SU863712A1 - Method of producing oxide coatings - Google Patents

Description

(54) METHOD OF OBTAINING OXIDE COATINGS

The invention relates to the preparation of oxide coatings on metals, mainly on steel, and can also be used to protect equipment operating in highly corrosive environments. A known method of producing oxide coatings on stainless steel by heat treating it in oxygen-containing gaseous media 1. However, the corrosion resistance of such coatings is insufficient for use in highly corrosive environments. The closest to the proposed technical essence and the achieved result is a method of producing oxide films on metals, including steel, including the treatment of the heated surface with metal compounds mixed with oxygen-containing gas, which uses oxygen, water vapor and carbon monoxide. , carbon dioxide, etc. In accordance with this method, coatings of chromium oxides can be obtained by hydrolysis of chromyl chloride or pyrolysis of acetylacetone and chromium in carbon dioxide or iron oxides ermicheskim decomposition or carbonyl iron acetylacetonate in an oxidizing environment, thus possible to obtain a coating of mixed oxides using a mixture of corresponding metal compounds 2. The disadvantage of this method is the relatively low adhesion of the resulting coatings to the substrate and the inadequate corrosion resistance in highly corrosive media. The purpose of the invention is to increase the adhesion and corrosion resistance of coatings. This goal is achieved by the fact that according to the method of obtaining oxide coatings, mainly from a mixture of chromium and iron oxides, on the surface of steel products by treating the heated surface with vapors of chromium and iron compounds in a mixture with oxygen-containing gas, the surface of the products is heated to 150,400 s and processed chromium and iron nitrate complexes, with their content in the gas mixture of 510–1.0 wt.% and consumption of 100–200 g / m and using nitrogen tetroxide as the oxygen-containing gas.

At the same time, as nitrate complexes of iron and chromium, mixtures of nitrosonium and / or nitronium nitrate complexes of iron and nitrosonium nitrate complexes of chromium are used in a ratio from 1: 1 to 1: 0.1.

The iron nitrate complexes used to treat the surface have the following structural formulas:

(NOj.) Fe (N03);

or

(N0) - Fe (NO,) G

Both of these forms, nitronium and nitrozonium, volatile, can go one into another, and, decomposing, give similar oxides on the surface,

Nitrosonium form is used for chromium.

(N0) Cr (NO) g I

The use of a chemically active compound, nitrogen tetroxide, as the oxygen-containing gas ensures good adhesion of the coatings to the substrate,

Processing by the specified nitrate complexes in a mixture with nitrogen tetroxide is carried out at a substrate temperature of 150 - 400 ° C, the content of nitrate complexes in a mixture of 5-10 - 1.0 May.% At their consumption of 100 - 200 g / m surface.

The coatings obtained on the surface are d-FeijOo solid solution, 78–75% and 22–25%, have a fibrous structure with an arrangement of fibers perpendicular to the surface, which, in turn, enhances their adhesion to the base and adhesion applied to them other coatings.

The optimal ratio between the H1 tract complexes of iron and chromium to obtain the most chemically resistant films in aggressive media is 1: 0.5. The chemical resistance of such films is so great that they do not dissolve in a mixture of nitric, sulfuric and hydrofluoric acids, designed to pickle austenitic stainless steels.

The test of tubular oxidized samples for flattening shows the absence in the zone of maximum compressive and tensile stresses, the absence of microcracks, tears and chipping, and an oxide film, which indicates a high adhesion of the coatings.

In addition, the resulting coatings do not collapse under the action of a gas stream at high temperatures and resist thermal cycling well in the temperature range of 80 700 ° C.

The use of the invention for producing coatings on steel 20 and steel X18H10T can be illustrated by the examples presented in Table. one.

The surface of the coated products is preliminarily cleaned and degreased.

0 The resulting coatings are tested for corrosion in various corrosive environments.

Corrosion resistance of the obtained coatings on steel 20 in accordance with 5 with examples 3, 5, 6 is presented in table. 2

The corrosion rate of coatings on steel Х18Н10Т in accordance with example 1, tested in a mixture for cold pickling of stainless steels, composition,%:

15

HNO3

five

HjS04

five

HF

75

at a temperature of 25 ° C is less than 0.001 mm / year.

As can be seen from the above data, the obtained coatings are distinguished by high corrosion resistance, which exceeds the resistance of coatings obtained in a known manner, due to the formation of a coating of a certain composition and a certain crpyKiiyra and its high adhesion, which will make it possible to widely use the invention in national economy. energy and chemical industry to protect the contours and devices for various purposes from corrosion.

Table

HNCj 20% H, S04 50%

Nz; E 30%

Claims (2)

1. A method of producing oxide coatings, mainly from a mixture of chromium and iron oxides, on the surface of steel products by treating the heated surface with vapors of chromium and iron compounds in a mixture with oxygen-containing gas, characterized in that, in order to increase the adhesion and corrosion resistance of coatings, the surface of the products heated to 150-400 ° C and the treatment is carried out in pairs of chromium and iron nitrate complexes; the content in the gas mixture 5-10 1.0 wt.%, consumption 100 - 200 g / m Continued. one table 2 4 C 0.01 and use as an oxygen-containing nitrogen tetroxide gas. 2. A method according to claim 1, characterized in that mixtures of nitrosonium and / or nitronium nitrate complexes of iron and nitrosonium nitrate complexes of chromium are used as iron and chromium nitrate complexes in a ratio from 1: 1 to 1: 0.1. Sources of information taken into account in the examination 1. US patent 4017336, cl. 148-635, 1977. 2. Deposition from the gas phase. Ed. C. Powell et al. M., Atom 1zdat, 1970, p. 302-314.