RU2338008C1 - Safety device for steel against corrosion and hydrogenation in mediums containing sulphatereducing bacterias - Google Patents

Abstract

FIELD: metalurgy.

SUBSTANCE: invention concerns protection against corrosion, hydrogenation and prevention of sulfate-reducing bacterium development in conditions of reduced aeration of machine components. Method includes introduction in medium of aqueous-alcoholic solution kinone 2.3-bromine-1.4-benzoquinone or hydroquinone 2.5-bromine-1.4-hydroquinone and 2.3-bromine-1.4-hydroquinone in amount of 1-5 millimole/l.

EFFECT: providing of advanced decreasing of steel corrosion rate with increasing of introduced organic matter concentration.

5 tbl, 1 ex

Description

The present invention relates to methods of corrosion protection, hydrogenation and preventing the development of sulfate reducing bacteria (SRB) in conditions of reduced aeration of machine parts, in particular engines, metal structures, oil, gas, autonomous river and sea equipment and other devices made of carbon and alloy steel, using aqueous or aqueous-alcoholic solutions circulating in a closed cycle.

Known inhibitor of hydrogen sulfide corrosion and hydrogenation of steel, containing the condensation product of monoethanolamine and coal phenol, as a solvent, monohydric isoalcohols introduced into an aggressive environment, described in RF patent No. 2225897, IPC C23F 11/04, application. 2001.11.26, publ. 2004.03.20.

The disadvantage of this inhibitor is that it does not have a biocidal effect against sulfate-reducing bacteria.

There is also a method of inhibiting the growth of sulfate-reducing bacteria and corrosion inhibition according to patent No. 2197605, IPC ЕВВ 43/22, decl. 2000.10.17, publ. 2003.01.27.

The known method is carried out by introducing an effective amount of a chemical reagent - a bactericide, and as the latter, the product of the interaction of monoethanolamine with formaldehyde is taken, taken in the molar ratio of monoethanolamine: formaldehyde = 1: (2.01-3.0). In this case, the co-action product is introduced in the form of an aqueous or aqueous-alcoholic solution previously obtained by reacting monoethanolamine with a 30-40% formaldehyde solution, preferably taken in the molar ratio of monoethanolamine: formaldehyde = 1: (2.01-3.0). Moreover, an aqueous or aqueous-alcoholic solution of the reaction product is introduced in an amount of 0.007-2.0 wt.% In an aggressive environment.

This method is, in our opinion, the closest to the claimed, and can serve as a prototype.

The disadvantage of this method is that it does not provide protection for the metal that corrodes under the influence of CRP from hydrogen embrittlement.

The tasks set by the authors of the proposed method are, firstly, the development of highly effective and economical corrosion inhibitors that combine the properties of biocides and hydrogen inhibitors of steel at the same time, and secondly, the expansion of the range of inhibitors for environments containing hydrogen sulfide.

The objectives are achieved due to the fact that in the method of protecting steel from corrosion in environments containing sulfate-reducing bacteria by introducing a water-alcohol solution of a chemical reagent, a solution of quinone or hydroquinone is introduced as a chemical reagent, while quinone has the general formula 2.3 -dibromo-1,4-benzoquinone (OS2)

where R ¹ = R ² = Br.

Hydroquinones have the general formula (2,5-dibromo-1,4-hydroquinone (OS1) and 2,3-dibromo-1,4-hydroquinone (OS3))

where 1. R ¹ = R ³ = Br;

2. R ¹ = R ² = Br.

In the inventive method, for the first time, quinones are used as biocides for sulfate-reducing bacteria and inhibitors of corrosion and hydrogenation of steel. It is known that substituted phenols have a wide spectrum of biocidal action, among them effective fungicides and bactericides were found. The biocidal effect of hydroquinones (diatomic phenols) is based on their ability to disrupt the functioning of enzymatic transport systems through biomembranes and, thus, disrupt cellular respiration. Many natural and synthetic quinones have high antimicrobial activity, which is due to the presence of carbonyl groups in their molecule, as well as the ability of these substances to form hydrogen bonds.

The high efficiency of the proposed inhibitors in water-salt environments is confirmed by the following: when quinones are used as corrosion and hydrogenation inhibitors of steel in these environments, physical adsorption of their molecules on iron is unlikely. The oxygen atom in the> CO group of quinones carries an excess negative charge. The subsequent reorientation of the dipoles of the quinone molecule is one of the conditions for its adsorption on the metal surface. The inhibitory effect of electron donors (organic inhibitors in the localized metal-inhibitor donor-acceptor bond, metal ions - electron acceptors) is associated with the presence of lone electron pairs that enter into chemisorption interaction with incomplete p- and d-sublevels of the metal. Therefore, on iron, which has an incomplete d-electron sublevel, specific adsorption (chemisorption) of the quinone molecules under consideration is possible.

The presence of inhibitor donors at the interface causes inhibition of the anodic corrosion process. The role of acceptor inhibitors (aromatic structures in hydroquinones, structures with multiple bonds in quinones) with respect to the metal consists in inhibiting the cathodic processes of hydrogen reduction. The metal-inhibitor adsorption bond will be the stronger, and the degree of corrosion protection the higher, the higher the electron density at the active center of the inhibitor molecule.

The oxygen atom in the -OH group of hydroquinones carries an excess positive charge. Physical adsorption of the molecules is therefore possible due to the electrostatic interaction with the -OH groups of the negatively charged (because _Fe E _{q = 0} = -0.37 V, and the potential of steel in a corrosive medium E _corr = -0.55 mV) of the iron surface. The presence of several adsorption centers in an organic molecule can lead to the formation of chelate complexes with the metal, which will provide a high degree of corrosion protection.

The claimed compounds quinone and hydroquinones in terms of the degree of protection of mild steel in water-salt medium from microbiological corrosion have proved to be good corrosion inhibitors, hydrogen inhibitors and biocides.

An example implementation of the method:

For testing, samples of sheet steel 50 × 20 × 1 mm are used as objects of study.

The selection of a corrosive medium is carried out in accordance with the following requirements:

1) ensuring the priority development of CRP;

2) the proximity in composition to the natural or technological environment;

3) high corrosion activity.

The inventive organic compounds are introduced into a corrosive environment at concentrations: C = 1; 2 and 5 mmol / L.

The samples were exposed for 170 h in a water-salt medium inoculated with CRP of the species Desulfovibrio desulfuricans, isolated by repeated reseeding on a selective Postgate B nutrient medium taken from a natural source (stream). During this time, the life cycle of the CRP population of the genus Desulfovibrio is completely completed in a limited volume of hermetically sealed vessel. CRP is an anaerobic culture and oxygen dissolved in the medium causes the bacterial cells to transition to a latent state.

The composition of the Postgate "B" medium: sodium chloride 7.5 g / l; magnesium sulfate 1.0 g / l; sodium sulfate 2.0 g / l; sodium carbonate 1.0 g / l; sodium dihydroorthophosphate 0.5 g / l; calcium lactate 2.0 g / l.

The following physicochemical parameters are determined daily during the exposure: pH, redox potential of the corrosive medium Eh, the concentration of biogenic hydrogen sulfide C _H2S in it, the number of bacteria (bacterial titer) n and the electrode potential of steel ε, immediately after the corrosion tests analyze the amount of hydrogen, absorbed by the samples.

Calculation of the number of cells of sulfate-reducing bacteria is carried out under a BIOLAM LOMO microscope in phase contrast in a Goryaev’s chamber.

By the end of the second day of exposure, the number of CRP cells in the medium increased to 8 · 10 ⁶ ml ^-1 . The latent phase of the development of bacteria in this medium is 48 hours, therefore, the claimed organic compounds (OS) with the supposed inhibitory activity and steel defatted and irradiated with a mercury-quartz lamp samples are introduced into the Postgate "B" medium 48 hours after inoculation with the same amount of CRP culture. The maximum number of bacteria in a medium without OS for 4 days is n = 24 · 10 ⁶ ml ^-1 . By the end of the exposure number CRP decreases to an average of 2 x 10 ⁶ ml ^-1 - due to the cessation of reproduction of microorganisms and dying during exhaustion of the nutrient medium and accumulating therein metabolic products. In samples containing 5 mMol / L of the studied OS, the number of CRP decreases to 12.5 · 10 ⁶ ml ^-1 with active growth by 3-4 days of the experiment, with its subsequent decline to 1.5 · 10 ⁶ ml ^-1 , t .e. suppression of the number of CRP over the entire exposure time under the influence of the OS is 1.7 times greater than its natural decline in the control series. In all OSs, bactericidal activity increases with increasing concentrations, with OS1 and OS3 showing less activity, and OS2 showing the greatest activity, with the lowest molar mass, which is explained by its better penetration through CRP cell membranes.

Hydrogen sulfide released by bacteria during the metabolism accelerates the corrosion process. Both pH and Eh, and ε steel depend on its concentration in the system. With _H2S , the medium is determined by precipitation iodometric titration, subject to all methods of preserving hydrogen sulfide: minimum sampling time, tightly closed plugs. After 2 days of exposure of the samples in a medium inoculated with CRP C _H2S = 136 mg / L. With the development of the life cycle, CRP C _H2S increases, reaches a maximum, and drops sharply by the 7th day of exposure. Under selected conditions, the maximum C _H2S corresponds to the maximum number of CRP.

In the series with the claimed running more sharply there is a decrease With _H2S, than in the control series, and it is greater, the higher the concentration of the investigated OS. Already very small concentrations (1 and 2 mmol / L) introduced into the corrosive medium lead to a sharp drop in n and the production of biogenic H ₂ S. ОС2 causes the greatest decrease in С _H2S in the corrosive medium.

The results of the study are presented in table. 1 and 2.

Measurements of Eh, pH of the corrosive medium and ε are carried out on the EV-74 universal ionomer using a Pt electrode, a glass electrode, and a silver-silver reference electrode.

These changes in time of pH, Eh, and ε during CRP initiated corrosion in the presence of 5 mMol / L of the claimed OS are presented in Table 3.

The acidity of Postgate "B" medium, inoculated with CRP and containing OS, is caused not only by the hydrolytic properties of the studied substances, but also by the accumulation of CRP metabolic products in it. It is known that a pH of 6 ... 7.5 is optimal for the growth of Desulfovibrio desulfuricans, but a wider pH range (5 ... 9) is also acceptable. In a corrosive environment inoculated with bacteria, in the absence of OS, the pH decreased from 8.8 to 4.2 by 4 days of exposure. The acidification of the environment is associated with the accumulation in it of the main vital activity product of sulfate reducers - H ₂ S and carboxylic acids. In the presence of OS, the pH decreases more slowly due to their suppression of metabolic processes in CRP cells, leading to the production of H ₂ S and acids. OS2 and OS1 are especially effective.

One of the important conditions for the development of CRP is the negative values of Eh of the medium. Until these values are reached, the conditions for the reproduction of cells are not favorable enough, their division is delayed, and the sizes, especially the length, increase markedly. In the early days of exposure, Eh≈-300 mV, which is a favorable condition for the development of CRP. With an increase in the exposure time, a shift of Eh to the region of positive values is observed, which is associated with an increase in the concentration of hydrogen sulfide in the system as a reduced form. The greatest shift in Eh was observed in the presence of OS2 introduced into the corrosive medium, the smallest with the introduction of OS3.

Table 1
Change in the abundance of n, С _H2S over time CRP initiated corrosion of steel samples in the presence of 5 mMol / L of OS-quinone and hydroquinones No. ext. Organic compound Exposure time τ, days n · 10 ⁶ ml ^-1 CH ₂ S, mg / l no additives no additives 2 8 136 3 fourteen 221 four 24 238 5 12 221 6 7 187 7 2 136 one 2,5-dibromo-1,4-hydroquinone (OS1) 2 8 136 3 9 153 four 12 180 5 9 153 6 four 136 7 3 68 2 2,3-dibromo-1,4-benzoquinone (OS2) 2 8 136 3 9 153 four 10 170 5 5 102 6 3 85 7 one 68 3 2,3-dibromo-1,4-hydroquinone (OS3) 2 8 136 3 13 187 four twenty 221 5 eleven 187 6 6 153 7 one 119

The maximum increase in potential is observed for 4 days. As a result of the death of microorganisms on the 5-7th day of exposure, the redox potential decreases and takes on relatively stable values, which is associated with a decrease in the concentration of hydrogen sulfide in the medium.

The change in the electrode potential of steel during exposure in a corrosive medium for the control series and environments with OS is fundamentally the same in nature. In the first 72 hours of exposure, ε is intensively shifted to the negative side, then its refinement takes place.

table 2
The effect of the studied OS quinone and hydroquinones on the number of CRP, a change in CH ₂ S in the medium No. ext. Organic compound OS concentration, mmol / l n · 10 ⁶ ml ^-1 CH ₂ S, mg / l one 2,5-dibromo-1,4-hydroquinone (OS1) 0 10 163 one 12 128 2 8 120 5 6 118 2 2,3-dibromo-1,4-benzoquinone (OS2) 0 10 163 one eleven 153 2 8 136 5 5 102 3 2,3-dibromo-1,4-hydroquinone (OS3) 0 10 163 one 12 150 2 10 145 5 8 143

However, OS adsorption on the surface of samples with corrosion products formed on it is reflected in ε. OS2, OS1 effectively shift ε to a less negative side compared to the control series; OS3 ennobles the potential less strongly. It should be emphasized that the intensity of the influence of OS on ε in all cases corresponds to their biocidal activity on CRP and their suppression of hydrogen sulfide production. OS2 and OS1 are especially effective.

The corrosion rate is determined gravimetrically. Data on the effect of OS on it are presented in Table 4.

They were recalculated for the protective effect of the claimed OS during corrosion and hydrogenation of steel samples. All investigated OSs reduce the corrosion rate, and the more, the higher their concentration. The corrosion rate of steel samples in a medium inoculated with CRP reaches 1.22 g · m ^-2 · h ^-1 .

The analysis of experimental data showed that the introduction of the studied compounds OS1 ... OS3 into the corrosive medium, depending on their concentration in it, causes a decrease in the corrosion rate to 0.54 g · m ^-2 · h ^-1 at C = 1 mmol / l , i.e. 2.2 times, and when introduced at C = 5 mmol / L, 4.2 times. The corrosion rate of samples when introduced into a corrosive medium OS2 is the lowest.

The inhibitory effect of the investigated OSs corresponds to their effect on the electrode potential at the steel / corrosive medium interface (Tables 3 and 4).

Anodic dissolution was chosen as a method for determining the hydrogenation of samples, which allows not only to estimate the total volume of hydrogen absorbed by the metal, but also the nature of its distribution over the metal cross section [1-3]. The obtained data of layer-by-layer anodic dissolution of steel samples are presented in Table 5.

From the table. Figure 5 shows that hydrogen is not distributed evenly over the entire thickness of the metal, the main amount of hydrogen absorbed by the steel is concentrated in the surface layer with a depth of not more than 30 μm for 170 hours of exposure in a hydrogen sulfide-containing medium, which is explained by the formation of a riveted surface metal layer due to the formation and development of collectors in it, filled with molecular hydrogen under high pressure, which deforms the crystal lattice of adjacent volumes of metal.

The special stress-strain state of the surface layers is responsible for the purely uneven distribution of hydrogen over the depth of the metal absorbed by it in such a non-uniform process as the cathodic evolution of hydrogen both under conditions of applying an external current to the processes of cathodic etching and electrodeposition, as well as during corrosion with hydrogen depolarization in an environment with a hydrogen stimulator (hydrogen sulfide).

The method for determining the hydrogen content used in our studies is based on layer-by-layer layer removal in steel during its anodic polarization [1-3]. It made it possible to obtain previously unknown data on the distribution of hydrogen over the steel cross section (depth from the corroded steel surface).

Table 3
Time-varying pH, Eh of the medium and ε potential of steel samples during CRP initiated steel corrosion in the presence of quinone and hydroquinones at a concentration of 5 mmol / L No. ext. Organic compound Exposure time τ, days pH -Eh, mV -ε, mV no additives no additives 2 8.8 299 0.6 3 7.5 255 0.7 four 7.4 254 0.75 5 7.5 255 0.46 6 7.51 257 0.44 7 7.55 264 0.35 one 2,5-dibromo-1,4-hydroquinone (OS1) 2 8.8 299 0.6 3 7.73 230 0.72 four 7.65 225 0.70 5 7.68 228 0.24 6 7.7 230 0.22 7 7.77 233 0.17 2 2,3-dibromo-1,4-benzoquinone (OS2) 2 8.8 299 0.6 3 7.83 245 0.73 four 7.67 219 0.65 5 7.77 220 0.23 6 7.82 226 0.22 7 7.94 231 0.12 3 2,3-dibromo-1,4-hydroquinone (OS3) 2 8.8 299 0.6 3 7.51 254 0.7 four 7.43 250 0.71 5 7.5 252 0.47 6 7.51 253 0.31 7 7.55 254 0.32

The amount of hydrogen refers to the average thickness of each removed metal layer, which was 10 microns in our experiments. The hydrogen content of steel increases significantly at a depth of 10-30 microns. The thickness of the whole layer taken in 6 receptions in the experiment was approx. 60 microns. Further layer-by-layer dissolution is impractical, since in doing so we get into the deep layers of the metal, where "metallurgical hydrogen" is located.

All the claimed OSs studied by us to varying degrees reduce hydrogen absorption during corrosion of steel in the presence of SRB, and the stronger the greater their concentration in the medium.

Table 4
Values of CRP initiated by corrosion of steel samples from the concentration of OS-quinone and hydroquinones and their protective effect No. ext. Organic compound OS concentration, mmol / l Corrosion rate K, g / m ² · day Protective effect, Z% in case of corrosion when hydrogenating samples one 2,5-dibromo-1,4-hydroquinone (OS1) one 0.44 28 29th 2 0.42 65 31 5 0.36 76 35 2 2,3-dibromo-1,4-benzoquinone (OS2) one 0.39 60 34 2 0.32 70 38 5 0.3 64 43 3 2,3-dibromo-1,4-hydroquinone (OS3) one 0.89 64 13 2 0.42 66 16 5 0.29 71 eighteen

Already at a minimum concentration (1 mmol / L), all three OCs significantly reduce the hydrogen content of steel, and an increase in C _OC significantly increases their efficiency.

The inventive OS at a concentration of 1 mmol / L reduces the hydrogenation of steel by 1.3 times, and at a concentration of 5 mmol / L by 1.5 times compared to the control series. OS2 showed the greatest hydrogenation inhibitory effect.

The inventive OS also exhibit a biocidal effect on CRP (Tables 1 and 2), which is especially pronounced in OS2, and to a lesser extent in OS3. The biocidal effect of the compounds results in the suppression of hydrogen sulfide genesis in a corrosive medium inoculated with CRP of the genus Desulfovibrio.

Quinone gives a protective effect of Z = 60% with microbiological corrosion at C = 1 mmol / L and Z = 83% at C = 5 mmol / L; when exposed to hydrogenation of steel samples, Z = 34% at C = 1 mmol / L, Z = 43% at C = 5 mmol / L.

Table 5
The distribution of hydrogen over the depth of steel samples after corrosion of steel samples 170 h in Postgate "B" in the presence of CRP and OS-quinone and hydroquinones at a concentration of 1.2.5 mmol / L No. ext. Organic compound Layer Depth δ, microns V (H ₂ ), ml / 100 g of metal, C = 1 mmol / L V (H ₂ ), ml / 100 g of metal, C = 2 mmol / L V (H ₂ ), ml / 100 g of metal, C = 5 mmol / L no additives no additives 10 22 22 22 twenty 29th 27 27 thirty 46 44 44 40 45 45 45 fifty 35 35 35 60 22 22 22 one 2,5-dibromo-1,4-hydroquinone (OS1) 10 twenty twenty twenty twenty 21 21 21 thirty 40 39 40 40 23 23 29th fifty 21 twenty 21 60 19 19 17 2 2,3-dibromo-1,4-benzoquinone (OS2) 10 19 19 16 twenty twenty 21 17 thirty 34 24 25 40 21 21 21 fifty 19 19 eighteen 60 eighteen 17 16 3 2,3-dibromo-1,4-hydroquinone (OS3) 10 22 22 22 twenty 27 27 27 thirty 44 44 42 40 34 29th 34 fifty 27 24 22 60 19 21 twenty

In microbiological corrosion, hydroquinones have a protective effect of Z = 28 ... 64% at C = 1 mmol / L and Z = 71 ... 76% at C = 5 mmol / L; when hydrogenating steel samples, Z = 13 ... 29% at C = 1 mmol / L and Z = 18 ... 35% at C = 5 mmol / L.

The inventive quinone and hydroquinones according to their protective effect in corrosion and hydrogenation in microbiological corrosion can be arranged in the series: OS2> OS1> OS3.

Information sources

1. Beloglazov S.M. Hydrogenation during electrochemical processes. - L .: publishing house of Leningrad State University, 1975 .-- 410 p.

2. Beloglazov S.M. Electrochemical hydrogen and metals. Behavior, struggle with embrittlement. Monograph. Kaliningrad: KSU publishing house, 2004 .-- 321 p.

3. Beloglazov S. M. On the determination of hydrogen in steel by the method of anodic dissolution. - Head. lab. - 1961. - T.27 - S.1468 - 1469.

Claims (1)

A method of protecting steel from corrosion and hydrogenation in aqueous-salt media containing sulfate-reducing bacteria, comprising introducing into the medium an aqueous-alcoholic solution of a chemical reagent-bactericide, characterized in that quinone 2,3-dibromo-1 is used as a chemical reagent-bactericide 4-benzoquinone or hydroquinone 2,5-dibromo-1,4-hydroquinone and 2,3-dibromo-1,4-hydroquinone in an amount of 1-5 mmol / l of the General formula:

where R ¹ = R ² = Br

where R ¹ = R ³ = Br or R ¹ = R ² = Br.