RU2299267C1 - Metal surface treatment composition - Google Patents

Abstract

FIELD: metal surface chemical treatment.

SUBSTANCE: invention relates to compositions for chemical treatment of metal surfaces preventing corrosion of metal and designed to prepare metal surface for deposition of lacquer coating without preliminary removal of corrosion products. Water-based composition contains 45-60% orthophosphoric acid, 2.0-3.5% zinc nitrate, 2.5-4.0% potassium ferrocyanide, and 0.1-0.3% nonionic fluorocarbon surfactant of general formula R_FCONH(C₂H₄O)_nH, wherein R_F represents C₆F₁₃-, C₈F₁₇-, or C₂F₅OC₃F₆OC₂F₄-, and n = 10-15.

EFFECT: prolonged service time of metal articles, prevented further corrosion of metal, and increased storage time of composition.

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Description

The invention relates to compositions for chemical treatment of a metal surface, preventing metal corrosion and intended for preparing a metal surface for applying paint coatings without first removing corrosion products.

The present invention can be used in the construction industry, engineering, transport, in the repair of household appliances.

Known composition containing orthophosphoric acid, aliphatic alcohol, for example isopropyl, nonionic hydrocarbon surfactants, emulsifier, for example sodium dodecyl sulfate, zinc oxide and / or titanium, zinc nitrate, alkali metal or ammonium fluoride, triethanolamine and water (RF №2027794, op. 27.01, op. 27.01 .95, Bull. No. 3). The composition provides the conversion of corrosion products into a protective anti-corrosion film. Its disadvantage is the obligatory preliminary cleaning of rust from metal surfaces and the main disadvantage is that the treated surfaces must be rinsed with water, which makes it impossible to use it for processing large-sized, complex products, especially in mass production.

The known composition (RF No. 2070945, op. 27.12.96, Bull. No. 36) containing phosphoric acid, isopropyl alcohol, zinc nitrate, ethanol and / or butanol, tartaric acid, triethanolamine, C ₃ -C ₇ alkyl acetate and / or tannin , yellow and / or red blood salt and water.

The composition also leads to the destruction of corrosion products and the formation of a protective film. The disadvantage is the large number of ingredients in the composition and the high cost of the product.

Closest to the claimed composition in terms of essential features is a composition for treating a metal surface (RF patent 2120495, op. 20.10.1998), containing phosphoric acid, zinc nitrate, potassium ferruginous, fluorocarbon compound of the general formula R _F ZQ, where R _{F F} = C ₆ F ₁₃ ^- , or C ₈ F ₁₇ ^- , or CF ₃ OS ₃ F ₆ OS ₂ F ₄ ^- ;

Z = —CO—, or —SO ₂ -,

Q = -NHC ₂ H ₄ OH, or

The main disadvantage of the composition selected as a prototype is the instability of fluorinated cationic surfactants in acidic and alkaline environments. In this solution, where pH <3, they, apparently, undergo anion exchange (reanionation) with the formation of compounds poorly soluble with low surface activity such as:

Confirmation of the transformations of fluorine-containing surfactants is an increase in surface tension in the finished composition over time.

An increase in the surface tension of the composition leads to a decrease in the wetting coefficient and the time of conversion of corrosion products, and accordingly the time of surface treatment, to a decrease in the conversion efficiency of rust, especially in microcracks and on a rough surface.

The objective of the invention is to increase the life of metal products having welds, a complex profile, etc., by treating the metal surface with a composition that converts the rust layer into a strong protective film and prevents further corrosion of the metal, including in microcracks, as well as the shelf life of the composition while maintaining its properties, which will allow during the application not to resort to various adjustments both in processing time and temperature of use of the composition.

The problem is solved in that the composition for treating a metal surface containing orthophosphoric acid, zinc nitrate, potassium ferruginate, fluorocarbon surfactant and water, as a fluorocarbon surfactant contains a nonionic compound of the general formula:

R _F CONH (C ₂ H ₄ O) _n H, where R _F = C ₆ F ₁₃ -, or C ₈ F ₁₇ -, or C ₂ F ₅ OC ₃ F ₆ OS ₂ F ₄ -, with n = 10- 15, in the following ratio of components, wt.%:

orthophosphoric acid 45-60 zinc nitrate 2.0-3.5 potassium ferruginous 2.5-4.0 nonionic fluorine-containing surfactant 0.1-0.3 water rest.

The essence of the proposed technical solution is as follows.

The qualitative and quantitative composition of the composition is selected in such a way as to achieve a technical result, which is as follows: a protective film is formed on the surface that prevents further corrosion development for a constant fixed time, and serves as a primer for paint coatings, the time required to process the metal surface is reduced, and also reduces the cost of the composition due to the low content and cost of non-ionic fluorine-containing surfactants.

Phosphoric acid mixed with iron-potassium potassium is a complexing agent for metal corrosion products dissolved under the action of acid, zinc nitrate in a mixture with phosphoric acid and iron-potassium potassium oxide promotes the formation of a strong and weather-resistant oxide and zinc phosphate film. Fluorocarbon nonionic surfactant contributes to the creation of high osmotic pressure, which leads to an increase in the wetting ability of the composition, including its penetration into microcracks.

In this case, the surface tension of the composition remains constant for a long time and is - 23 mN / m. Under storage conditions of the composition, this value of surface tension is constant for at least 6 months.

The joint presence of each of these components in the inventive composition for surface treatment of the metal provides high corrosion resistance of the processed products, and also creates the conditions for the subsequent application of paints and varnishes with complete bonding of corrosion products.

The inventive composition is prepared by dissolving in water these components with mechanical stirring and a temperature of 20-30 ° C.

In this case, chemicals produced by the industry are used:

phosphoric acid in accordance with GOST 6552-80

zinc nitrate in accordance with GOST 5106-77

potassium ferruginous (yellow blood salt) in accordance with GOST 6816-79

nonionic fluorine containing surfactant

distilled water in accordance with GOST 6709-72

The prepared composition is applied to a metal surface without first removing corrosion products using a tampon, brush or spray, and then dried at a temperature of 20-40 ° C.

To determine the operational characteristics of the claimed composition were prepared three compositions with different contents of the ingredients:

Composition 1

phosphoric acid (85%) 45 zinc nitrate 2,5 potassium ferruginous 2,5 nonionic fluorine - surfactant C ₆ F ₁₃ CONH (C ₂ H ₄ O) ₁₄ N 0.15 water rest.

Composition 2

phosphoric acid (85%) fifty zinc nitrate 3 potassium ferruginous 3,5 nonionic fluorine - surfactant CF ₃ OC ₃ F ₆ OC ₂ F ₄ SO ₂ NH (C ₂ H ₄ O) ₁₁ N 0.2 water rest.

Composition 3

phosphoric acid (85%) 55 zinc nitrate 3,5 potassium ferruginous 4.0 nonionic fluorine - surfactant C ₈ F ₁₇ CONH (C ₂ H ₄ O) ₁₅ H 0.3 water rest.

Each of the above samples was processed 12 plates (total - 36) of st - 20 according to GOST 16523-70. The initial rust layer on the plates was up to 90 μm. Drying was carried out for 12 hours at 20-30 ° C, after which they were placed in thermostats over pairs of a 3.5% aqueous solution of sodium chloride at the temperature of the latter 80 ± 0.1 ° C and kept for 400 hours.

Control measurements of the area of destruction of the coating after 400 hours showed that the plates of all three compositions, and the method of lattice cuts with a unit square of 2 × 2 mm, according to GOST 15140-78, showed:

2 points for composition 1;

1 point for composition 2;

1 point for composition 3.

Thus, it can be seen that the inventive composition for metal processing has significant advantages compared with known means designed to achieve the same goal, namely: the ability to form a high-strength anti-corrosion coating on the metal surface in a short time without first removing the rust layer. The film coating can serve as the basis for applying paint and varnish materials to them.

Claims (1)

Composition for treating a metal surface containing orthophosphoric acid, zinc nitrate, potassium ferruginate, fluorocarbon surfactant and water, characterized in that it as a fluorocarbon surfactant - surfactant contains a nonionic compound of the General formula R _F CONH (C ₂ H ₄ O) _n H, where R _F = C ₆ F ₁₃ -, or C ₈ F ₁₇ -, or C ₂ F ₅ OC ₃ F ₆ OS ₂ F ₄ -, n = 10-15, in the following ratio of components, wt.%: Orthophosphoric acid 45-60 Zinc Nitrate 2.0-3.5 Potassium ferruginous 2.5-4.0 Nonionic fluorocarbon surfactant 0.1-0.3 Water Rest