RU2630149C1 - Method of protection of steel from corrosion and hydrogenation by organic compounds in medium containing sulphate reducing bacteria - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the protection of metals from corrosion, hydrogenation and the development of sulfate-reducing bacteria (CRB) and can be used in aqueous-salt media containing CRB. The method includes the introduction of a bactericide inhibitor into the corrosive medium, the organic compound, a coordinatively saturated cobalt complex with two perpendicularly located tridentate ligands, the Schiff base of 5-Br-salicylaldehyde and the (S)-amino acid: asparagine, is used as the bactericide inhibitor, glycine, glutamine or leucine in an amount of 1, 2, 5, 10 mmol/l of the general formula

, where R is the variable portion of the (S)-amino acid.

EFFECT: increasing the corrosion resistance of steel and expansion of assortment of inhibitors-bactericides.

4 tbl, 1 ex

Description

The invention relates to the protection of metals from corrosion, hydrogenation and preventing the development of sulfate-reducing bacteria (CRP) by using organic inhibitors in aqueous-salt media containing CRP. It can be used in the oil industry, engineering, gas industry, shipbuilding for the protection of various structures, oil wells, equipment, underground pipelines, parts and structures made of carbon and low alloy steels, which, under operating conditions, come into contact with aqueous solutions of salts, acids, industrial and household wastewater, sea water, and also moistened soils.

The following inventions are known from the prior art, which can be considered as analogues of the proposed development: “A method for protecting steel from acid and hydrogen sulfide corrosion” (Patent No. 584579, 07.20.2001, C23F 11/00); “A method of protecting steel from corrosion in mineralized water-oil environments” (patent No. 2353708, 04/27/2009, C23F 11/14); “A method of protecting steel against hydrogen sulfide corrosion” (patent No. 2543018, 02/27/2015, C23F 11/14); "A method of protecting steel from corrosion" (Patent No. 2144579, 01/10/1999, C23F 11/18, C23F 11/167).

The disadvantage of these analogues is that the substances used as corrosion inhibitors (In) either do not have a bactericidal effect, or have not been investigated for the presence of a bactericidal effect in relation to CRP.

Closest to the technical nature of the claimed method is the "Method of protecting steel from corrosion and hydrogenation in environments containing sulfate-reducing bacteria" (RF Patent No. 23338008, 10.11.2008, C23F 11/12).

The disadvantage of this method is the dependence of the decrease in the rate of corrosion of steel on the increase in the concentration of the introduced compounds - In. In this case, the achievement of the desired technical result requires the introduction of a higher concentration of organic substances into the system, and this, in turn, requires the synthesis of a larger amount of In, which leads to an increase in both material costs and labor costs in the synthesis of substances.

The specificity of the corrosive medium formed in the presence of CRP is that the metabolic products of CRP — hydrogen sulfide and organic acids — make the corrosive environment aggressive and stimulate corrosion and hydrogenation processes.

The problem to which the invention is directed, is the development of highly effective and economical inhibitors of corrosion and hydrogen pickling of steel, combining also the properties of bactericides with respect to CRP.

The problem is solved in that in the proposed method for the protection of steel from corrosion and hydrogenation in aqueous salt media containing sulfate-reducing bacteria by introducing organic inhibitors, according to the invention, coordination-saturated complexes based on (S) amino acids and Schiff bases 5-Br- are used salicylic aldehyde, when introduced into the water-salt medium, there is a rapid decrease in the rate of corrosion and hydrogen pickup of steel, as well as a strong bactericidal effect in relation to CRP. Moreover, high efficiencies of the corrosion-inhibiting effect and bactericidal effect were noted even at the lowest inhibitor concentration (In), namely, in an amount of 1 mmol / L.

The claimed OSs are chiral complexes, which are coordination-saturated cobalt complexes with two perpendicularly located tridentate ligands - Schiff bases of 5-Br-salicylic aldehyde and (S) -amino acids: asparagine (OS1), glycine (OS2), glutamine (OS3) leucine (OS4). The general formula of the compounds is

where R is the changing part of (S) -amino acids.

OS1, OS2, OS3, OS4 is a conditional inhibitor code associated with various amino acids used for the synthesis of the studied complexes.

The technical result of the proposed invention is to increase corrosion resistance, obtaining highly effective corrosion inhibitors, combining the properties of bactericides and hydrogenation inhibitors at the same time, providing a high degree of steel protection against corrosion and hydrogenation, as well as a high bactericidal effect with respect to CRP in a corrosive environment at low concentrations of organic compounds (OS).

Experimental studies have shown that the advantages of the proposed corrosion inhibitor of steel in comparison with the inhibitor described in the prototype are as follows.

1. A high degree of corrosion protection of complexes based on (S) -amino acids and Schiff bases of 5-Br-salicylic aldehyde (68.2-90.1%) compared with the prototype (28.0-76.0%).

2. The decrease in the corrosion rate of steel in the presence of complexes based on (S) amino acids and Schiff bases of 5-Br-salicylic aldehyde with a maximum concentration of 5.86 times, and in the presence of a prototype inhibitor of a maximum concentration of 4.2 times.

3. A high degree of protection against hydrogen pickup in steel complexes based on (S) amino acids and Schiff bases of 5-Br-salicylic aldehyde (20-78%) compared with the prototype inhibitor (13.0-43.0%).

4. High bactericidal effect. The average number of CRPs was reduced during exposure due to complexes based on (S) amino acids and Schiff bases of 5-Br-salicylic aldehyde with a concentration of 5 mmol / L, 4.39 times, and in the presence of the prototype inhibitor, 1.7 times more its natural decline in the control series.

5. The use of the claimed invention allows to achieve a more rapid inhibition of vital activity of CRP, a progressive decrease in the rate of corrosion of steel and its hydrogenation by introducing the inventive OS in water-salt at concentrations lower than in the experiment with the prototype.

In the inventive method for the first time used as corrosion and hydrogenation inhibitors are coordination-saturated complexes based on (S) amino acids and Schiff bases 5-Br-salicylic aldehyde. These compounds were first used in the claimed method and as bactericides on CRP.

The use of the active base of corrosion inhibitors - coordination-saturated complexes based on (S) amino acids and Schiff bases of 5-Br-salicylic aldehyde promotes the shift and retention of the physicochemical parameters of the closed system in the range of values at which the aggressive effect on steel St. 3 corrosive environments. Also, the use of these OSs contributes to a significant and rapid inhibition of the vital activity of sulfate-reducing bacteria of the species Desulfovibrio desulfuricans, which characterizes these compounds as good bactericides. Protective properties against corrosion of mild steel, as well as a bactericidal effect, were exhibited by all of the claimed OS even at the lowest concentration of In, which opens up the possibility of using these In in minimal quantities.

An example implementation of the method.

For testing, samples of mild steel, Art. 3, a surface area of 20 cm ² . As a nutrient medium for the cultivation of CRP, the choice was made in favor of a microbiological medium - Postgate "B", containing calcium lactic acid as an organic substrate. This medium well supports the development of anaerobic CRPs of the species Desulfovibrio desulfuricans, and the latter, in turn, are distinguished by the production of a large amount of biogenic hydrogen sulfide, which is an active stimulator of the processes of corrosion, hydrogenation, and hydrogen embrittlement. Bacteria are cultivated from a natural source - mud deposits of a stream.

The composition of the Postgate "B" medium, g / l: NaCl - 7.5; K ₂ HPO ₄ - 0.5; MgSO ₄ ⋅ 7H ₂ O - 1.0; Na ₂ SO ₄ - 2.0; Na ₂ CO ₃ - 1.0; Ca lactate - 2.0.

The inventive OS is introduced into the corrosive medium in concentrations (With _OS ) of 1, 2, 5 and 10 mmol / L.

The experimental exposure cycle is 8 days. During this period, on average, the life cycle of the CRP population of the genus Desulfovibrio, located in a limited enclosed volume of the medium, passes. During this period, the following physicochemical parameters of the water-salt medium inoculated with CRP are monitored daily: the pH and redox potential of the medium, the number of bacteria cells in CRP (bacterial titer) and the concentration of biogenic hydrogen sulfide in the medium, and the electrode potential of the samples. At the end of the exposure, the corrosion rate and the layered hydrogen content of the samples are determined.

The effectiveness of the invention and the essence of the claimed technical solution is confirmed by tables 1, 2, 3, 4.

A progressive decrease in steel corrosion is shown in Table 1 by the values of the effectiveness of the corrosion inhibiting effect (EICD). In the transition from one concentration of organic substances introduced into the system to another, the values of EICs change insignificantly and even at low concentrations of In the effectiveness of the corrosion-inhibiting action is high.

The volume of hydrogenation of steel samples is determined by the method of anode layer-by-layer dissolution. This method allows us to determine both the total volume of absorbed hydrogen and the nature of its distribution over the cross section of steel samples [1, 2]. The method is based on a decrease in the concentration of oxygen dissolved in the electrolyte, which interacts in the presence of a platinum catalyst with hydrogen released during anodic dissolution using Safranin T as an oxygen reagent. The data obtained during the experiments allow us to judge the concentration of hydrogen absorbed by the steel in the surface layers of the steel at a depth 10-30 microns. This is due to the deformation of the crystal lattice of the metal due to the formation of a riveted surface layer of the metal and the development of a large number of regions filled with molecular hydrogen under high pressure in this layer [3]. In total, the hydrogen content was measured during the layer-by-layer removal of six layers; the thickness of one layer was 10 μm. Data on the effectiveness of the use of the claimed OS as Hydrogen infusion are given in table 2.

The effectiveness of the inhibition of hydrogenation is more dependent on the concentration of In, but already at a concentration of 5 mmol / L, an EIND value of more than 55% was observed for all of the claimed OS. With an increase in the In concentration, a progressive decrease in the hydrogen content of the samples is observed.

Laboratory tests of the claimed group of steel corrosion and hydrogen inhibitors showed that in the test medium, in the presence of CRP, a degree of protection of up to 90% is ensured.

As biogenic hydrogen sulfide accumulates in the medium, such an environment becomes a favorable source for corrosion processes. Hydrogen sulfide is the main waste product of CRP, therefore, by the accumulation or absence of hydrogen sulfide in the system, we can safely judge how favorable this system is for the development of this kind of bacteria, and, as a result, judge the possibility of corrosion of metal structures in direct contact with this Wednesday. The concentration of hydrogen sulfide also affects other parameters of the system: pH, redox potential of the medium and electrode potential of the sample, corrosion rate.

On the second day of the experiment, the average concentration of hydrogen sulfide is 134.85 mg / L. With the development of the life cycle of CRP, the concentration of hydrogen sulfide in the natural environment increases to a maximum of 4 days, which corresponds to the maximum number of CRP in these conditions; and then decreases. In cases of conducting an experiment with the studied OS at all concentrations, the hydrogen sulfide content decreases without its preliminary increase. By the last day of the experiment, a constant value of the concentration of biogenic hydrogen sulfide is established. It was observed that in the presence OC1 (C _OS = 1 mmol / l), the number of SRB cells is the last day of exposure 5,33⋅10 ⁶ ml ^-1 in the presence OC2 - 4,00⋅10 ⁶ ml ^-1. However, the concentration of biogenic hydrogen sulfide on the 8th day of the experiment in the presence of OS1 of the same concentration is very low and amounts to 22.5 mg / L, and in the presence of OS2 it is 22.95 mg / L. In some cases, low concentration of hydrogen sulfide in the system may not correspond to the minimum values of the number of CRP cells. This is possible in the case when the bactericidal effect is carried out by the OS, not only due to a significant and rapid inhibition of the vital activity of sulfate-reducing bacteria, but also due to a decrease in their functional activity, and in this case, the ability to produce H ₂ S. Thus, a strong decrease in the presence of OS concentration of biogenic hydrogen sulfide, causing serious complications in the operation of all mining equipment and pipelines, makes the environment much less corrosive and aggressive Willow, which reduces the rate of corrosion and, accordingly, increases the corrosion resistance of steel.

Changes in the concentration of biogenic hydrogen sulfide are presented in table 3.

The bactericidal effect is determined by direct counting of microorganisms (MO) using a ZEISS Axio cam Primostar microscope and a Goryaev camera. The number of sulfate-reducing bacteria of the species Desulfovibrio desulfuricans in a closed system for 8 days (the full life cycle of the CRP population of the genus Desulfovibrio) in the presence of the studied In corrosion is presented in table 4.

After the latent phase of bacterial development (in this medium 48 hours), the studied OS with the proposed inhibitory activity was introduced into Postgate "B" medium after inoculation with the same amount of CRP accumulative culture. The blackening of the water-salt medium, the walls of the tubes, and then the surface of the samples served as a visual criterion for the development and activity of bacteria.

In the control series of samples, the maximum number of CRP is observed on the 3-4th day of the experiment. Indeed, the bacterial culture during this period continues its development and accumulates in the environment. After 4 days, a decrease in the number of CRP cells is observed. This is due to the fact that most of the nutrients in the environment are already exhausted by microorganisms, and the amount of toxic metabolic products in the environment, on the contrary, is already quite large. There is a slowdown in the growth and division of bacteria.

In the presence of all OSs, irrespective of concentration, inhibition of CRP activity is observed, and there is no maximum number of CRP. The decrease in the number of CRP cells occurs already on the 3rd day of the experiment in the presence of all tested compounds.

On average, on the second day of exposure, the number of CRP cells in the medium is 15.49⋅10 ⁶ ml ^-1 . The maximum number of bacteria in a medium without OS on day 4 is N = 20⋅10 ⁶ ml ^-1 . By the end of the exposure, the number of CRP decreases on average to 4.25⋅10 ⁶ ml ^-1 in the presence of OS and to 10.66⋅10 ⁶ ml ^-1 in the absence (control). The suppression of the number of CRPs on average over the entire exposure time under the influence of OS is 2.24 times greater than its natural decline in the control series at С _OS = 1 mmol / l; 2.73 times with C _OS = 2 mmol / L; 4.39 times with C _OS = 5 mmol / L; 4.0 times at C _OS = 10 mmol / L.

The use of the claimed invention allows to achieve a progressive decrease in the rate of corrosion and hydrogenation of steel, as well as a decrease in the number and viability of CRP cells by introducing OS - coordinated saturated complexes based on (S) -amino acids and Schiff bases 5-Br-salicylic aldehyde into the water-salt medium in concentrations of 1, 2, 5, 10 mmol / l. Based on the studies, we can conclude that the OS of the claimed invention can improve the corrosion resistance of steel, and also combine the properties of corrosion inhibitors, hydrogen pickup and bactericides.

Information sources

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

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

3. Beloglazov S.M. Distribution of hydrogen absorbed during cathodic treatment in acid in steel and its effect on microhardness. - FMM. - T. 15. - S. 885-889.

Claims (3)

A method of protecting steel from corrosion and hydrogenation in aqueous-salt media containing sulfate-reducing bacteria, comprising introducing a bactericidal inhibitor into a corrosive medium, characterized in that an organic compound is used as a bactericidal inhibitor - a coordinated saturated cobalt complex with two perpendicularly located tridentate ligands - Schiff base of 5-Br-salicylic aldehyde and (S) -amino acid in the form of asparagine, glycine, glutamine or leucine in an amount of 1, 2, 5, 10 mmol / l of the General formula

where R is the changing part of the (S) -amino acid.