Wikipedia quotes the electro-chemical reaction in a NiFe battery as follows:
2 Ni(OH)₂ + 2 OH⁻ ↔ 2 NiO(OH) +2 H₂O +2 e⁻ (eq. 1)
at the positive plate. This is for the discharging case as you are reading left to right. For changing, you must read the above half equation right to left. The reaction is exactly the same in reverse so, the reaction is entirely reversible. That’s what the symbol ↔ means. Good to have in a rechargeable battery, right?

Now, that was a half reaction at one terminal. They say the other half looks like:
Fe + 2 OH⁻ ↔ Fe(OH)₂ + 2e⁻ (eq. 2)
at the negative plate. The iron of the plate is clearly part of the reaction. Hmmm. That means the iron is attacked in the process.

Only one problem here. The reaction is entirely WRONG! Boy, oh boy, that will mess with your head as you try to make sense of other ‘documentation’ floating around out there. Ask me how I know.
[UPDATE: Wikipedia has corrected their page.]

Since Wikipedia got it wrong, now what? Well, this paper gives the correct primary reaction from the discharging point of view as:
2NiO(OH) +Fe + 2H₂O ↔ 2Ni(OH)₂ +Fe(OH)₂ (eq. 3)
E0 = 1.37 V

Great, and the iron of the plate is still part of the reaction? But wait! That’s not the whole story. It seems there is a second step reaction Wikipedia never mentions and it could be more important in day to day operations of NiFe batteries:
NiO(OH) + Fe(OH)₂ + H₂O ↔ Ni(OH)₂ + FeO(OH) · H₂O (eq. 4) E0 = 1.05 V

So, here we have a reaction that doesn’t eat directly at the plate’s structural iron. We see that the charge and discharge of NiFe batteries involves the transfer of oxygen (or probably more correctly, hydroxyl groups) from one electrode to the other; i.e. from one group of plates to the other. Hence this type of cell is sometimes called an oxygen lift cell. In a charged cell the active stuff of the positive plates is super-oxidized, and the material of the negative plates is in a spongy or reduced state.

When a NiFe battery is charged, the green nickel II hydroxide (Ni(OH)₂) on the positive terminal becomes black nickel III hydroxide (NiO(OH)). On discharge, it reverts to nickel II. Let me say that another way. In a charged state, the cathode of our battery is made up of mostly black nickel III hydroxide, NiO(OH). The discharged state finds mostly green nickel II hydroxide, Ni(OH)₂ at this positive electrode. Is it any wonder that confusion abounds when it comes to determining what material is used where, when or how?

Remembering this can save an incredible amount of confusion when reading descriptions of Edison cells. It will really help cut through the BS out there.

If we were to combine these two reactions into one discharge equation we could say:
3NiO(OH) + Fe + 3H₂O ↔ 3Ni(OH)₂ + FeO(OH)·H₂O (eq. 5)
supplying one electron for each molecule of hydroxide, provided receptor sites are available. We might avoid eating iron if we provide a suitable oxide of iron instead. And, of course, charging is the exact reverse of this equation.