CS235803B1 - Chemically resistant metal coating made from vitreous powders - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a chemically resistant metal coating formed from vitreous powders, particularly for surface protection of sheet steel products exposed to aggressive environments.

The enameling of these products is carried out so far by the so-called wet process, ie the glass frit is milled with additives and water to a suspension, which is applied to the pre-treated products, dried and fired. This procedure is repeated several times as necessary. The properties of the coating are influenced by the properties of the frit and additives, for example refractory, used in the preparation of the enamel suspension.

The enamel coating technology of the electrostatic field application method envisages the application of specially treated enamel frit powders of a suitable chemical composition to the pretreated metal either directly or on an intermediate enamel powder interlayer, wherein both the base and cover layers can be fired together. No additives to frits, as is common in the above-mentioned wet conventional process, can be used for technical and hygienic reasons.

The known coatings produced by this process and prepared from common enamels do not form a sufficiently compact surface and in particular do not exhibit the desired functional properties, in particular high chemical resistance.

- 2 23S 803

These disadvantages are overcome by the chemically resistant metal coating formed from the vitreous powders of the invention. Its essence is that it contains 50 to 70% of silica, 1: silica, 7 to 19% by weight of boron oxide, 10 to 20% of Group I metal oxides, for example sodium, lithium and potassium oxides. , 1 to 6% wtW · metal oxides II. and 0.5 to 4% by weight of the holding oxides, i.e., cobalt and / or nickel oxide. The coating may further comprise 0.1 to 1.5

4.5% hvoof. % alumina and / or 0.1 to 4 wt. zirconium dioxide and / or 0.1 to 1 wt.% antimony trioxide and / or 0.1 to 2 wt.% manganese oxide. It is preferred that the coating further comprises 0.1 to 4.5% gamma. fluorine Fg with a view to increasing its wettability.

The coating according to the invention is characterized by a high corrosion resistance in an aggressive acidic, weakly alkaline environment and in a hot water and steam environment. It also exhibits high abrasion resistance.

The coating is prepared by melting the ground frit powders onto the base metal at a baking temperature of 780-840 ° C. The frit is prepared by melting and frying in a conventional manner. The powder is prepared by grinding the frit to a granulometry such that it has a residue in the range of 2 to 10 wt. It is treated by hydrophobization by addition of 0.05-0.25% silicone oil with catalyst. It is applied to metal pre-treated by mechanical or chemical method in high-voltage electrostatic field. The thickness of the baked-on coating is 0.08 to 0.4 mm. The coating exhibits high resistance.

The invention is further explained in more detail by way of examples of a specific embodiment thereof.

Example 1 235 803 i *

A coating with a chemical composition in% by weight, based on the total weight of the coating

Si02 58.70 & A12 ° 3 0.49 % ^β 2 ° 3 12.70 % Na ^ 13.29 % to ₂ ° 2.32 % ^Li2 ° 2.59 % ^Ti O> 3.68 % CaO 1.98 % CoC 0.61 / 0 Nothing 1.15 % MnO 0.28 % BaC 0.63 % ^F 2 1.58

This coating has been tested on steels 11320 and 11330 and exhibited a consistent surface and good corrosion resistance at high wetting rates during normal single-layer pre-treatment.

Example 2

Si ^ 2 69.12 % B2 ° 3 10.92 % 9 ^At ₂ 0 9.65 % and; ₂ o 3.16 % * li ₂ 0 2.60 % TÍ02 1.95 % CaO 0.65 % NiO 1.95 %

The coating is suitable for strongly aggressive corrosion conditions, such as low temperature corrosion. Its composition has been tested in pilot plant on 11300 steel and provides high chemical resistance during normal pre-treatment.

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Example 3 235 803 Composition of composition SiO ₂ 58,14% ai ₂ o ₃ 0.49% B ₂ 0 ^ 12,98% At ₂ 0 13.29% « ₂ o 2.32% Li ₂ 0 3,59% T10 ₂ 3.68% CaO 1.98% CoO 0.61% NiO 1,15% MnO 0.28% BaO 1,63% was tested in laboratory conditions for steel grades 11

and showed a favorable chemical resistance when deposited approximately 200 µm.

The invention is applicable to the enamelling of all kinds of sheet steel products requiring increased resistance in aggressive environments. ^:

Claims (2)

A chemically resistant metal coating formed from vitreous powders by dry melting in a high-voltage electrostatic field, characterized in that it contains 50 to 70 wt. SiO 2, 7 to 19 wt. boron oxide ®2θ3 'θ' ^{1 and 5} Tioga titanium dioxide, 10 to 20% Hma /. Group I metal oxides, for example sodium oxide NagO, potassium KgO and lithium LigO, 0.1-6% by weight of metal oxides II. % of barium oxide, for example, barium oxide BaO and 0.5 to 4% hmaZ of cobalt cobalt and / or nickel NiO retaining oxides. i'c £ y Ct / ofay ’ 2.povlak according to claim 1 _(wherein it contains 0.1 to 3% hmlV algo · alumina-and / or 0.1 to 4 wt.% Zirconia ZrgO and / or 0.1 to 1% hmflr- antimony trioxide SbgO 4 and / or 0.1 to 2 wt% MnO manganese oxide. 2. The method of claim 1, further comprising from about 0.1% to about 4.5% by weight of N-fluorine Fg.