A report is given of recent investigations of anodically formed coatings on magnesium, zinc, and cadmium in and solutions. The growth of the coatings was followed by means of x‐ray and electron diffraction and electron microscopy. It was found that the metal oxide was favored as initial product. Depending upon the relative magnitude of the solubility products, the coatings remained in the form of oxides or were converted into the respective hydroxides or carbonates. The semiconductance of the initial coatings was significant in determining the electrochemical behavior of the electrodes.