  Electrical-insulating coatings are of great importance for liquid-metal
breeder/coolant based systems relevant to fusion power plants. In specific to
Pb-16Li eutectic, a candidate breeder material, such coatings are being
actively investigated for their criticality in addressing various
functionalities. For such applications, a candidate coating must be
demonstrated for its compatibility with corrosive media, high operational
temperatures and integrity of electrical-insulation over long durations without
substantial degradation. At present, no relevant in-situ insulation resistance
(IR) data is available for performance assessment of coated substrates within
PbLi environment. To address this shortfall, an experimental study was
performed at IPR towards application of high-purity alumina coatings on SS-316L
substrates and further rigorous validation in static PbLi environment. The
adopted coating process required a low-temperature heat treatment (< 430C) and
could yield average coating thicknesses in the range of 100-500 micron. Coated
samples were validated for their electrical insulation integrity in static PbLi
over two test campaigns for continuous durations of over 700 h and 1360 h,
including thermal cycling, at operational temperature between 300C-400C.
Estimated volumetric electrical-resistivity remained of the order of 109-1011
ohm-cm without significant degradation. In-situ estimations of thermal derating
factors establish excellent electrical-insulation characteristics after long
term exposure to liquid PbLi. This paper presents details of utilized coating
application methods, coating thickness estimations, liquid-metal test set-up,
insulation performance and critical observations from SEM/EDX and XRD analysis
on the tested samples.
