Acidic environments (1 Viewer)

[dingding]

I had a quick search and i couldnt find anything about it.

For the dot point "explain that acidic environments accelerate corrison.." i always that that it was becasue

1/2O2 +H20 +2e- <--> 2OH-

was replaced by

1/2O2 + 2H^+ +2e^- <--> H2O​

as the dominate reduction reaction and since it has a higher reduction potential it acclerated the process.

But, it produces H2O not OH- which is needed for the rest of the rust process.

So my question is, is this the right explanation? andif it is, where does the OH- come from that is needed to continue the corrosion proccess?

 

[Not Too Bright]

my teacher told me something different from that H+ ions can oxidise iron

Fe(s) + 2H+ --> Fe2+(aq) +H2(g)

and for anaerobic bacteria

S042- + 10H+ 8e- --> H2S + 4H20
sulfate ion

 

[maatsby]

its about le chatelier's principle.
during corrosion OH- ions are produced. in acidic conditions u are adding H+ ions which react with the OH- ions, taking them out of the system. The equilibrium shifts to oppose the change by favouring the reaction that will produce more OH- ions (to replace those taken out by H+), in this case the forward reaction ie. corrosion.
this is another reason why corrosion occurs quickly at great depths. sulfate reducing bacteria also produce H+ ions thus making the environment more acidic and accelerating corrosion.

 

[steve_ell]

in acidic environments compared with neutral or basic the is the presence of the H+ ion. The H+ ions are able to react with metals and hence corrode.

Fe(s) + 2H+ --------> Fe2+ + H2(g)

you can alos talk about how the reducing potential of oxygen and hydrogen is greater than the redcing potential of oxygen and water.

2O2(l) + 4H+ + 4e- -----> 2H2o E0 = +1.23

2O2 (g) + 2H2O + 4e- -----> 2OH- EO = +0.40

this shows that there is a greater rate of reaction and happens in preference when H+ is in the water.

you also need to talk about SRB

 

[Xayma]

There is a difference between rusting and corrosion, rusting is a form of corrosion but it is not the only way.

If it is HCl for example FeCl₂ will be formed as a dissolved salt.