Differential aeration, principles

The differential-aeration principle can also be exemplified by the underground corrosion of an iron pipe that runs partly through sand with high oxygen permeability and partly through clay soil with low oxygen permeability (Fig. 12.30) the portion of the pipe in the clay corrodes more heavily than the portion in the sand. 

Gladysheva, V. P. and Shatalov, A. Ya., Electrochemical Principles of the Operation of Differential Aeration Couples ,/zv. Vyssh. Ucheb. Zavad., Khim. iKhim. Tekhnoi., 16, 1508 (1973) C.A., 80, 43386Z... 

Pourbaix has shown by means of E-i diagrams (Wagner and Traud type) that the differential principle is applicable only at certain pH values, and the situation when the pH is the same in both the aerated and non-aerated zones is as follows ... 

---