Brush coating passivation paste for helicopter surface in-situ repair and brush coating method

Abstract

The invention belongs to the technical field of metal part surface corrosion protection, and relates to brush coating passivation paste for helicopter surface in-situ repair and a brush coating method. The passivation paste comprises the following components in percentage by mass: 10%-20% of citric acid, 3%-5% of acrylic resin, 3%-10% of a cellulose inorganic thickener, 3%-5% of magnesium nitrate, 0.5%-2% of urotropin, a flatting agent, 0.5%-2% of bentonite and the balance of deionized water. The problems that an existing brush coating passivation solution flows, and protective layers such as paint layers, plating layers and chemical conversion layers of peripheral parts of to-be-repaired parts are prone to being polluted or damaged during on-machine repairing are solved. And meanwhile, a needle tube type packaging and brushing tool is adopted, so that the operation during on-machine repair and the control on the dosage of the paste are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of metal parts surface corrosion protection, and relates to a brush-coated passivation paste for in-situ repair of helicopter surface and a brush-coating method. Background Art

[0002] Stainless steel parts (assemblies) of various types of helicopters have problems such as local passivation film damage and reduced protective performance during assembly and service. Some parts are too large to fit into the surface treatment tank due to limited volume. The assembled components cannot be disassembled or need secondary positioning for reinstallation after disassembly. In order to meet the needs of product design, manufacturing and application, solution brush passivation technology is generally used for the preparation and local repair of surface passivation film. At present, the domestic brush passivation process generally uses self-prepared 25% to 35% nitric acid or commercially available Gardacid P4325 solution (supplier: CHEMETALL, 51rue Pierre92588 Clichy Cedex, the main component is 25% to 35% nitric acid). The above brush passivation solutions and their construction processes all have the following problems:

[0003] (1) During the preparation of local protective layers and in-situ repair of stainless steel parts on the aircraft, the working conditions around the parts are relatively complex, and strong oxidizing passivation solutions flow, which poses a risk of contamination and damage to the plating, paint and oxide layers on the surfaces of surrounding parts.

[0004] (2) Nitric acid solution is highly oxidizing, has poor environmental friendliness, and has poor construction and operation safety.

[0005] (3) During the on-board repair process, the use of organic solvents such as alcohol and acetone also poses the risk of contaminating surrounding painted parts. At the same time, materials such as alcohol and acetone have poor safety. Alcohol has a low flash point and is flammable, while acetone is prone to explosion. The use of both has been restricted at production sites.

[0006] Based on the above deficiencies, the preparation of a series of stainless steel brush passivation pastes and research on paste-type brush passivation technology were carried out to solve problems such as solution brush flow and poor safety, and to provide technical support and safety guarantees for on-machine in-situ repair of stainless steel parts.

[0007] Existing brush passivation technologies include: strong oxidizing brush passivation solutions such as nitric acid and solution brush passivation processes. As follows:

[0008] 1. Existing brush-coated passivation solution

[0009] 25% to 35% nitric acid or commercially available Gardacid P4325 solution (supplier: CHEMETALL, 51 rue Pierre 92588 Clichy Cedex, the main component is 25% to 35% nitric acid).

[0010] 2. Existing brush passivation process

[0011] 2.1 Stainless steel brush passivation process: Isolation (on demand) - organic solvent degreasing - polishing - brush passivation - deionized water cleaning - drying - inspection

[0012] 2.2 Main process description:

[0013] Isolation: Isolate and protect non-painted surfaces as needed. Use lightweight protective tape and other materials to isolate and protect the areas around the painted areas and components around the parts to be painted.

[0014] Organic solvent degreasing: For the surface to be painted, use a pure cotton cloth dipped in ethanol, trichloroethane, acetone and other organic solvents to wipe and degrease. For the surface to be painted of the sprayed parts, grind along the painted area to remove the coating, and wash thoroughly with water to remove traces of paint stripper.

[0015] Grinding: This process is performed according to the surface condition of the part. Use sandpaper of No. 400 or above, industrial scouring pad, or pure cotton cloth dipped in abrasive to grind the area to be painted until the base material is exposed. Do not use silicone sandpaper.

[0016] After grinding, rinse the surface to be painted with deionized water for ≥2s. When painting on the machine, it is allowed to use clean absorbent cotton dipped in deionized water to wipe the painted surface of the parts.

[0017] Brush passivation: Use a brush to apply the passivation liquid on the entire surface, moisten the surface of the part, and do not allow the surface to dry completely or partially. Continue for 14-16 minutes to form a passivation film.

[0018] Deionized water cleaning: Use deionized water to clean the painted surface, and the washing time should be ≥2s. When painting on the machine, it is allowed to use clean absorbent cotton dipped in deionized water to wipe the painted surface of the parts.

[0019] Drying: After cleaning with deionized water, wipe dry with absorbent cotton within 5 minutes or blow dry with clean, dry compressed air. Wear clean cotton gloves to touch the passivated parts if necessary, and do not pick them up with bare hands.

[0020] The existing solution brush passivation process has the following problems:

[0021] 1) When repairing the passivation film on the surface of parts in situ on the machine, the brushing of the passivation solution is very likely to contaminate the surrounding parts, and the surrounding parts must be strictly protected;

[0022] 2) The solutions and ointments used in the operation cannot be quantified, and the amount used is controlled only by the operator's skills;

[0023] 3) There is no method or means to detect or judge the cleaning effect after degreasing and passivation. Summary of the invention

[0024] Purpose of the Invention

[0025] The invention aims to provide a paste for brushing passivation on the surface of stainless steel and a brushing passivation method thereof.

[0026] The patent of this invention replaces inorganic nitric acid with organic acids such as citric acid, which has the functions of degreasing and oil removal and effectively removing iron elements from the surface of stainless steel metal substrates, making the nickel and chromium on the surface of the metal substrate in an oxygen-rich environment, making the surface of the workpiece passive, thereby improving the corrosion resistance of the workpiece surface; utilizing its chelating agent performance to lay the foundation for the subsequent preparation of high-stability pastes.

[0027] A paste is prepared to solve the problem that the existing brush-applied passivation solution flows and easily contaminates or damages the paint layer, plating layer, chemical conversion layer and other protective layers of the parts around the parts to be repaired during on-machine repair. At the same time, needle-tube packaging and brush-applying tools are used to facilitate the operation during on-machine repair and the control of the amount of paste.

[0028] Technical Solution

[0029] The invention discloses a brush-coated passivation paste for in-situ repair of a helicopter surface. The passivation paste comprises the following mass percentages: 10%-20% citric acid, 3%-5% acrylic resin, 3%-10% cellulose inorganic thickener, 3%-5% magnesium nitrate, 0.5%-2% urotropine, 0.5%-2% leveling agent and bentonite, and the balance is deionized water.

[0030] Furthermore, the above materials are sequentially added into 30% of the deionized water required for preparation, and a uniformly mixed passivation paste is prepared by manual stirring and ultrasonic process.

[0031] Furthermore, the invention also includes a method for using the passivation paste: the injection-type injection packaging also functions as a brushing tool, the passivation paste is placed in the packaging tool, and according to the size of the area to be brushed, the extrusion head at one end is pressed to squeeze the passivation paste on the surface. One end of the injection packaging tool is a breathable felt, which directly contacts the surface to be brushed, and repeatedly wipes the surface to be brushed to achieve the purpose of passivation.

[0032] Furthermore, a degreasing paste is prepared. The degreasing paste comprises the following mass percentages: 3%-5% acrylic resin, 65%-75% water-based degreasing agent, 5%-13% cellulose inorganic thickener, 3%-5% magnesium nitrate, and 0.5%-2% leveling agent and bentonite.

[0033] Furthermore, the above materials are sequentially added into 30% of the deionized water required for preparation, and a uniformly mixed degreasing paste is prepared by manual stirring and ultrasonic process.

[0034] Furthermore, the invention also includes a method for using the degreasing paste: the injection-type injection packaging also functions as a brushing tool, the degreasing paste is placed in the packaging tool, and according to the size of the area to be brushed, the extrusion head at one end is pressed to squeeze the degreasing paste on the surface. One end of the injection packaging tool is a breathable felt, which directly contacts the surface to be brushed, and repeatedly wipes the surface to be brushed to achieve the purpose of degreasing.

[0035] Further, the brushing method includes the following:

[0036] 2.1 Brush passivation process:

[0037] Wiping - Isolation and protection - Degreasing - Wiping - Deionized water washing - pH value testing - Polishing - Deionized water washing - Brushing passivation - Deionized water rinsing - pH value testing - Drying - Inspection

[0038] 2.2 Process Description

[0039] 2.2.1 Wipe Use clean cotton cloth, absorbent cotton, etc. to wipe and initially remove pollutants on the surface of the workpiece.

[0040] 2.2.2 Isolation Protection Use isolation protection tape to stick on the non-painted area, press it tightly to make it fit the non-painted area fully, and remove the isolation after the brush passivation is completed.

[0041] 2.2.3 Degreasing, take out the injection needle-type packaging and brushing tool containing the degreasing paste from the portable brush passivation box, open the cover of the outlet, and the outlet is perpendicular to the surface to be brushed, so that the paste falls on the surface to be brushed in a dot shape, improve the precise dosage, and achieve precise control of the contact range between the paste and the surface to be brushed. Extrude at an angle of 30° or 45° to increase the contact area between the paste extruded from the needle and the surface to be brushed, and the area controllability is poor. Press the extrusion head at the other end to control the extrusion amount of the degreasing agent or degreasing paste, apply the degreasing paste to the surface to be brushed through the breathable felt, and directly use the brushing tool to brush the metal surface to be brushed back and forth, so that the degreasing paste and the surface to be brushed fully react to remove the oil stains on the surface to be brushed.

[0042] 2.2.4 Wipe Use clean cotton cloth or absorbent cotton to wipe off the degreasing paste on the surface of the workpiece to be painted. Then put it into the storage bag in the portable box and handle it centrally after the paint passivation construction is completed.

[0043] 2.2.5 Deionized water washing: Use deionized water to wash the surface to be painted, or wipe the surface to be painted with a clean cotton cloth or cotton wool dipped in deionized water. Then put it in the storage bag in the portable box and centrally handle it after the paint passivation construction is completed.

[0044] 2.2.6 pH value detection Use a wide range of pH test paper to detect the pH value on the surface of the test piece. If the pH value is 7, it is qualified. Otherwise, the deionized water washing process shall be repeated until the test is qualified.

[0045] 2.2.7 Grinding This process is carried out according to the surface condition of the workpiece. When there are residual paint marks, plating or other pollutants on the surface of the workpiece that cannot be removed by the previous process, or there are corrosion pits on the surface to be painted, take out the industrial scouring pad or sandpaper to grind the area to be painted. When grinding the inner wall of the hole, you can use an ear cleaning ball to blow out the grinding products in the hole and wipe it off with clean absorbent cotton or dust-free cloth.

[0046] 2.2.8 Deionized water washing: Use deionized water to wash the surface to be painted, or wipe the surface to be painted with a clean cotton cloth or cotton wool dipped in deionized water. Then put it in the storage bag in the portable box and centrally handle it after the paint passivation construction is completed.

[0047] 2.2.9 Brush passivation Take out the injection-type needle packaging and brush coating tool containing the passivation solution or passivation paste from the portable brush passivation box, open the cover of the outlet, touch the outlet vertically to the surface to be brushed, press the extrusion head at the other end to control the extrusion amount of the passivation paste, apply the passivation paste to the surface to be brushed through the breathable felt, and use the brush coating tool to brush the surface to be brushed back and forth to make the passivation paste fully react with the surface to be brushed, remove the surface to be brushed to expose the fresh substrate, oxidize its surface and naturally oxidize in oxygen-rich air to further generate a thin and dense mixture of nickel and chromium oxides, i.e., a passivation layer, thereby improving the corrosion resistance of the stainless steel surface.

[0048] 2.2.10 Deionized water washing: Use deionized water to wash the surface to be painted, or wipe the surface to be painted with clean cotton cloth or absorbent cotton dipped in deionized water. Then put it into the storage bag in the portable box and centrally handle it after the paint passivation construction is completed.

[0049] 2.2.11 pH value detection Use a wide range of pH test paper to detect the pH value on the surface of the test piece. If the pH value is 7, it is qualified. Otherwise, the deionized water washing process shall be repeated until the test is qualified.

[0050] 2.2.12 Drying: Use clean absorbent cotton or dust-free cloth to absorb any residual water on the painted surface, blow dry with clean compressed air or allow to dry naturally.

[0051] Furthermore, it also includes 2.2.13 inspection

[0052] (1) After the in-situ repair construction, the in-situ performance inspection requirements and methods are as follows:

[0053] a. Appearance inspection Visual inspection of the surface after brush passivation under natural scattered light should be the original color of the base metal, such as silver white, gray white or steel gray. It is allowed that the same part surface has different colors and glosses due to different material surface conditions. Excessive corrosion such as dust hanging on the surface of the test piece, exposed clean tissue and pits is not allowed.

[0054] b. Film integrity inspection

[0055] Use a rubber-tipped dropper to drop the following solution on the surface of the test piece after the paste-type brush passivation treatment for 1d-2d, wipe it clean after 5 minutes, and check whether there is red copper deposition product. No red copper deposition product appears, which is qualified.

[0056] (2) The technical indicators and tests that can be achieved on the stainless steel surface after passivation by brushing with passivation paste can be tested by selecting test pieces or parts separately.

[0057] The beneficial effects of this application are:

[0058] The brush-coated passivation solution flows and easily contaminates the non-brush-coated area during on-board repair; the corrosion resistance of the existing passivation solution after brush coating cannot meet the requirements of helicopter service conditions in the marine environment; the presence of acetone, alcohol, etc. in the process of process construction poses risks such as flammability; and there is a lack of simple and easy-to-operate detection methods and means in the process control of the process construction. The above problems are solved through the research on stainless steel brush-coated passivation paste and brush-coated passivation process. The advantages of the present invention are:

[0059] 1. The present invention provides a method for preparing a degreasing paste and a passivation paste for brush passivation. Organic acid is used to replace inorganic acid to prepare the brush passivation paste, and the degreasing paste is prepared at the same time, and the state and performance of the two pastes are stable.

[0060] The preparation of brush-on passivation paste and degreasing paste solves the problem of existing brush-on passivation solution flowing and contaminating surrounding parts during in-situ repair on a helicopter; the degreasing paste prepared at the same time can solve the problems of flowing, contamination, flammability, etc. that are easy to occur when degreasing with organic solvents such as acetone and alcohol. Degreasing paste and passivation paste can improve the safety of operation and are not easy to cause personal injury to the operator.

[0061] 2. The paste passivation method proposed in the present invention is suitable for the surface treatment of various types of martensitic and austenitic stainless steels. The corrosion resistance of the treated surface is greatly improved compared with the solution passivation corrosion resistance, which can meet the requirements of helicopter environmental tests and provide protection for helicopters to serve in harsh environments such as the ocean.

[0062] 3. The present invention specifically provides a paste-type brush passivation method, including specific process flow, process parameters, and brush quality detection means. The operator can complete the operation according to the steps and parameters, and the operator's skills are not required to be high. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical scheme and advantages of the implementation of the present invention clearer, the technical scheme in the embodiment of the present invention will be described in more detail in combination with the embodiment of the present invention. In the example, the same or similar reference numerals throughout represent the same or similar originals or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, not all of them. The embodiments described below by reference are exemplary and intended to be used to explain the present invention, and should not be construed as limitations on the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present invention. The following is a detailed description in combination with the embodiments of the present invention.

[0064] 1. Preparation of brush-coated passivation paste

[0065] Conduct research on the synthesis technology of a series of ointments that are environmentally friendly, pollution-free, and safe to operate, and form a series of preparation technologies for stainless steel brush-coated passivation ointments, including degreasing ointment (KT-106Y) and passivation ointment (KT-106D). The main component of the existing stainless steel brush-coated passivation solution is dilute nitric acid, and the pre-treatment of brushing uses solvent degreasing, nitric acid-hydrofluoric acid deoxidation, industrial scouring pad polishing and other methods. This project will optimize and improve the existing stainless steel brush-coated passivation solution and solvent degreasing method, and formulate a series of synthetic ointments based on low polymers and gel-like carriers without changing the properties of the liquid. The main components are composed of water-based cleaning agents / organic acids, sustained-release agents, thickeners, etc. in a certain proportion. The performance of brush-coated passivation ointments is studied. In the research, adjustments, optimizations and verifications will be made on this basis to obtain the best synthesis technology.

[0066] The specific proportion of the passivation paste (mass percentage): 10%-20% citric acid, 3%-5% acrylic resin, 3%-10% cellulose inorganic thickener, 3%-5% magnesium nitrate, 0.5%-2% urotropine, 0.5%-2% leveling agent, bentonite, and the balance is deionized water. The above materials are sequentially added to the 30% amount of deionized water required for preparation, and a uniformly mixed passivation paste is prepared by manual stirring and ultrasonic process.

[0067] With reference to the preparation technology of passivation paste, a degreasing paste was prepared. The degreasing paste ratio (mass percentage): acrylic resin 3%-5%, water-based degreasing agent 65%-75%, cellulose inorganic thickener 5%-13%, magnesium nitrate 3%-5%, leveling agent, bentonite 0.5%-2%. The above materials were sequentially added to the 30% amount of deionized water required for the preparation, and the degreasing paste was prepared by manual stirring and ultrasonic process to mix well.

[0068] The performance indicators of the passivation paste and degreasing paste are shown in Table 1 below. There is no decomposition when stored at 5℃-38℃ for 180 days.

[0069] Table 1 Performance indexes of passivation paste and degreasing paste

[0070]

[0071] Packaging and use of degreasing paste and passivation paste: The injection-type injection packaging also has the function of a brushing tool. The degreasing paste and pickling paste are placed in the packaging tool respectively. According to the size of the area to be brushed, press the extrusion head at one end to squeeze the paste on the surface. One end of the injection packaging tool is a breathable felt, which directly contacts the surface to be brushed and repeatedly wipes the surface to be brushed to achieve the purpose of degreasing or passivation.

[0072] 2. Paste brush passivation method

[0073] 2.1 Brush passivation process:

[0074] Wiping - Isolation and protection (as needed) - Degreasing - Wiping - Deionized water washing - pH value testing - Polishing (as needed) - Deionized water washing - Brushing passivation - Deionized water rinsing - pH value testing - Drying - Inspection

[0075] 2.2 Process Description

[0076] 2.2.1 Wipe Use clean cotton cloth, absorbent cotton, etc. to wipe and initially remove pollutants on the surface of the workpiece.

[0077] 2.2.2 Isolation Protection Use isolation protection tape to bond to the non-brushing area, press it tightly to make it fit fully with the non-brushing area to prevent the paste or deionized water from penetrating into the non-brushing surface during the brushing process, causing pollution or causing adverse damage. Remove the isolation after the brushing passivation is completed.

[0078] 2.2.3 Degreasing Take out the injection needle-type packaging and brushing tool containing the degreasing paste from the portable brush passivation box (in order to improve the controllability of the amount of paste, reduce and avoid the risk of contamination to other areas, facilitate carrying, and avoid the operator getting it on his hands, this packaging method is adopted, and the brush head is breathable felt, which has the function of brushing, and direct brushing does not require an additional brush), open the cover of the outlet, and the outlet is perpendicular to the surface to be brushed (so that the paste falls on the surface to be brushed in dots, improves the precise amount, and realizes the precise control of the contact range between the paste and the surface to be brushed. If Extrude at an angle of 30° or 45° to increase the contact area between the paste squeezed out of the needle and the surface to be painted, and the area controllability is poor), press the extrusion head at the other end to control the extrusion amount of the degreasing agent or degreasing paste, and apply the degreasing paste to the surface to be painted through the breathable felt (① the degreasing paste penetrates from the breathable felt and directly acts on the surface to be painted; ② the breathable felt is soft and does not damage the stainless steel substrate to be painted), and use the brush tool to reciprocately brush the metal surface to be painted, so that the degreasing paste and the surface to be painted fully react to remove the oil stains on the surface to be painted.

[0079] 2.2.4 Wipe Use clean cotton cloth or absorbent cotton to wipe off the degreasing paste on the surface of the workpiece to be painted. Then put it into the storage bag in the portable box and handle it centrally after the paint passivation construction is completed.

[0080] 2.2.5 Deionized water washing Use deionized water to rinse the surface to be painted, or wipe the surface to be painted with a clean pure cotton cloth or cotton wool dipped in deionized water. Then put it in the storage bag in the portable box and centrally handle it after the brush passivation construction is completed. (① The purpose of deionized water washing is to clean and remove the degreasing paste on the surface to be painted. The degreasing paste is alkaline (pH value is 10). If there is residue on the surface to be painted, it will react with the passivation paste (pH value is 2) when the passivation paste is applied, reducing the performance of the passivation paste, thereby affecting the passivation quality. ② Centralized treatment of used pure cotton cloth and cotton wool can avoid being left in the helicopter as redundant items on board, causing adverse effects on the mechanical and transmission parts of the helicopter during flight. ③ The quality of deionized water meets the requirements of HB5472. Since deionized water does not contain metal elements such as Ca, Mg, and Cl, it can avoid secondary pollution of the surface to be painted, thereby affecting the subsequent brush passivation effect. Therefore, deionized water washing is used.)

[0081] 2.2.6 pH value detection Use a wide range of pH test paper to detect the pH value of the test piece surface. The test result is qualified when the pH value is 7. Otherwise, the deionized water washing process is repeated until the test is qualified. (The purpose is to detect the cleaning quality of 2.2.4. The degreasing paste is alkaline (pH value is 10). After cleaning, the surface to be painted is neutral, that is, the pH value is 7. This method is simple to operate and easy to observe. At the same time, pH test paper is easy to obtain and carry. This method is highly operational.)

[0082] 2.2.7 Grinding This process is carried out according to the surface condition of the workpiece. When there are residual paint marks, plating or other contaminants on the workpiece surface that cannot be removed by the previous process, or there are corrosion pits on the surface to be painted, take out the industrial scouring pad or sandpaper to grind the area to be painted. When grinding the inner wall of the hole, you can use an ear bulb to blow out the grinding products in the hole, and wipe them off with a clean cotton wool or dust-free cloth. (The purpose of this process is to obtain a complete and smooth passivation film and lay the foundation for meeting the repair quality index requirements. The specific functions of grinding are: ① Thoroughly clean the residual paint marks on the surface of the workpiece and other contaminants that cannot be removed by the previous process; ② For the surface to be painted with corrosion pits on the surface, the grinding process can also be used to level the surface to achieve a smooth transition; ③ The burrs on the surface to be painted can be removed by grinding, etc.)

[0083] 2.2.8 Deionized water washing: Use deionized water to rinse the surface to be painted, or wipe the surface to be painted with a clean cotton cloth or cotton wool dipped in deionized water. Then put it in the storage bag in the portable box and centrally process it after the brush passivation construction is completed (① Clean and remove the polishing residue to prevent the residue of paint, plating or other pollutants from isolating the chemical reaction between the passivation paste and the surface to be painted during the brush passivation, affecting the integrity of the generated passivation film layer; ② Centralized processing of used cotton cloth and cotton wool can avoid being left in the helicopter as redundant items on board, causing adverse effects on the mechanical and transmission parts of the helicopter during flight. ③ The quality of deionized water meets the requirements of HB 5472. Since deionized water does not contain metal elements such as Ca, Mg, and Cl, it can avoid secondary pollution of the surface to be painted, thereby affecting the subsequent brush passivation effect. Therefore, deionized water washing is used.)

[0084] 2.2.9 Brush passivation Take out the injection-type needle packaging and brush coating tool containing the passivation solution or passivation paste from the portable brush passivation box, open the cover of the outlet, touch the outlet vertically to the surface to be brushed, press the extrusion head at the other end to control the extrusion amount of the passivation paste, apply the passivation paste to the surface to be brushed through the breathable felt, and use the brush coating tool to brush the surface to be brushed back and forth to make the passivation paste fully react with the surface to be brushed, remove the surface to be brushed to expose the fresh substrate, oxidize its surface and naturally oxidize in oxygen-rich air to further generate a thin and dense mixture of nickel and chromium oxides, i.e., a passivation layer, thereby improving the corrosion resistance of the stainless steel surface.

[0085] 2.2.10 Deionized water washing: Use deionized water to rinse the surface to be painted, or wipe the surface to be painted with a clean pure cotton cloth or cotton wool dipped in deionized water. Then put it in the storage bag in the portable box and centrally handle it after the brush passivation construction is completed. (① Remove the passivation paste remaining on the brushed surface by washing with deionized water. The passivation paste has an acidic pH value of 2. Long-term presence will further corrode the part and the surrounding area; ② Centralized treatment of used pure cotton cloth and cotton wool can avoid being left in the helicopter as redundant items on board, causing adverse effects on the mechanical and transmission parts of the helicopter during flight. ③ The quality of deionized water meets the requirements of HB 5472. Since deionized water does not contain metal elements such as Ca, Mg, and Cl, it can avoid secondary pollution of the surface to be painted, which in turn affects the subsequent brush passivation effect. Therefore, deionized water washing is used.)

[0086] 2.2.11 pH value detection Use a wide range of pH test paper to detect the pH value on the surface of the test piece. If the pH value is 7, it is qualified. Otherwise, the deionized water washing process shall be repeated until the test is qualified.

[0087] 2.2.12 Drying: Use clean absorbent cotton or dust-free cloth to absorb any residual water on the painted surface, blow dry with clean compressed air or allow to dry naturally.

[0088] 2.2.13 Inspection

[0089] (1) After the in-situ repair construction, the in-situ performance inspection requirements and methods are as follows:

[0090] a. Appearance inspection Visual inspection under natural scattered light (if necessary, use a 3-5 times magnifying glass to inspect). The surface after brush passivation should be the original color of the base metal, such as silver white, gray white or steel gray. It is allowed that the same part surface has different colors and glosses due to different material surface conditions. Excessive corrosion such as dust hanging on the surface of the test piece, exposed clean tissue and pits is not allowed.

[0091] b. Film integrity inspection

[0092] Use a rubber-tipped dropper to drop the following solution on the surface of the test piece after the paste-type brush passivation treatment for 1d-2d, wipe it clean after 5 minutes, and check whether there is red copper deposition product. No red copper deposition product appears, which is qualified.

[0093] Take the preparation of 1L of test solution as an example:

[0094] Copper sulfate (CuSO4.5H2O) chemically pure 8 grams

[0095] 2 ml of chemically pure sulfuric acid (H2SO4 specific gravity 1.84)

[0096] Deionized water balance

[0097] (2) The technical indicators and test methods that can be achieved on the stainless steel surface after passivation by brushing with passivation paste are shown in Table 1 below. Test pieces or parts can be selected for inspection separately.

[0098] Table 1 Performance indicators and test methods

[0099]

[0100]

[0101]

[0102] Embodiment 1:

[0103] Passivation paste ratio: 10% acrylic resin, 30% citric acid aqueous solution, 15% cellulose inorganic thickener, 10% magnesium nitrate, 5% urotropine, 1% leveling agent and bentonite, and the balance deionized water.

[0104] After preparation, the viscosity was measured by a rotational viscometer to be 1200 mPa.s, which meets the viscosity requirement of the passivation paste.

[0105] Three days later, the viscosity was measured by a rotational viscometer to be 1000 mPa.s.

[0106] Six days later, the viscosity was measured by a rotational viscometer to be 700 mPa.s.

[0107] Ten days later, the viscosity measured by the rotary viscometer was 200 mPa.s, which no longer met the viscosity requirements of the passivation paste. Conclusion: The failure reason is that sodium carboxymethyl cellulose, as an organic thickener, undergoes a degradation process in 30% citric acid, which reduces the viscosity of the system and eventually causes the passivation paste to fail. The ratio of citric acid is greater than that of the present invention, and the preparation of the passivation paste fails.

[0108] Embodiment 2:

[0109] The passivation paste ratio is: 5% acrylic resin, 75% 35% nitric acid solution, 15% cellulose and inorganic thickener, 3% magnesium nitrate, 1% hexamethylenetetramine, 1% leveling agent and bentonite, and the balance is deionized water.

[0110] After preparation, the viscosity was measured by a rotational viscometer to be 1500 mPa.s, which met the viscosity requirements of the passivation paste;

[0111] Three days later, the viscosity was measured by a rotational viscometer to be 1300 mPa.s;

[0112] After six days, the viscosity was measured by a rotational viscometer to be 1000 mPa.s;

[0113] Ten days later, the viscosity was measured by a rotational viscometer to be 800 mPa.s;

[0114] Twenty days later, the viscosity was measured by a rotational viscometer to be 500 mPa.s;

[0115] Forty days later, the viscosity measured by the rotational viscometer was 200 mPa.s, which no longer met the viscosity requirement of the passivation paste.

[0116] Conclusion: The failure reason is that the cellulose organic thickener degrades in the nitric acid system, which reduces the viscosity of the system and eventually causes the passivation paste to fail. The experiment also shows that the addition of organic acid and inorganic thickener reduces the degradation rate of the organic thickener, which effectively extends the service life of the passivation paste. Compared with the method proposed in the present invention using citric acid as the main acid, the passivation paste prepared using nitric acid as the main acid has poor performance stability.

[0117] Embodiment 3:

[0118] The passivation paste ratio is: 5% acrylic resin, 20% organic acid aqueous solution, 20% cellulose inorganic thickener, 10% magnesium nitrate, 3% urotropine, 2% leveling agent and bentonite, and the balance is water.

[0119] After preparation, the viscosity was measured by a rotational viscometer to be 1700 mPa.s, which met the viscosity requirements of the passivation paste;

[0120] Three days later, the viscosity was measured by a rotational viscometer to be 1500 mPa.s;

[0121] After six days, the viscosity was measured by a rotational viscometer to be 1400 mPa.s;

[0122] Ten days later, the viscosity was 1200 mPa.s as measured by a rotational viscometer;

[0123] Twenty days later, the viscosity was measured by a rotational viscometer to be 1000 mPa.s;

[0124] After forty days, the viscosity was measured by a rotational viscometer to be 900 mPa.s;

[0125] After sixty days, the viscosity was measured by a rotational viscometer to be 800 mPa.s;

[0126] After one hundred days, the viscosity was measured by a rotational viscometer to be 600 mPa.s;

[0127] After one hundred and fifty days, the viscosity was measured by a rotational viscometer to be 500 mPa.s, indicating no failure.

[0128] Conclusion: The combination of cellulose organic thickener and inorganic thickener can effectively reduce the degradation process in a certain organic acid aqueous solution system, so that the effective use time of the passivation paste prepared in a certain organic acid aqueous solution is greatly extended. For this reason, the paste preparation ratio proposed in the present invention is the best.

[0129] It is understood by those skilled in the art that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of ordinary technicians in the field to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and unless defined as here, will not be interpreted with idealized or overly formal meanings. The specific implementation methods described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Within the spirit and principle of the present invention, any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment of equivalent changes for application in other fields, but any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution content of the present invention, any modification, equivalent replacement, improvement, etc., made according to the technical essence of the present invention, should be included in the protection scope of the present invention.

Claims

1. A brush-on passivation paste for in-situ repair of helicopter surfaces, characterized in that: The passivation paste has the following mass percentages: citric acid 10%-20%, acrylic resin 3%-5%, cellulose inorganic thickener 3%-10%, magnesium nitrate 3%-5%, hexamethylenetetramine 0.5%-2%, leveling agent, bentonite 0.5%-2%, and the balance is deionized water.

2. The passivation paste according to claim 1, characterized in that The above materials are sequentially added into 30% of the deionized water required for preparation, and a uniformly mixed passivation paste is prepared by manual stirring and ultrasonic process.

3. The passivation paste according to claim 2, characterized in that: It also includes the use of passivation paste: the injection-type needle packaging also has the function of a brushing tool. The passivation paste is placed in the packaging tool, and according to the size of the area to be brushed, the extrusion head at one end is pressed to squeeze the passivation paste onto the surface; one end of the injection packaging tool is a breathable felt, which directly contacts the surface to be brushed, and repeatedly wipes the surface to be brushed to achieve the purpose of passivation.

4. A brush-on degreasing paste for in-situ repair of helicopter surfaces, characterized in that: The mass percentage of the degreasing paste is as follows: acrylic resin 3%-5%, water-based degreasing agent 65%-75%, cellulose inorganic thickener 5%-13%, magnesium nitrate 3%-5%, leveling agent, bentonite 0.5%-2%.

5. The degreasing paste according to claim 4, characterized in that: The above materials are sequentially added into 30% of the deionized water required for preparation, and a uniformly mixed degreasing paste is prepared by manual stirring and ultrasonic process.

6. The degreasing paste according to claim 5, characterized in that: It also includes the use of degreasing paste: the injectable injection packaging also has the function of a brushing tool. The degreasing paste is placed in the packaging tool, and according to the size of the area to be brushed, the extrusion head at one end is pressed to squeeze the degreasing paste onto the surface; one end of the injection packaging tool is a breathable felt, which directly contacts the surface to be brushed, and repeatedly wipes the surface to be brushed to achieve the purpose of degreasing.

7. A brush coating method of the passivation paste as claimed in claim 3, characterized in that: The steps include: 2.1 Brush passivation process: Wiping - Isolation and protection - Degreasing - Wiping - Deionized water washing - pH value testing - Polishing - Deionized water washing - Brushing passivation - Deionized water rinsing - pH value testing - Drying - Inspection 2.2 Process Description 2.2.1 Wipe Use clean cotton cloth or absorbent cotton to wipe and remove pollutants on the surface of the workpiece; 2.2.2 Isolation protection Use isolation protection tape to stick to the non-painted area, press it tightly to make it fit the non-painted area fully, and remove the isolation after the brush passivation is completed; 2.2.3 Degreasing, take out the injection needle-type packaging and brushing tool containing the degreasing paste from the portable brush passivation box, open the cover of the outlet, and the outlet is perpendicular to the surface to be brushed, so that the paste falls on the surface to be brushed in a dot shape, improve the precise dosage, and realize the precise control of the contact range between the paste and the surface to be brushed; extrude at an angle of 30° or 45° to increase the contact area between the paste extruded from the needle tube and the surface to be brushed, and the area controllability is poor, press the extrusion head at the other end, control the extrusion amount of the degreasing agent or degreasing paste, apply the degreasing paste to the surface to be brushed through the breathable felt, and directly use the brushing tool to brush the metal surface to be brushed back and forth, so that the degreasing paste and the surface to be brushed fully react to remove the oil stains on the surface to be brushed; 2.2.4 Wipe with clean cotton cloth or absorbent cotton to remove the degreasing paste on the surface of the workpiece to be painted; then put it into the storage bag in the portable box and handle it centrally after the paint passivation construction is completed; 2.2.5 Deionized water washing: Use deionized water to rinse the surface to be painted, or wipe the surface to be painted with a clean cotton cloth or absorbent cotton dipped in deionized water; then put it into the storage bag in the portable box and centrally handle it after the paint passivation construction is completed; 2.2.6 pH value detection Use a wide range of pH test paper to detect the pH value on the surface of the test piece. If the pH value is 7, it is qualified. Otherwise, the deionized water washing process is repeated until the test is qualified. 2.2.7 Grinding This process is carried out according to the surface condition of the workpiece. When there are residual paint marks, plating or other pollutants on the surface of the workpiece that cannot be removed by the previous process, or there are corrosion pits on the surface to be painted, take out the industrial scouring pad or sandpaper to grind the area to be painted; when grinding the inner wall of the hole, you can use an ear cleaning bulb to blow out the grinding products in the hole, and wipe it off with clean absorbent cotton or dust-free cloth; 2.2.8 Deionized water washing: Use deionized water to rinse the surface to be painted, or wipe the surface to be painted with a clean cotton cloth or cotton wool dipped in deionized water; then put it into the storage bag in the portable box and centrally handle it after the paint passivation construction is completed. 2.2.9 Brushing passivation Take out the injection-type injection packaging and brushing tool containing the passivation solution or passivation paste from the portable brushing passivation box, open the cover of the outlet, vertically touch the outlet to the surface to be brushed, press the extrusion head at the other end to control the extrusion amount of the passivation paste, apply the passivation paste to the surface to be brushed through the breathable felt, and use the brushing tool to brush the surface to be brushed back and forth to make the passivation paste fully react with the surface to be brushed, remove the surface to be brushed to expose the fresh substrate, oxidize its surface and oxidize naturally in oxygen-rich air to further generate a thin and dense mixture of nickel and chromium oxides, i.e., a passivation layer, to improve the corrosion resistance of the stainless steel surface; 2.2.10 Deionized water washing: Use deionized water to rinse the surface to be painted, or wipe the surface to be painted with a clean cotton cloth or absorbent cotton dipped in deionized water; then put it into the storage bag in the portable box and centrally handle it after the paint passivation construction is completed; 2.2.11 pH value detection Use a wide range of pH test paper to detect the pH value on the surface of the test piece. If the pH value is 7, it is qualified. Otherwise, the deionized water washing process is repeated until the test is qualified. 2.2.12 Drying: Use clean absorbent cotton or dust-free cloth to absorb any residual water on the painted surface, blow dry with clean compressed air or allow to dry naturally.

8. The brush coating method according to claim 7, characterized in that: Also includes 2.2.13 inspection (1) After the in-situ repair construction, the in-situ performance inspection requirements and methods are as follows: a. Appearance inspection Visual inspection of the surface after brush passivation under natural scattered light should be the original color of the base metal, such as silver white, gray white or steel gray; different colors and glosses are allowed on the surface of the same part due to different surface conditions of the material; dust hanging on the surface of the test piece, exposed clean tissue and pitting and excessive corrosion are not allowed; b. Film integrity inspection Use a rubber-tipped dropper to drop the following solution on the surface of the test piece after the paste-type brush passivation treatment for 1d-2d, wipe it clean after 5min, and check whether there is red copper deposition product there; if there is no red copper deposition product, it is qualified; (2) The technical indicators and tests that can be achieved on the stainless steel surface after passivation by brushing with passivation paste can be tested by selecting test pieces or parts separately.

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