RU2261292C2 - Corrosion inhibitor of metals in hydrochloric acid and sulfuric acid - Google Patents

Abstract

FIELD: inhibitors for metals corrosion protection in hydrochloric acid and sulfuric acids.

SUBSTANCE: the invention is pertaining to the field of protection of metals from corrosion in hydrochloric acid and sulfuric acids with the help of inhibitors and may be used at etching treatment of metals in hydrochloric acid and sulfuric acids, and also for acid cleanout of equipment. The inhibitor contains(in mass %): n- iodobensal-2-amino-5- nitrophenol - 20.9-29.2; 5- bromine-3-fluorine-buhyl-6-methyluracil - 33.5-42.9; urotropin - 27.5-45.6. Utilization of the inhibitor allows to increase a degree of protection of steel, titanium and chromium against corrosion and also to reduce hydrogenation of steel.

EFFECT: the invention allows to improve protection of steel, titanium and chromium against corrosion, to reduce hydrogenation of steel.

2 tbl, 3 ex

Description

The present invention relates to the field of protection of metals from corrosion in hydrochloric and sulfuric acids using an inhibitor.

It is known to use urotropin to protect steel in sulfuric and hydrochloric acids (Altsybeeva A.I., Levin S.Z. Metal corrosion inhibitors - L .: Chemistry, 1968, p. 28-29). However, the protective effect of urotropine for steel is small and much less for other metals. The disadvantages of urotropin include a large dose to achieve a protective effect (the concentration of the inhibitor is 2% or about 20 g / l, which is much more than the usual portion of the corrosion inhibitor).

The closest to the proposed inhibitor in technical essence and the result obtained is the product of the condensation of aniline and capric aldehyde (Turbina E.G., Klyuchnikov N.G. Protection of steel from corrosion in hydrochloric acid by the condensation products of amines and aldehydes. Collection of articles "Metal corrosion inhibitors" Central Research Institute of Shipbuilding Technology, ed. Shipbuilding, 1965, pp. 124-129). The known inhibitor protects steel better than urotropin, but the degree of protection is still not large enough (in 3, 5, 7 and hydrochloric acid, they make up 92.07, 95.50 and 97.29%, respectively). Even less protection for titanium and chromium. A known inhibitor weakly inhibits the hydrogenation of steel.

The problem to which the invention is directed, is to create an acid corrosion inhibitor not only of steel, but also of titanium and chromium. The developed inhibitor, consisting of 3 components, has a protective ability that is significantly superior to that for the known inhibitor for all three metal names and, in addition, significantly reduces the hydrogenation of steel. The high efficiency of the proposed inhibitor is associated with the mutual enhancement of the joint protective action (synergism) of the inhibitor components. To achieve this technical problem, it is proposed to add an inhibitor to solutions of sulfuric and hydrochloric acids. Containing in its composition the condensation product of amine and aldehyde, which is taken as n-iodobenzal-2-amino-5-nitrophenol, 5-bromo-3-sec-butyl-6-methyl-uracil and urotropin. The first two substances have the following structure.

The components of the inhibitor are taken in the following concentrations, wt.%:

n-iodobenzal-2-amino-5-nitrophenol 20.9-29.2 5-bromo-3-sec-butyl-6-methyl-uracil 33.5-42.9 urotropin 27.5-45.6

The dissolution of the components is carried out in the sequence: a condensation product, a derivative of uracil, urotropin.

The experiments on changing the corrosion rate were carried out by the gravimetric method, the hydrogenation of steel was determined on a K-5 twisting machine by the number of revolutions of the steel sample before breaking.

The results of the experiments are collected in tables 1 (experiments proposed by the inhibitor) and 2 (with known). In addition, examples of conducted experiments are given.

Example 1. In 500 ml of 5 N sulfuric acid, 2.5 inhibitors were introduced containing 29.2% of the condensation product, 42.9% of the uracil derivative and 27.9% of urotropine. The components individually in the above sequence were dissolved in sulfuric acid with vigorous stirring. Three steel samples having a size of 30 × 20 × 0.8 mm were tested in each experiment. At 20 ± 1 ° C, the experiment lasted 50 hours, at 90 ± 1 ° C for 0.5 hours. Samples were pretreated with a fine emery cloth, degreased with acetone, kept in a desiccator over calcium chloride for 2 hours and weighed on an analytical balance. The corrosion rate of steel in pure acid obtained by weighing was 9.2 × 10 ^-4 g / dm ² · h at 20 ° C, 45.87 g / dm ² · h at 90 ° C and 7.9 × respectively in inhibited acid 10 ^-6 and 0.297 g / dm ² · hour.

(где V₁ и V₂ - скорости коррозии соответственно в чистой и ингибированной кислотах) при 20°С, равные 119,2 и 158,1 при 90°С. Найденные из K₁ степени защиты составили для 20°С 99,16 или 99,2%, для 90°С 99,37 или 99,4%.Inhibitor inhibitory factors were calculated from the indicated corrosion rates

(where V ₁ and V ₂ are corrosion rates in pure and inhibited acids, respectively) at 20 ° С, equal to 119.2 and 158.1 at 90 ° С. The degrees of protection found from K ₁ were 99.16 or 99.2% for 20 ° C and 99.37 or 99.4% for 90 ° C.

Conducted similar experiments with the individual components of the inhibitor gave the following values of K ₁ for the condensation product of 3.4% for the uracil derivative of 3.9; for urotropin 2.1. The theoretical drag coefficient for the mixture, found by the partial coefficients for each component, is 27.8, that is, 4 times less than the experimental value K ₁ = 119.2. Therefore, the combined action of the components leads to a significant increase in the protective effectiveness of the proposed inhibitor on steel. Indirectly, the same effect is indicated by an increase in cathodic and anodic polarization in the presence of the proposed inhibitor, which reaches 120-140 metals (for the cathodic curve) and 70 - 80 metals (for the anodic), respectively. If individual components of the inhibitor are introduced into the acid, the polarization is 3.4 times lower.

, степень защиты от наводороживания

. Опыты проводились в 5-10 повторностях.To determine the hydrogenation of steel, wire samples of its length of 150 mm were twisted to break in a twisting machine. In the case of samples that were not etched in acid, the number of revolutions before breaking was 55, for etching the samples in pure acid 2, for an acid supplemented with the proposed inhibitor 27, the decrease in the number of revolutions for samples in pure acid Δn ₁ = 53, in inhibited Δn ₂ = 28, from here the hydrogen reduction coefficient was calculated

degree of protection against hydrogenation

. The experiments were carried out in 5-10 replicates.

In the last series of experiments of this example, the degrees of protection against corrosion and hydrogenation were determined for a known inhibitor (concentration of 5 g / l). The method of work was the same as in the experiments with the proposed inhibitor. The degree of corrosion protection of steel was 91.7%; from hydrogenation 8%.

Example 2. The inhibition of corrosion of titanium in 7 N hydrochloric acid at 90 ° C was determined using the proposed and known inhibitors.

The methodology of experiments and calculations did not differ from that used in example 1 for corrosion tests.

The inhibitory coefficient found for titanium by the proposed inhibitor was 12.4, and the degree of protection was 91.9%. For individual components of the inhibitor, the partial braking coefficients were equal: 1.3 for the condensation product; for the derivative of uracil 2.1 and urotropine 1.4. Thus, the theoretical coefficient was 3.8, or almost three times less than for the proposed inhibitor. Therefore, in this case, too, there is a clear increase in the mutual influence of the components of the braking of titanium corrosion.

For a known inhibitor, which was taken at a concentration of 5 g / l, the degree of protection of titanium in 7 N hydrochloric acid at 90 ± 1 ° C was 45.9%.

Example 3. Inhibition of chromium corrosion in 5 N hydrochloric acid at 90 ± 1 ° C was determined. The concentration of the proposed inhibitor and other conditions were not noted from the experiment in example 1 (only the size of the sample was halved, and the experiment time was 2 times increased). The degree of protection (and braking coefficients) for a temperature of 90 ± 1 ° C is 79.2% (4.8). For the individual components of the inhibitor, the braking coefficients are: for the condensation product 1.3; for the uracil derivative 1.3; for urotropin 1.1. The theoretical drag coefficient is 1.8, that is, more than two times less than the results obtained in the experiments. Thus, for the proposed inhibitor and for chromium there is a significant effect of the synergism of the components, if we take the proposed inhibitor as a whole.

A comparison of the results given in the tables and examples allows us to draw the following conclusions:

1. The proposed inhibitor protects the tested metals more effectively than the known, which is especially noticeable for titanium and chromium.

2. The superiority of the proposed inhibitor is very significant in comparison with the steel hydrogenation known for braking.

An additional comparative study of the proposed inhibitor with the PB-5 inhibitor widely used in practice was carried out, testifies to the advantage of the former both in slowing down steel corrosion (for example, the braking coefficients for the proposed inhibitor are more than 100, and for the known one about 40), and also in stability in etching solutions (the proposed inhibitor does not coagulate in any of the tested acids, while PB-5 coagulates in both acids).

Coagulation of the PB - 5 inhibitor is observed upon accumulation of salts in the etching solution, which sharply reduces the protective effect of the inhibitor. In the same conditions, the effectiveness of the proposed inhibitor remains high.

The proposed inhibitor can be recommended for the etching of steel, titanium and chrome parts, as well as for acid cleaning of the surfaces of these metals.

Table 1
Inhibition of corrosion of steel, titanium and chromium and deceleration of hydrogenation of steel in sulfuric and hydrochloric acids by the proposed inhibitor No.
p / p Metal The concentration of inhibitor components, wt.% Acid and its concentration, g / equiv. / L Temperature ° C Degree of protection, % Against corrosion From hydrogenation Condensation product Uracil derivatives Urotropin 1 2 3 4 5 6 7 8 nine 1 Steel 20.9 33.5 45.6 HCl 3 twenty 98.9 23.1 2 Steel 25.0 38.7 36.3 HCl 3 twenty 99.6 3 Steel 29.2 42.9 27.9 HCl 3 twenty 99.8 34.3 4 Steel 20.9 33.5 45.6 HCl 5 twenty 98.1 24.3 5 Steel 25.0 38.7 36.3 HCl 5 twenty 98.7 6 Steel 29.2 42.9 27.9 HCl 5 twenty 99.7 35,4 7 Steel 20.9 33.5 45.6 HCl 7 twenty 94.0 8 Steel 25.0 38.7 36.3 HCl 7 twenty 96.9 nine Steel 29.2 42.9 27.9 HCl 7 twenty 99.5 10 Steel 20.9 33.5 45.6 HCl 3 90 94.5 eleven Steel 25.0 38.7 36.3 HCl 3 90 96.3 12 Steel 29.2 42.9 27.9 HCl 3 90 99.7 thirteen Steel 20.9 33.5 45.6 HCl 5 90 94.9 14 Steel 25.0 38.7 36.3 HCl 5 90 97.6 fifteen Steel 29.2 42.9 27.9 HCl 5 90 99.7 16 Steel 20.9 33.5 45.6 HCl 7 90 96.0 17 Steel 25.0 38.7 36.3 HCl 7 90 98.2 eighteen Steel 29.2 42.9 27.9 HCl 7 90 99,2 19 Steel 20.9 33.5 45.6 H ₂ SO ₄ 3 twenty 96.2 23.1 twenty Steel 25.0 38.7 36.3 H ₂ SO ₄ 3 twenty 96.3 21 Steel 29.2 42.9 27.9 H ₂ SO ₄ 3 twenty 98.1 32,2 22 Steel 20.9 33.5 45.6 H ₂ SO ₄ 5 twenty 95.8 23.3 23 Steel 25.0 38.7 36.3 H ₂ SO ₄ 5 twenty 97.1 24 Steel 29.2 42.9 27.9 H ₂ SO ₄ 5 twenty 99,2 47 25 Steel 20.9 33.5 45.6 H ₂ SO ₄ 3 90 94.2 26 Steel 25.0 38.7 36.3 H ₂ SO ₄ 3 90 97.7 27 Steel 29.2 42.9 27.9 H ₂ SO ₄ 3 90 99.3 28 Steel 20.9 33.5 45.6 H ₂ SO ₄ 5 90 93.9 29th Steel 25.0 38.7 36.3 H ₂ SO ₄ 5 90 97.3 thirty Steel 29.2 42.9 27.9 H ₂ SO ₄ 3 90 99,4

1 2 3 4 5 6 7 8 nine 31 Titanium 20.9 33.5 45.6 HCl 7 twenty 76.5 32 Titanium 25.0 38.7 36.3 HCl 7 twenty 79.2 33 Titanium 29.2 42.9 27.9 HCl 7 twenty 81.1 34 Titanium 20.9 33.5 45.6 HCl 7 90 85.5 35 Titanium 25.0 38.7 36.3 HCl 7 90 87.9 36 Titanium 29.2 42.9 27.9 HCl 7 90 91.9 37 Titanium 20.9 33.5 45.5 H ₂ SO ₄ 8 twenty 70.3 38 Titanium 25.0 38.7 36.3 H ₂ SO ₄ 8 twenty 73.3 39 Titanium 29.2 42.9 27.9 H ₂ SO ₄ 8 twenty 75.1 40 Titanium 20.9 33.5 45.6 H ₂ SO ₄ 8 90 79.2 41 Titanium 25.0 38.7 36.3 H ₂ SO ₄ 8 90 80.9 42 Titanium 29.2 42.9 27.9 H ₂ SO ₄ 8 90 87.0 43 Chromium 20.9 33.5 45.6 HCl 5 90 69.2 44 Chromium 25.0 38.7 36.3 HCl 5 90 73.5 45 Chromium 29.2 42.9 27.9 HCl 5 90 79.2 46 Chromium 20.9 33.5 45.6 H ₂ SO ₄ 5 90 65,2 47 Chromium 25.0 38.7 36.3 H ₂ SO ₄ 5 90 68,4 48 Chromium 29.2 42.9 27.9 H ₂ SO ₄ 5 90 73.8

table 2
Inhibition of corrosion of steel, titanium and chromium, as well as a decrease in hydrogenation of steel in sulfuric and hydrochloric acids by a known inhibitor (a product of the condensation of aniline with capric aldehyde 5 g / l). Metal Acid and its concentration, equiv / l Temperature ° C Degree of protection, % Against corrosion From hydrogenation 1 2 3 4 5 Steel HCl 3 twenty 92.07 2 Steel HCl 5 twenty 95.5 3 Steel HCl 7 twenty 97.29 5 Steel HCl 3 90 92.9 Steel HCl 5 90 94.3 Steel HCl 7 90 95.6 Steel H ₂ SO ₄ 3 twenty 91.9 6 Steel H ₂ SO ₄ 5 twenty 91.3 8 Steel H ₂ SO ₄ 3 nine 92.3 Steel H ₂ SO ₄ 5 90 94.1 Titanium HCl 7 twenty 30.1 Titanium HCl 7 90 45.9 Titanium H ₂ SO ₄ 8 twenty 32.3 Titanium H ₂ SO ₄ 8 90 33.5 Chromium HCl 5 90 43.3 Chromium H ₂ SO ₄ 5 90 49.1

Claims (1)

Corrosion inhibitor of metals in hydrochloric and sulfuric acids based on the product of the condensation of amine with aldehyde and urotropin, characterized in that it contains n-iodobenzal-2-amino-5-nitrophenol as a condensation product and additionally includes 5-bromo-6 -but-butyl-6-methyluracil at the following concentrations of components, wt.%: n-iodobenzal-2-amino-5-nitrophenol 20.9-29.2 5-bromo-6-sec-butyl-6-methyluracil 33.5-42.9 Urotropin 27.9-45.6