe so Manti - but I am just a little sceptical of these you-tube vids you see of a totally rusted bumper becoming gleaming again after a can of coke has simply been poured over it. Those types of vids are also sometimes used to suggest that coke is bad for you by the anti chem folks- "look what it does to rust! what's it doing to your gut!?!?!" - (I am pretty sure this emoticon used to have a different name... one we can't use anymore on the forum - lol).

 

Yeah, those are total bullshit. Phosphoric acid (which is what Coke contains) converts iron oxide into iron phosphate. Effectively, the flaky rust changes into a stable coating (more compact than the rust - which is why it could free my valve). This phosphate coating then protects against further rust.

Edited April 27, 2017 by Manticore

[DrP]

Looking it up:

 

Phosphoric acid + Iron Oxide -> Iron Phosphate + Water

 

 

So it seems it converts to the phosphate rather than back to iron as I said. Sorry, makes sense though.

[John Cuthber]

By reducing the oxide back to the metal as I said above. It is a reduction reaction. Look up REDOX reactions and start from there.

Be careful saying things like that: someone might do what you say.

[hypervalent_iodine]

Looking it up:

 

Phosphoric acid + Iron Oxide -> Iron Phosphate + Water

 

 

So it seems it converts to the phosphate rather than back to iron as I said. Sorry, makes sense though.

 

 

Just to be a little more explicit than John Cuthber... The oxidation states of the iron on either side of that equation are what? Because that doesn't look like any redox process I've heard of. Moreover, acids tend not to be great at reducing things, making your statement that it turns back to the metal a bit off.

[DrP]

 

The oxidation states of the iron on either side of that equation are what? Because that doesn't look like any redox process I've heard of. Moreover, acids tend not to be great at reducing things, making your statement that it turns back to the metal a bit off.

 

Yea - it doesn't turn it back to the metal, it goes to the phosphate, which then helps protect from further rusting - I was wrong about the rust being reduced back to iron.... partly why I said "So it seems to convert to the phosphate rather back to the iron as I said, Sorry.." I just assumed at first it was a reduction back from the oxide, which, after looking it up I saw that it wasn't.

 

It's not hard to look it up though... typing 'rust conversion' into google give you loads of info about it.