RU2008368C1 - Process of enameling metal articles - Google Patents

Abstract

FIELD: kitchen utensils. SUBSTANCE: process of enameling includes deposition of slip of under-coat enamel having inorganic additives promoting solidification, drying and deposition of slip of cover-coat enamel followed by firing. Inorganic additives are added to slip in comminuted form after their fusing to glassy state. EFFECT: improved quality of articles, prolonged usage. 2 tbl

Description

 The invention relates to the protection of metals from corrosion, and in particular to methods of enameling metal products for the production of chemical equipment, household products, in electronic equipment.

 A known method of enameling metal products, including applying a slip of soil enamel containing organic additives previously introduced into it, which use various complexing substances with carbon atoms up to 50 in one molecule (saccharides, polyethylene glycol, etc.), drying, applying slip enamel slip followed by firing [1].

 The disadvantage of this method are defects such as "scum", "bubbles", orange peel, resulting from the decomposition of hydrocarbons during the firing process.

 A known method of enameling metal products, including applying a slip of soil enamel, impregnating it with hydrophobic compositions based on silicones, drying, applying a layer of top-coat enamel and firing [2].

 The disadvantage of this method is the surface defects of the coating, caused by the decomposition of hydrocarbons during firing.

 Closest to the proposed technical essence and the achieved result is a method of enameling metal products, including applying a slip of soil enamel containing inorganic additives that contribute to hardening of the slip during drying, drying, applying a layer of coating enamel and firing [3]. At the same time, alkali metal phosphates and aluminates, aluminum hydroxide, etc. are used as inorganic additives.

 The disadvantage of this method is the low quality of the enamel coating, due to the low strength of the dried soil coating, which leads to the mixing of the layers even before firing the enamel, reduces the adhesion of the enamel to the metal and its mechanical strength.

 Common signs of known methods and the present invention is the principle of two-time application - single firing.

 In the proposed method for enameling metal products, including applying a slip of ground enamel containing hardening inorganic additives, drying, applying a slip of coating enamel, followed by firing, inorganic additives are introduced into the slip in a crushed form after they are fused together to a glassy state.

 The essence of the method consists in the fact that inorganic additives are fused together before entering the slip of enamel into a glassy state, crushed and applied as a mechanical mixture to the surface of a metal product, dried, after which a layer of coating enamel is applied and fired. The preliminary fusion of inorganic additives to a glassy state, their grinding, and application of soil enamel as a part of a slip make it possible to obtain a denser compact and uniform thickness layer that is firmly “glued” after drying to the metal surface. Such a layer does not interact with moisture, so that in the further enameling procedure, it becomes possible to apply a layer of coating enamel a second time using a wet slip method.

 Significant hardening of the soil layer is achieved due to the formation of active low-melting eutectics (products of the interaction of molten additives with the surface of the soil particles) at the drying temperature at the grain boundaries of the soil enamel, which reduce the surface tension and provide "cementation" of the soil enamel particles both between themselves and with a metal substrate, significantly reducing the number of macro hollows filled with gases, the release of which during the firing process causes defects in the enamel coating.

 By the interaction of the molten additives with the surface of the soil particles, the surface tension decreases and the "cementation" of the enamel particles occurs both between themselves and with the metal substrate.

 As inorganic additives, as in the prototype, phosphates and aluminates of alkali and alkaline earth metals, aluminum hydroxide, as well as lead borate and manganese and zinc phosphates are used.

 Due to the high strength of ground enamel, due to the presence of pre-fused and crushed inorganic additives in the slip, the proposed method also allows to expand its versatility by expanding the range of processed products. The method allows to apply a slip of primer and top-coat enamel by traditional methods - by pouring or dipping with mechanical leveling for products of complex shape. In addition, the method reduces the duration of high-temperature firing due to the reduction of gas generation provided by the preliminary fusion of inorganic additives, and, therefore, reduces the energy consumption, increases the productivity of the process, allows to save raw materials by reducing the consumption of soil enamel.

 New in the method of enameling products is the introduction of ground enamel pre-fused to a glassy state of inorganic additives in a crushed form into a slip of enamel. The specified technique is not found in the sources of information or practical use, which implies that the inventive method meets the criteria of the invention of "novelty."

 The inventive method was practiced in the laboratory UralNIIchermet.

The following compounds were used as inorganic additives, g: 1. NaH ₂ AlO ₃ 1,8 Al (OH) ₃ 2,2 NaH ₂ PO ₄ 2,7 (NH ₄ ) H ₂ PO ₄ 4,4 2. NaH ₂ AlO ₃ 1.8 Al (OH) ₃ 2.2 NaH ₂ PO ₄ 2.7 (NH ₄ ) H ₂ PO ₄ 4.4 3. KH ₂ PO ₄ 7.0 ZnHPO ₄ 4.5 4. LiH ₂ PO ₄ 11.0 ZnHPO ₄ 9.0 5. Pb (HBO ₃ ) 10.5 6. Ca (H ₂ PO ₄ ) ₂ 24.0 (NH ₄ ) H ₂ PO ₄ 6.0 7. Na (H ₂ PO ₄ ) 3.4 (NH ₄ ) H ₂ PO ₄ 1.8 8. Ca (H ₂ PO ₄ ) ₂ 6.0 Mn (H ₂ PO ₄ ) ₂ 2.0 (NH ₄ ) H ₂ PO ₄ 3.0
Composition 1 corresponds to the composition specified in the prototype method.

 Composition N 2 is similar, but the chemical compounds were previously fused and then ground before being introduced into the slip.

 Compounds 3-8 correspond to the proposed method.

Additives were fused at 1100-1200 ^о С in the indicated proportions and milled dry to a fraction of less than 60 microns. The hydrogen solubility of the obtained glassy substance was determined by the grain method by the decrease in the weight of the milled powder after exposure to water at room temperature for one day.

The softening temperature was determined by the dilatometric method. Abrasion resistance was determined by the slip coating weight loss after abrasion jet moistened quartz sand falling on the inclined (at an angle of ⁴⁵ °) of the test plate from a height of 0.3 m for 1 min.

 The properties of the fused additives, as well as the properties of the coatings are given in table. 1.

 A comparative analysis of the known and claimed methods of enameling metal products is given in table. 2.

 This method of enameling metal products can improve the quality of enamel coating, reduce the consumption of soil enamel by 40%, electricity by 30%, and increase labor productivity. (56) 1. German patent N 3203101, cl. C 23 D 5/02, publ. 1984.

 2. The patent of Germany N 2538601, cl. C 23 D 5/02, publ. 1977.

 3. The patent of Germany N 1621405, CL C 23 D 5/02, publ. 1975.

Claims (1)

 METHOD FOR ENAMELING METAL PRODUCTS, including applying a slip of soil enamel containing hardening inorganic additives, drying and applying a slip of coating enamel with subsequent firing, characterized in that the inorganic additives are introduced into the slip in a crushed form after they are fused together to a glassy state.

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