shipwrecks, corrosion n conservation (2 Viewers)

[MuffinMan]

magnesium is more reactive than iron
therefore OXIDATION OCCURS HERE
hence it is the anode
hence anode --> cathode (electrons flow neg --> pos)
hence magnesium ions will deposit on iron strip
wrong way around

 

[Firnovvwen]

the beaker that the student set up is NOT a galvanic cell, as such, because the reactions that take place aren't physically separated and there isn't an external conductor that carries electrons from one electrode to the next and so forth....

I didn't think it was a galvanic cell, and it wasn't electrolysis either. I hope I was right.

lol the exams over...just relax buddies

I agree. It's all over now so don't let it worry you.

Lol, I kinda just contradicted myself.

 

[Dumsum]

I said there is also a possibility of the iron rusting slightly due to the presence of water and tiny amounts of oxygen.

 

[Captain Gh3y]

I said there is also a possibility of the iron rusting slightly due to the presence of water and tiny amounts of oxygen.

I would have thought that because the iron is constantly undergoing reduction because of the magnesium, it cannot corrode.

 

[MuffinMan]

but the magnesium provided the cathodic protection so....the iron rusted less than if the magnesium wasnt there right?

 

[~ ReNcH ~]

I would have thought that because the iron is constantly undergoing reduction because of the magnesium, it cannot corrode.

Did you say that the iron deposits on the nail, or that it deposits on the bottom of the beaker? I said that it was a galvanic cell, though I'm most likely incorrect on second thought...I wonder if I'd be marked down. On that note, if you fulfil the criteria to get 4/4 and you then state something incorrect (provided it doesn't contradict what you said previously), do you still get 4/4 or are you penalised?

 

[Dumsum]

So a galvanic cell was produced? I didn't think that was a galvanic cell setup, considering the two metals weren't connected.

 

[mattplaysguitar]

i checked with my teacher and she agreed with this. we all know that the mg is more active, therefore it acts as a sactraficial anode and corrodes before then iron nail, once it has completely corroded, the iron nail is now capable of corroding itself, but the mg must be gone first...although she didnt look at the question wrong and has been known to make mistakes and work the real answer out later...

 

[mattplaysguitar]

So a galvanic cell was produced? I didn't think that was a galvanic cell setup, considering the two metals weren't connected.

the two metals were connected via the ions in the solution

 

[gogogadgetbrain]

there couldnt have been cathodic protection as there was no direct contact...

and i reckon the iron nail and iron deposits on the magnesium ribbon would have rusted

 

[thunderdax]

Everything that Abtari said in his post I 100% agree with. Thats exactly what I put for this question.

Also, with that 7 marker, i hope to god they don't mark it as an english question but instead see it as a way to test students' knowledge about different corrosion resistance methods.

 

[Dumsum]

the two metals were connected via the ions in the solution

There is no complete circuit. this is more like a "straight line" so to speak. So the way I viewed it was they were two completely separate systems, so the magnesium would displace iron ions out of solution and the iron could rust slightly. This was essentially the crux of my answer.

 

[thunderdax]

there couldnt have been cathodic protection as there was no direct contact...

and i reckon the iron nail and iron deposits on the magnesium ribbon would have rusted

Tell me, is there any real difference in terms of electrochemistry between the two metals touching each other and being separated by a few centimetres by an electrolyte? There isn't if you're talking about corrosion protection.

 

[gogogadgetbrain]

Tell me, is there any real difference in terms of electrochemistry between the two metals touching each other and being separated by a few centimetres by an electrolyte? There isn't if you're talking about corrosion protection.

yeah, for sure there is. when the magnesium oxidises the electrons are used to reduce the iron ions (in solution) instead of the iron metal (where they prevent rust).

 

[Dumsum]

OK. It seems everyone agrees that the magnesium and iron ions will undergo a displacement reaction. Think of it this way:

The magnesium is only going to displace iron ions that come into contact with it, so that means the ions that are on that side of the beaker. What takes place is an electron transfer: Mg + Fe²⁺ => Fe + Mg²⁺. Does this have ANY effect whatsoever on the goings-on over on the OTHER side of the beaker? I think not...

 

[The_Crow]

I don't know why you guys are arguing over it, it's quite simple, just read over your notes for cathodic protection. We have magnsium as the sacrificial anode, oxidizing, causing iron to be reduced at the iron cathode. It doesn't matter whether the two are touching, they are connected via an electrolyte, a conducting solution!!

 

[Dumsum]

IF, however, the two items were connected. Then as the magnesium oxidises, electrons could flow directly over to the iron, rendering it as a cathode. Iron ions in soluction could be reduced OVER THERE then, and thus the iron would not rust, and there would be iron deposits forming on the nail.

 

[Dumsum]

I don't know why you guys are arguing over it, it's quite simple, just read over your notes for cathodic protection. We have magnsium as the sacrificial anode, oxidizing, causing iron to be reduced at the iron cathode. It doesn't matter whether the two are touching, they are connected via an electrolyte, a conducting solution!!

The difference is in this the magnesium is ATTACHED to the iron hull. Read my above two posts for explanation.

 

[Mellonie]

Tell me, is there any real difference in terms of electrochemistry between the two metals touching each other and being separated by a few centimetres by an electrolyte? There isn't if you're talking about corrosion protection.

I agree with thunderdax i think he has hit the damn spot.

They gave us a solution Magnesium sulgate/iron(ii) sulfate solution allowing ions to be flowing or swapping or wateva

The same rules apply, magnesium will corrode, cuz its more reactive. The diagram is just the same thing Galvani set up, with two metals and a frog. Cuz the forg acted as the alectrolyte. and here the electrolyte is Magnesium Sulfate/iron (ii) sulafate solution

 

[gogogadgetbrain]

there is NO electron transfer between the magnesium and iron nail...therefor no cathodic protection