Metal objects coated with cermet and then silicate glaze - where cement consists of vitreous enamel frits mixed with aluminium powder, and glaze forms outer sealed coating

摘要

A metal substrate is coated with a cermet underlayer (I), and then a top layer of silicate glaze (II) resistant to chemicals and corrosion. Layer (II) pref. has min. thickness 5 microns, and average thickness 15-25 microns, with compsn. by wt. 40-65% SiO2, 10-35% alkali oxides, and, all maxima, 20% B2O3, 5% Al2O3, 20% alkaline earth oxides, 20% TiO2 and/or ZrO2, 2% P2O5, 5% F, and 3% V2O5 and/or MoO3. Layer (II) is pref. formed at least partly by a spodumene or beta-eucryptite frit, whereas cermet (I) is pref. obtd. by electrophoretic coating using an aq. slurry, which may contain an organic, water-soluble cpd. providing electric insulation, e.g. an acrylic resin. The coating withstands thermal shock, vibration and corrosion.