A method for preparing a hydrogen barrier coating and a corrosion-resistant hydrogen barrier composite coating at room temperature

Abstract

The design of the present invention belongs to the technical field of metal surface anti-corrosion coatings, and specifically discloses a method for preparing a hydrogen-barrier coating and an anti-corrosion hydrogen-barrier composite coating at room temperature. The method adopts a room-temperature electric-assisted method to prepare a black oxide hydrogen-barrier coating, and then an organic resin is coated on the hydrogen-barrier coating to construct a double-layer composite coating. This composite coating has excellent hydrogen barrier properties and adhesion, and has long-term corrosion resistance. It can solve the problem that traditional single organic resin coatings do not have hydrogen barrier function and cannot provide long-term corrosion protection in hydrogen-related environments.

Description

Technical Field

[0001] The present invention relates to the technical field of metal pipeline coatings, and in particular to a method for preparing a hydrogen barrier coating and an anti-corrosion hydrogen barrier composite coating at room temperature. Background Art

[0002] The hydrogen damage problem of downhole tubing and high-strength pipeline steel in oil and gas drilling and production has greatly restricted the exploration and development of hydrogen sulfide oil and gas reservoirs and the development of existing natural gas pipeline hydrogen transportation technology. Once the material suffers hydrogen damage, it will undergo brittle fracture or cracking, which will seriously affect the material's performance and service life and threaten its safety in service.

[0003] Preparing an oxide-type hydrogen-barrier coating on the surface of a material is one of the important means to address the problem of hydrogen damage to metal materials. Currently, the protective coatings used on the inner surfaces of oil casing and steel natural gas pipelines for oil and gas gathering and transportation are mainly liquid epoxy resin coatings or epoxy powder coatings, and research on preparing hydrogen-barrier coatings on these surfaces is relatively rare. However, when in contact with hydrogen-containing media, hydrogen can diffuse into the pores of the epoxy resin coating and reach the interface of the metal coating, causing hydrogen damage to the metal underneath the coating. In addition, as service time increases, once the metal underneath the coating corrodes, the presence of corrosion products can cause bubbling in the coating, which in turn reduces the coating's adhesion and leads to coating failure. Therefore, it is necessary to upgrade the existing epoxy resin coating system used on oil casing and steel natural gas pipelines for oil and gas gathering and transportation to impart hydrogen-barrier properties and further improve the coating's adhesion, thereby enhancing its protective effect. Summary of the Invention

[0004] The purpose of the present invention is to address the defects of the existing technology and provide a room temperature preparation method for hydrogen barrier coatings and anti-corrosion hydrogen barrier composite coatings. A black oxide hydrogen barrier coating is prepared by a room temperature electric-assisted method, and then an organic resin coating is applied on the hydrogen barrier coating to construct a double-layer composite coating. This composite coating not only has excellent hydrogen barrier properties, but also improves the adhesion of the coating, thereby having long-lasting protective performance.

[0005] The technical solution of the present invention is:

[0006] A method for preparing a hydrogen barrier coating at room temperature comprises the following steps:

[0007] (1) Prepare blackening solution: dissolve 3-6 parts of copper sulfate, 3-6 parts of nickel sulfate, 13-16 parts of sodium dihydrogen phosphate, 1-5 parts of sodium citrate, and 1-5 parts of ammonium molybdate in clean tap water or deionized water, and then adjust the pH value to 2-3;

[0008] (2) Electrochemical deposition: Place the metal substrate as the cathode in the blackening solution, then select the electrode material as the anode and place it in the blackening solution, connect it to a DC power supply, and set the current density of the DC power supply to 15~20mA / cm 2 , so that a hydrogen barrier coating is formed on the surface of the substrate;

[0009] Preferably, the clean tap water or deionized water in step 1 is 800-1000 parts.

[0010] Preferably, hydrochloric acid, sulfuric acid, phosphoric acid or citric acid is used to adjust the pH value in step 1.

[0011] Preferably, during the electrochemical deposition in step 2, the blackening solution is stirred, and the temperature of the blackening solution is stabilized at 20-30°C.

[0012] Preferably, the electrode material in step 2 is a Pt sheet or a graphite rod.

[0013] A method for preparing an anti-corrosion and hydrogen-blocking composite coating comprises the following steps:

[0014] (1) A hydrogen barrier coating is prepared by applying the above-mentioned room temperature preparation method of a hydrogen barrier coating;

[0015] (2) Applying an organic resin coating on the surface of the hydrogen barrier coating, and forming an anti-corrosion hydrogen barrier composite coating on the surface of the substrate after curing.

[0016] Preferably, the organic resin coating comprises epoxy resin, a curing agent and an organic solvent, the mass ratio of the epoxy resin to the curing agent is 1:1, and the amount of the organic solvent is 10% of the mass of the epoxy resin.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The present invention adopts a room-temperature electrically assisted method to prepare a black oxide hydrogen barrier coating, and then applies an organic resin coating on the hydrogen barrier coating to construct a double-layer composite coating. This composite coating not only has excellent hydrogen barrier properties, but also improves the adhesion of the coating, thereby having long-lasting protective properties, solving the problem that traditional coatings using a single organic resin coating cannot provide long-term corrosion protection.

[0019] In addition, the coating manufacturing method of the present invention has low cost, simple process and high promotion and application value. Especially when applied to the surface of hydrogen-related steel materials such as oil drilling casing or hydrogen pipeline, it has stronger hydrogen resistance and anti-corrosion performance than existing coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a scanning electron microscope image of the hydrogen barrier coating;

[0021] Figure 2 This is the XRD image of the hydrogen barrier coating;

[0022] Figure 3 This is a scanning electron microscope image of the surface of the anti-corrosion and hydrogen-blocking composite coating:

[0023] Figure 4 This is a scanning electron microscope image of the cross section of the anti-corrosion and hydrogen-barrier composite coating;

[0024] Figure 5 These are the hydrogen permeation curves of different coatings of the present invention.

[0025] Figure 6 This is an electron scanning microscope image of the interface between the hydrogen barrier coating and the resin layer;

[0026] Figure 7 This is a comparison chart of the bonding strength of anti-corrosion and hydrogen-blocking composite coatings;

[0027] Figure 8 This is the electrochemical impedance curve of the anti-corrosion and hydrogen-blocking composite coating; DETAILED DESCRIPTION

[0028] The present invention is further described below with reference to the accompanying drawings and embodiments. Example 1

[0029] A method for preparing a hydrogen barrier coating at room temperature comprises the following steps:

[0030] First, X65 pipe steel with a size of 10 mm × 10 mm × 5 mm was selected as the substrate of the coating, leaving 1 cm 2 The area is used as the working surface, and the rest of the parts are all sealed with resin, and the working surface is polished and cleaned;

[0031] Next, prepare the blackening solution:

[0032] Place 3g of copper sulfate, 3g of nickel sulfate, 13g of sodium dihydrogen phosphate, 1g of sodium citrate, and 1g of ammonium molybdate in a beaker. Add 1000mL of deionized water and mix. Then adjust the pH to 2 with hydrochloric acid (hydrochloric acid, phosphoric acid, citric acid, sulfuric acid, etc. can also be used to adjust the pH).

[0033] Next step, electrochemical deposition:

[0034] The prepared blackening solution was stirred and the temperature was controlled using a thermal constant temperature heating magnetic stirrer, and the temperature was set to 25 degrees Celsius.

[0035] Place the substrate as the cathode in the blackening solution, and place the Pt sheet as the anode in the blackening solution (graphite rod can also be used as the anode);

[0036] Connect to a DC power supply, and set the current density of the DC power supply to 15 mA / cm 2 After 25 minutes of placement, a black oxide hydrogen barrier coating is formed on the working surface of the substrate;

[0037] Next, the substrate was taken out and allowed to stand for 5 min, then rinsed with deionized water and dried at room temperature.

[0038] Finally, the hydrogen barrier coating was tested and analyzed as follows:

[0039] like Figure 1 , it can be seen that the black oxide layer is composed of closely connected micro-nano oxide particles.

[0040] As shown in Figure 2, the XRD pattern was obtained, in which three CuO peaks (49°, 68° and 75°), one Fe3O4 peak (43°) and one Fe peak in the substrate (45°) appeared, indicating that the main components of the oxide layer are CuO and Fe3O4.

[0041] The use of a molybdate-copper salt system in the preparation process of the present invention can replace selenite (a toxic substance) to prepare the black oxide layer, which is essentially a redox reaction on the steel surface;

[0042] When steel parts are immersed in a blackening solution containing copper sulfate and ammonium molybdate, a microscopic corrosion cell of iron-copper salt and iron-molybdate is formed in the system. Since copper ions are simple hydrated cations, their polarization degree for cathode reduction reaction on the iron base is small, so Cu 2+ Active copper particles are quickly deposited on the iron-based surface, while iron dissolves into Fe 2+ (Fe+Cu 2 +→[Cu]+Fe 2+ Molybdate is a complex anion, and its polarization degree during cathodic reduction reaction on the iron-based surface is relatively large, and is significantly affected by the acidity of the solution.

[0043] This suggests that the initial corrosion reaction between the iron substrate and the copper salt dominates the system. Once copper ions are deposited on the iron substrate, molybdate ions, under acidic conditions, release reactive oxygen species [O] that adsorb onto the active copper particles [Cu], directly reacting with the copper to form a black CuO film: [Cu] + [O] → CuO (black)↓.

[0044] At the same time, under acidic conditions, hydrogen (Fe+2H + →Fe 2 ++H 2 ↑), which is very unfavorable for the formation of black oxide film. The addition of oxidant molybdate can directly oxidize hydrogen atoms and play a depolarizing role. Example 2

[0045] This embodiment is a comparative experiment based on the above embodiment, specifically:

[0046] This example is basically the same as Example 1, except that when preparing the blackening solution, 6 g of copper sulfate, 6 g of nickel sulfate, 16 g of sodium dihydrogen phosphate, 5 g of sodium citrate, and 5 g of ammonium molybdate are placed in a beaker, 1000 mL of deionized water is added and mixed, and then sulfuric acid is used to adjust the pH value to 3. The preparation concentration is appropriately increased compared to Example 1;

[0047] Then, a hydrogen barrier coating was formed on the working surface of the substrate by electrochemical deposition. This time, the current density of the DC power supply was increased to 20 mA / cm 2 ;

[0048] Finally, a scanning electron microscope image of the hydrogen barrier coating shows that it is also composed of tightly connected micro-nanostructured oxide particles. Example 3

[0049] This example is based on the hydrogen barrier coating prepared in Example 1 to produce a composite coating, specifically:

[0050] Preparation of organic resin coating:

[0051] Epoxy resin E44, polyamide 650 curing agent and xylene organic solvent were mixed to prepare organic resin coating.

[0052] First, dilute the epoxy resin with xylene at a rate of 10% of the epoxy resin, then add polyamide 650 curing agent at a mass ratio of 1:1 to the epoxy resin, and stir thoroughly to mix.

[0053] Next, the evenly mixed organic epoxy resin coating is applied on the surface of the hydrogen barrier coating, and then placed at room temperature for curing. After thorough curing, an anti-corrosion and hydrogen barrier composite coating is formed on the surface of the substrate.

[0054] Finally, the anti-corrosion and hydrogen-blocking composite coating was tested and analyzed, as follows:

[0055] like Figure 3 and Figure 4 The cross-sectional structure of the anti-corrosion and hydrogen-blocking composite coating shows that the black oxide layer has a dense structure and a uniform thickness of about 15 µm, and is tightly bonded to the substrate, thus effectively preventing the intrusion of corrosive substances.

[0056] like Figure 5 The anti-corrosion and hydrogen-blocking composite coating reduces the hydrogen permeation current density, which can block the hydrogen in the corrosive medium and the hydrogen that penetrates into the organic resin layer from further diffusing to the surface of the metal substrate, thereby preventing it from causing hydrogen damage to the metal substrate.

[0057] like Figure 6 and Figure 7 , the organic coating can penetrate into the pores of the black layer very well, and the presence of the black hydrogen barrier coating also greatly increases the bonding strength between the coating and the substrate, preventing bubbling of the coating;

[0058] like Figure 8 The electrochemical impedance spectroscopy test results of the new black oxide / organic resin composite coating in a 3.5 wt.% sodium chloride solution show that the impedance value of the coating has been significantly improved, thus giving the coating a long-term anti-corrosion effect. Compared with the existing technology;

[0059] It is worth noting that organic coatings have excellent chemical resistance, electrical insulation, wear resistance and corrosion resistance, and are one of the most widely used heavy-duty anti-corrosion coatings;

[0060] However, in the case of hydrogen corrosion, hydrogen ions can diffuse into the pores of the organic resin coating and reach the interface of the metal coating, resulting in a decrease in the barrier properties of the coating. In addition, the corrosion of the metal under the coating will accelerate the loss of adhesion of the coating. Therefore, traditional coatings using a single layer of organic resin coating cannot provide long-term corrosion protection.

[0061] The present invention first performs a blackening treatment on the surface of the steel, that is, prepares a black oxide hydrogen-barrier coating, which is an effective method to give the coating hydrogen-barrier properties, enhance the adhesion of the coating, and thus improve the corrosion protection performance, solving the problem that traditional single organic resin coatings cannot provide long-term corrosion protection.

[0062] The present invention adopts a room temperature electric-assisted method to prepare a black oxide hydrogen barrier coating, and then applies an organic resin coating on the hydrogen barrier coating to construct a double-layer composite coating. This composite coating not only has excellent hydrogen barrier performance, but also has high adhesion, and thus has long-lasting corrosion resistance.

[0063] In addition, the entire preparation process of the coating mentioned in the present invention does not require large and expensive equipment and can be prepared at room temperature. It has the advantages of low production cost and simple process, and has high promotion and application value. Especially when applied to the surface of hydrogen-related steel materials such as oil drilling casing or hydrogen pipelines, it has stronger hydrogen resistance and anti-corrosion performance than existing coatings.

Claims

1. A method for preparing a hydrogen barrier coating at room temperature, characterized in that: The following steps are involved: (1) Prepare blackening solution: dissolve 3-6 parts of copper sulfate, 3-6 parts of nickel sulfate, 13-16 parts of sodium dihydrogen phosphate, 1-5 parts of sodium citrate, and 1-5 parts of ammonium molybdate in clean tap water or deionized water, and then adjust the pH value to 2-3; (2) Electrochemical deposition: Place the steel as the cathode in the blackening solution, then select the electrode material as the anode and place it in the blackening solution, connect it to a DC power supply, and set the current density of the DC power supply to 15~20mA / cm 2 , so that a hydrogen-barrier coating is formed on the surface of the substrate.

2. The method for preparing a hydrogen barrier coating at room temperature according to claim 1, characterized in that: The clean tap water or deionized water described in step 1 is 800-1000 parts.

3. The method for preparing a hydrogen barrier coating at room temperature according to claim 1, wherein: In step 1, hydrochloric acid, sulfuric acid, phosphoric acid or citric acid is used to adjust the pH value.

4. The method for preparing a hydrogen barrier coating at room temperature according to claim 1, wherein: During the electrochemical deposition in step 2, the blackening solution is stirred, and the temperature of the blackening solution is stabilized at 20-30°C.

5. The method for preparing a hydrogen barrier coating at room temperature according to claim 1, characterized in that: In step 2, the electrode material is a Pt sheet or a graphite rod.

6. A method for preparing an anti-corrosion and hydrogen-blocking composite coating, characterized by: The following steps are involved: (1) A hydrogen barrier coating is prepared by applying a method for preparing a hydrogen barrier coating at room temperature as claimed in any one of claims 1 to 5; (2) Applying organic resin coating on the surface of hydrogen barrier coating, and forming anti-corrosion hydrogen barrier composite coating on the surface of substrate after curing.

7. The method for preparing a corrosion-resistant and hydrogen-blocking composite coating according to claim 6, characterized in that: The organic resin coating comprises epoxy resin, a curing agent and an organic solvent, the mass ratio of the epoxy resin to the curing agent is 1:1, and the amount of the organic solvent is 10% of the mass of the epoxy resin.

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