Experiments on tracking enhancement by copper

In an attempt to explain the difference in results obtained with the use of copper electrodes as compared to platinum electrodes, two hypotheses were investigated. The first advanced the supposition that copper salts accumulate on the surface and increase the electrical conductivity. Oscillograms of the electric current failed to support this hypothesis. The second hypothesis tested is that the copper changed the wetting of the surface. However, when the surface wetting was changed using platinum electrodes and inert powders no significant reduction occurred in the variation of the Comparative Tracking Index (CTI) test by the International Electrotechnical Commission (IEC) publication 112. The investigation has shown that the substantial difference in results which occurs when comparative tracking tests use copper rather than platinum electrodes cannot be explained by increased conductivity or by improved wetting ability of the liquid