RU2347854C1 - Inhibitor of metal corrosion in sulphuric, hydrochloric and sulfamic acids - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to protection of metals from corrosion and can be implemented in machine engineering at etching, in power and food industries for acid cleaning of equipment and also at acid washing of wells. Inhibitor contains, wt %: 5-nitrosalycylalsulphathiazole 29.0-23.3; 3-dodecylbenzimidazole iodide 9.6-19.5; polyethylene-polyamine 61.3-57.1.

EFFECT: upgraded efficiency of protecting steel, titanium and aluminium from corrosion and also increased inhibition of hydrogen pick-up.

2 tbl, 3 ex

Description

The invention relates to the protection of metals from acid corrosion using inhibitors and can be used in mechanical engineering during etching, for acid cleaning of equipment in the energy and food industries, as well as for acid washing of wells.

It is known the use of polyethylene polyamine (PEPA) as an inhibitor in corrosion of steel in 5-10 N. hydrochloric acid (Brynza A.P., Gerasyutina L.N., Fedash V.P., Beybarova E.Ya. "Polyethylene polyamine - an inhibitor of steel corrosion in hydrochloric acid", "Protection of metals", 1983, v.19, p. 961). PEPA slows down the corrosion of steel in hydrochloric acid in a wide temperature range of 20-90 ° C, but its protective effect is quite small, amounting to 61-95% (degree of protection).

The closest to the proposed solution in technical essence and the achieved result is a known acid corrosion inhibitor containing the condensation product of aniline with capric aldehyde (Turbina V.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.” - M.: Central Research Institute for Technology, Shipbuilding, 1965, p.124-129). A known inhibitor protects steel better than PEPA. However, the degree of protection is still not large enough: 92.07; 95.50 and 97.29% respectively in 3.5 and 7 N. hydrochloric acid solutions. For titanium and aluminum, the protection efficiency is even lower. In addition, the known inhibitor slightly slows down the hydrogenation of steel.

The technical task of the invention is to increase the efficiency of corrosion protection in acids for steel, titanium and aluminum, as well as to increase the braking of hydrogenation of steel.

This technical problem is solved by introducing a corrosion inhibitor into sulfuric, hydrochloric and sulfamic acid containing the condensation product of amine and aldehyde, polyethyleneamine and additionally 3-dodecylbenzimidazole iodide, and 5-nitrosalicylalsulfathiazole as the condensation product.

The last component has the following structure:

Structure of 3-dodecylbenzimidazole iodide

Polyethylenepolyamine is a mixture of high molecular weight fractions of polyamines with an average molecular weight of 150-170 amu

The main components of PEPA are tetraethylene pentamine

H ₂ NCH ₂ CH (NH ₂ ) CH ₂ CH (NH ₂ ) C ₂ H ₂ CH (NH ₂ ) CH ₂ CHNH ₂

and triethylenetetramine

H ₂ NCH ₂ CH (NH ₂ ) CH ₂ CH (NH ₂ ) CH ₂ CHNH ₂ .

These substances are part of the developed inhibitor in the following concentrations (wt.%):

5-nitrosalicylalsulfathiazole 29.0-23.3 3-dodecylbenzimidazole iodide 9.6-19.5 PEPA 61.3-57.1

For the convenience of preparing inhibited acid solutions, the concentrations of the inhibitor components in the same sequence are given, expressed in g / l: 0.9-1.8; 0.3-1.5 and 1.9-4.4. To accelerate the dissolution of the condensation product, it is recommended to pre-dissolve it in 2-3 ml of acetone (it has been experimentally shown that acetone practically does not affect the protective properties of the inhibitor). The introduction of components into acid solutions is carried out in the following sequence: a benzimidazole derivative (with vigorous stirring), then PEPA and, finally, a condensation product (or its acetone solution).

The corrosion rate of samples of steel, titanium and aluminum was measured by the volume of hydrogen released and the gravimetric method from the loss of mass of the samples. Hydrogenation of steel was determined on a K-5 twisting machine by the number of revolutions of wire samples before they broke.

The results of the experiments are shown in tables 1 and 2, as well as in the examples.

Example I. In 1 liter of 5 N. H ₂ SO _{4 was} dissolved 5.2 g of the inhibitor (condensation product 26.1, benzimidazole derivative 14.8, PEPA 59.1 wt.%). Samples of steel, cleaned with thin sandpaper, degreased with acetone, aged for 2 hours in a desiccator over calcined calcium chloride, were weighed on an analytical balance and then immersed in pure and inhibited sulfuric acid. At 20 ° C, the experiment lasted 48 hours, at 90 ° C - 0.5 hours. All experiments on measuring the corrosion rate were carried out in no less than 5 replicates.

и

По полученным таким образом коэффициентам торможения γ₂₀ и γ₉₀ вычислялись степени защиты от коррозииInhibition coefficients were determined on the basis of experimental results, from which the average change in sample mass Δm ₁ for pure acid and Δm ₂ for acid with an inhibitor was found

and

Using the braking coefficients γ ₂₀ and γ ₉₀ obtained in this way, the degrees of corrosion protection were calculated

At 20 ° С Z = 99.5%, for 90 ° С Z = 98.9%. For a known inhibitor, the same values are 90.5 and 87.7%, respectively.

Then, the inhibition coefficients were determined for the individual components of the inhibitor, which were taken at the same concentrations at which they are part of the three-component inhibitor.

The braking coefficients have the following values (at 20 ° C):

condensation product 2.9 benzimidazole derivative 3.8 PEPA 3.3

The product of the coefficients gives a value of 36.4, which is significantly lower than for a three-component inhibitor. Therefore, we can state that there is a noticeable synergy, i.e. mutual strengthening of the protective action of the components.

A similar picture occurred at 90 ° C, the values of the braking coefficients in the same sequence of components are 3.0; 3.5; 3.4; product of partial coefficients 35.7. Synergism is manifested to a lesser extent, but the presence of mutual enhancement of the action of the components is undoubted.

The conclusion about the synergistic effect in the mixture of components is also confirmed by polarization measurements, which showed an increase in both cathodic and anodic polarization (about 3 and 2 times, respectively).

As already noted above, corrosion protection with the proposed inhibitor is significantly higher than with the known. Even more significant is the effect of reducing the hydrogenation of the proposed inhibitor compared to the known one: in this case, the degree of protection is increased several times (for the proposed inhibitor, it is 45% in sulfuric acid, and only 9% for the known).

Example II Similar experiments were carried out with a three-component inhibitor on titanium in 7 N. HCl. The degree of protection at 20 ° C was 90.2%, at 90 ° C - 91.5%. For a known inhibitor, respectively, 71.7 and 70.9%. A comparison of the braking factors for the proposed inhibitor (a mixture of 3 components) and the product of particular braking coefficients for the individual components also indicates the presence of synergy between the components in the mixture (for the mixture γ = 12.4, for the product γ of the individual components γ = 5.8).

Example III In 1 N. a solution of sulfamic acid experiments were conducted with aluminum samples with the proposed and known inhibitors (their concentrations are the same as in examples I and II). The inhibitory coefficient for the proposed inhibitor is 34.6, for the known much lower - 24.5. Mutual enhancement of the protective effect of the components of the proposed inhibitor was also found for aluminum: to produce partial braking coefficients, a value of 10.5 was obtained, which is more than 3 times less than γ for the mixture.

Thus, for all three tested metals, the proposed mixture of components showed synergism, as a result of which the three-component inhibitor was more effective than the known one. The advantage of the proposed inhibitor was found both in the inhibition of corrosion, and, especially significantly, to reduce hydrogenation.

In additional experiments with the PB-5 inhibitor, known and widely used in anticorrosion practice, it was found that it is significantly inferior to the proposed inhibitor in two respects: firstly, by the braking coefficient of steel of 3 N. HCl (respectively, for PB-5, γ = 41, and for the proposed γ = 83.3); secondly, PB-5 coagulates upon accumulation of iron salts, while the proposed one does not coagulate.

The proposed inhibitor can be recommended for the etching of steel, titanium and aluminum in the above acids, as well as for cleaning equipment in which the listed metals are present.

Table 1
The dependence of the degrees of protection against corrosion and hydrogenation of steel, titanium and aluminum in sulfuric, hydrochloric and sulfamic acids on the concentration (wt.%) Of the components of the proposed inhibitor and temperature. No. p / p Metal The concentration of inhibitor components, wt.% Acid, its concentration, equiv / l t, ° С Degree of protection, % condensation product benzimidazole derivative PEPA against corrosion from hydrogenation one 2 3 four 5 6 7 8 9 one steel 29.0 9.6 61.3 H ₂ SO ₄ , 3 twenty 95.7 25.8 2 - // - 26.1 14.8 59.1 - // - 96.0 33.3 3 - // - 23.3 19.5 57.1 - // - 97.8 37.1 four - // - 29.0 9.6 61.3 H ₂ SO ₄ , 3 90 94.8 5 - // - 26.1 14.8 59.1 - // - 98.1 6 - // - 23.3 19.5 57.1 - // - 99.6 7 - // - 29.0 9.6 61.3 H ₂ SO ₄ , 5 twenty 96.9 38.7 8 - // - 26.1 14.8 59.1 - // - 99.5 45.0 9 - // - 23.3 19.5 57.1 - // - 99.6 49.2 10 - // - 29.0 9.6 61.3 - // - 90 97.1 eleven - // - 26.1 14.8 59.1 - // - 98.9 12 - // - 23.3 19.5 57.1 - // - 99.5 13 - // - 29.0 9.6 61.3 HCl, 3 twenty 98.8 23.3 fourteen - // - 26.1 14.8 59.1 - // - 99,2 fifteen - // - 23.3 19.5 57.1 - // - 99.9 35.1 16 - // - 29.0 9.6 61.3 - // - 90 94.5 17 - // - 26.1 14.8 59.1 - // - 98.7 eighteen - // - 23.3 19.5 57.1 - // - 99.9 19 - // - 29.0 9.6 61.3 HCl, 5 twenty 98.3 24.9 twenty - // - 26.1 14.8 59.1 - // - 98.9 21 steel 23.3 19.5 57.1 HCl, 5 twenty 99.9 36.3 22 - // - 29.0 9.6 61.3 HCl, 5 90 92.9 23 - // - 26.1 14.8 59.1 - // - 98.0 24 - // - 23.3 19.5 57.1 - // - 99.7 25 - // - 29.0 9.6 61.3 HCl, 7 twenty 98.3 22.9 26 - // - 26.1 14.8 59.1 - // - 99.9 27 - // - 23.3 19.5 57.1 - // - 99.9 41.1 28 - // - 29.0 9.6 61.3 HCl, 7 90 96.1 29th - // - 26.1 14.8 59.1 - // - 97.5 thirty - // - 23.3 19.5 57.1 - // - 99.3 31 - // - 29.0 9.6 61.3 NH ₂ SO ₂ OH, 1 twenty 75.8 27.0 32 - // - 26.1 14.8 59.1 - // - 76.5 33 - // - 23.3 19.5 57.1 - // - 79.2 34 - // - 29.0 9.6 61.3 - // - 90 67.3 35 - // - 26.1 14.8 59.1 - // - 80.9 36 - // - 23.3 19.5 57.1 - // - 92.3 37 titanium 29.0 9.6 61.3 H ₂ SO ₄ , 8 twenty 71.9 38 - // - 26.1 14.8 59.1 - // - 73.0 39 - // - 23.3 19.5 57.1 - // - 73.8 40 - // - 29.0 9.6 61.3 - // - 90 857.1 41 - // - 26.1 14.8 59.1 - // - 90.2 42 - // - 23.3 19.5 57.1 - // - 91.9 43 - // - 29.0 9.6 61.3 HCl, 7 twenty 87.7 44 - // - 26.1 14.8 59.1 - // - 90.2 45 - // - 23.3 19.5 57.1 - // - 91.7 46 - // - 29.0 9.6 61.3 - // - 90 90.0 47 - // - 26.1 14.8 59.1 - // - 91.5 48 titanium 23.3 19.5 57.1 HCl, 7 90 92.2 49 - // - 29.0 9.6 61.3 NH ₂ SO ₂ OH, 1 twenty 73.1 fifty - // - 26.1 14.8 59.1 - // - 74.5 51 - // - 23.3 19.5 57.1 - // - 80.3 52 aluminum 29.0 9.6 61.3 H ₂ SO ₄ , 3 twenty 85.9 53 - // - 26.1 14.8 59.1 - // - 86.1 54 - // - 23.3 19.5 57.1 - // - 87.7 55 - // - 29.0 9.6 61.3 90 83.0 56 - // - 26.1 14.8 59.1 - // - 83.3 57 - // - 23.3 19.5 57.1 - // - 85.3 58 - // - 29.0 9.6 61.3 HCl, 3 twenty 92.9 59 - // - 26.1 14.8 59.1 96.6 60 - // - 23.3 19.5 57.1 99.9 61 - // - 29.0 9.6 61.3 90 93.0 62 - // - 26.1 14.8 59.1 99,2 63 - // - 23.3 19.5 57.1 99.8 64 - // - 29.0 9.6 61.3 NH ₂ SO ₂ OH, 1 twenty 70.1 65 - // - 26.1 14.8 59.1 71.1 66 - // - 23.3 19.5 57.1 73.3

table 2
Inhibition of corrosion of steel, titanium and chromium and inhibition of hydrogenation in hydrochloric, sulfuric and sulfamic acids by a known inhibitor (condensation product of aniline with capric aldehyde, concentration 5 g / l) No. p / p Metal Acid and its concentration, equiv / l t ° C Degree of protection, % against corrosion from hydrogenation one 2 3 four 5 one steel H ₂ SO ₄ , 3 twenty 91.5 5 2 - // - H ₂ SO ₄ , 5 - // - 90.9 9 3 - // - H ₂ SO ₄ , 3 90 90.8 four - // - H ₂ SO ₄ , 5 - // - 87.7 5 - // - HCl, 3 twenty 92.5 3 6 - // - HCl, 5 - // - 94.5 3 7 - // - HCl, 7 - // - 97.3 four 8 - // - HCl, 3 90 90.2 9 - // - HCl, 5 - // - 90.0 10 - // - HCl, 7 - // - 96.2 eleven - // - NH ₂ SO ₂ OH, 1 twenty 68.7 12 - // - -//-, one 90 63.3 13 aluminum H ₂ SO ₄ , 3 twenty 65.5 fourteen - // - -//-, 5 - // - 65.7 fifteen - // - - // -, 3 90 45.9 16 - // - -//-, 5 - // - 52,2 17 - // - HCl, 3 twenty 41.1 eighteen - // - -//-, 5 - // - 53.6 19 - // - - // -, 3 90 56.3 twenty - // - -//-, 5 90 68.5 21 - // - NH ₂ SO ₂ OH, 1 twenty 61.9 22 - // - -//-, one 90 58.8 23 titanium H ₂ SO ₄ , 8 twenty 63.0 24 - // - -//-, 8 90 75.8 25 - // - HCl, 7 twenty 71.7 26 - // - - // -, 7 90 70.9 27 - // - NH ₂ SO ₂ OH, 1 twenty 59.2

Claims (1)

A metal corrosion inhibitor in sulfuric, hydrochloric and sulfamic acids containing the product of the condensation of an amine with an aldehyde, characterized in that it additionally contains 3-dodecylbenzimidazole iodide and polyethylene polyamine, and 5-nitrosalicylalsulfathiazole in the following ratio of components, wt.%:
5-nitrosalicylalsulfathiazole 29.0-23.3 3-dodecylbenzimidazole iodide 9.6-19.5 polyethylene polyamine 61.3-57.1