The high-voltage spark testing method for protective and functional dielectric coatings on a conductive substrate: increasing sensitivity and results reliability

V A Syasko and A S Musikhin
Constanta Ltd, Pob 89, St Petersburg 198095, Russia
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The high-voltage spark testing method of protective dielectric coatings is applied in almost all manufacture areas and is governed by ISO, ASTM, etc. However, it does not pay proper attention to high-voltage forming (DC or AC) and its polarity, influence of environment, electric field inhomogeneity. In this paper, a detailed analysis of air gap breakdown forming processes is given. A dependence of electric field strength on an interelectrode gap length is given for homogeneous and highly inhomogeneous electric fields. It is shown that a breakdown voltage of air gaps in a highly inhomogeneous field is substantially less than in a homogeneous field. The paper also discusses the way in which the breakdown voltage of air gaps with positive polarity is less than with negative polarity. The possibility of controlling coatings of substantially smaller thickness while reducing the control voltage without reducing the reliability of the results is shown.