RU2305143C1 - Active reducing agent of compound for removal of scale and corrosion deposits from various surfaces - Google Patents

Abstract

FIELD: chemical agents used for cleaning metals, plastics and other materials from scale and corrosion; cleaning power and technological equipment, boilers, heat exchangers, water heaters, refrigerators, water ducts, turbines, pumps.

SUBSTANCE: proposed agent contains ammonium salts and/or salts of alkaline metals of ascorbic acid. It may be used for cleaning the surfaces, painted surfaces inclusive, from scale and corrosion.

EFFECT: extended field of application of chemical agents; increased rate of removal of scale and corrosion.

2 cl, 2 tbl

Description

The use of ammonium salts or alkali metal salts of ascorbic acid as an active reducing agent in the removal of scale deposits from various surfaces.

The invention relates to chemicals used for cleaning metal products, plastics and various types of substrates coated with scale-corrosion deposits (hereinafter, NPOs) of corrosion products, for example, when cleaning energy and technological equipment for water supply (boilers, heat exchangers, water heaters, refrigerators , water conduits, turbines, pumps of all types, etc.).

There are various mechanical methods for cleaning metals and metal products from rust: metal brushes, scrapers, emery skins, tumbling, waterjet cleaning. They also use gas-flame cleaning with additional treatment with metal brushes.

To remove rust from the metal, chemical-thermal treatment, treatment with molten salts, as well as special detergent compositions based on synthetic surfactants are used. One of the effective ways to remove corrosion products from the surface of metal products is etching using aqueous solutions of acids, acid salts or alkalis (A.A. Mikhailova et al. Anticorrosive protection of agricultural machinery. Handbook. M., Rosselkhozizdat, 1981, p. 100- 118). All of these methods are not without drawbacks, because they are expensive, time-consuming, insufficiently effective and environmentally harmful, and also do not exclude the tendency to re-rust. In addition, these methods are not applicable when cleaning specific surfaces.

One of the ways to reduce the aggressive effect on a metal when removing NCO washing solutions is to use complexones (complexing agents that bind metal cations that are part of NCOs and other deposits), such as ethylenediaminetetraacetic acid and its salts (T.Kh. Margulova. Use of complexones in heat power engineering, M., Energy, 1973, p. 263).

So, a solution for chemical cleaning of scale, rust, scale, containing Trilon B (complexon) 0.5-1.2%; citric acid 0.5-1.5%; hydrazine hydrate 0.1-0.2%; ammonia to pH 7-9 and the rest of the water (SU 283772.1970). This composition is quite effective, but due to the presence of ammonia in it, it is toxic, and, in addition, when it is used, a high dissolution rate of steel and especially copper alloys is also observed during the period of NPO removal.

Another means for removing NCOs is also known, which is an aqueous solution of a salt or a mixture of salts of nitric and some organic acids. The aqueous solution contains: a) ions from the group of aluminum, iron (II) ions and mixtures thereof; and b) acid anions from the group of nitric, sulfamic, formic, acetic, propionic, lactic, tartaric, citric acids and mixtures thereof (US 4264463, 04/28/81).

The known composition is quite effective, but differs in selectivity with respect to the type of deposits containing calcium oxalate as the main component.

Another composition is known for removing glass lubricant from the surface of metal products, for example, hot-pressed pipes, including hydrofluoric acid, sulfuric acid, ammonium persulfate and organic acid such as tartaric, citric, and oxalic (SU 747908, 07.15.1980). This grease removal time is 30 minutes. The composition is also of limited use due to the presence in it of such strong (aggressive) acids as hydrofluoric and sulfuric, and is intended mainly for the removal of lubricants.

It is known from RU 2026325, 01/09/1995, the use of ascorbic acid in an amount of 10-35 g / l in combination with a complexing agent, for example, such as Trilon B (disodium salt of ethylenediaminetetraacetic acid), ammonium oxalate, etc. and water, in a method for removing rust from the surface of ferrous metals. However, firstly, this known method is multi-stage: after surface treatment with a mixture of ascorbic acid with complexon and water, it necessarily contains the next step - treatment with a passivating corrosion inhibitor. Secondly, in this way only rust up to 200 microns thick is removed.

From RU 2114215, 06/27/1998 it is known the use of ascorbic acid in an amount of 1.0-3.0 g / l in combination with complexon, water. Processing is carried out with a hot solution with a temperature of more than 60 ° C. However, this composition removes NPOs of small thickness with a density of 1.9-2.3 g / cm ³ with a sufficiently long action of the composition.

From RU 2154109,10.08.08.2000 it is known to use ascorbic acid in a method for cleaning the internal surfaces of blast furnace refrigerators from NCOs in an amount of 1.0-3.0 kg / m ³ in combination with complexon, water and active additives forming water-soluble complexes with NCOs, such as sodium salts of sulfosalicylic acid. However, this method removes deposits of small thickness, and, in addition, the cleaning speed is not high.

From RU 2206034, 10.06.2003 it is known to use ascorbic acid in an amount of 12.0-24.0 g / l in a particular composition in combination with a complexing agent - ammonium citrate, tartaric acid, a dissolution promoter - sodium carbonate (bicarbonate), water. The treatment is carried out with a hot solution heated to a temperature above 60 ° C. This composition allows you to remove NPOs with a density of up to 2500 kg / m ³ and higher, however, it does not provide the necessary speed for cleaning NPOs of especially large-sized products (removal rate of 0.5-0.6 kg / m ² · hour at a flow rate of 0.7-1, 0 kg of the preparation / kg of NPO depending on the thickness of the deposits).

The technical task of the claimed invention is to expand the arsenal of chemicals that are environmentally friendly for removing NPOs from various surfaces, as well as increasing the rate of removal of NPOs.

The stated technical problem is achieved by the use of ammonia (ammonium) salts and / or alkali metal salts of ascorbic acid as an active reducing agent in the composition for removing NPOs from various metal and nonmetallic surfaces, including painted these surfaces. The above ammonia salts and alkali metal salts of ascorbic acid are used, in particular, in compositions for removing NCO in combination with various target additives, such as complexing additives, active additives in the form of organic acids and / or salts of organic acids, as well as in combination with such additives like corrosion inhibitors and dissolution promoters.

As the complexing agent, as used NCO removers using various complexing chelate type, such as "Trilon B '(disodium edetate), sulfosalicylic acid, ammonium acetate, ammonium oxalate, dietilentetraminpentauksusnuyu, geksametilendiamintetrauksusnuyu, 2-oksietiliminodiuksusnuyu, oksietilendifosfonovuyu acid et al. (Complexing binds ions Cu + 2, Zn + 2, Fe + 2, Ca + 2, reducing sludge formation).

Various water-soluble atmospheric corrosion inhibitors are used as an inhibitor in the method, for example, borax (Na ₂ B ₄ O ₇ ), water glass, phosphorus-containing compounds (trisodium phosphate, sodium disodium phosphate), catamine, urea, urotropine, etc.

As a dissolution promoter, for example, sodium carbonate, sodium bicarbonate, etc. are used.

As active additional additives, various organic acids are used, such as tartaric acid, sodium salts of sulfosalicylic acid.

The use of ammonium salts or alkali metal salts allows you to remove NPOs and rust of various thicknesses (up to 200 microns) from the surface of ferrous metals (steel, iron, various alloys) of both painted and unpainted metal surfaces, as well as from non-metallic surfaces, for example, plastic surfaces .

Compositions using the claimed as the invention salts of ammonium or alkali metals of ascorbic acid are prepared, for example, by dissolving these salts and various target components in water, heated, for example, to 60 ° C and above with stirring, or by mixing dry powders of ammonium salts or alkali salts metals of ascorbic acid and, for example, with a complexing agent and / or other target additives. Dissolution of NCO is carried out, for example, by washing surfaces with a composition heated, for example, to a temperature of 60 ° C.

The method of cleaning surfaces from NPOs using ammonium salts or alkali metal salts of ascorbic acid depends on the type of object being cleaned, the type of equipment, the material of the surface being cleaned (metal, glass, plastic, paint). For example, the composition is poured or pumped through the system (equipment, volume) to be cleaned. The cleaning process is carried out at a temperature of 60 ° C and above. The upper limit of the cleaning temperature is determined by the type of material (steel, copper alloys, etc.). The corrosion rate of metal substrates cleaned in this way does not exceed 10 ^-8 - 10 ^-9 g / cm ² · hour. Either the product with a rust layer is treated with the composition using the ascorbic acid salts of the invention (large products are immersed in an aqueous solution with a removal agent-converter for a time depending on the size of the product and the thickness of the rust layer), and the solution-converter of the invention is applied to small products or surfaces for example with a dampened swab. Then the surface is dried and treated with a water-soluble corrosion inhibitor (either by dipping with the traditionally used inhibitor concentration up to 10 g / l, or by applying the inhibitor solution with a wet swab depending on the size of the product).

The removal (conversion) of rust using the salts of ascorbic acid according to the invention is effective (a high degree of purity is ensured), without etching the metal surfaces and / or the integrity of the coating. In addition, the composition of the remover according to the claimed invention is very technological, environmentally friendly and non-toxic.

Table 1 presents examples illustrating the invention, for example, in the form of compositions containing ammonium and alkaline salts of ascorbic acid as an active reducing agent.

Table 2 presents data on the effectiveness of the composition depending on the type of substrate and the density of the NCO.

As follows from the tables, the invention allows to ensure the removal efficiency of high-density NCOs, increased removal rate, constant quality of the surface being cleaned (metal, polymers, other coatings), slowing down the rate of corrosion processes and environmental safety while reducing the consumption of substances used.

Table 1 Examples of formulations using ammonium and alkaline salts of ascorbic acid Component Name The content of components, g / l according to examples In compositions for the removal of NPOs based on hardness salts In compositions for removing iron oxide deposits one 2 3 four one 2 3 four Salts of ascorbic acid (ammonia or alkali metals) one one one one 5 5 10 10 Ethylenediaminetetraacetic acid tetrasodium salt eighteen fifteen - fifteen - - thirty thirty Ammonium Citric Acid Salts - - 25 - thirty twenty - - Dissolution promoter *) 2 one 10 3 one 10 3 four Corrosion inhibitor*)*) one one 2 one 3 2 one one Water up to 1 l up to 1 l up to 1 l up to 1 l up to 1 l up to 1 l up to 1 l up to 1 l Note. In example 1, ammonium salts of ascorbic acid; In example 2, potassium salts of ascorbic acid; In example 3, sodium salts of ascorbic acid; In example 4, a mixture of the above salts. *) Dissolution promoter - Na ₂ CO ₃ ; *) *) Corrosion inhibitor - borax, urea, sodium benzoate, etc. table 2 Key sediment removal process indicators Indicators NPOs based on hardness salts. Examples of compositions from table 1 Iron oxide NPOs. Examples of compositions from table 1. one 2 3 four one 2 3 four The average rate of removal of NCO, kg / m ² · h 0.8 1,2 0.9 1,0 0.7 0.7 0.7 0.8 The consumption of the drug, kg (dry powder) / kg NPO 0.2 0.2 0.4 0.4 0.2 0.3 0.3 0.4

Claims (2)

1. The use of ammonia salts and / or alkali metal salts of ascorbic acid as an active reducing reagent composition for removing scale-corrosion deposits from various metallic and non-metallic, including painted, surfaces. 2. The use according to claim 1, characterized in that said salts are used in combination with additives selected from the group consisting of a complexing agent, an organic acid and / or its salt, a dissolution promoter, and a corrosion inhibitor.