MD1726Z - Process for corrosion protection of steel in water - Google Patents

Abstract

The invention relates to the field of protection of metals against corrosion in water and can be used to inhibit corrosion in closed systems of steel pipes. The process of protecting steel from corrosion in water consists in introducing acid dihydrazide into the aqueous medium that contacts the steel surfaces succinic in an amount of 0.1...0.75 g/L and an aqueous extract of walnut leaves in an amount of 10...30 mL/L. Inhibitors can be introduced into the aqueous environment simultaneously or successively. The aqueous extract of walnut leaves is obtained by heating the raw material in water in a mass ratio of (2...4):10, in a water bath at a temperature of 70...100°C for 1...3 hours, and separating the obtained solution.

Description

The invention relates to the field of protecting metals against corrosion in water and can be used to inhibit corrosion in closed steel piping systems.

It is known that natural or processing water, which contains active chloride and sulfate ions, is a rather aggressive environment, in which steel corrosion occurs at an increased rate. Thus, in Chisinau in the water from the aqueduct, which contains, mg/L: Ca2+ - 42.5, Mg2+ - 19.5, HCO3 - - 97.6, SO4 2- - 203.7, Cl- - 56.7, with a total salt content of 0.457 g/L, the corrosion rate of carbon steel at 8 hours of testing is high, reaching 21 g/m2·day. With increasing exposure time, the corrosion rate decreases (e.g. 12 g/m2·day at 24 hours, 6.6 g/m2·day at 72 hours and 4.0 g/m2·day at 240 hours test) due to the formation on the corrosion surface of the oxide-hydroxide film of corrosion products, as well as calcite CaCO3. Although SO4 2- ions cause a general, fairly uniform corrosion, indentations can form on the inner surface of the pipes due to the presence of active chlorine ions in the water. In some cases they can be punctured, which can cause damage to piping systems. Moreover, ionized iron, passing into the water and accumulating there, worsens the quality of the water. (Parshutin V. V., Sholtoyan N. S., Sidelnikova S. P., Volodina G. F. Inhibition of calcium borogluconate corrosion of carbon steel St. 3 in water. I. Corrosion in the conditions of natural aeration and forced convection. Electronic processing of materials , 1999, No. 5, p. 42-56).

In order to reduce the corrosion of the pipes in the water, different inhibitors are introduced that brake the corrosion process. For example, sodium succinate NaOOCCH2CH2COONa is used as a steel corrosion inhibitor in water and aqueous salt solutions in a minimum concentration of 2 mmol/L [1]. The disadvantage of this inhibitor is that the inhibition process is not stable enough.

A corrosion inhibitor for coolants and antifreeze is known, which contains in wt%: 3...4 sebacic acid, 8...9 adipic acid, 6.5...7.5 sodium hydroxide, 3 .5...4.0 benzoic acid, 30...40 water, 0.25...0.5 benzotriazole, 1...2 sodium bicarbonate, the rest is ethylene glycol. The result of its application is an increase in the corrosion resistance of all the constructive materials of the cooling system of internal combustion engines, preventing the danger of mineral deposits on its surface and a decrease in the toxicity of coolants [2].

A corrosion inhibitor for coolants and antifreeze is also known, which contains in mass %: 3.5...4.5 succinic acid, 7...8 adipic acid, 7.5...8.5 sodium hydroxide, 2.5...3.5 benzoic acid, 30...40 water, 0.25...0.5 benzotriazole, 1.5...2.5 sodium bicarbonate, the rest is glycerin . The result of its application is an increase in the corrosion resistance of all construction materials of heat supply systems, prevention of mineral deposits on the surfaces of its elements and a decrease in the toxicity of the coolant in the heat carrier [3].

A corrosion inhibitor is known for coolants and antifreeze, which contains, in wt.%: 5.5...6.5 sebacic acid, 3...4 adipic acid, 6...7 sodium hydroxide, 2...3 benzoic acid, 2.5...3.5 succinic acid, 35...40 water, 0.25...0.5 benzotriazole, 0.02...0.04 N-phenyl -2-naphthylamine, the remainder is ethylene glycol. As a result of the use of this inhibitor, an increase in the corrosion resistance of all constructive materials of the cooling system is observed, as well as the prevention of corrosion on the surface of steel and cast iron [4].

However, the known inhibitors have a very complex multicomponent composition and contain components in high concentrations. At the same time, these inhibitors only reduce the toxicity of cooling liquids without eliminating it.

There are known corrosion inhibitors of steel in water based on dihydrazides, for example, adipic acid:

,

used in concentrations of 0.05...1.0 g/L [5] or succinic acid:

,

used in concentrations of 0.025...0.75 g/L [6]. Despite the fact that they can significantly reduce the corrosion rate, these inhibitors have a significant disadvantage - corrosion suppression is extremely uneven. Inhibitors are only effective for up to 72 hours, and with longer exposure (240 hours or more), the effectiveness drops sharply. This can be seen from the values of the braking coefficients, which decrease significantly. This makes it impossible to use these inhibitors in extended steel piping systems due to the high cost and difficulty in maintaining effective inhibitor concentrations.

There are known methods of protection against corrosion in water with the use of different corrosion inhibitors, which are extracts from vegetable raw materials, for example, from fenugreek seeds, lupine, dried palm fruits, eggplant or beetroot [7]. The disadvantages of these extracts are that they can only be used to inhibit the corrosion of metals in acidic solutions. In water, which is a neutral medium, their effect on reducing corrosion losses is insignificant. At the same time, the extraction methods used do not ensure an extraction of all substances that suppress corrosion in the solution.

A process for protecting steel from corrosion in water is known, which consists in introducing 0.5...1.5 g/L of potassium permanganate KMnO4 and 10...30 mL/L extract into a corrosive environment water from walnuts, obtained by extraction from dry leaves in water at a mass ratio of (2...4):10 at a temperature of 70...100 °C for 1...3 hours, followed by filtration [8].

The disadvantages of this method are the high concentrations of the inhibitor components through which maximum corrosion suppression is achieved, which increases the cost of the inhibitor and the low value, up to 10.8 times, of the corrosion inhibition coefficient. In addition, potassium permanganate is unstable at high temperatures, which means that in systems with a high temperature of the heat carrier, its rapid consumption will occur.

The problem solved by the invention consists in the development of a harmless ecological process, with the use of cheap and accessible inhibitors, based on the aqueous extract of walnut leaves, which will ensure the significant reduction of corrosion losses of closed systems of steel pipes through which water circulates.

The problem is solved by applying a corrosion protection procedure, which provides for the combined or successive introduction of two inhibitors into the aqueous medium that contacts the steel surfaces, at the same time succinic acid dihydrazide is used as inhibitors in a quantity of 0.1... 0.75 g/L and an aqueous extract, obtained from walnut leaves, in a quantity of 10...30 mL/L.

The vegetable raw material for the realization of the invention is very accessible in the walnut growing area. The aqueous extract of walnut leaves is obtained from dry leaves by heating the raw material with water in a water bath, at a temperature of 70...100°C for 1...3 hours at a mass ratio of (2.. .4):10, followed by separation of the resulting solution.

The technical result of the invention shows a significant reduction of corrosion losses up to 25.4 times following the synergistic action of a combined use of two inhibitors: succinic acid dihydrazide and an aqueous extract of walnut leaves.

The advantages of the invention consist in the fact that in the proposed method of protecting steel from corrosion in water, a combination of two cheap and accessible components is used, which act synergistically. As a result, corrosion losses are significantly reduced compared to when using each component separately.

Example of realization of the invention

The aqueous extract of walnut leaves was obtained from dry leaves by heating them in a water bath, at a temperature of 70...100°C for 1...3 hours at a solid mass:liquid ratio of (2.. .4):10, followed by the separation of the resulting solution by filtration or decantation.

Corrosion tests of steel samples St. 3 with the size of 50×25×3 mm were performed at a complete immersion in the solution at the same depth and with the provision of air access. The initial roughness of the samples was carried out by grinding. Corrosion losses were recorded gravimetrically. The effect of the action of the inhibitor was determined quantitatively by the corrosion rate k, g/m2·day, and by the value of the braking coefficient γ = k/k1, where k1 and k - the corrosion rate of the metal, in the presence of the inhibitor and respectively in the absence of the latter . The given coefficient indicates how many times the corrosion speed is reduced as a result of the action of the inhibitor.

The influence of the concentration of the inhibitor, of its separate components, of the test time on the corrosion rate k, as well as of the braking coefficient γ, are presented in tables 1-3.

Table 1

The influence of the addition of succinic acid dihydrazide on

parameters of the corrosion process of St. steel. 3 in water

Inhibitor concentration, g/L Test time, τ, hours Corrosion rate, k, g/m2·day Braking coefficient, γ 0.0 8 24 72 240 21.0 12.0 6.6 4.0 - - - - 0.025 8 24 72 240 4.82 3.6 1.8 1.09 4.36 3.3 3.6 3.66 0.05 8 24 72 240 2.95 1.89 0.97 0.695 7, 1 6.35 6.8 5.76 0.1 8 24 72 240 1.83 0.87 0.635 0.586 11.5 13.8 10.4 6.8 0.25 8 24 72 240 1.188 0.804 0.842 0.789 17, 7 14.9 7.85 5.1 0.5 8 24 72 240 1.579 0.612 0.328 0.997 13.3 19.6 20.1 4.01 0.75 8 24 72 240 1.98 0.96 0.81 1 .01 16.6 12.5 8.15 3.96

Table 2

The influence of the concentration of the aqueous extract from walnut leaves

on the corrosion process of steel St. 3 in water

Extract concentration, mL/L Test time, τ, hours Corrosion rate, k, g/m2·day Braking coefficient, γ 0 8 24 48 72 168 21.0 12.0 8.8 6.6 4.2 - - - - - 10 8 24 48 72 168 5.0 2.29 1.96 1.53 1.0 4.2 5.25 4.5 4.3 4.2 20 8 24 48 72 168 4.9 2.24 1.91 1.47 0.88 4.3 5.35 4.6 4.5 4.8 30 8 24 48 72 168 3.96 2.33 1.6 1.22 0.75 5, 3 5.15 5.5 5.4 5.6

From Table 1 it can be seen that the greatest effect is obtained when using the inhibitor containing 0.025...0.75 g/L of succinic acid dihydrazide. Already at an inhibitor concentration of 0.05 g/L and with test durations of 8 and 72 hours, corrosion losses are reduced by 7.1 and 6.8 times, respectively. At a concentration of 0.5 g/L and a test duration of 24 and 72 h, the corrosion rate decreases by 19.6 and 20.1 times, respectively, but during subsequent holding up to 240 h, the inhibitor wears out (consumes) quickly and the braking coefficient drops to 4.0.

From the data in table 2, it can be seen that when only walnut leaf extract is introduced into the corrosive environment, the corrosion losses decrease, the suppression of corrosion levels decreases as a function of time, but the values of the braking coefficient do not exceed 5.6 (at 30 mL/L and 168 hours of testing).

Next, the corrosion inhibition effect was tested when using both inhibitors introduced together. The inhibitors used in the invention can be introduced into the water environment either separately or in the form of a pre-dosed mixture. As can be seen from table 3, the use of a mixture of an aqueous extract of walnut leaves and succinic acid dihydrazide allows, as a result of the synergistic effect of the interaction of the inhibitory components, to significantly reduce corrosion losses. In this case, it is important that a uniform protection of the steel against corrosion is ensured at different test intervals, and that the braking coefficient does not decrease with increasing test duration. The maximum achieved value of the inhibition coefficient γ is 25.4 at a concentration of succinic acid dihydrazide of 0.5 g/L and of the plant extract of 30 mL/L for an exposure interval of 48 hours.

Table 3

The influence of the combined action of the aqueous extract of walnut leaves and succinic acid dihydrazide on the corrosion process of steel St. 3 in water

Concentration of aqueous extract of walnut leaves, mL/L Concentration of succinic acid dihydrazide, g/L Test time, hours Corrosion rate, k, g/m2·day Braking coefficient, γ 0 0 8 24 48 72 240 21.0 12.0 8.8 6.6 4.0 - - - - 10 0.1 8 24 48 72 240 1.75 0.839 0.629 0.471 0.299 12.0 14.3 14.0 14.0 13.4 0.25 8 24 48 72 240 1.117 0.69 0.518 0.434 0.278 18.8 17.4 17.0 15.2 14.4 0.5 8 24 48 72 240 1.329 0.569 0.376 0.314 0.196 15.8 21.1 23.4 21 ,0 20.4 0.75 8 24 48 72 240 1.16 0.822 0.579 0.478 0.296 18.1 14.6 15.2 13.8 13.5 20 0.1 8 24 48 72 240 1.68 0.811 0.579 0 ,429 0.267 12.5 14.8 15.2 15.4 15.0 0.25 8 24 48 72 240 1.099 0.642 0.48 0.402 0.265 19.1 18.7 18.3 16.4 15.1 0.5 8 24 48 72 240 1.135 0.519 0.364 0.296 0.186 18.5 23.1 24.2 22.3 21.5 0.75 8 24 48 72 240 1.044 0.741 0.533 0.428 0.265 20.1 16.2 16.5 15.4 15 .1 30 0.1 8 24 48 72 240 1.489 0.789 0.533 0.402 0.242 14.1 15.2 15.9 16.4 16.5 0.25 8 24 48 72 240 1.04 0.619 0.447 0.365 0.238 20.2 19 .4 19.7 18.1 16.8 0.5 8 24 48 72 240 1.029 0.48 0.346 0.266 0.174 20.4 25.0 25.4 24.8 23.0 0.75 8 24 48 72 240 0.977 0.628 0.447 0.343 0.210 21.5 19.1 19.7 19.2 19.0

In conclusion, an effective, accessible and quite ecological process is proposed for the protection of steels from corrosion in water, a fact that allows to reduce corrosion losses by about 25 times, at the same time the decrease of losses depending on time takes place quite quickly uniform.

1. Alcybeeva A.I., Levin S.Z. Metal corrosion inhibitors. L., 1968, p. 152

2. RU 2302479 C1 10.07.2007

3. RU 2303083 C1 20.07.2007

4. RU 2393271 C1 27.06.2010

5. MD 359 Y 2011.04.30

6. MD 1025 Y 2016.04.30

7. Saleh R. M., Ismail A. A., Hosary A. A. Corrosion inhibition by extract compounds. Express information. Corrosion and corrosion protection. М., 1985, № 1, p. 22-25

8. MD 1494 Y 2021.01.31

Claims (1)

Process for the protection of steel from corrosion in water, which consists in the combined or successive introduction into the aqueous medium, which is in contact with the steel surfaces, of 0.1...0.75 g/L of succinic acid dihydrazide and 10 ...30 mL/L of aqueous extract of walnut leaves, obtained by heating dry walnut leaves in water in a mass ratio of (2...4):10, in a water bath at a temperature of 70... 100°C, for 1...3 hours, and separation of the obtained solution.