The velocity of corrosion from the electrochemical standpoint. Part II

In Part I of this series of papers, an electrochemical survey was made of those types of corrosion, where large distinct anodic and cathodic areas are met with. Measurements showed that the corrosion produced was equivalent to the electric current flowing, whilst potential movements suggested that this current was largely controlled by polarisation at the cathodic areas. Cathodic polarisation curves were obtained by means of a cell fitted with a platinum anode, this material being chosen in order to avoid complications due to the destruction of the cathodically produced alkali by metallic salts from the anode; the character of these curves suggested the principle governing the ratio of the cathodic and anodic areas on a corroding specimen. Papers expressing views consonant with those of the authors have been published by Herzog and Chaudron, Endo and Kanazawa, and by Forrest Roetheli, Brown and Cox, whilst divergent opinions have been expressed by Bengough, Lee and Wormwell, and by Liebreich. Bengough’s objections are dealt with elsewhere, whilst Liebreich’s attitude has been criticised by Werner and Baisch, by Cassel and Erdey-Gruz and by Schikorr. Liebreich’s contention that the distribution of corrosion is the same in presence and absence of oxygen has been examined experimentally in this laboratory by C. W. Borgmann, and found to be quite untrue.