whats actually happening behind RUST?!

hi all,
there are 2 things about this chemical process that i find confusing.

first, the cathode. is the cathode also the iron (which plays the part of an anode as well) or it is oxygen?

second, the equation of the reduction of oxygen (O_sub_2). sources dont seem to be agreed on this. some say O2 (g) + 2 H2O + 4e- ------> 4 OH- , others say O2 (g) + 4 H+ (aq) + 4e- ------> 2 H2O(l) . which one is more correct then?

i understand perfectly how a voltaic cell works; but when it comes to how this applies to corrosion (and rusting to be specific), i am completely lost, so any help would be appreciated. thanks a lot.

Reply 1

Eau

If I remember correctly, cathode is the place where reduction takes place. Iron is not included as the cathode as it is being oxidised.

As for the 2nd question, both equations should be correct, one being in acid conditions, the other in basic. Both equations suggest rusting is faster in acidic conditions - do you see why?

Reply 2

poccapokie

Eau

As for the 2nd question, both equations should be correct, one being in acid conditions, the other in basic. Both equations suggest rusting is faster in acidic conditions - do you see why?