Abstract
Anodic oxidation products in 
of both planar and porous iron electrodes have been investigated with SEM techniques. On the first discharge level well‐defined crystallites of 
are formed, while on continued discharge the products become sludge formed, probably consisting of hydrated
. The morphologies support the dissolution‐precipitation mechanism during the first discharge step. The second anodic level proceeds probably via migration of ions and electrons in the solid phase. The crystallite size increases with temperature which depends on that the relative supersaturation decreases.