Erosion of needle electrodes in pulsed corona discharge in water

Abstract

Erosion of needle electrodes in the pulsed corona discharge in water with a pulse energy of ∼ 2÷; 3 J was investigated in dependence on the electrode material (platinum, tungsten and stainless-steel) and the solution conductivity (100 and 500 µS/cm). Erosion of electrodes remarkable increased with the higher solution conductivity for all three tested metals. The highest erosion rates were determined for tungsten while platinum was the least eroded material. In addition to the dominant melting effect, release of anode material by the electrolysis significantly contributed to the total erosion of needle electrodes. The highest contribution of electrolysis was determined for stainless-steel electrodes that released up to 40-50 % of eroded metal in the form of iron ions. Peculiar protrusions were observed on the surface of eroded tungsten electrodes.

Influence of High Voltage Needle Electrode Material on Hydrogen Peroxide Formation and Electrode Erosion in a Hybrid Gas–Liquid Series Electrical Discharge Reactor

“…Needle electrodes made of tungsten carbide and tungsten copper alloy were characterized by erosion rates three times higher than materials with the lowest erosion rates. The gravimetric erosion rate measured for stainless steel (0.55 lg/s) is in good agreement with the result published by Lukes et al [10]. The erosion rates for thoriated tungsten and the diamond-coated tungsten electrode (1.43 and 1.28 lg/s) were within the range of the value measured for pure tungsten by Lukes et al [10].…”

“…Plasma pressure and shockwaves cause bursting of these bubbles and the release of electrode material into the surrounding media [14,16]. To our knowledge, very few studies on electrode erosion in an aqueous high voltage discharge reactor have been reported in the literature [7][8][9][10]. Kirkpatrick and Locke [8] found using platinum and nickel chromium needle electrodes that approximately 0.55 lg/s of both electrode materials were released into the solution during 1 h of operation of the reference reactor.…”

“…Kirkpatrick and Locke [8] found using platinum and nickel chromium needle electrodes that approximately 0.55 lg/s of both electrode materials were released into the solution during 1 h of operation of the reference reactor. The most recent paper on electrode erosion by Lukes et al [10] described an electrode mass loss for a solution conductivity of 100 lS/cm of about 0.3, 0.53 and 1.0 lg/ s for a platinum, stainless steel and tungsten electrodes, respectively. The erosion rates intensified strongly with increasing solution conductivity.…”

“…The erosion rates intensified strongly with increasing solution conductivity. The observation of crater-like morphologies on the surface of the electrode tips [8,10] indicated that in the case of a pulsed electrical discharge in water the electrode material releases into solution by formation and bursting of bubbles made of molten metals. These previous studies were conducted in a conventional reference reactor, characterized by positioning of both the high voltage and the grounded electrode in the water.…”

“…Only a few studies are known to the authors describing the phenomenon of electrode erosion [7,8] and quantifying erosion rates of different high voltage electrode materials [9,10] for a conventional reference reactor, characterized by positioning of both the high voltage and the grounded electrode in the water. The data basis of erosions rates seems to be clearly limited in particular by the number of electrode materials tested.…”