Water electrolysis - what is happening to an iron anode?
On an anode made of iron, some of the removed electrons may be used oxidizing iron metal to ferrous iron(II) ions, or oxidizing iron(II) ions to iron(III), rather than bubbling off oxygen gas.  Pushing more current through the cell is likely to result in gas evolution alongside the iron oxidation, since all three of these processes will run simultaneously.

$$\ce{Fe(metal) -&gt; Fe^{2+}(aq) + 2 e^- }$$
$$\ce{Fe^{2+}(aq) -&gt; Fe^{3+}(aq) + e^- }$$ 
$$\ce{2H_2O(liquid) -&gt; O_2 (gas) + 4H^+ (aq) + 4e^- }$$  

Ferrous iron(II) ion solutions are a pale green, but rapidly oxidize in air to vivid red-brown ferric iron(III).  Iron oxides and hydroxides form precipitates and slimes in a variety of colors including black (magnetite), red (iron(III) oxide), and yellow (iron(III) hydroxide).