Electrical properties and structural study of paintings for the aircraft lightning protection

Paint coatings which should behave as insulating materials in their steady state and as conductors just before or after the leader impact are investigated. An ionization process at the coating surface in a lightning environment must ensure a high conductivity, so that flashover of the sensitive area will be facilitated with respect to the breakdown. The morphology and the electrical surface properties related to different chemical compositions are pointed out. The purpose of the present study is not to demonstrate the lightning protection character of these point coatings, but to study their surface charge transport. Thus, surface potential measurements are performed in order to select a chemical composition and to analyze the effect of external parameters such as moisture and temperature. A fast charge decay is observed on homogeneous surface samples, i.e., the pigment/binder ratio P/B=2. On the other hand, nonconductive grain boundaries in the coating layers induce a very slow charge transport when P/B=1