Discussion on “electrolytic corrosion of iron by direct current in street soil” (Ganz), Boston, Mass., June 25, 1912. (see proceedings for June, 1912)

Carl Hering: It seems to me that the tests made b y Professor Ganz are very valuable, and we are fortunate to have had the benefit of his experience. But I think that to speak of voltage as Professor Ganz does in this paper, is somewhat misleading. The voltage for the electrolytic corrosion of iron is negative. Therefor it should be possible that with no external voltage at all there might be some corrosion. There are always two voltages, one at each electrode, and we generally refer to their sum, as it is difficult to separate them. The result described was perhaps due largely to “over-voltage” at the copper electrode which he used. In my opinion there is also an important mechanical effect in underground electrolysis in the form of the rate of diffusion of the liquid which does the elctrolyzing. If that liquid cannot circulate rapidly there will be much less electrolysis than if it can, and it therefore seems to me that this effect of the circulation of the liquid through the soil is an important factor in determining whether the corrosion will be bad or not; it must also have a very decided effect on the voltage. Professor Ganz says nothing about the inside of the pipe and whether the results there are the same or not.