Fe mechanisms Mechanism #1 (pH 2) Anode: ${\text{2Fe}}_{\left(\text{s}\right)}-{\text{4e}}^{-}\to {\text{2Fe}}_{\left(\text{aq}\right)}^{2+}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=+0.\text{447}\text{\hspace{0.17em}}\text{V}\right)$ (1) ${\text{2H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}-{\text{4e}}^{-}\to {\text{O}}_{\text{2}\left(\text{g}\right)}+{\text{4H}}_{\left(\text{aq}\right)}^{2+}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=-\text{1}.\text{229}\text{\hspace{0.17em}}\text{V}\right)$ (2) Solution: ${\text{2Fe}}_{\left(\text{aq}\right)}^{2+}+{\text{4OH}}_{\left(\text{aq}\right)}^{-}\to \text{2Fe}{\left(\text{OH}\right)}_{\text{2}\left(\text{s}\right)}$ (3) Cathode: ${\text{8H}}_{\left(\text{aq}\right)}^{+}+{\text{8e}}^{-}\to {\text{4H}}_{\text{2}\left(\text{g}\right)}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=0.000\text{\hspace{0.17em}}\text{V}\right)$ (4) Total: ${\text{2Fe}}_{\left(\text{s}\right)}+{\text{6H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\to {\text{O}}_{\text{2}\left(\text{g}\right)}+{\text{4H}}_{\text{2}\left(\text{g}\right)}+\text{2Fe}{\left(\text{OH}\right)}_{\text{2}\left(\text{s}\right)}$ (5) Mechanism #2 (pH 7) Anode: ${\text{2Fe}}_{\left(\text{s}\right)}-{\text{4e}}^{-}\to {\text{2Fe}}_{\left(\text{aq}\right)}^{2+}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=+0.\text{447}\text{\hspace{0.17em}}\text{V}\right)$ (1) ${\text{Fe}}_{\left(\text{aq}\right)}^{2+}-{\text{e}}^{-}\to {\text{Fe}}_{\left(\text{aq}\right)}^{3+}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=-0.\text{771}\text{\hspace{0.17em}}\text{V}\right)$ (6) ${\text{Fe}}_{\left(\text{s}\right)}-{\text{3e}}^{-}\to {\text{Fe}}_{\left(\text{aq}\right)}^{3+}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=+0.0\text{37}\text{\hspace{0.17em}}\text{V}\right)$ (7) Solution: ${\text{Fe}}_{\left(\text{aq}\right)}^{2+}+{\text{2OH}}_{\left(\text{aq}\right)}^{-}\to \text{Fe}{\left(\text{OH}\right)}_{\text{2}\left(\text{s}\right)}$ (3) ${\text{2Fe}}_{\left(\text{aq}\right)}^{3+}+{\text{6OH}}_{\left(\text{aq}\right)}^{-}\to \text{2Fe}{\left(\text{OH}\right)}_{3\left(\text{s}\right)}$ (8) Cathode: ${\text{8H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}+{\text{8e}}^{-}\to {\text{4H}}_{\text{2}\left(\text{g}\right)}+{\text{8OH}}_{\left(\text{aq}\right)}^{-}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=-0.\text{828}\text{\hspace{0.17em}}\text{V}\right)$ (9) Total: ${\text{3Fe}}_{\left(\text{s}\right)}+{\text{8H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\to \text{Fe}{\left(\text{OH}\right)}_{\text{2}\left(\text{s}\right)}+\text{2Fe}{\left(\text{OH}\right)}_{3\left(\text{s}\right)}+{\text{4H}}_{\text{2}\left(\text{g}\right)}$ (10) Mechanism #3 (pH 12) Anode: ${\text{2Fe}}_{\left(\text{s}\right)}-{\text{6e}}^{-}\to {\text{2Fe}}_{\left(\text{aq}\right)}^{3+}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=+0.0\text{37}\text{\hspace{0.17em}}\text{V}\right)$ (7) Solution: ${\text{2Fe}}_{\left(\text{aq}\right)}^{3+}+{\text{6OH}}_{\left(\text{aq}\right)}^{-}\to \text{2Fe}{\left(\text{OH}\right)}_{3\left(\text{s}\right)}$ (8) Cathode: ${\text{6H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}+{\text{6e}}^{-}\to {\text{3H}}_{\text{2}\left(\text{g}\right)}+{\text{6OH}}_{\left(\text{aq}\right)}^{-}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=-0.\text{828}\text{\hspace{0.17em}}\text{V}\right)$ (9) Total: ${\text{2Fe}}_{\left(\text{s}\right)}+{\text{6H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\to \text{2Fe}{\left(\text{OH}\right)}_{3\left(\text{s}\right)}+{\text{3H}}_{\text{2}\left(\text{g}\right)}$ (11) Al mechanism Mechanism (pH 7) Anode: ${\text{Al}}_{\left(\text{s}\right)}-{\text{3e}}^{-}\to {\text{Ale}}_{\left(\text{aq}\right)}^{3+}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=+\text{1}.\text{66}\text{\hspace{0.17em}}\text{V}\right)$ (12) ${\text{2H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}-{\text{4e}}^{-}\to {\text{O}}_{\text{2}\left(\text{g}\right)}+{\text{4H}}_{\left(\text{aq}\right)}^{+}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=-\text{1}.\text{229}\text{\hspace{0.17em}}\text{V}\right)$ (2) Solution: ${\text{Al}}_{\left(\text{aq}\right)}^{3+}+{\text{3OH}}_{\left(\text{aq}\right)}^{-}\to \text{Al}{\left(\text{OH}\right)}_{3\left(\text{s}\right)}$ (12) $\text{Al}{\left(\text{OH}\right)}_{4\left(\text{aq}\right)}^{-}\to {\text{OH}}_{\left(\text{aq}\right)}^{-}+\text{Al}{\left(\text{OH}\right)}_{3\left(\text{s}\right)}$ (13) Cathode: ${\text{4H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}+{\text{4e}}^{-}\to {\text{2H}}_{\text{2}\left(\text{g}\right)}+{\text{4OH}}_{\left(\text{aq}\right)}^{-}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\left(E°=-0.\text{828}\text{\hspace{0.17em}}\text{V}\right)$ (9) ${\text{Al}}_{\left(\text{s}\right)}+{\text{4OH}}_{\left(\text{aq}\right)}^{-}-{\text{3e}}^{-}\to \text{Al}{\left(\text{OH}\right)}_{4\left(\text{aq}\right)}^{-}$ (14) Total: ${\text{2Al}}_{\left(\text{s}\right)}+{\text{8H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\to {\text{5H}}_{\text{2}\left(\text{g}\right)}+\text{2Al}{\left(\text{OH}\right)}_{3\left(\text{s}\right)}+{\text{O}}_{\text{2}\left(\text{g}\right)}$ (15)