DC Self-Discharge Path Between Metal Rod-to-Water Electrodes in Atmospheric Air

The self-discharge phenomenon is experimentally examined in a small gap of 10-30 mm between a metal rod and the surface of tap water, which were the electrodes. The main results obtained were as follows: 1) The discharge threshold voltage of the negative rod was slightly lower than that of the positive rod for a water conductivity of 23.9 mS/m. 2) A concave region was observed under the rod due to the corona wind toward the water surface, and it was independent of the rod polarity. 3) The discharge path was characterized by a main path and its lower branches above the water surface. 4) A connection point between the strong and the weak emission paths was always observed at the negative rod electrode.