WO2022116598A1

WO2022116598A1 - Steel corrosion prevention method employing microbial technology

Info

Publication number: WO2022116598A1
Application number: PCT/CN2021/113381
Authority: WO
Inventors: 钱春香; 范文斌; 芮雅峰; 陈燕强
Original assignee: 东南大学
Priority date: 2020-12-04
Filing date: 2021-08-19
Publication date: 2022-06-09
Also published as: CN112680733A

Abstract

Disclosed is a steel corrosion prevention method employing microbial technology, comprising the following steps: inoculating spores of Bacillus species into a suitable medium and cultivating same, so as to obtain a concentrated bacterial liquid of the Bacillus species; adding a calcium source to the bacterial liquid, dissolving same, acquiring a microbial suspension, and leaving the suspension to stand for future use; and adding a rust-removed and dried steel sample to the microbial suspension, leaving same at room temperature and performing a protective-layer deposition operation, and forming an organic-inorganic composite protective layer on a surface of the steel sample, wherein an organic protective layer is composed of microbial extracellular polymers, and an inorganic protective layer is composed of spherical calcium carbonate. The present invention uses microbial-induced deposition and metabolism to deposit a dense protective layer on the surface of the steel, so as to isolate the corrosion resulting from a material exchange (a chemical or electrochemical reaction) between a substrate material of the steel and the outside environment, thereby significantly improving the anti-corrosion performance of the steel. In addition, the method is simple and easy to implement, and is environmentally friendly and pollution-free.

Description

A kind of anti-corrosion method of steel based on microbial technology

technical field

The invention relates to an anti-corrosion method for steel, in particular to a method for anti-corrosion of steel based on microbial technology, and belongs to the technical field of metal anti-corrosion.

Background technique

As we all know, steel materials have high strength and hardness, and at the same time meet the requirements of good plasticity and processability. They are the most widely used structural materials and are widely used in infrastructure projects. However, whether it is used in the atmosphere for a long time or placed in the atmospheric environment for a long time, the surface of the steel will gradually undergo chemical or electrochemical action with the surrounding medium, causing surface corrosion. Mild rust can make the surface lose its metallic luster and reduce the accuracy. In severe cases, rust pits will occur on the surface, which will deteriorate the mechanical properties of steel products and even break them, affecting their service life. At the same time, the research found that the main reason affecting the durability of reinforced concrete is the deterioration of components caused by the corrosion of steel bars. It is very necessary and beneficial to study the corrosion causes of steel and propose corresponding anti-corrosion measures.

The more common anti-corrosion measures are generally to use coatings containing tin, copper, zinc and other heavy metals or volatile organic compounds to coat the surface of the material substrate. Although this kind of coating has good anti-corrosion effect and is easy to be widely used, it also brings Potential health threat and not conducive to the concept of green environmental protection. The cathodic protection method is to add a more active metal to the surface of the steel structure to replace the corrosion of the steel. Often used for underwater or underground steel corrosion protection. The electrochemical protection method is a method of anti-corrosion protection of steel based on the principle of the galvanic cell theory. According to the galvanic cell theory, as long as the reaction of the galvanic cell that causes chemical corrosion can be eliminated, the anti-corrosion of steel can be achieved. Although the cathodic protection method and the electrochemical protection method have good protection effect on steel corrosion, but the treatment cycle is long and energy-consuming and time-consuming, which is not conducive to the ecological concept of greening and environmental protection.

For reinforced concrete projects, rust inhibitors containing organic components are usually used to improve the corrosion resistance of reinforced concrete. . Therefore, the development of renewable environment-friendly anti-corrosion technology is an inevitable trend at present.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the problems existing in the existing steel anti-corrosion measures, the present invention provides a steel anti-corrosion method based on microbial technology, through which the microorganism induces mineralization deposition and metabolites to form an organic-inorganic composite protective layer on the steel surface, essentially blocking the The chemical and electrochemical reaction between the steel matrix and the outside world improves the corrosion resistance of the steel surface.

Technical scheme: the anti-corrosion method for steel based on microbial technology according to the present invention comprises the following steps:

(1) the spore of bacillus is inoculated in suitable substratum to cultivate, obtain the concentrated bacterial liquid of bacillus; In this bacterial liquid, add calcium source, dissolve, obtain microbial suspension, leave standstill for subsequent use;

(2) Add the rust-removed and dried steel sample to the microbial suspension, place it in a room temperature environment to deposit a protective layer, and form an organic-inorganic composite protective layer on the surface of the steel sample, wherein the organic protective layer is composed of microbial cells The outer polymer, the composition of the inorganic protective layer is spherical calcium carbonate;

(3) Take out the sample, wash and dry it.

During the soaking process of the steel sheet, first, the metabolism of microorganisms secretes a layer of organic layer-extracellular polymer, which is tightly wrapped on the surface of the steel, and then in the presence of an organic calcium source, a layer of inorganic layer-calcium carbonate is deposited with the microorganisms, which adheres to the organic layer. In order to realize the protective layer structure of the organic-inorganic composite layer, prevent the cathodic depolarizers such as oxygen from reaching the metal surface, block electron transfer, and achieve the effect of preventing steel corrosion.

In step (1), the calcium source is preferably an organic calcium source, and the addition amount thereof is preferably (1.0-1.3) g/200ml.

The components of the medium can include beef extract, peptone, and ammonium or sodium salt; preferably, each liter of medium contains 3-5 g beef extract, 5-8 g peptone, and 0-3 g ammonium salt or 3-5 g sodium salt.

Preferably, the preparation method of the concentrated bacterial liquid is as follows: powdery bacillus is dissolved in deionized water by mass (10-20) g/L, and the germinated spores are inoculated into a corresponding medium for cultivation. Wherein, the culturing process of Bacillus may include: preparing a culture medium, then sterilizing the prepared culture medium, after the sterilization is over, inoculating spores with 10 ml of bacterial liquid per liter of culture medium, and then inoculating the inoculated culture medium It is placed in a shaking incubator for cultivation, and the total number of cells is cultivated until the OD value reaches 1 or more, and then taken out to obtain the concentrated bacterial liquid of the bacillus. Preferably, the sterilization conditions of the culture medium are as follows: the culture medium is placed in a sterilization tank, and at a temperature of 115 to 121° C., the pressure is maintained at 0.1 to 0.12 MPa for sterilization for 20 to 30 minutes. Further, the culture temperature in the shaking incubator is set to 25-30°C.

In the above step (2), the deposition time of the protective layer is preferably 2 to 5 days.

Beneficial effects: Compared with the prior art, the advantages of the present invention are: (1) The present invention soaks the steel sample in the bacterial suspension, and deposits a dense protective layer on the surface of the steel through microbial induced mineralization deposition and metabolism. , isolating the corrosion caused by the material exchange (chemical or electrochemical reaction) between the steel matrix material and the outside world, thereby significantly improving the anti-corrosion performance of the steel; at the same time, the method is simple and easy to operate; (2) the present invention induces mineralization through microbial technology The composition of the protective layer deposited on the surface of the steel is similar to the composition of concrete, and will not have a deteriorating effect on the mechanical properties of concrete, so it can be applied to reinforced concrete engineering; (3) The microorganisms used in the present invention are mineralizing microorganisms, which can produce Spores, suitable for the field of engineering materials, are green, environmentally friendly, pollution-free, and harmless to the human body.

Description of drawings

Fig. 1 is the schematic diagram that steel sample is immersed in microbial suspension to form protective layer; Wherein, 1 is steel sheet sample, 2 is copper wire, and 3 is microbial suspension;

Fig. 2 is a graph showing the surface rust state of the steel sample after immersion in the microbial suspension (a) and the calcium source solution (b) of the culture medium without bacterial liquid for 5 days after mineralization;

Figure 3 shows the SEM micrograph and energy spectrum of the protective layer deposited on the steel sample immersed in the microbial suspension, in which (a) is the SEM image of the organic protective layer-extracellular polymer formed by microbial metabolism on the steel surface; (b) is The energy spectrum of the extracellular polymer formed by the microbial metabolism on the steel surface; (c) is the SEM image of the inorganic protective layer-calcium carbonate formed by the microorganisms on the steel surface; (d) is the inorganic protective layer-calcium carbonate formed by the microorganisms on the steel surface energy spectrum;

Figure 4 shows the electrochemical test impedance spectra of steel samples immersed in different solutions.

Detailed ways

The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

In order to better improve the anti-corrosion performance of steel, the present invention provides a method for anti-corrosion of steel based on microbial technology, which utilizes microbial technology to deposit an organic-inorganic composite protective layer on the surface of steel in a green, environmentally friendly and low-cost manner, essentially preventing the steel matrix from interacting with The chemical and electrochemical reactions of the outside world can significantly improve the anti-corrosion performance of the steel surface.

Example 1

(1) After derusting and grinding the steel sample, put it into an oven for use;

The steel sample is ordinary carbon steel, and the sample size is 20mm x 20mm x 10mm. The rust removal process of steel samples is as follows: firstly prepare 50ml of pickling solution with the ratio of industrial hydrochloric acid and deionized water (1:1), in which the purity of hydrochloric acid is 36.48%, and then prepare two 3% Na ₂ CO ₃ neutralizing solutions 100ml. Put the steel sample to be rust-removed into pickling solution, shake it for 5 to 10 minutes, take out the sample and put it in the first 3% Na ₂ CO ₃ neutralizing solution for 3 to 10 minutes after the surface is free of rust. 5 minutes to remove the residual hydrochloric acid solution, then take it out again, and put in another ₃ % _Na2CO3 neutralization solution for 20-30 minutes to passivate the surface. Then take it out, wash it with distilled water and dry it. Sand the sample with 400/600/800 grit waterproof sandpaper successively until the surface is smooth and free of rust pits. Finally, the polished samples were washed with anhydrous ethanol, dried and placed in an oven for later use.

(2) According to beef extract 3g/L, peptone 5g/L, NaCl 5g/L, (NH ₄ ) ₂ SO ₄ 1g/L, the above components were weighed, configured into a liquid culture medium, placed in a temperature controlled at 120 ℃, Sterilize under the condition of 0.1～0.12MPa for 30min.

(3) After the sterilization, the spores of Bacillus are inoculated into the prepared medium, and then placed in a shaking incubator for cultivation. After culturing for two days, the absorbance value (OD value) was determined to be 1.02 with a microplate reader. Backup for testing.

(4) Next, weigh 200 ml of the inoculated and cultured concentrated bacterial solution, add 1.3 g of organic calcium source solution, and obtain a microbial suspension after complete dissolution. As shown in Figure 1, the steel sample 1 that has been rusted and polished is tied with a copper wire 2, suspended in the microbial suspension 3, and placed in a ventilated and dry room temperature environment for mineralization. At the same time, the same method was used to put the rust-removed and dried steel samples into a medium calcium source solution containing only the same medium and calcium source components for mineralization, as control group 1; another group of control group 2 was set up. Using the same method, the derusted and dried steel samples were soaked in deionized water.

After soaking for five days, the three groups of steel samples were taken out, washed, dried in a drying oven, and the surface rust condition of the samples was observed with a stereo microscope. Figure 2(a) is a picture of the surface rust state of the steel sample after being mineralized in the microbial suspension (a) for 5 days. The surface of the steel sample placed in the microbial suspension has no rust and has a film-like protective layer on the surface; Figure 2( b) is a picture of the surface rust state of the steel sample of control group 1 after being immersed in the medium calcium source solution (b) without bacterial liquid for 5 days, the surface of the steel sample has been significantly rusted, and there is no protective layer formed on the surface of the sample.

Next, the microstructure and morphology of the protective layer on the surface of the steel sample were observed with a field-emission scanning electron microscope (SEM), and it was found that a layer of organic-inorganic composite film was deposited on the surface of the sample. The results of the energy spectrometer showed that the organic components were elongated microbial extracellular polymers (EPS) containing more C and O elements, as shown in Figures 3(a)-3(b); the inorganic components were C, O, Spherical calcium carbonate with three elements of Ca, as shown in Figures 3(c)-3(d).

The steel samples with organic-inorganic composite protective layers deposited on the surface and the steel samples immersed in control group 1 and control group 2 were tested for corrosion resistance. NaCl solution, the test frequency range of AC impedance spectrum is (10 ^-2 ～ 10 ⁵ ) Hz, the range of disturbance amplitude is ±10mv, the steel sheet sample is selected as the working electrode, the stainless steel sheet is used as the auxiliary electrode, and the saturated calomel electrode is used as the reference Electrode, the electrochemical properties of steel samples with organic-inorganic composite protective layer deposited on the surface, steel samples soaked in control group 1 and steel samples soaked in control group 2 were tested respectively. Fig. 4 is the electrochemical performance test results of three groups of steel samples. The results show that the electrochemical impedance spectrum of the steel samples with the organic-inorganic composite protective layer deposited on the surface prepared by the present invention shows that the capacitive reactance radius is the largest, and the open circuit potential is -165mv, The open circuit of the steel sample in control group 1 is -529mv, and the open circuit of the steel sample in control group 1 is -723mv; according to the metal corrosion standard of China's metallurgical industry, when the potential is greater than -250mv, there is no corrosion, and when the potential is less than -400mv, there is no corrosion. corrosion. It can be seen that the organic-inorganic composite protective layer deposited on the surface of the sample in the present invention slows down the corrosion effect of the corrosive medium on the steel, and shows a better anti-corrosion effect.

Example 2

(1) With reference to the method of Example 1, the steel sample was derusted and polished and put into an oven for later use.

(2) According to beef extract 4g/L, peptone 6g/L, NaCl 3.5g/L, NH ₄ Cl 1g/L, the above-mentioned components were weighed, configured into a liquid culture medium, put into the temperature control at 121 ° C, and the pressure at ( Sterilize under the condition of 0.1～0.12)MPa for 30min.

(3) after the sterilization is finished, the spores of bacillus are inoculated into the prepared medium, then put into the shaking incubator to cultivate, and after culturing for two days, the absorbance value (OD value) measured with a microplate reader is 1.12. Backup for testing.

(4) Next, weigh 200ml of inoculated and cultivated concentrated bacterial liquid, add 1.1 g of organic calcium source solution, after dissolving, tie the rust-removed and polished sample with iron wire, and hang it on the concentrated bacterial liquid of dissolved calcium source in an open, ventilated and dry environment for mineralization.

After five days of microbial mineralization, the steel samples were taken out and dried in a drying oven. The surface of the samples was observed with a stereoscopic microscope, and it was found that the surface of the samples was free of rust and had a film-like protective layer on the surface.

The microstructure and morphology of the protective layer on the surface of the steel sample were observed with a field-emission scanning electron microscope, and it was found that an organic-inorganic composite film was deposited on the surface of the sample. The results of energy dispersive spectrometer confirmed that the composite membrane was composed of long extracellular polymer EPS organic layer and spherical calcium carbonate inorganic layer.

The test method of Example 1 was used to test the corrosion resistance of the steel sample with the organic-inorganic protective layer deposited in this example. The electrochemical test results showed that its corrosion potential was similar to that of Example 1, and was -158mv.

Example 3

(2) According to beef extract 4.5g/L, peptone 7g/L, NaCl 4g/L, (NH ₄ ) ₂ SO ₄ 2g/L, the above components were weighed, configured into a liquid culture medium, and placed in a temperature controlled at 121° C. , sterilize under the condition of (0.1～0.12)MPa for 30min.

(3) After the sterilization, inoculate the spores of Bacillus into the prepared medium, and then put it into a shaking incubator for cultivation. After culturing for two days, the absorbance value (OD value) was determined to be 1.28 with a microplate reader. Backup for testing.

(4) Next, weigh 200ml of inoculated and cultivated concentrated bacterial liquid, add 1.2 g of organic calcium source solution, after dissolving, tie the rust-removed and polished sample with iron wire, and hang it on the concentrated bacterial liquid of dissolved calcium source in an open, ventilated and dry environment for mineralization.

The corrosion resistance of the steel sample with the organic-inorganic protective layer deposited in this example is tested by the test method of Example 1. The electrochemical test results show that the corrosion potential is similar to that of Example 1, which is -164mv.

Claims

A kind of steel anticorrosion method based on microbial technology, is characterized in that, comprises the steps:

(1) the spore of bacillus is inoculated in suitable substratum to cultivate, obtains the concentrated bacterial liquid of bacillus; In this bacterial liquid, add calcium source, dissolve, obtain microbial suspension, leave standstill for subsequent use;

(2) adding the rust-removed and dried steel sample to the microbial suspension, placing it in a room temperature environment to carry out protective layer deposition, and forming an organic-inorganic composite protective layer on the surface of the steel sample, wherein the organic protective layer is composed of Microbial extracellular polymer, the composition of inorganic protective layer is spherical calcium carbonate;

(3) Take out the sample, wash and dry it.
The method for anticorrosion of steel based on microbial technology according to claim 1, characterized in that, in step (1), the calcium source is an organic calcium source, and the addition amount is (1.0-1.3) g/200ml.
The method for preserving steel based on microbial technology according to claim 1, wherein in step (1), the components of the culture medium include beef extract, peptone and ammonium salt or sodium salt, wherein, in each liter of culture medium Contains 3-5g beef extract, 5-8g peptone and 0-3g ammonium salt or 3-5g sodium salt.
The method for anti-corrosion of steel based on microbial technology according to claim 1, characterized in that, in step (1), the preparation method of the concentrated bacterial liquid is as follows: L was dissolved in deionized water, and the germinated spores were inoculated into the corresponding medium for culture.
The method for preserving steel based on microbial technology according to claim 4, wherein the culture medium is prepared first, and then the prepared culture medium is sterilized. The spores are inoculated, and then the inoculated medium is placed in a shaking incubator for cultivation, and the total number of cells is cultured until the OD value reaches 1 or more, and then taken out to obtain the concentrated bacterial liquid of the bacillus.
The method for anti-corrosion of steel based on microbial technology according to claim 5, characterized in that, the culture medium is placed in a sterilization tank, and at a temperature of 115-121°C, the pressure is maintained at 0.1-0.12MPa for sterilization for 20-20°C. 30min.
The anti-corrosion method for steel based on microbial technology according to claim 5, wherein the culture temperature in the shaking incubator is 25-30°C.
The method for anticorrosion of steel based on microbial technology according to claim 1, characterized in that, in step (2), the deposition time of the protective layer is 2-5 days.