Method for preparing a corrosion protection layer for the inner wall of a pipeline

Abstract

The application discloses a preparation method of a biological accumulation anticorrosion layer of a pipeline inner wall. The pipeline, on which magnesium molybdate is attached, is soaked in seawater solution containing Pseudoalteromonas sp. to form a dense calcium magnesium carbonate mineralization layer on the inner wall surface of the pipeline, so as to achieve the anticorrosion purpose. The Pseudoalteromonas sp. is uniformly and directionally attached to the inner wall of the pipeline by using the affinity of the Pseudoalteromonas sp. to molybdenum elements, and then a dense biological mineralization layer is uniformly formed through metabolism of the bacteria, so that the anticorrosion effect can be effectively achieved, especially in the application of the inner wall of a small-diameter pipeline.

Description

Technical Field

[0001] This invention belongs to the field of biomineralization technology, specifically relating to a method for preparing a biodeposited anti-corrosion layer on the inner wall of a pipeline. Background Technology

[0002] Marine pipelines are diverse and complex, and steel seawater pipelines typically require anti-corrosion treatment of their inner walls. Traditional corrosion treatment methods include internal painting, plastic coating, thermal spraying, and sleeve coating. However, these coatings are easily damaged and fail during service due to various factors, and they rarely possess good self-healing capabilities. For small-diameter pipes, especially those below Φ20, these methods are also difficult to implement. Furthermore, in the high-temperature, high-salt, high-humidity, and microbial-rich marine environment, coatings are more prone to peeling and failure.

[0003] Biomineralization refers to the process by which organisms generate inorganic minerals through the regulation of biological macromolecules. Its biggest difference from general mineralization lies in the involvement of biological macromolecules, organismal metabolism, cells, and organic matrices. It involves organisms transforming ions in solution into solid-phase minerals at specific sites under certain physicochemical conditions and under the control or influence of organic matter. Biomineralization can construct a dense, in-situ anti-corrosion coating on the surface of metallic materials, utilizing the organism's own activity to achieve dynamic repair and thus provide long-term protection. The process of microbial corrosion of carbon steel leading to the formation of corrosion product films can also be called biomineralization. The structure of the biomineralized film determines the corrosion behavior of the steel; a dense biomineralized film provides good protection for the substrate, while a porous, loose passivation film can promote the corrosion of metallic materials.

[0004] A search revealed that patent document CN114231963A discloses a method for controlling carbon steel corrosion based on the principle of biomineralization. This method utilizes the mineralization principle of microorganisms to form a dense biomineralized film on the metal surface, thereby inhibiting metal corrosion. The biomineralized film is composed of nanoparticles with a particle size of less than 10 nm, using chemoautotrophic *Pseudomonas Stutzeri* to form a dense biomineralized film on the surface of X80 pipeline steel. The main components of the mineralized film are Fe3O4 and FeOOH. However, this mineralized film is not dense enough and will still be corroded after prolonged immersion in seawater.

[0005] Patent document CN108754506A discloses a biological corrosion inhibitor and its protective method for inhibiting the corrosion of metallic materials in seawater environments. This biological corrosion inhibitor contains *Pseudoalteromonas lipolytica*, which forms a stable organic-inorganic composite film with a calcite structure on the surface of the metallic material, greatly improving the resistance of the metallic material to uniform corrosion and pitting corrosion. Furthermore, this film has self-healing properties after formation. However, this document only uses *Pseudoalteromonas lipolytica*, resulting in low mineralization integrity and a continued risk of corrosion, producing layered and cracked corrosion product layers. The literature [Research Progress on the Inhibition of Metal Corrosion Behavior by Microbial Mineralization, Hao Xiangping et al., Surface Technology, Vol. 50, No. 11, 2021, p. 26] proposes that to obtain a more stable and durable corrosion inhibition effect, other anti-corrosion methods can be introduced on the basis of microbial mineralization corrosion inhibition. This can be achieved by combining the inhibitor with a corrosion inhibitor to suppress corrosion, thereby compensating for the corrosion problems caused by incomplete mineralization layers in the early stages of the mineralization process. However, corrosion inhibitors can only reduce the corrosion rate and cannot prevent seawater corrosion. Furthermore, long-term immersion in seawater can cause corrosion inhibitors to be washed away, leading to increased corrosion. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a bio-accumulated anti-corrosion layer on the inner wall of a pipeline, so as to solve the problem that it is difficult to apply anti-corrosion coating to the inner wall of small-diameter steel pipes in the prior art, and the problem that the existing biomineralization technology is not dense enough.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] The present invention discloses a method for preparing a biodeposited anticorrosive layer on the inner wall of a pipe, characterized in that a pipe with attached magnesium molybdate is soaked in a seawater solution containing Pseudomonas lipolyticis to form a dense calcium magnesium carbonate mineralization layer on the inner wall surface of the pipe, thereby achieving the purpose of corrosion prevention.

[0009] More specifically, the method for preparing the bio-accumulated anti-corrosion layer on the inner wall of the pipe according to the present invention is characterized by comprising the following steps: (1) dissolving an excess of magnesium molybdate in pure water to form a saturated solution, which fills the inside of the pipe; (2) heating the pipe to a certain temperature, and then allowing it to cool down naturally, so that magnesium molybdate precipitates on the inner wall surface of the pipe, and then draining the solution; (3) first treating the seawater with antibacterial agents, then adding Pseudomonas lipolyticis to the seawater to form a bacterial solution, and then filling the inside of the pipe with the bacterial solution and allowing it to stand for 5 to 9 days, thereby obtaining a bio-accumulated anti-corrosion layer on the inner wall of the pipe;

[0010] The *Pseudoalteromonas lipolytica* described is a Gram-negative aerobic bacterium. This *Pseudoalteromonas lipolytica* was obtained from the National Microbiology Data Center, strain number: DSM 22356, original number: ZJ1201, strain source: Second Institute of Oceanography, State Oceanic Administration, depositary: Xu Xuewei, direct source: China National Library, deposit date: September 17, 2008.

[0011] The seawater is the supernatant liquid of natural seawater after sedimentation;

[0012] The pure water is deionized water with a temperature of 10–50°C;

[0013] The heating temperature in step (2) is 40-100°C, preferably 60-80°C;

[0014] Since the growth curve of *Pseudomonas lipolyticis* peaks at 7 days, which is also the peak concentration of this microorganism, the preferred settling time of the bacterial solution inside the pipeline is 7 days.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention, based on extensive research, has discovered that *Pseudomonas lipolyticis* possesses an affinity for molybdenum. While magnesium molybdate has corrosion-inhibiting properties, its primary function is not corrosion inhibition, but rather acting as an anchor point for biomineralization by *Pseudomonas lipolyticis*. Utilizing the affinity of *Pseudomonas lipolyticis* for molybdenum, it is directed and evenly distributed to adhere to the inner wall of the pipe. Through bacterial metabolism, a dense biomineralized layer is uniformly formed, effectively providing corrosion protection, especially in small-diameter pipes. The method of this invention is simple to operate, inexpensive, and capable of achieving corrosion protection for the inner walls of small-diameter marine pipelines.

[0017] If the steel already contains molybdenum, it can promote the directional attachment of *Pseudomonas lipolyticis*, but the effect is not as good as immersion in magnesium molybdate. Commonly used pipeline steels (X20, X30, X80, etc.) do not contain molybdenum, and therefore cannot achieve the requirement of uniform mineralization. While other molybdates, such as sodium molybdate, also have corrosion inhibition effects, this invention has found that sodium molybdate cannot achieve the effect of anchoring *Pseudomonas lipolyticis* for directional biomineralization. Attached Figure Description

[0018] Figure 1 This is a surface morphology diagram of the bio-accumulated anti-corrosion layer in Example 1.

[0019] Figure 2 This is a surface morphology diagram of the bio-accumulated anti-corrosion layer in Example 2.

[0020] Figure 3 This is a surface morphology diagram of the biologically deposited anti-corrosion layer in Comparative Example 1. Detailed Implementation

[0021] Those skilled in the art should recognize that this embodiment is only used to illustrate the present invention and is not intended to limit the present invention. Any changes or modifications to the embodiment within the scope of the present invention are within the scope of the claims of the present invention.

[0022] Example 1

[0023] A method for preparing a biodegradable anticorrosive layer on the inner wall of a pipe includes the following steps: (1) dissolving excess magnesium molybdate in pure water at 25°C to form a saturated magnesium molybdate solution with a concentration of approximately 160 g / L, and filling the inside of the pipe with the saturated magnesium molybdate solution; (2) heating the pipe to 60°C, allowing it to stand for 15 minutes to cool naturally, so that magnesium molybdate precipitates on the inner wall surface of the pipe, and then draining the solution; (3) first sterilizing the seawater, and then adding *Pseudomonas lipolyticis* to the sterile seawater to form a concentration of 10 g / L. 4 A bacterial solution containing CFU / mL was used to fill the inside of the pipe. After standing for 7 days, a biofilm was formed on the inner wall of the pipe. The morphology of the biofilm is shown in the attached figure. Figure 1 .

[0024] Example 2

[0025] A method for preparing a biodegradable anticorrosive layer on the inner wall of a pipe includes the following steps: (1) dissolving excess magnesium molybdate in pure water at 25°C to form a saturated magnesium molybdate solution with a concentration of approximately 160 g / L, and filling the inside of the pipe with the saturated magnesium molybdate solution; (2) heating the pipe to 80°C, allowing it to stand for 10 minutes to cool naturally, so that magnesium molybdate precipitates on the inner wall surface of the pipe, and then draining the solution; (3) first sterilizing the seawater, and then adding *Pseudomonas lipolyticis* to the sterile seawater to form a solution with a concentration of 10 g / L. 5 A bacterial solution containing CFU / mL was used to fill the inside of the pipe. After standing for 7 days, a biofilm was formed on the inner wall of the pipe. The morphology of the biofilm is shown in the attached figure. Figure 2 .

[0026] Comparative Example 1 (with added sodium molybdate)

[0027] A method for preparing a biodegradable anticorrosive layer on the inner wall of a pipe includes the following steps: (1) dissolving excess sodium molybdate in pure water at 25°C to form a saturated sodium molybdate solution with a concentration of approximately 160 g / L, and filling the inside of the pipe with the saturated sodium molybdate solution; (2) heating the pipe to 60°C, allowing it to stand for 15 minutes to cool naturally, so that sodium molybdate precipitates on the inner wall surface of the pipe, and then draining the solution; (3) first treating seawater with antibacterial agents, and then adding *Pseudomonas lipolyticis* to sterile seawater to form a solution with a concentration of 10 g / L.4 A bacterial solution containing CFU / mL was used to fill the tube, and the solution was allowed to stand for 7 days; the morphology of the accumulated layer is shown in the appendix. Figure 3 .

[0028] Comparative Example 2 (without molybdate added)

[0029] A method for preparing a biodegradable anticorrosive layer on the inner wall of a pipe includes the following steps: first, seawater is treated with antibacterial agents, and then *Pseudomonas lipolyticis* is added to sterile seawater to form a concentration of 10... 4 Fill the tube with a bacterial solution containing CFU / mL and let it stand for 7 days.

[0030] Electrochemical tests were conducted on the pipe bio-accumulation anti-corrosion coatings obtained in Examples 1-2 and Comparative Example 1, and the results are listed in Table 1.

[0031] Table 1. Test results of pipeline anti-corrosion coating performance in Examples 1-3 and Comparative Example 1.

[0032] Original pipeline 719 Example 1 6290 Example 2 7484 Comparative Example 1 4352 Comparative Example 2 3319

[0033] Table 1 shows that the corrosion resistance of Examples 1-2 is significantly improved compared to Comparative Example 1. Figure 1 , Figure 2 and Figure 3 The comparison shows that the *Pseudomonas lipolyticis* bacteria in Examples 1 and 2 are directionally and evenly distributed and attached to the inner wall of the pipe, and then form a dense biomineralized layer evenly through bacterial metabolism. Figure 1 and Figure 2 All exhibit relatively thick mineralized deposits of triangular rhomboid mineral sediments, especially Figure 2 The mineralized layer exhibits higher integrity, thus effectively providing a preservative effect. Comparative Example 1, while containing sodium molybdate, still showed uneven adhesion and distribution of *Pseudomonas lipolyticis*, leading to... Figure 3 The resulting layer of corrosion products, consisting of layers and cracks, fails to achieve complete mineralization and corrosion protection. Therefore, in this invention, magnesium molybdate does not serve as a corrosion inhibitor, but rather as an anchor point for biomineralization by *Pseudomonas lipolyticis*.

Claims

1. A method for preparing a biodegradable anti-corrosion layer on the inner wall of a pipe, characterized in that, The steps include: (1) dissolving excess magnesium molybdate in pure water to form a saturated solution that fills the inside of the pipe; (2) heating the pipe to a certain temperature and then letting it cool down naturally so that magnesium molybdate precipitates on the inner wall surface of the pipe, and then draining the solution; (3) first treating the seawater with antibacterial agents, then adding Pseudomonas lipolyticis to the seawater to form a bacterial solution, and then filling the inside of the pipe with the bacterial solution and letting it stand for 5 to 9 days to form a dense layer of calcium magnesium carbonate mineralization on the inner wall surface of the pipe. The pipeline is a ship pipeline with an inner diameter of no more than 20 mm; the magnesium molybdate serves as an anchor point for biomineralization by *Pseudomonas lipolyticis*, utilizing the affinity of *Pseudomonas lipolyticis* for molybdenum to ensure its directional and uniform distribution and attachment to the inner wall of the pipeline.

2. The method for preparing the bio-accumulated anti-corrosion layer on the inner wall of a pipeline according to claim 1, characterized in that, The aforementioned *Pseudoalteromonas lipolytica* is a Gram-negative aerobic bacterium.

3. The method for preparing the bio-accumulated anti-corrosion layer on the inner wall of a pipeline according to claim 1, characterized in that, The seawater is the supernatant liquid of natural seawater after sedimentation; the pure water is deionized water with a temperature of 10-50℃.

4. The method for preparing the bio-accumulated anti-corrosion layer on the inner wall of a pipeline according to claim 1, characterized in that, The heating temperature in step (2) is 40 to 100°C.

5. The method for preparing the bio-accumulated anti-corrosion layer on the inner wall of a pipeline according to claim 1, characterized in that, The heating temperature in step (2) is 60-80℃.

6. The method for preparing the bio-accumulated anti-corrosion layer on the inner wall of a pipeline according to claim 1, characterized in that, The bacterial solution is left to stand inside the pipeline for 7 days.

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