ENAMELING SLIP FOR PRIMER COAT, METHOD OF ENAMELING AND ENAMEL COAT OF METAL ARTICLES Russian patent published in 2005 - IPC

FIELD: protection of metals against corrosion; production of silicate enamels for coats of metal articles.

SUBSTANCE: proposed enameling slip for primer coats on metal articles contains the following constituents, parts by mass: first frit, 8-14; second frit, 35-48; third frit, 41-52; quartz sand, 10-45; borax, 0.1-0.3; clay, 5-7; water, 45-5o; frits contain barium and have the following constituents, mass-%: first frit: SiO₂, 28-36; B₂O₃, 23-26; Al₂O₃, 1-3; Na₂O, 12-18; TiO₂, no more than 1.0; CaO, 0.5-2.5; MgO, no more than 3.0; Fe₂O₃, no more than 2.0; Co₂O₃, 1.0-1.5; Ni₂O₃, 1-3; MnO, no more than 3.0; BaO, 20-25: F, above 100% no more than 3.0 parts by mass; second frit SiO₂, 32-38; B₂O₃, 21-24; Al₂O₃, 1-3; Na₂O, 12-17; TiO₂, no more than 1.0; CaO, 1-3; MgO, no more than 1.0; Fe₂O₃, no more than 2.0; Co₂O₃, 2-6; Ni₂O₃, 1-3; MnO, no more than 3.0; BaO, 16-19; F above 100% no more than 3.0 parts by mass; third frit : SiO₂, 37-43; B₂O₃, 19-22; Al₂O₃, 0.5-3.5; Na₂O, 11-15; TiO₂, no more than 2.0; CaO, 0.5-3.5; Fe₂O₃, no more than 2.0; Co₂O₃, 2-6; Ni₂O₃, 0.5-3.0; BaO, 13-18; F above 100% no more than 3.0 parts by mass. Method of enameling metal articles includes application of primer layer and cover slip followed by roasting for forming the enamel coat. Ratio of temperature coefficient of linear expansion of primer enamel slip and metal ranges from 0.79 to 0.96. Ratio of surface tension of enamels of primer and cover slips ranges from 1.2 to 1.4. Difference in surface wetting temperatures ranges from 100 to 120°C at lower roasting temperature (by 30-50°C) and viscosity of melt within (5-8)·10² of primer enamel as compared with cover enamel. Enamel coat is made with the use of slip whose frits have definite composition.

EFFECT: high complex of technological properties (adhesion, resistance to burning-out, homogeneous microstructure, spreadability).

4 cl, 2 tbl