Oxidation damage of spark plug electrodes

The temperature-dependent erosion behavior of platinum, iridium, silver and nickel in spark plug electrodes was investigated under the conditions of pure nitrogen and dry air atmospheres. It is found that oxidation is the dominant erosion mechanism. Platinum shows a temperature independent erosion behavior, whereas the wear of the other materials increases with temperature. At lower temperatures, oxidation in the cathode spot was the only contribution to electrode wear for all materials and appeared to be independent of the electrode temperature. It was suggested that the oxidation is assisted by the influence of the discharge plasma, where highly reactive species like atomic oxygen is formed, thus leading to higher oxidation rates.