Shipwrecks DP (1 Viewer)

[underthesun]

Explain that acidic environments accelerate corrosion in non-passivating metals

The question is, why? Is it because there are more H+ ions, or what?

 

[PoLaRbEaR]

Yeh it's caused by the presence of more protons...
The H+ removes OH- from the reduction half equation:
H2O + O2 + 2e --> 2OH-
By Le Chatelier's Principle the equilibrium shifts to the right...
The protons are also being reduced in another equation:
2H+ +2e --> H2
More electrons are being removed from the metal, ie corrosion is accelerated...

 

[underthesun]

Thenk yu veri mache', det meid mi anderstend things beter

 

[PoLaRbEaR]

you spelt 'things' correctly...how appalling.. =)

 

[underthesun]

Jast wan mor thing, de ridakshon half ekwashon iz not a riversibel / ekwilibriyum riakshon, so hau ken it epplai tu de ekwashon?

H2O + O2 + 2e --> 2OH-

de ebav iz not ekwilibriyum, rait?

 

[Ragerunner]

Hmm.... am i on another planet?

 

[underthesun]

yur dringking tu mache' bir, mait!

bat siriusli, iz ridakshon half ekwashon a riversibel riakshon?

 

[PoLaRbEaR]

Originally posted by underthesun
Jast wan mor thing, de ridakshon half ekwashon iz not a riversibel / ekwilibriyum riakshon, so hau ken it epplai tu de ekwashon?

H2O + O2 + 2e --> 2OH-

de ebav iz not ekwilibriyum, rait?

Hmm sorry I might have been wrong then...
I think this makes more sense: when the H+ removes the OH- it produces H2O, which undergoes reduction, hence the cycle is repeated, meaning increased corrosion..

 

[Chand]

Originally posted by underthesun
yur dringking tu mache' bir, mait!

ragerunner:
i think he's sayin ur drinking too much

...mate

 

[Ragerunner]

Originally posted by Chand
ragerunner:
i think he's sayin ur drinking too much

...mate

hahaha

only 8 glasses at once

 

[Constip8edSkunk]

it is an equilibrium and polarbear's first post is correct

psst... 2 glasses, 1 head > 8 glasses, 8 heads

 

[underthesun]

Originally posted by Constip8edSkunk
it is an equilibrium and polarbear's first post is correct

psst... 2 glasses, 1 head > 8 glasses, 8 heads

So it is an equilibrium? Crap.. my notes are gonna be x2 messy now.. can someone confirm?

demmit!

 

[Azn fairies]

well according to conquering chem. it's equillubrm, but maclialn and excel say it's not ..also my teacher say it is ..so yeah ??

 

[jims]

i rmbr reading in the prelim chem excel book last yr that the most abundant element on earth (lithosphere) is silicon.

but back to the question, its probably the eqm thing. but what about this reaction:
Fe(s) + 2H(+)(aq) --> Fe(2+)(aq) + H2(g)
wouldnt that also help increase corrosion?

 

[Azn fairies]

yeah corrortion equations are at equillbrum...aslo jims ur equation:
Fe(s) + 2H(+)(aq) --> Fe(2+)(aq) + H2(g)

this is basically the rusting process..lol the fe is beening oxidise and the water is beening reduced..so the fe is rusting bascially..(galvaic cell)

 

[Constip8edSkunk]

yep, i think this is what that dot point is alluding to, in deep ocean anoxic conditions

 

[Affinity]

actually it's because when there's excess H+

the cathod reaction effectively becomes

O2 + 4H+ + 4e- -> 2 H2O E= +1.23 Volts

as compared to

O2 + 2H2O + 4e- -> 4OH- E = +0.40 volts

 

[ND]

And also because the OH- from O2 + 2H2O + 4e- -> 4OH- reacts with the H3O+, removing the product from the reaction and so speeding it up. I haven't read this explanation in any textbooks (most textbooks have the reason Affinity posted), but i remember reading this from an exemplar sample.

 

[xiao1985]

i fink the addition of h+ ions facilitates this reduction half reaction to occur:

o2 + 4h+ + 4e- <-------> 2h2o e = 1.23 v

which is more spontaneous than the corrosion equation in normal condition:

o2 + 2h20 + 4e- <---------> 4oh- e = 0.40 v

hence there is a greater potential, and makin the corrosion more readily.....

edit: guesss i type a bit slow .......