RU2371517C1 - Converter of metal surface - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to chemical surface treatment of metallic materials and formation on its surface of metal-protective coatings for protection against corrosion. Surface converter contains, wt %: orthophosphoric acid (85%) 40.0 - 50.0, ferrocyanide potassium (potassium ferrocyanide) 3.0 - 4.0, nitro-acid zinc 2.0 - 3.0, anion-active surface acoustic wave 0.05 - 0.15 and water is the rest. In the capacity of anion-active surface acoustic wave it is used alkyl benzene of sodium sulfonate of total formula RC₆H₄SO₃Na, where R=C₂H₅ or C₃H₇.

EFFECT: invention provides expanding of functional capabilities of usage of metal surface converter with simultaneous cost reduction for its manufacturing.

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Description

The invention relates to the field of applied chemistry, in particular to compositions for chemical surface treatment of metallic materials and the formation of metal-protective coatings on their surface, and can be used in the preparation of metal structures for applying coatings and preventing corrosion processes during their operation, including under the influence of adverse external conditions, for example chemically aggressive liquids and gases, and also - for temporary protection against corrosion of internal and external surfaces the rest of products from ferrous metals and their alloys, including for the preservation of sheet and profile products, pipes, equipment and spare parts.

The well-known "Composition for accelerated phosphating of metals", designed to protect metals from corrosion, mainly metal surfaces that have already been subjected to corrosion processes (see RF patent No. 2070945, CL 23/07, publ. 1996.12.27), containing, by weight .%: phosphoric acid 30-55; isopropyl alcohol 20-40; water 10-20; zinc nitrate 0.1-3.0; ethanol and / or butanol 1.0-15.0; hydroquinone 0.1-4.0; tartaric acid 0.1-2.0; triethanolamine 0.01-10; C ₃ -C ₇ alkyl acetate and / or tannin 1.0-10.0 and yellow and / or red blood salt 0.2-5.0.

The well-known "Rust Converter", intended for the chemical treatment of metal surfaces, mainly already corroded (see RF patent No. 2294981, CL 23/20, publ. 2005.07.29), containing, wt.%: Phosphoric acid (85 %) 45-65; potassium ferruginous (yellow blood salt) 3.0-4.0; aluminum nitrate 2.0-3.0; zinc nitrate 0.5-1.5; fluorocarbon compound of 0.01-0.1 and water up to 100%.

Also known is the “Rust Converter", intended for the chemical treatment of metal surfaces without first removing corrosion products from them in order to prepare them for applying coatings (see RF patent No. 2205896, class C23C 22/20, publ. 2003.06.10), containing, wt.%: phosphoric acid (85%) 50-60; potassium ferruginous (yellow blood salt) 3.0-4.0; aluminum nitrate 2.5-4.0; zinc nitrate 1.0-2.5; non-ionic detergent 0.1-0.2 and water up to 100%.

The greatest effectiveness of the above compositions is achieved when they are used to treat metal surfaces that have already undergone corrosion damage and with corrosion products already in their composition.

The disadvantage of these technical solutions-analogues is a significant number of individual components included in their composition and, accordingly, low manufacturability and the complexity of the method of preparing the final product, as well as its high cost.

The closest technical solution to the claimed as for its purpose, and for most of the matching features, including quantitative, adopted as the closest analogue of the prototype of the invention, is the "Composition for processing a metal surface", designed to process the metal surface without first removing products corrosion and cleaning its surface from rust, mainly large and complex structures (according to the patent of the Russian Federation 2120495, class C23C 22/13, 22/36, publ. 1998.10.20), containing : Wt% orthophosphoric acid (85%) 50,0-60,0;. zinc nitrate 2.5-3.0; potassium ferruginous (yellow blood salt) 3.0-4.0; a fluorocarbon compound of the general formula R _f ZQ 0.3-0.6 and water up to 100%.

The disadvantage of the closest analogue (prototype) is the low efficiency of using the composition to protect against corrosion of the surfaces of non-corrosive metal, for example, steel sheet when applying the composition immediately after the manufacturing process (rolled), as well as the use of very expensive ingredients as one of its ingredients organofluorine compounds.

In addition, the disadvantage is the need to allocate additional material costs aimed at ensuring environmental safety of work and technological processes, due to the significant expense and concentration used in the composition of phosphoric acid.

The present invention is aimed at eliminating the disadvantages of the closest analogue (prototype), including reducing material costs for the manufacture of the composition (including its cost) while simplifying the production technology and expanding the functionality of its use.

At the same time, the task of creating an economically more profitable solution, especially in large-scale production, and at the same time a simple and effective metal surface transducer, the composition of which and the quantitative content of the ingredients, significantly expand the functionality of its use, was solved.

In addition, in parallel, the task of increasing the adhesive properties of the transducer and creating additional stronger tread protection of the base metal was solved.

This is achieved by the fact that the proposed metal surface transducer containing orthophosphoric acid, potassium ferruginous, zinc nitrate and water, in contrast to the prototype, additionally includes an anionic surfactant, and these components are taken in the following ratio, wt.%:

Phosphoric Acid (85%) 4.0-50.0 Potassium ferruginous (yellow blood salt) 3.0-4.0 Zinc Nitrate 2.0-3.0 Anionic Surfactant 0.05-0.15 Water rest,

while anionic surfactants used sodium alkylbenzene sulfonate of the General formula:

RC ₆ H ₄ SO ₃ Na,

where R = C ₂ H ₅ or C ₃ H ₇ .

The technical result indicated in the object of the invention is achieved both by a combination of the components of the proposed metal surface transducer, and by the quantitative ratio of the ingredients included in it.

In addition, the goal is achieved by using a specially designed anionic surfactant in the converter, which is used sodium alkylbenzene sulfonate of the general formula: RC ₆ H ₄ SO ₃ Na, where R = C ₂ H ₅ or C ₃ H ₇ , and its initial amount taken so that in the finished composition its total value was in the range of 0.05-0.15 wt.%.

The quantitative composition of these components is selected experimentally by the authors. It is their content that provides a solution to the problem, i.e. the transformation of products on the surface of the processed corrosive metal into a uniform protective coating that is resistant to both atmospheric corrosion and virtually any other aggressive liquids, gases and vapors.

Thus, the presence of each of the components in the inventive composition for surface treatment of the metal, as well as the quantitative composition of the composition in combination leads to the achievement of these technical results.

The Converter is prepared as follows.

In the General case, the composition of the Converter is prepared by known methods using known chemicals. In this case, standard components manufactured by the industry are used: orthophosphoric acid according to GOST - 6552-80, potassium ferruginate according to GOST 6816-79, zinc nitrate according to GOST - 5106-77 and distilled water according to GOST 6709-72.

The inventive converter is obtained by alternately dissolving these components in water with mechanical stirring and a temperature of 18-22 ° C, followed by merging the resulting solutions also with continuous stirring and a temperature of 18-22 ° C and adding alkylbenzene sodium sulfonate - a specially designed anionic surfactant common formulas: RC ₆ H ₄ SO ₃ Na, where R = C ₂ H ₅ or C ₃ H ₇ , which imparts specific physicochemical properties to the entire composition of the converter.

The essence of the impact of the proposed Converter on the surface of the corrosive metal is as follows.

Taken within the above quantitative ratios, phosphoric acid in a chemical compound with potassium ferruginous is a complexing agent for metal corrosion products dissolved under it (acid), while zinc nitrate in a chemical compound with said complexing agent promotes the formation of a strong protective oxide-phosphate film that is very resistant to adverse environmental conditions, such as atmospheric or chemically aggressive liquids and gases. An additional introduction to the transducer of an anionic surfactant, namely sodium alkylbenzene sulfonate (general formula: RC ₆ H ₄ SO ₃ Na, where R = C ₂ H ₅ or C ₃ H ₇ ), due to leakage on the surface the processed metal of specific physico-chemical processes and influences ensures the penetration of the inventive converter into a layer of corrosive metal (metal with rust) to a depth of 300 microns, as well as a high penetration rate and the process of forming a protective film. At the same time, the introduction of sodium alkylbenzene sulfonate ensures uniform wetting of the treated surface, increases adhesion and creates additional protective protection of the base metal.

Thus, when the inventive converter processes the metal surfaces that have already corroded, a very strong water-insoluble oxide-phosphate protective film is formed.

On the other hand, the introduction of the above-mentioned anionic surfactant into the composition of the proposed converter makes it possible to use it (the converter) as a protective preservation composition for temporary corrosion protection of non-corrosive ferrous metal, mainly rolled metal, because the sodium alkylbenzene sulfonate used in its composition performs the function of the active displacer of an aggressive electrolyte, initially formed on the surface of a non-corrosive metal (manufactured by kata) in the actual atmosphere in the form of moisture films with dissolved therein a corrosion-aggressive agents atmosphere conducive to intensive development of corrosion processes.

Thus, the proposed Converter allows you to equally effectively use it to protect against corrosion of surfaces of both corrosive (metal structures already in operation) and non-corrosive metal (rolled ferrous metals immediately after manufacture), for example, during periods of its interoperational storage, which is confirmed by the following the following experimental data.

The resulting composition of the Converter has the following main technologically important properties:

- the depth of conversion of corrosive metal reaches ~ 300

microns;

- the coating has the properties of a strong dielectric insulator (see Table No. 1;

- the coating has the effect of tread protection, which creates the potential between the formed oxide-phosphate film and pure metal up to ~ 0.15 V (see Table No. 2).

Using in practice materials made of black steel (processed by this composition) during welding, the authors noticed a significant increase in the electrical resistance of the surface layer after it was processed by the claimed composition. Thus, a strong film with the properties of a strong dielectric is created on the metal surface, while the resistance for a non-corrosive metal increases N times, where N = `` 'R _cp /''R _cf , and is ~ 200000 times (see Table 1 ); and for a metal already susceptible to corrosion, this indicator

(N ₁ ) is ~ 1000 times, where N ₁ = '''R _cp /''R_cp; R _cp ... '''R _cp - average values of the resistance of the surface layer over five values of the measured values for each sample, respectively.

The characteristics noted above confirm the manifestation of the protective properties of the converter, which directly protects the metal itself during mechanical destruction of the zinc oxide phosphate film on its surface, playing the role of anode protection and dissolving, first of all, zinc deposited on the surface of the treated metal.

To determine the value of the resistance of the coating obtained as a result of processing metal that is not susceptible to corrosion and metal susceptible to corrosion (processed in accordance with GOST 5009-82 to degree St2 according to ISO 8501-1) with the indicated surface transducer, 20 × 20 × samples were used 2 mm, grade St.3. The measurement results were obtained using a digital voltmeter.

To determine the stationary potential of steel samples treated with this converter, we used samples of steel BCt3 Sp2, size 20 × 20 × 2 mm, cleaned of loose weakly bonded rust with a 20 grit sandpaper in accordance with GOST 5009-82 to degree St2 in accordance with ISO 8501-1. Before starting the measurements, the samples were kept in the room for two days. The potential was measured relative to the silver chloride electrode. A hollow glass cup was glued to the sample and filled with a 3% NaCl solution, held for 30 minutes, and the potential was measured with a PI-50 potentiostat (see Table 2). Thus, applying a surface transducer to a metal treated to a St2 degree according to ISO 8501-1 shifts the stationary potential in the electrolyte (3% NaCl) to the positive side by 0.12 V.

The authors also conducted experimental studies of the proposed Converter in comparison with the identified closest analogue (prototype) - RU No. 2120495; the obtained comparison results are presented in Table No. 3, examples 1-4.

To conduct a comparative assessment, tests were performed according to the above method using manufactured compositions with different proportions of components, including their boundary values, as well as in accordance with the closest analogue (prototype). We used samples of steel BCt3 Sp2, size 20 × 20 × 2 mm, cut from a sheet of non-corroded steel. Four samples were used, on which the composition was applied by dipping. After application of the converter, all samples were aged for 48 hours at a temperature of 18 ± 3 ° C. Three measurements were made on each sample. The average values for three readings for each sample are presented in Table No. 3.

Table 1 Specimen characteristic Sample No. Resistance value, Ohm one 83 Non-corrosive 2 56 metal 3 70 four 25 5 twenty R _cp = 50.8 one 19 · 10 ³ Corrosion metal 2 3.310 ³ 3 5,410 ³ four 9.310 ³ 5 8.2 · 10 ³ 'R _cp. = 9.0410 ³ one 5.610 ⁶ Corrosive metal 2 4.0 · 10 ⁶ coated 3 1.5 · 10 ⁶ four 10.1 · 10 ⁶ 5 16.310 ⁶ '' R _cp. = 7.5 · 10 ⁶ one 8.4 · 10 ⁶ Non-corrosive 2 7.8 · 10 ⁶ coated metal 3 18.2 · 10 ⁶ composition four 20.510 ⁶ 5 4.310 ⁶ '''R _cp. = 11.84 · 10 ⁶

table 2 Character pattern Sample No. The value of the stationary potential, In Samples processed
composition one -0.28 2 -0.29 3 -0.29 φ _cp = -0.29 Samples not treated with the composition one -0.40 2 -0.42 3 -0.40 'φ _cp = -0.41

Table 3 Examples of the implementation of the composition of the Converter and the prototype one 2 3 4 (Prototype) Components Mas. at % Phosphoric Acid (85%) 45 40 fifty fifty Zinc Nitrate 2.5 2.0 3.0 3.0 Potassium ferruginous 3,5 3.0 4.0 4.0 Sodium alkylbenzene sulfonate 0.1 0.05 0.15 - Carbon Compound - - - 0.3 Water rest rest rest rest Stationary potential, (V) -0.19 -0.21 -0.20 -0.40

Obtained during comparative tests of the inventive converter, including with the prototype (see Table 2 and Table 3), the results confirm that in the case of using non-corrosive metal processed by the claimed composition and the known prototype composition, the stationary potential is shifted in the positive direction by 0, 20-0.22 V (in the first case) and 0.1 V (in the prototype), respectively, which confirms the significantly higher effectiveness of the protective effect on the metal surfaces of the newly created composition of the claimed conversion The gentleman.

The Converter is used as follows.

In one case, the proposed Converter is applied to the corroded metal surface to be treated without first eliminating corrosion products from it by any known method (dipping, spraying, brushing, etc.), dried at room temperature for 24 hours, and the paintwork is applied after drying.

In another case, the composition of the Converter is also applied by any known method to the non-corrosive metal surface of the rolled product and then dried by any known method, for example at room temperature for the technologically necessary time, for example 24 hours.

Reducing the number of ingredients present in the transducer, ease of preparation and use of the latter can reduce the cost of the transducer for processing metal surfaces and, accordingly, significantly increase the possibility of its use in large-scale production for the processing of almost any large-sized products with a significant surface area.

Claims (1)

A metal surface transducer containing orthophosphoric acid, potassium ferruginate, zinc nitrate and water, characterized in that it further includes an anionic surfactant, and these components are taken in the following ratio, wt.%:
phosphoric acid (85%) 40.0-50.0 potassium ferruginous (yellow blood salt) 3.0-4.0 zinc nitrate 2.0-3.0 anionic surfactant 0.05-0.15 water rest,
while as anionic surfactants used sodium alkylbenzene sulfonate of the General formula:
RC ₆ H ₄ SO ₃ Na,
where R = C ₂ H ₅ or C ₃ H ₇ .