The effect of insulating coatings on the magnetic properties of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloy is investigated. A wide range of phosphate-silicate coatings and conditions of their application is tested. The chemical mechanism of insulating coating formation on the alloy's surface is considered. Toroidal specimens with insulating coating, which retain the high magnetically soft properties of the nanocrystalline alloy, are obtained.