Abstract: There is disclosed an insulated metal substrate, consisting of a dielectric oxide coatings of high crystallinity (>vol 90%) on aluminium, magnesium or titanium and high thermal conductivity (over 6 Wm?1K?1), formed by plasma electrolytic oxidation on a surface comprising aluminium, magnesium or titanium. There is also disclosed a plasma electrolytic oxidation process for generating dielectric oxide coatings of controlled crystallinity on a surface of a metallic workpiece, wherein at least a series of positive pulses of current are applied to the workpiece in an electrolyte so as to generate plasma discharges, wherein discharge currents are restricted to levels no more than 50 mA, discharge durations are restricted to durations of no more than 100 ?s and are shorter than the durations of each the positive pulses, and/or by restricting the power of individual plasma discharges to under 15W.

Abstract: There is disclosed an insulated metal substrate, consisting of a dielectric oxide coatings of high crystallinity (>vol 90%) on aluminium, magnesium or titanium and high thermal conductivity (over 6 Wm?1K?1), formed by plasma electrolytic oxidation on a surface comprising aluminium, magnesium or titanium. There is also disclosed a plasma electrolytic oxidation process for generating dielectric oxide coatings of controlled crystallinity on a surface of a metallic workpiece, wherein at least a series of positive pulses of current are applied to the workpiece in an electrolyte so as to generate plasma discharges, wherein discharge currents are restricted to levels no more than 50 mA, discharge durations are restricted to durations of no more than 100 ?s and are shorter than the durations of each the positive pulses, and/or by restricting the power of individual plasma discharges to under 15W.