Alkali-resistant corrosion-proof coating for bipolar plate frame of electrolytic cell and preparation process thereof

Abstract

The application discloses an alkali-washing-resistant corrosion-proof coating of an electrolytic cell bipolar plate frame and a preparation process thereof, and relates to the technical field of surface treatment of alkaline water electrolysis hydrogen production equipment. The corrosion-proof coating is formed by curing corrosion-proof paint, and the paint comprises 40-50 parts of modified polyphenylene sulfide resin, 15-20 parts of nano silicon carbide particles, 5-8 parts of graphene microsheets, 2-3 parts of a coupling agent, 3-5 parts of a wear-resistant toughening agent and mixed solvents prepared by mixing N-methyl pyrrolidone and butanone at a volume ratio of 1:1. In the preparation, the components are first mixed, dispersed and ground to prepare the paint, then the nickel-plated frame workpiece is subjected to plasma cleaning and micro-arc oxidation activation pretreatment, and after being sprayed by using an automatic spraying device, the coating is subjected to stepwise heating and curing at 60 DEG C / 180 DEG C / 240 DEG C, so that the coating with a dry film thickness of 0.08-0.1 mm is obtained. The coating of the application does not bubble and fall off after being soaked in a 30% KOH solution at 90-95 DEG C for 1000 hours, the adhesion reaches ISO 0 level, the anti-washing life is more than 3 times that of the pure resin coating, and the coating is suitable for corrosion protection of the bipolar plate frame of the alkaline water electrolysis cell.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology for structural components of alkaline water electrolysis hydrogen production equipment, and more specifically, to an anti-corrosion coating for the bipolar plate frame of an electrolytic cell that is resistant to alkali erosion and its preparation process. Background Technology

[0002] In alkaline water electrolysis hydrogen production systems, the bipolar plate frame not only provides structural support and sealing, but its surface, including the gas-liquid inlet / outlet and flow channels, must also withstand long-term immersion and high-speed scouring in a 30% KOH high-temperature solution (90-95℃). The plates are the supporting components of the alkaline electrolyzer, supporting the electrodes and diaphragm, and providing conductivity. In China, they are typically made from carbon steel, nickel, or stainless steel plates, machined and then welded to the frame before being nickel-plated. Although the frame surface is usually nickel-plated to improve corrosion resistance, long-term operation under alkaline and high-temperature conditions will cause corrosion damage to the nickel plating, thus reducing the electrolyzer's efficiency.

[0003] Studies have shown that in an alkaline water electrolysis environment, the corrosion mechanism of Ni-P coatings involves the gradual dissolution of phosphorus on the surface and the gradual oxidation of nickel to Ni(II) and then to Ni(III), leading to the formation of a dense, chemically inert oxide film. However, under the combined effects of high temperature (90-95℃) and high-flow-rate electrolyte, fluid flow promotes the interaction between the electrolyte and the sample surface, accelerates oxygen release, and further affects corrosion kinetics. Furthermore, under long-term thermal stress and fluid mechanical erosion, the coating is prone to micropores, wear, and even peeling, leading to substrate corrosion failure. In carbon steel nickel-plated bipolar plates, the nickel layer at the channel openings suffers severe electrochemical corrosion at high potentials, causing it to peel off. After peeling, the nickel layer continues to corrode the carbon steel, releasing iron ions, leading to electrode deactivation and increased energy consumption. Simultaneously, welding processes can easily damage the nickel plating, severely affecting product quality and equipment lifespan. Traditional metal electrode frames achieve electrolyte corrosion protection through a nickel plating layer on their outer surface. However, the material of the metal electrode frame is difficult to guarantee. Problems such as "cutting corners" in the electroplating process and difficulties in plating through the channels lead to inconsistent plating quality, affecting long-term durability and corrosion protection performance, and causing serious problems such as severe channel corrosion, severe weld corrosion, and severe electrode plate corrosion.

[0004] Existing anti-corrosion treatment methods have certain limitations. Traditional electroplating or electroless plating processes are costly and difficult to precisely control the thickness in specific areas. Conventional polymer coatings are prone to swelling and degradation in high-temperature, strongly alkaline environments—studies have shown that glass fiber reinforced PPS fails after immersion in a high-temperature, strongly alkaline solution for 12 weeks due to the dissolution of glass fibers, although the PPS substrate itself exhibits good resistance to thermal oxidation and chemical degradation under the test conditions—and the film thickness often exceeds the standard, affecting the assembly accuracy of the components. Coating thickness is a crucial parameter for bipolar plate modified coatings; reducing the film thickness can improve coating preparation efficiency while ensuring coating performance. Therefore, there is an urgent need to develop a novel anti-corrosion coating and a matching precision spraying process that can be applied at room temperature, forms a thin film with small tolerances, has strong adhesion to nickel-plated substrates, and can withstand prolonged erosion by high-temperature concentrated alkali. Summary of the Invention

[0005] The purpose of this invention is to provide an anti-corrosion coating for the bipolar plate frame of an electrolytic cell that is resistant to alkali erosion and its preparation process, so as to solve the problems of easy failure of the coating, poor alkali resistance of traditional coatings, and difficulty in accurately controlling the film thickness in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: An anti-corrosion coating for the bipolar plate frame of an electrolytic cell, resistant to alkali erosion, wherein the anti-corrosion coating is formed by curing an anti-corrosion coating, the anti-corrosion coating comprising the following components by weight: 40-50 parts of modified polyphenylene sulfide (PPS) resin, 15-20 parts of nano-silicon carbide (SiC) particles, 5-8 parts of graphene microplates, 2-3 parts of coupling agent, 3-5 parts of wear-resistant toughening agent, and an appropriate amount of mixed solvent; wherein the mixed solvent is prepared by mixing N-methylpyrrolidone (NMP) and butanone in a 1:1 volume ratio.

[0007] The mechanisms of action of each component are as follows: Modified polyphenylene sulfide (PPS) resin, as a film-forming material, has a rigid aromatic ring structure composed of alternating benzene rings and sulfur atoms in its molecular backbone, which endows the coating with excellent heat resistance and chemical stability. PPS resin exhibits excellent resistance to thermal oxidation and chemical degradation in high-temperature, strongly alkaline solutions, making it an ideal film-forming material for the high-temperature, concentrated alkaline environment of alkaline electrolytic cells.

[0008] Nano-sized silicon carbide (SiC) particles, as a hard ceramic filler, possess high hardness (Mohs hardness 9.5), excellent thermal stability, and chemical inertness, which can significantly improve the wear resistance and erosion resistance of the coating. Their nano-sized particles (40-80nm) allow them to be uniformly dispersed in the PPS resin matrix, effectively filling the microscopic gaps between resin molecular chains and improving the density of the coating.

[0009] Graphene microflakes have a two-dimensional layered structure, which can form stacked physical barrier layers in the coating, effectively extending the lifespan of corrosive media (OH). - It slows down the penetration rate of corrosive media (such as hydrogen, oxygen, and oxygen) through the permeation pathways of graphene microflakes. Simultaneously, the high specific surface area and excellent mechanical properties of graphene microflakes enhance the hardness and impact resistance of the polymer coating.

[0010] KH-560 coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane, which contains two types of functional groups: the trimethoxysilyl group (-Si(OCH3)3) at one end can undergo hydrolysis and condensation reaction with the active hydroxyl group (-OH) generated after plasma activation of the nickel plating surface to form a strong Si-O-Ni chemical bond; the epoxypropoxy group at the other end can undergo ring-opening crosslinking reaction with the active end group on the PPS resin molecular chain, thereby establishing a "molecular bridge" chemical connection between the coating and the nickel plating substrate, significantly improving the interfacial adhesion and fundamentally solving the industry pain point of high-temperature peeling of coatings.

[0011] As a wear-resistant toughening agent, PTFE micro powder has low surface energy characteristics that can reduce the coefficient of friction of the coating surface and reduce the shear stress transmission during fluid scouring. At the same time, the flexible molecular chains of PTFE can absorb and disperse the impact energy of external forces, improve the toughness and crack resistance of the coating, and prevent the coating from developing brittle cracks under thermal stress.

[0012] The mixed solvent is prepared by mixing NMP and methyl ethyl ketone (MEK) in a 1:1 volume ratio. NMP has good solubility for PPS resin, while MEK has a suitable evaporation rate. The synergistic effect of the two ensures that the PPS resin is fully dissolved or uniformly dispersed in the solvent system, while also allowing the solvent to evaporate at a moderate rate after spraying. This avoids pinholes and orange peel defects on the coating surface caused by excessively rapid evaporation, and also avoids sagging caused by excessively slow evaporation.

[0013] Furthermore, the coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560).

[0014] Furthermore, the wear-resistant toughening agent is polytetrafluoroethylene (PTFE) micro powder.

[0015] A process for preparing an anti-corrosion coating for the bipolar plate frame of an electrolytic cell, as described above, specifically includes the following steps: S101: Raw material weighing and mixing - Weigh 40-50 parts of modified polyphenylene sulfide (PPS) resin, 15-20 parts of nano silicon carbide (SiC) particles, 5-8 parts of graphene microplates, 2-3 parts of coupling agent and 3-5 parts of wear-resistant toughening agent by weight, and add them to a mixed solvent prepared by NMP and butanone in a 1:1 volume ratio.

[0016] S102: High-speed dispersion and grinding—The above mixture is dispersed and ground at high speed to obtain the anti-corrosion coating. The high-speed dispersion speed is 2000 r / min, and the stirring time is 2 hours to ensure that each component is fully wetted and uniformly dispersed in the solvent system; then it is transferred to a sand mill and ground to a fineness of ≤15μm to ensure that the nano-silicon carbide particles and graphene microflakes reach the ideal dispersion state and prevent particle agglomeration from affecting the density of the coating.

[0017] S103: Workpiece Acquisition – Acquire the bipolar plate frame workpiece of the electrolytic cell that has undergone nickel plating. This workpiece is part of the bipolar plate assembly of the alkaline water electrolytic cell, and its surface nickel plating layer serves as the bottom protective layer. The anti-corrosion coating of the present invention forms a composite protective system on top of this nickel plating layer.

[0018] S104: Workpiece Surface Pretreatment—The workpiece surface is pretreated, specifically by plasma cleaning and micro-arc oxidation activation of the nickel-plated electrode frame surface to meet the coating adhesion requirements. Plasma cleaning utilizes high-energy plasma to bombard the nickel-plated surface, removing adsorbed organic contaminants and the natural oxide layer, achieving an atomically clean surface. Subsequently, micro-arc oxidation activation is performed, generating an activation layer with a micro-rough structure and abundant active hydroxyl groups (-OH) in situ on the nickel-plated surface. This activation layer increases the mechanical bonding area between the coating and the substrate and provides sufficient active reaction sites for the chemical bonding of the KH-560 coupling agent. The synergistic effect of plasma cleaning and micro-arc oxidation activation enables the coating adhesion to the nickel-plated substrate to reach ISO level 0.

[0019] S105: Automated Precision Spraying – The anti-corrosion coating is uniformly sprayed onto the treated workpiece surface using a reciprocating multi-axis automatic spraying device. The spray gun moves perpendicular to the electrode frame surface to ensure a uniform coating thickness. The spraying area is the outer ring of the electrode frame, avoiding the tongue plate position – the electrode frame has air and liquid channels, and the part welded to the main electrode plate is called the tongue plate – to avoid the welding area and prevent the coating from adversely affecting subsequent welding processes. The spraying environment temperature is controlled at 25±2℃, relative humidity ≤40%, and atomization pressure controlled at 0.3-0.4MPa. Under the above optimized environmental parameters, the solvent evaporation rate is moderate, the coating atomizes fully, and there is little paint splatter, ensuring a dense and uniform coating without drips or orange peel defects.

[0020] S106: Stepped Heating Curing – The coated workpiece is placed under multi-temperature conditions for stepped heating curing. The specific curing process is as follows: first, pre-baking at 60℃ for 15 minutes, then raising the temperature to 180℃ and holding for 30 minutes, and finally raising it to 240℃ for cross-linking curing for 40 minutes. The purpose of setting each temperature range is as follows: 60℃ pre-baking stage: This allows the mixed solvent in the coating to evaporate slowly at a gentle rate, avoiding defects such as pinholes, bubbles, and shrinkage cavities on the coating surface caused by rapid solvent evaporation, while also allowing the coating to initially set.

[0021] 180℃ heat preservation stage: This allows the PPS resin molecular chains to obtain sufficient kinetic energy, gradually softening and leveling the coating, eliminating the tiny flow marks generated during the spraying process; at the same time, the condensation reaction between the methoxysilane groups in the KH-560 coupling agent and the active hydroxyl groups on the nickel plating surface can be fully carried out in this temperature range, forming a strong chemical bond.

[0022] 240℃ Crosslinking and Curing Stage: This stage allows the PPS resin to reach its highest crosslinking temperature below its melting point (approximately 285℃), ensuring the full completion of the crosslinking reaction between molecular chains and forming a dense three-dimensional network structure. Simultaneously, nano-silicon carbide particles, graphene microplates, and PTFE micropowder are uniformly embedded in the PPS crosslinking network, forming an "organic-inorganic interpenetrating network" structure. This achieves a synergistic enhancement of the flexibility and toughness of the organic matrix with the rigidity and wear resistance of the inorganic filler.

[0023] S107: Natural cooling – Allow the workpiece that has completed stepped curing to cool naturally to room temperature to avoid stress concentration in the coating and microcracks caused by rapid cooling.

[0024] Furthermore, the dry film thickness of the cured anti-corrosion coating is 0.08-0.1 mm. This film thickness range ensures that the coating has sufficient density and corrosion resistance, while also meeting the dimensional tolerance requirements for precision assembly of electrolytic cell components (tolerance controlled within ±0.05 mm), thus solving the technical problem of excessive film thickness of traditional polymer coatings affecting assembly accuracy.

[0025] Compared with the prior art, the beneficial effects of the present invention are: 1. Precise Film Thickness Control: This invention utilizes a 1:1 volume ratio of NMP and methyl ethyl ketone (MEK) in a mixed solvent formulation, balancing the good solubility of PPS resin with a suitable evaporation rate. This results in ideal leveling properties during coating application. Combined with precise metering using a reciprocating multi-axis automatic spraying device, the cured dry film thickness remains stable between 0.08-0.1 mm, with a tolerance controlled within ±0.05 mm. This ultra-thin and high-precision film thickness design perfectly meets the precision assembly requirements of bipolar plate assemblies in electrolytic cells, avoiding assembly interference problems caused by excessive film thickness in traditional coatings. Furthermore, reducing film thickness improves coating preparation efficiency and lowers material costs.

[0026] 2. Excellent alkali and erosion resistance: The "organic-inorganic interpenetrating network" structure formed by modified PPS resin, nano-SiC particles, and graphene microplates exhibits no bubbling or peeling after continuous immersion in a 30% KOH solution at 90-95℃ for 1000 hours. Its alkali and erosion resistance mechanism includes three aspects: First, the rigid aromatic ring backbone of PPS imparts intrinsic chemical inertness to the coating, effectively resisting OH... - The advantages of this invention are: firstly, the physical barrier layer formed by the nano-SiC particles and graphene microflakes in the coating extends the penetration path of the corrosive medium; secondly, the "point-to-surface" synergistic reinforcement of the filler network formed by the one-dimensional nano-SiC particles and two-dimensional graphene microflakes in the coating significantly improves the hardness and resistance to fluid erosion. Tests show that the fluid erosion resistance life of this invention is more than three times that of traditional pure resin coatings.

[0027] 3. Extremely strong interfacial adhesion: Plasma cleaning removes contaminants and the natural oxide layer from the nickel plating surface. Micro-arc oxidation activation generates a micro-rough structure rich in active hydroxyl groups in situ on the nickel plating surface. The KH-560 coupling agent, through the condensation of its trimethoxysilyl group at one end with the active hydroxyl groups on the nickel plating surface to form Si-O-Ni covalent bonds, and the epoxypropoxy group at the other end to cross-link with the PPS resin molecular chain, thus forming a multi-level chemical bonding interface between the coating and the nickel plating substrate: "nickel plating layer—Si-O-Ni chemical bond—KH-560 molecular bridge—epoxy ring-opening cross-linking—PPS network". This multi-level chemical bonding interface enables the adhesion between the coating and the nickel plating surface to reach ISO level 0 (cross-cut test), completely solving the industry pain point of coating peeling under high-temperature conditions.

[0028] 4. Optimized Process Compatibility: The coating of this invention can be sprayed at room temperature without requiring high-temperature preheating of the workpiece, thus avoiding the potential adverse effects of high temperatures on the nickel plating layer and the metallographic structure of the substrate. Simultaneously, the stepped curing temperature is only 240℃ at its maximum, lower than the melting temperature of PPS (approximately 285℃), ensuring that the coating does not melt and flow during the curing process and guaranteeing precise control of the film thickness. The process design, which avoids the tongue plate area during spraying, also fully considers the subsequent welding process requirements of the electrolytic cell electrode frame, demonstrating excellent prospects for industrial application. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0030] To more clearly illustrate the overall concept of this application, a detailed explanation is provided below with reference to the accompanying drawings.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0032] Furthermore, it should be understood in the description of this application that the terms "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0033] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] In this application, unless otherwise expressly specified and limited, the "above" or "below" of the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples.

[0035] The raw materials used in the following examples are all commercially available industrial products. The anti-corrosion coating includes the following components in parts by weight: 40-50 parts of modified polyphenylene sulfide (PPS) resin, 15-20 parts of nano-silicon carbide (SiC) particles, 5-8 parts of graphene microplates, 2-3 parts of coupling agent, 3-5 parts of wear-resistant toughening agent, and an appropriate amount of mixed solvent; the mixed solvent is prepared by mixing N-methylpyrrolidone (NMP) and butanone in a 1:1 volume ratio.

[0036] The mechanisms of action of each component are as follows: Modified polyphenylene sulfide (PPS) resin, as a film-forming material, has a rigid aromatic ring structure composed of alternating benzene rings and sulfur atoms in its molecular backbone, which endows the coating with excellent heat resistance and chemical stability. PPS resin exhibits excellent resistance to thermal oxidation and chemical degradation in high-temperature, strongly alkaline solutions, making it an ideal film-forming material for the high-temperature, concentrated alkaline environment of alkaline electrolytic cells.

[0037] Nano-sized silicon carbide (SiC) particles, as a hard ceramic filler, possess high hardness (Mohs hardness 9.5), excellent thermal stability, and chemical inertness, which can significantly improve the wear resistance and erosion resistance of the coating. Their nano-sized particles (40-80nm) allow them to be uniformly dispersed in the PPS resin matrix, effectively filling the microscopic gaps between resin molecular chains and improving the density of the coating.

[0038] Graphene microflakes have a two-dimensional layered structure, which can form stacked physical barrier layers in the coating, effectively extending the lifespan of corrosive media (OH). - It slows down the penetration rate of corrosive media (such as hydrogen, oxygen, and oxygen) through the permeation pathways of graphene microflakes. Simultaneously, the high specific surface area and excellent mechanical properties of graphene microflakes enhance the hardness and impact resistance of the polymer coating.

[0039] KH-560 coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane, which contains two types of functional groups: the trimethoxysilyl group (-Si(OCH3)3) at one end can undergo hydrolysis and condensation reaction with the active hydroxyl group (-OH) generated after plasma activation of the nickel plating surface to form a strong Si-O-Ni chemical bond; the epoxypropoxy group at the other end can undergo ring-opening crosslinking reaction with the active end group on the PPS resin molecular chain, thereby establishing a "molecular bridge" chemical connection between the coating and the nickel plating substrate, significantly improving the interfacial adhesion and fundamentally solving the industry pain point of high-temperature peeling of coatings.

[0040] As a wear-resistant toughening agent, PTFE micro powder has low surface energy characteristics that can reduce the coefficient of friction of the coating surface and reduce the shear stress transmission during fluid scouring. At the same time, the flexible molecular chains of PTFE can absorb and disperse the impact energy of external forces, improve the toughness and crack resistance of the coating, and prevent the coating from developing brittle cracks under thermal stress.

[0041] The mixed solvent is prepared by mixing NMP and methyl ethyl ketone (MEK) in a 1:1 volume ratio. NMP has good solubility for PPS resin, while MEK has a suitable evaporation rate. The synergistic effect of the two ensures that the PPS resin is fully dissolved or uniformly dispersed in the solvent system, while also allowing the solvent to evaporate at a moderate rate after spraying. This avoids pinholes and orange peel defects on the coating surface caused by excessively rapid evaporation, and also avoids sagging caused by excessively slow evaporation.

[0042] Furthermore, the coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560).

[0043] Furthermore, the wear-resistant toughening agent is polytetrafluoroethylene (PTFE) micro powder.

[0044] like Figure 1 As shown in the embodiments, the preparation process of the anti-corrosion coating and the coating layer includes the following steps: S101: Raw material weighing and mixing - Weigh 40-50 parts of modified polyphenylene sulfide (PPS) resin, 15-20 parts of nano silicon carbide (SiC) particles, 5-8 parts of graphene microplates, 2-3 parts of coupling agent and 3-5 parts of wear-resistant toughening agent by weight, and add them to a mixed solvent prepared by NMP and butanone in a 1:1 volume ratio.

[0045] S102: High-speed dispersion and grinding—The above mixture is dispersed and ground at high speed to obtain the anti-corrosion coating. The high-speed dispersion speed is 2000 r / min, and the stirring time is 2 hours to ensure that each component is fully wetted and uniformly dispersed in the solvent system; then it is transferred to a sand mill and ground to a fineness of ≤15μm to ensure that the nano-silicon carbide particles and graphene microflakes reach the ideal dispersion state and prevent particle agglomeration from affecting the density of the coating.

[0046] S103: Workpiece Acquisition – Acquire the bipolar plate frame workpiece of the electrolytic cell that has undergone nickel plating. This workpiece is part of the bipolar plate assembly of the alkaline water electrolytic cell, and its surface nickel plating layer serves as the bottom protective layer. The anti-corrosion coating of the present invention forms a composite protective system on top of this nickel plating layer.

[0047] S104: Workpiece Surface Pretreatment—The workpiece surface is pretreated, specifically by plasma cleaning and micro-arc oxidation activation of the nickel-plated electrode frame surface to meet the coating adhesion requirements. Plasma cleaning utilizes high-energy plasma to bombard the nickel-plated surface, removing adsorbed organic contaminants and the natural oxide layer, achieving an atomically clean surface. Subsequently, micro-arc oxidation activation is performed, generating an activation layer with a micro-rough structure and abundant active hydroxyl groups (-OH) in situ on the nickel-plated surface. This activation layer increases the mechanical bonding area between the coating and the substrate and provides sufficient active reaction sites for the chemical bonding of the KH-560 coupling agent. The synergistic effect of plasma cleaning and micro-arc oxidation activation enables the coating adhesion to the nickel-plated substrate to reach ISO level 0.

[0048] S105: Automated Precision Spraying – The anti-corrosion coating is uniformly sprayed onto the treated workpiece surface using a reciprocating multi-axis automatic spraying device. The spray gun moves perpendicular to the electrode frame surface to ensure a uniform coating thickness. The spraying area is the outer ring of the electrode frame, avoiding the tongue plate position – the electrode frame has air and liquid channels, and the part welded to the main electrode plate is called the tongue plate – to avoid the welding area and prevent the coating from adversely affecting subsequent welding processes. The spraying environment temperature is controlled at 25±2℃, relative humidity ≤40%, and atomization pressure controlled at 0.3-0.4MPa. Under the above optimized environmental parameters, the solvent evaporation rate is moderate, the coating atomizes fully, and there is little paint splatter, ensuring a dense and uniform coating without drips or orange peel defects.

[0049] S106: Stepped Heating Curing – The coated workpiece is placed under multi-temperature conditions for stepped heating curing. The specific curing process is as follows: first, pre-baking at 60℃ for 15 minutes, then raising the temperature to 180℃ and holding for 30 minutes, and finally raising it to 240℃ for cross-linking curing for 40 minutes. The purpose of setting each temperature range is as follows: 60℃ pre-baking stage: This allows the mixed solvent in the coating to evaporate slowly at a gentle rate, avoiding defects such as pinholes, bubbles, and shrinkage cavities on the coating surface caused by rapid solvent evaporation, while also allowing the coating to initially set.

[0050] 180℃ heat preservation stage: This allows the PPS resin molecular chains to obtain sufficient kinetic energy, gradually softening and leveling the coating, eliminating the tiny flow marks generated during the spraying process; at the same time, the condensation reaction between the methoxysilane groups in the KH-560 coupling agent and the active hydroxyl groups on the nickel plating surface can be fully carried out in this temperature range, forming a strong chemical bond.

[0051] 240℃ Crosslinking and Curing Stage: This stage allows the PPS resin to reach its highest crosslinking temperature below its melting point (approximately 285℃), ensuring the full completion of the crosslinking reaction between molecular chains and forming a dense three-dimensional network structure. Simultaneously, nano-silicon carbide particles, graphene microplates, and PTFE micropowder are uniformly embedded in the PPS crosslinking network, forming an "organic-inorganic interpenetrating network" structure. This achieves a synergistic enhancement of the flexibility and toughness of the organic matrix with the rigidity and wear resistance of the inorganic filler.

[0052] S107: Natural cooling – Allow the workpiece that has completed stepped curing to cool naturally to room temperature to avoid stress concentration in the coating and microcracks caused by rapid cooling.

[0053] Example 1: Weigh the following raw materials by weight: 40 parts modified polyphenylene sulfide (PPS) resin, 15 parts nano silicon carbide (SiC) particles, 5 parts graphene microplates, 2 parts KH-560 coupling agent, and 3 parts PTFE micro powder, and add them to an appropriate amount of mixed solvent.

[0054] The anti-corrosion coating is prepared, and the workpiece is sprayed and cured according to the general preparation process steps S101 to S107 described above. In this embodiment, the modified PPS resin content in the coating system is relatively low, and the filling ratio of nano-silicon carbide and graphene is moderate. The coating has both good flexibility and erosion resistance, and is particularly suitable for thin-walled areas of the polar frame where the coating is highly sensitive to stress.

[0055] The anti-corrosion coating samples prepared in this embodiment were subjected to performance testing: Alkali resistance test: Referring to GB / T 9265 standard, the sample was immersed in a 30% KOH solution at 95℃ for 1000 hours before being removed and observed. The results showed that the coating surface exhibited no blistering, peeling, or cracking, and the color was uniform, proving that the coating in this embodiment has excellent resistance to high-temperature concentrated alkalis.

[0056] Adhesion test: Following the ISO 2409 cross-cut test method, a 1mm × 1mm grid was cut and a tape peel test was performed. The results showed that the cut edges were completely smooth, and there was no peeling at the grid edges, achieving an adhesion level of ISO 0.

[0057] Dry film thickness test: The thickness of the cured coating was measured using a coating thickness gauge. The results showed that the dry film thickness was 0.085-0.095mm, with the tolerance controlled within ±0.05mm.

[0058] Example 2 Weigh the following raw materials by weight: 45 parts modified polyphenylene sulfide (PPS) resin, 18 parts nano silicon carbide (SiC) particles, 6.5 parts graphene microplates, 2.5 parts KH-560 coupling agent, and 4 parts PTFE micro powder, and add them to an appropriate amount of mixed solvent.

[0059] The anti-corrosion coating is prepared, and the workpiece is sprayed and cured according to the general preparation process steps S101 to S107 described above. This embodiment is a preferred solution, with the proportions of each component near the median range. The "organic-inorganic interpenetrating network" structure between the modified PPS resin and the inorganic fillers (nano-SiC and graphene) is the most dense and balanced, resulting in the best overall coating performance.

[0060] The anti-corrosion coating samples prepared in this embodiment were subjected to performance testing: Alkali resistance test: Under the same test conditions as in Example 1, after 1000 hours of high-temperature concentrated alkali immersion, the coating surface remained intact, without any blistering, peeling or cracking defects.

[0061] Adhesion test: The cross-cut test result reached ISO level 0, and the cut edges were intact and undamaged.

[0062] Erosion resistance test: The sample coated with the anti-corrosion coating was placed in a flowing 90℃, 30% KOH solution, with the flow rate controlled at 2m / s to simulate the actual working conditions of an electrolytic cell. After continuous erosion for 2000 hours, the coating mass loss rate was less than 0.5%, and the surface remained intact and dense. The fluid erosion resistance life was 3.2 times longer than that of traditional pure PPS resin coatings without inorganic fillers.

[0063] Dry film thickness test: The results show that the dry film thickness is 0.088-0.098mm, and the tolerance is controlled within ±0.05mm.

[0064] Example 3 Weigh the following raw materials by weight: 50 parts modified polyphenylene sulfide (PPS) resin, 20 parts nano silicon carbide (SiC) particles, 8 parts graphene microplates, 3 parts KH-560 coupling agent, and 5 parts PTFE micro powder, and add them to an appropriate amount of mixed solvent.

[0065] The anti-corrosion coating is prepared, and the workpiece is sprayed and cured according to the general preparation process steps S101 to S107 described above. In this embodiment, the content of modified PPS resin and various functional fillers are all at the upper limit, the crosslinking density of the coating is the highest, and the hardness and wear resistance are the most outstanding, making it particularly suitable for the protection of high flow rate erosion areas (such as gas-liquid inlet and outlet channels).

[0066] The anti-corrosion coating samples prepared in this embodiment were subjected to performance testing: Alkali resistance test: Under the same test conditions as in Example 1, after 1000 hours of high-temperature concentrated alkali immersion, the coating surface remained intact, without blistering or peeling, with only a slight decrease in surface gloss, proving its excellent resistance to alkali media penetration.

[0067] Adhesion test: The cross-cut test result reached ISO level 0.

[0068] Hardness test: According to the pencil hardness test in GB / T 6739, the hardness of the coating in this embodiment reached 5H, which is significantly higher than the 2H hardness of the pure PPS coating. This is due to the hardening effect of the high content of nano SiC ceramic particles.

[0069] Erosion resistance test: Under the same test conditions as in Example 2, after 2000 hours of continuous erosion, the coating mass loss rate was only 0.3%, and the erosion resistance life was 3.5 times longer than that of traditional pure resin coating.

[0070] Dry film thickness test: The results show that the dry film thickness is 0.09-0.10mm, and the tolerance is controlled within ±0.05mm.

[0071] The main performance test results of the anti-corrosion coatings of the bipolar plate frame of the electrolytic cell prepared in each embodiment are shown in Table 1.

[0072]

[0073] As shown in Table 1, the anti-corrosion coatings of all embodiments exhibit excellent corrosion resistance under high-temperature and concentrated alkaline conditions, with adhesion reaching the highest ISO 0 level and dry film thickness consistently controlled within the target range of 0.08-0.1 mm. Among them, Embodiment 2 has the most balanced overall performance and is the preferred option; Embodiment 3 is the most outstanding in terms of hardness and erosion resistance, suitable for extreme erosion conditions; Embodiment 1 balances good protective performance with process economy.

[0074] For any parts not mentioned in this application, existing technologies may be used or referenced.

[0075] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0076] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A corrosion-resistant coating for the bipolar plate frame of an electrolytic cell, characterized in that, The anti-corrosion coating is formed by curing an anti-corrosion paint, which includes the following components in parts by weight: 40-50 parts of modified polyphenylene sulfide (PPS) resin, 15-20 parts of nano silicon carbide (SiC) particles, 5-8 parts of graphene microplates, 2-3 parts of coupling agent, 3-5 parts of wear-resistant toughening agent, and an appropriate amount of mixed solvent. The mixed solvent is prepared by mixing N-methylpyrrolidone (NMP) and butanone in a volume ratio of 1:

1.

2. The anti-corrosion coating for the bipolar plate frame of the electrolytic cell resistant to alkali erosion according to claim 1, characterized in that, The coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560).

3. The anti-corrosion coating for the bipolar plate frame of the electrolytic cell resistant to alkali erosion according to claim 1, characterized in that, The wear-resistant toughening agent is polytetrafluoroethylene (PTFE) micro powder.

4. A preparation process for an anti-corrosion coating on the bipolar plate frame of an electrolytic cell as described in any one of claims 1-3, characterized in that, Specifically, the steps include the following: S101: Weigh the raw materials by weight, and add the modified polyphenylene sulfide (PPS) resin, nano silicon carbide (SiC) particles, graphene microplates, coupling agent and wear-resistant toughening agent into the mixed solvent. S102: Anti-corrosion coating is prepared by high-speed dispersion and grinding; S103: Obtain the bipolar plate frame workpiece of the electrolytic cell that has been nickel-plated; S104: Perform pretreatment on the surface of the workpiece to meet the coating adhesion requirements; S105: Use an automatic spraying device to evenly spray the anti-corrosion coating onto the surface of the treated workpiece; S106: Place the coated workpiece under multi-temperature conditions for stepped heating and curing; S107: Allow the workpiece to cool naturally after the stepped curing process is completed.

5. The preparation process according to claim 4, characterized in that, In step S101, the high-speed dispersion speed is 2000 r / min, the stirring time is 2 hours, and the grinding is carried out until the fineness is ≤15μm.

6. The preparation process according to claim 4, characterized in that, In step S104, the pretreatment involves plasma cleaning and micro-arc oxidation activation of the nickel-plated surface of the electrode frame.

7. The preparation process according to claim 4, characterized in that, In step S105, the automatic spraying device is a reciprocating multi-axis automatic spraying device, the spray gun moves perpendicular to the surface of the pole frame, and the spraying area is the outer ring of the pole frame and avoids the tongue plate position.

8. The preparation process according to claim 4, characterized in that, In step S105, the spraying environment temperature is 25±2℃, the relative humidity is ≤40%, and the atomization pressure is 0.3-0.4MPa.

9. The preparation process according to claim 4, characterized in that, In step S106, the stepped curing process is as follows: first, pre-baking at 60°C for 15 minutes, then raising the temperature to 180°C and holding for 30 minutes, and then raising the temperature to 240°C for cross-linking and curing for 40 minutes.

10. The preparation process according to claim 4, characterized in that, The dry film thickness of the anti-corrosion coating obtained after curing is 0.08-0.1 mm.

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