An acid pickling solution and its use in silane etching surface treatment
Patent Information
- Application Number
- CN202610853085.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-12
- Publication Date
- 2026-09-22
AI Technical Summary
然而，该技术在本领域大规模、立体化的工厂装置区应用场景中具有明显局限性：其一，手工操作效率低下，难以适应大面积、结构复杂的现场施工需求，导致作业速度缓慢；其二，膏体中通常需添加增稠剂等辅助成分，成本较高且有效利用率低，经济性较差；其三，现场涂抹厚度不易均匀控制，易造成局部除锈不彻底或对金属基体造成过度腐蚀，影响后续防护涂层的附着效果与长期防护性能
[0020]本发明的酸洗液，按照质量百分含量包括氢氟酸3%-10%、硝酸10%-20%、余量为水。通过利用HF对SiO2的特效溶解性，从根本上瓦解了硅烷腐蚀层。且引入HNO3的钝化功能，在清洗的同时主动构建保护层，变被动清洗为主动防护。并采用喷涂替代手工涂抹，实现了对大尺寸、复杂结构设备的高效、快速、均匀处理，且液体配方成本低于膏体。另外，通过精确控制pH值和反应时间，实现了对腐蚀产物的选择性去除，而最大限度地保护了金属基底。从而实现高效除锈、主动防锈、施工便捷高效、经济性好、基底友好的技术效果。
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Abstract
Description
Technical Field
[0001] This application relates to the field of industrial cleaning and metal surface treatment, and in particular to an acid pickling solution and its application in silane corrosion surface treatment. Background Technology
[0002] In polysilicon production, silane gas is widely used as a key reactant in chemical vapor deposition (CVD) processes. However, silane gas is prone to hydrolysis or oxidation under high temperature and pressure, generating corrosion products such as silicon dioxide and metal oxides. These corrosion products adhere to metal surfaces such as equipment, pipes, and insulation layers, forming a dense and difficult-to-remove stubborn layer. This leads to problems such as reduced heat transfer efficiency, pipe blockage, and weakened structural strength, seriously threatening production safety and equipment lifespan.
[0003] Currently, the cleaning of these stubborn corrosion products mainly relies on two techniques: high-pressure water jet rinsing and manual application of acid pickling paste. While high-pressure water jet rinsing, as a conventional physical cleaning method, can remove surface rust, its rinsing force is limited and it's difficult to completely remove firmly attached rust substrates. Residual corrosion can easily cause rapid rust re-emergence on the equipment surface, failing to achieve a fundamentally clean substrate treatment. On the other hand, manual application of acidic paste is a common chemical method for metal rust removal. However, this technology has significant limitations in large-scale, three-dimensional factory plant applications: firstly, manual operation is inefficient and difficult to adapt to the needs of large-area, complex on-site construction, resulting in slow operation speed; secondly, the paste usually requires the addition of thickeners and other auxiliary ingredients, leading to high costs and low utilization rates, resulting in poor economic efficiency; thirdly, the on-site application thickness is difficult to control evenly, easily causing incomplete rust removal in some areas or excessive corrosion of the metal substrate, affecting the adhesion and long-term protective performance of subsequent protective coatings.
[0004] Therefore, existing rust removal technologies have systemic shortcomings when dealing with stubborn corrosion layers mainly composed of silica formed by silane corrosion: they not only struggle to completely remove this type of corrosion product, but also easily induce rust re-rusting of the base metal after cleaning, lacking long-term protection; simultaneously, their cleaning efficiency is low and their economic efficiency is poor, making them unsuitable for the rapid, large-area on-site treatment needs of large industrial installations; furthermore, their reliance on manual operation leads to high labor intensity and uneven treatment results, failing to meet the requirements of efficient, uniform, and reliable surface pretreatment in modern industry. Therefore, it is essential to develop a pickling solution that is highly efficient in rust removal, actively prevents rust, is convenient and efficient to apply, economical, and substrate-friendly. Summary of the Invention
[0005] This invention provides a pickling solution that achieves the technical effects of efficient rust removal, active rust prevention, convenient and efficient construction, good economy, and substrate-friendly properties.
[0006] This invention provides a method for treating silane-corroded surfaces, achieving the technical effects of efficient rust removal, active rust prevention, convenient and efficient construction, good economy, and substrate-friendly properties.
[0007] In a first aspect, the present invention provides a pickling solution comprising, by mass percentage, 3%-10% hydrofluoric acid, 10%-20% nitric acid, and the balance being water, wherein the pH value of the pickling solution is 0.5-2.
[0008] In one possible embodiment, the pickling solution described above further includes 0.1%-2% surfactant by mass percentage.
[0009] In one possible embodiment, such as the pickling solution described above, the surfactant includes at least one of perfluoroalkyl sulfonates and perfluoroalkyl carboxylates.
[0010] Secondly, the present invention provides a method for treating a silane-etched surface, comprising the following steps:
[0011] Step 1): Apply the pickling solution according to any one of claims 1-3 to the surface to be treated;
[0012] Step 2): Let the reaction stand for 5-40 minutes;
[0013] Step 3): Rinse the surface with water.
[0014] In one possible embodiment, as described above, the pickling solution is applied to the surface to be treated by spraying.
[0015] In one possible embodiment, as described above, the settling time is preferably 25-35 minutes.
[0016] In one possible embodiment, as described above, the rinsing process includes: using a water gun with a pressure of 0.5-1.5 MPa to perform high-pressure rinsing on the surface to be treated.
[0017] In one possible embodiment, as described above, after the rinsing process, the surface to be treated is neutralized with an alkaline solution of pH 8-9.
[0018] In one possible embodiment, as described above, after the neutralization treatment, the surface to be treated is subjected to ultraviolet irradiation.
[0019] In one possible embodiment, as described above, after the rinsing process, the method further includes adding lime slurry to the waste liquid after the rinsing process for neutralization and precipitation.
[0020] The pickling solution of this invention comprises, by mass percentage, 3%-10% hydrofluoric acid, 10%-20% nitric acid, and the balance being water. By utilizing the specific solubility of HF in SiO2, the silane corrosion layer is fundamentally broken down. Furthermore, the passivation function of HNO3 is introduced, actively building a protective layer during cleaning, transforming passive cleaning into active protection. Spraying replaces manual application, achieving efficient, rapid, and uniform treatment of large-sized, complex-structured equipment, with a liquid formulation cost lower than paste. In addition, by precisely controlling the pH value and reaction time, selective removal of corrosion products is achieved, maximizing the protection of the metal substrate. Thus, it achieves the technical effects of efficient rust removal, active rust prevention, convenient and efficient construction, good economy, and substrate-friendly properties. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0022] In polysilicon production, silane gas is widely used as a key reactant in chemical vapor deposition (CVD) processes. However, silane gas is prone to hydrolysis or oxidation under high temperature and pressure, generating corrosion products such as silicon dioxide and metal oxides. These corrosion products adhere to metal surfaces such as equipment, pipes, and insulation layers, forming a dense and difficult-to-remove stubborn layer. This leads to problems such as reduced heat transfer efficiency, pipe blockage, and weakened structural strength, seriously threatening production safety and equipment lifespan.
[0023] Existing rust removal technologies have systemic shortcomings when dealing with stubborn corrosion layers mainly composed of silica formed by silane corrosion: they are not only difficult to completely remove this type of corrosion product, but also easily cause the base metal to rust again after cleaning, lacking long-term protection; at the same time, their cleaning efficiency is low and their economy is poor, making them unsuitable for the rapid and large-area on-site treatment needs of large industrial plants; in addition, the reliance on manual operation leads to high labor intensity and uneven treatment results, making it difficult to meet the requirements of efficient, uniform and reliable surface pretreatment in modern industry.
[0024] The pickling solution of this invention comprises, by mass percentage, 3%-10% hydrofluoric acid, 10%-20% nitric acid, and the balance being water. By utilizing the specific solubility of HF in SiO2, the silane corrosion layer is fundamentally broken down. Furthermore, the passivation function of HNO3 is introduced, actively building a protective layer during cleaning, transforming passive cleaning into active protection. Spraying replaces manual application, achieving efficient, rapid, and uniform treatment of large-sized, complex-structured equipment, with a liquid formulation cost lower than paste. In addition, by precisely controlling the pH value and reaction time, selective removal of corrosion products is achieved, maximizing the protection of the metal substrate. Thus, it achieves the technical effects of efficient rust removal, active rust prevention, convenient and efficient construction, good economy, and substrate-friendly properties.
[0025] In a first aspect, the present invention provides a pickling solution comprising, by mass percentage, 3%-10% hydrofluoric acid, 10%-20% nitric acid, and the balance being water, and the pH value of the pickling solution is 0.5-2.
[0026] Hydrofluoric acid (HF) selectively etches the Si-O bonds on the surface of silicon-containing materials. HF reacts with silicon dioxide or the silicon-oxygen network to form soluble hexafluorosilicates, thereby removing the surface oxide or silane layer. Controlling the HF concentration within the range of 3%-10% ensures sufficient etching power for effective surface dissolution and structural reconstruction, while avoiding over-etching due to excessive concentration. This concentration range also strikes a balance between reaction rate and controllability, resulting in a gentler and more uniform etching process. This setup allows for controlled removal and micro-coarsening of silane-etched surfaces, improving the uniformity of subsequent processing and reducing defect formation.
[0027] Nitric acid can oxidize low-valence silicon on silicon surfaces or in silane layers, transforming it into an oxidized state structure that is more easily dissolved by hydrofluoric acid, thus forming a synergistic oxidation-dissolution mechanism. Nitric acid can also inhibit localized reduction reactions, preventing the formation of uneven corrosion zones on the surface. Controlling the nitric acid concentration between 10% and 20% ensures stable oxidation capacity while avoiding surface passivation or runaway reactions caused by excessive oxidation. Within this range, a dynamic equilibrium is formed between nitric acid and hydrofluoric acid, allowing the surface to continuously undergo alternating processes of slight oxidation and dissolution, resulting in a more uniform treated surface.
[0028] Water, used as a surplus, dilutes hydrofluoric acid and nitric acid, thereby regulating the overall reaction rate and preventing the strong acid system from severely attacking the surface. An appropriate water content promotes the uniform distribution of reactants at the interface. It also facilitates the dissolution and diffusion of reaction products, allowing the formed silicon-fluorine complexes to leave the surface promptly, reducing secondary deposition or localized enrichment.
[0029] Within a pH range of 0.5-2, the H in the system +A higher concentration promotes the oxidation of nitric acid and the dissociation of hydrofluoric acid, thereby enhancing overall reactivity. Simultaneously, this pH range ensures that fluoride ions possess reactivity without causing uncontrolled corrosion due to excessive dissociation. If the pH is too low, the reaction becomes overly vigorous, easily leading to localized over-corrosion; if the pH is too high, the corrosive ability is insufficient, affecting the treatment effect.
[0030] This invention constructs a highly controllable pickling system by synergistically designing the proportions of hydrofluoric acid, nitric acid, and water, and precisely controlling the system's pH. Hydrofluoric acid provides the dissolution ability of the silicon-oxygen structure, while nitric acid provides oxidation; together, they form a dynamic oxidation-dissolution cycle mechanism, thereby achieving continuous and uniform treatment of silane-corroded surfaces. Water, as a solvent, not only regulates the reaction rate but also improves mass transfer conditions, making the reaction process more stable. Simultaneously, by controlling the pH within the range of 0.5-2, the system maintains sufficient reactivity while avoiding excessive corrosion, thus achieving a balance between efficiency and quality. Overall, this pickling solution achieves controllable corrosion and cleaning of silane surfaces through the synergistic effect of its multiple components.
[0031] In one possible embodiment, the pickling solution described above further includes 0.1%-2% surfactant by weight percentage.
[0032] In this embodiment, because surfactant molecules possess both hydrophilic and hydrophobic groups, they can oriented at the liquid-solid interface, significantly reducing the surface tension of the pickling solution. This makes it easier for the solution to spread on the silane-corroded surface, reducing uneven liquid film thickness and ensuring uniform distribution of the acid solution in microstructures, pores, or rough areas. Furthermore, surfactants can promote the desorption and diffusion of products during the reaction process, reducing the retention of reaction products on the surface, thereby minimizing secondary deposition or localized corrosion inhibition.
[0033] In one possible embodiment, such as the pickling solution described above, the surfactant includes at least one of perfluoroalkyl sulfonic acid and perfluoroalkyl carboxylate.
[0034] In this embodiment, perfluoroalkyl sulfonates or perfluoroalkyl carboxylates are selected as surfactants primarily based on their excellent stability and unique interfacial properties in strong acid and oxidizing environments. Fluorocarbon chains possess strong chemical inertness and low polarity, making these surfactants less prone to degradation or side reactions in hydrofluoric acid and nitric acid systems, thus maintaining interfacial activity over a long period. Simultaneously, their extremely low surface tension significantly improves the wetting ability of the pickling solution on silane surfaces, allowing the liquid to quickly cover complex microstructure regions, thereby reducing bubble adhesion and uncontacted areas. Specifically, perfluorooctane sulfonic acid, perfluorohexane sulfonic acid, perfluorobutane sulfonic acid and their salts, perfluorooctanoic acid, perfluorohexanoic acid, perfluorobutyric acid and their salts can be selected, but this invention is not limited thereto.
[0035] This application does not limit the preparation method of the pickling solution. For example, the following preparation method can be used: In an acid-resistant container, first add a measured amount of water, and then slowly add a measured amount of concentrated nitric acid and concentrated hydrofluoric acid under continuous stirring and cooling. Mix evenly to obtain the pickling solution. Further, add concentrated hydrofluoric acid and concentrated nitric acid to the aqueous solution in two stages. First add concentrated hydrofluoric acid and stir until completely dissolved, then add concentrated nitric acid and continue mixing.
[0036] Specifically, a two-stage addition sequence is adopted, first adding concentrated hydrofluoric acid and then concentrated nitric acid. The principle behind this is to isolate the direct and intense exothermic reaction between concentrated hydrofluoric acid and concentrated nitric acid in aqueous solution. Allowing the hydrofluoric acid to fully dissolve in water first effectively avoids the instantaneous high heat caused by the strong oxidation-reduction reaction when the two come into direct contact. This significantly reduces localized overheating during the mixing process, mitigates thermal stress damage to acid-resistant containers, and improves operational safety.
[0037] A second aspect of the present invention provides a cleaning method, comprising the following steps:
[0038] Step 1): Apply the pickling solution according to any one of the first aspects of the present invention to the surface to be treated;
[0039] Step 2): Let the reaction stand for 5-40 minutes;
[0040] Step 3): Rinse the surface with water.
[0041] Specifically, in step 1), the hydrofluoric acid, nitric acid, and possibly surfactants in the pickling solution work synergistically. The fluoride ions in the hydrofluoric acid and fluorosilicic acid rapidly initiate a complexation attack on the rust layer, starting the dissolution process. The strong oxidizing acid simultaneously provides an oxidizing environment, beginning the conversion of low-valence metal ions in the rust layer. If surfactants are present, they immediately reduce surface tension and enhance wetting and penetration in this step, ensuring that the pickling solution can quickly and evenly cover and penetrate complex crevices or the bottom of loose rust layers, laying a physical foundation for efficient rust removal and convenient, efficient construction.
[0042] In step 2), within the minimum time limit of 5 minutes, the pickling solution, aided by the surfactant, has fully penetrated the rust layer. The main dissolution and oxidation reactions of hydrofluoric acid and nitric acid on the rust layer are effectively carried out, removing most of the loose rust and beginning to form a preliminary protective film. The upper limit of 40 minutes ensures sufficient reaction time for even thicker, denser rust layers or situations requiring the formation of a complete phosphate conversion film, allowing the cleaning and film-forming processes to reach a thorough and uniform state. This achieves thorough and efficient rust removal and the construction of a stable and continuous active rust-preventive film. This settling process eliminates the need for continuous stirring or heating, simplifying the process and demonstrating convenient, efficient, and economical construction.
[0043] In step 3), rinsing with water is a crucial step in terminating the chemical reaction and removing residual reaction products and excess acid. The water flow quickly carries away dissolved rust ions, residual acid, and reaction byproducts, preventing them from redepositing on the surface after drying or adversely affecting the formed protective film. It also provides a clean and activated substrate for subsequent processes such as coating.
[0044] In one possible embodiment, as described above, the pickling solution is applied to the surface to be treated by spraying.
[0045] In this embodiment, the fine droplets formed during the spraying process can spread rapidly on the surface and more easily penetrate microscopic rough structures, pores and complex areas. Compared with traditional soaking or brushing, the spraying method is very suitable for large-area, three-dimensional operations in industrial sites, which greatly improves work efficiency and reduces labor intensity.
[0046] In one possible embodiment, as described above, the settling time is preferably 25-35 minutes.
[0047] In this embodiment, during the 20-30 minute settling reaction period, the fluoride ions in the hydrofluoric acid fully penetrate and undergo a deep complexation reaction with the stubborn rust layer, ensuring the complete dissolution and stripping of the silicon layer. Simultaneously, the passivation effect of nitric acid forms a continuous, dense, and stable protective layer, reducing the risk of excessive corrosion.
[0048] In one possible embodiment, as described above, the rinsing process includes: using a water gun with a pressure of 0.5-1.5 MPa to perform high-pressure rinsing on the surface to be treated.
[0049] In this embodiment, the high-pressure water flow generates shear and impact forces on the surface, effectively removing reaction products, residual acid, and loose particles adhering to the surface and preventing them from remaining or redepositing. Controlling the pressure within the range of 0.5-1.5 MPa ensures cleaning efficiency while avoiding adverse effects on the surface structure.
[0050] In one possible embodiment, as described above, after rinsing, the surface to be treated is neutralized with an alkaline solution with a pH of 8-9.
[0051] In this embodiment, some adsorbed acidic and fluorine-containing substances may remain after rinsing, which can easily trigger subsequent slow corrosion and lead to unstable surface structure. OH- in the alkaline solution... - Can be combined with residual H +A neutralization reaction occurs, simultaneously promoting the desorption of fluoride ions from the surface into the solution, thereby reducing the content of surface residues. Maintaining the pH within the range of 8-9 ensures the neutralization effect while preventing secondary corrosion of the surface by strong alkalis.
[0052] In one possible embodiment, as described above, after the neutralization treatment, the surface to be treated is subjected to ultraviolet irradiation.
[0053] In this embodiment, ultraviolet irradiation can generate a high-energy excitation effect on the surface, causing residual organic matter such as surfactants to undergo photo-oxidative decomposition, while simultaneously introducing active functional groups such as hydroxyl groups onto the surface, thereby increasing the surface energy. This process can significantly improve the surface's hydrophilicity and wettability, reduce the contact angle, and enhance the adhesion of subsequent coatings or functionalization treatments.
[0054] In one possible embodiment, the treatment method described above further includes, after rinsing, adding lime slurry to the waste liquid after rinsing for neutralization and precipitation.
[0055] In this embodiment, the calcium hydroxide in the lime slurry can neutralize hydrogen ions in the waste liquid and react with fluoride ions to form insoluble calcium fluoride precipitate, thereby achieving effective fluoride removal. Furthermore, some metal ions or impurities can also precipitate and be separated under alkaline conditions. By controlling the amount added, the pH of the system can be raised to neutral or weakly alkaline. This step not only reduces the corrosiveness of the waste liquid but also improves the overall environmental friendliness and safety of the process.
[0056] In addition, when using the above-mentioned cleaning methods, operators must wear safety protective equipment including chemical protective clothing, acid and alkali resistant gloves, and gas masks. This prevents direct contact between highly corrosive components such as hydrofluoric acid and the human body to avoid injury, ensuring that operators can stably perform each step under controlled conditions and preventing occupational safety risks.
[0057] The present invention will be further described below through specific embodiments.
[0058] Example 1
[0059] The pickling solution in this embodiment comprises, by mass percentage: 5% hydrofluoric acid, 15% nitric acid, and 80% water.
[0060] The pickling solution is prepared as follows: In an acid-resistant container, a measured amount of water is first added, and then, under continuous stirring and cooling conditions, a measured amount of concentrated nitric acid and concentrated hydrofluoric acid are slowly added and mixed evenly to obtain the pickling solution.
[0061] The above-mentioned pickling solution treatment methods include:
[0062] Step 1): First, put on a chemical protective suit, acid and alkali resistant gloves and a gas mask. Then, inject the pickling solution into the sprayer and spray it evenly on a square carbon steel corrosion surface with a surface area of 25 square centimeters and a thickness of 3 mm (this corrosion surface is obtained by immersing smooth and uniform carbon steel in a 5 wt% FeCl3 solution at room temperature for 2 hours and then leaving it in the air for 8 hours).
[0063] Step 2): Let the reaction stand for 30 minutes.
[0064] Step 3): Rinse with a high-pressure water gun at 1 MPa for 10 minutes.
[0065] Example 2
[0066] The pickling solution in this embodiment comprises, by mass percentage: 5% hydrofluoric acid, 15% nitric acid, 0.5% perfluorooctane sulfonic acid surfactant, and 79.5% water.
[0067] The preparation and treatment methods of the pickling solution are the same as those in Example 1.
[0068] Example 3
[0069] This embodiment is basically the same as Example 1, except that after rinsing, the sample is soaked in a sodium carbonate aqueous solution with a pH of 8 for 30 minutes, washed with water 3 times, and then dried.
[0070] Comparative Example 1
[0071] A high-pressure water gun with a pressure of 1 MPa is used to apply impact force to the corroded surface, and the attached corrosion products are removed by physical peeling.
[0072] Comparative Example 2
[0073] In the existing technology, an acidic paste-like preparation is manually applied to the corroded surface. After standing and reacting, the corroded surface is subjected to impact force by a high-pressure water gun with a pressure of 1 MPa and then rinsed with clean water.
[0074] Test case
[0075] The effect of pickling solution on metal substrates was evaluated using the weight loss method. The mass ratio of samples from Examples 1-3 and Comparative Examples 1 and 2 before and after pickling was recorded, and the cleaning efficiency was calculated. The pickled samples were then exposed at 25-30°C and 50%-70% relative humidity for 48 hours, and the corrosion area ratio was calculated. The results are shown in Table 1.
[0076]
[0077] As can be seen from the data in the table, compared with the comparative example, the pickling agent system provided in this application significantly improves the cleaning efficiency of the corroded carbon steel surface and can also effectively inhibit subsequent re-corrosion.
[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A pickling solution, characterized in that, The pickling solution comprises 3%-10% hydrofluoric acid, 10%-20% nitric acid, and the balance being water, with a pH value of 0.5-2.
2. The pickling solution according to claim 1, characterized in that, The pickling solution also includes 0.1%-2% surfactant by weight percentage.
3. The pickling solution according to claim 2, characterized in that, The surfactant includes at least one of perfluoroalkyl sulfonates and perfluoroalkyl carboxylates.
4. A method for treating a surface etched by silane, characterized in that, Includes the following steps: Step 1): Apply the pickling solution according to any one of claims 1-3 to the surface to be treated; Step 2): Let the reaction stand for 5-40 minutes; Step 3): Rinse the surface with water.
5. The processing method according to claim 4, characterized in that, The pickling solution is applied to the surface to be treated by spraying.
6. The processing method according to claim 4 or 5, characterized in that, The preferred time for the static reaction is 25-35 minutes.
7. The processing method according to any one of claims 4-6, characterized in that, The rinsing process includes: using a water gun with a pressure of 0.5-1.5 MPa to perform high-pressure rinsing on the surface to be treated.
8. The processing method according to any one of claims 4-7, characterized in that, After the rinsing treatment, the surface to be treated is neutralized with an alkaline solution with a pH of 8-9.
9. The processing method according to claim 8, characterized in that, After the neutralization treatment, the surface to be treated is subjected to ultraviolet irradiation.
10. The processing method according to any one of claims 5-9, characterized in that, After the rinsing treatment, the process further includes adding lime slurry to the waste liquid after the rinsing treatment for neutralization and precipitation.