RU2548850C2 - Corrosion inhibitor for ferrous metals in aqueous and aggressive media - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: inhibitor includes, wt %: a sodium salt of polypropylene-β-aminoethanoic acid 68.5-69.5; polyacrylamide 3.25-3.51; calcined soda 6.5-8.0 and water - the balance.

EFFECT: producing a corrosion inhibitor for ferrous metals operating in a harsh aqueous, alkaline and acidic media.

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Description

The present invention relates to compositions for protecting metals from corrosion in aqueous and corrosive environments and can be used to protect equipment from corrosion in aggressive environments.

A known corrosion inhibitor consisting of a copolymer of N, N-dimethyl-N, N-diallylammonium chloride with sulfuric anhydride in the following ratio, wt.%: Copolymer of N, N-dimethyl-N, N-diallylammonium chloride with sulfuric anhydride 99.9, sodium chloride 0.1 (RU 2087592, MKI C1 C23F 11/04, 11/14, 1997).

This corrosion inhibitor can be used in the engineering industry for the etching of metals in sulfuric acid at high temperatures.

The disadvantage of this corrosion inhibitor is its use in the etching of metals in sulfuric acid and is not suitable for the protection of cast iron steels of grades 3 and 10 from exposure to other aggressive environments.

A known corrosion inhibitor is a bactericide, which is obtained by the interaction of fatty acid (C ₅ -C ₁₆ ) and aminoparaffin (C ₁₀ -C ₁₆ ) or by mixing with a corrosion inhibitor O-alkylphosphite-N-alkylammonium or N-alkyl-2-methyl-5 -ethylpyridinium bromide, or with ammonium salts of monoalkylphosphorous acids at a ratio of 1-0.25: 075, respectively. The content of the corrosion inhibitor is a bactericide 30-60 wt.%, The solvent (aliphatic alcohol or aromatic solvent) - the rest (RU 2116380, MKI C23F 11/14, 27/07, 1998).

The corrosion inhibitor is designed to protect oilfield equipment from corrosion.

The disadvantage of this corrosion inhibitor is its low efficiency when used to protect cast iron and steel in hard water.

A known corrosion inhibitor of ferrous metals in aqueous systems containing a mixture of monomers and oligomers of 1,3-diaminopropanol-2 7-12 wt.%, Sodium chloride 4-7 wt.%, Sodium hydroxide 0.5-1 and water.

The composition is introduced into the corrosive medium at a concentration of 0.3-0.5% (SU 1503338, MKI C23F 11/08, 20/01, 1978).

The disadvantage of this corrosion inhibitor is its use in neutral aqueous solutions in closed cooling systems.

Closest to the invention in technical essence and the achieved result is a method for producing a corrosion inhibitor based on the condensation products of hexamethylenediamine with phosphoric acid and urea in the presence of glycerol. The resulting corrosion inhibitor at a concentration of 25-100 mg / l gives a protective effect in neutral water with a total salinity of 200 mg / l of 83-99% (RU 2108408, MKI C23F 11/14, 10/04, 1998).

The disadvantage of this inhibitor is the low protective effect in alkaline and acidic environments, as well as in water with a total hardness of up to 7 mEq / l.

The basis of the present invention is the creation of a corrosion inhibitor of ferrous metals steel 3 and steel 10 and cast iron in hard water with a total hardness of up to 7 mEq / l, operating in an alkaline and acidic environment.

The problem is solved in that the composition of the proposed corrosion inhibitor includes the sodium salt of polypropylene-β-aminoethanoic acid, polyacrylamide and soda ash in the following ratio, wt.%:

polypropylene-β-aminoethanoic acid sodium salt 68.50-69.50 polyacrylamide 3.25-3.51 soda ash 6.5-8.0 water rest

The polypropylene-β-aminoethanoic acid sodium salt is a polymer of the formula:

C _a H _b O _c N _d Na _e , where a is from 43 to 54; b from 51 to 71; c from 13 to 23; d from 4 to 12; e from 1 to 4, with the content of fragments in Na from 23.41 to 27.54 mol%. formulas:

-CH ₂ CH-CH ₂ -NH-CH ₂ -COONa

Polyacrylamide grade A 930 TU 6-02-00209912-41-94.

Drinking water GOST 2874-73.

Soda ash technical GOST 5100-85.

Working solutions can have the following g / l concentrations: from 0.025 to 0.1.

An analysis of the known solutions selected in the search process showed that in science and technology there is no object similar in terms of the claimed combination of features and the presence of the above properties, which allows us to conclude that the claimed object meets the criteria of “novelty” and “inventive step”.

To prove compliance of the claimed invention with the criterion of "industrial applicability" we give examples of specific performance.

Example 1 (prototype)

11.6 g (0.1 mol) of hexamethylenediamine, 17.8 g (0.18 mol) of phosphoric acid and 2.76 g (0.03 mol) of glycerol are placed in a round bottom flask. The resulting mixture was heated to form a homogeneous mixture and 13.2 g (0.22 mol) of urea were added with stirring. Then heated to 130 ° C and heated at this temperature for 1.5 hours. Working solutions with a concentration of 25, 50 and 100 mg / L were prepared from the obtained polymer using hard water with a total hardness of 2 mEq / L.

Corrosion inhibitors were tested according to GOST 6243-75.

The test procedure is as follows: distilled water is poured into a quadrangular glass vessel to a height of about 1 cm. The supports for the plates are lowered to the bottom of the vessel and a household psychrometer is fixed. Using a porcelain spatula, cast-iron shavings (two servings weighing 2.5 g each) are placed on steel plates made of steel 10 with dimensions 115 × 50 × 5 mm. Each portion of cast-iron shavings is moistened with 2 cm ^{3 of a} working solution of a corrosion inhibitor prepared in hard water (up to 7 mEq / l).

Plates are placed in a quadrangular vessel, hermetically sealed with a lid and kept at a temperature of 25 ° C and a relative humidity of 95-97% for 180 hours. Every 24 hours, cast-iron shavings are moistened with 2 cm ³ of the inhibitor's working solution. The test results of the corrosion inhibitor are presented in the table.

Example 2 (proposed)

In the conditions of example 1, but when used to determine the corrosion rate of a mixture of water-soluble components, wt.%:

polypropylene-β-aminoethanoic acid sodium salt 68.5 polyacrylamide 3.25 soda ash 6.5 water rest

Working solutions with a concentration of 100 mg / l were prepared from the obtained aqueous solution using water with a total hardness of 2 mEq / l. The test results are shown in the table.

Example 3

In the conditions of example 2, but when used to determine the corrosion rate of a mixture of water-soluble components, wt.%:

polypropylene-β-aminoethanoic acid sodium salt 68.8 polyacrylamide 3.3 soda ash 6.8 water rest

Working solutions with a concentration of 50 mg / L were prepared from the obtained aqueous solution using water with a total hardness of 2 mEq / L.

The test results are shown in the table.

Example 4

In the conditions of example 2, but when used to determine the corrosion rate of a mixture of water-soluble components, wt.%:

polypropylene-β-aminoethanoic acid sodium salt 69.0 polyacrylamide 3.4 soda ash 7.2 water rest

Working solutions with a concentration of 50 mg / L were prepared from the obtained aqueous solution using water with a total hardness of 2 mEq / L.

The test results are shown in the table.

Example 5

In the conditions of example 2, but when used to determine the corrosion rate of a mixture of water-soluble components, wt.%:

polypropylene-β-aminoethanoic acid sodium salt 69.2 polyacrylamide 3.4 soda ash 7.5 water rest

From the resulting aqueous solution, working solutions with a concentration of 25 mEq / L are prepared using water with a total hardness of 7 mEq / L. The test results are shown in the table.

Example 6

In the conditions of example 2, but when used to determine the corrosion rate of a mixture of water-soluble components, wt.%:

polypropylene-β-aminoethanoic acid sodium salt 69.5 polyacrylamide 3.51 soda ash 8.0 water rest

Working solutions with a concentration of 25 mg / dm were prepared from the obtained aqueous solution using water with a total hardness of 7 mEq / l. The test results are shown in the table.

Table The effectiveness of the corrosion inhibitor of steel 3 and cast iron Example No. Concentration Speed Power Coefficient

inhibitor, mg / l corrosion, g / m ² h protection,% braking 1 (prototype) 100.0 0.0035 ** 99 ^* - 100.0 ^a 0.0066 ^*** 10.71 1.12 2 100.0 ^a 0.0014 99.6 - 3 50.0 ^a 0.0012 83.79 6.17 four 50.0 ^a 0.0011 85.14 6.73 5 25.0 ^b 0.0048 35.06 1.54 6 25.0 ^b 0.0046 37.89 1.61 Note: * - tested on samples of steel 10 with dimensions 10 × 50 × 1.5 mm, which are immersed in a stirred corrosive medium with a volume of 1 l, which is used as tap water with a pH of 7 and a total salinity of 200 mg / l. Test time 120 hours. Test temperature 20 ° C. ** - corrosion rate in the absence of inhibitor, 0.35 mm / year, test time 120 hours; *** - corrosion rate in the absence of inhibitor, 0.0074 g / m ³ h, time 180 hours; a - water with a total hardness of 2 mEq / l; b - water with a total hardness of 7 mEq / L. Corrosion rate K = m _o -m _l / tS t is the test time, h; S is the sample area, m ² ; m _o , m _l - weight of the sample before and after corrosion tests, Degree of protection Z = (1-1 / γ) 100% Braking coefficient γ = J _o / Jin J _o - corrosion rate in the absence of a corrosion inhibitor; Jin is the corrosion rate in the presence of an inhibitor.

Claims (1)

Corrosion inhibitor of ferrous metals in aqueous and aggressive environments, including a mixture of organic and inorganic reagents, characterized in that it contains sodium salt of polypropylene-β-aminoethanoic acid and polyacrylamide as organic reagents, and soda ash as an inorganic reagent, in the following ratio reagents, in wt.%:
polypropylene-β-aminoethanoic acid sodium salt 68.5 - 69.5 polyacrylamide 3.25 - 3.51 soda ash 6.5 - 8.0 water rest