Corrosion-resistant bolt surface treatment process

Abstract

The invention provides a corrosion-resistant bolt surface treatment process. The corrosion resistance is enhanced by forming a compact zinc coating on the surface of a bolt. The zinc coating is composed of alloy elements in a specific proportion, comprises multiple trace elements such as Mg, Cu and Si, and is prepared through an accurately-controlled hot galvanizing process. The process comprises the steps of pre-plating treatment, hot-dip galvanizing and post-plating treatment, and pre-treatments such as chemical deoiling, acid pickling and plating assisting are adopted, so that the quality of a plating layer is ensured. The plating assistant agent is optimized in formula and rigorous in preparation process, and ensures that a plating layer is uniform and compact. The finally obtained bolt has excellent corrosion resistance and is suitable for various severe environments.

Description

Technical Field

[0001] The invention belongs to the field of fastener anti-corrosion, and specifically discloses a corrosion-resistant bolt surface treatment process. Background Art

[0002] In the bolt manufacturing industry, the corrosion resistance of bolts has always been an important indicator to measure their quality and service life. Although traditional bolt surface treatment methods, such as electroplating and mechanical galvanizing, can improve the corrosion resistance of bolts to a certain extent, they often have problems such as uneven coating, poor adhesion, and easy shedding. Especially in harsh environments (such as high humidity, high salt spray, strong corrosive media, etc.), these defects are particularly obvious, which greatly reduces the corrosion resistance of bolts and affects the safety and stability of the overall structure.

[0003] In addition, although the traditional hot-dip galvanizing process can form a relatively dense zinc coating on the surface of the bolt, the alloy element ratio in the plating solution is often relatively simple, lacking alloy components optimized for specific environments, resulting in limited improvement in the corrosion resistance of the coating. At the same time, the preparation process of the plating solution is also relatively extensive, lacking refined control and regulation, making it difficult to ensure the quality of the coating, and there are defects such as pores and inclusions, which further reduces the corrosion resistance of the bolt.

[0004] In summary, the bolt surface treatment methods in the prior art have obvious deficiencies in improving corrosion resistance and cannot meet the increasingly stringent industrial application requirements. Therefore, a new type of corrosion-resistant bolt surface treatment process is urgently needed to optimize the plating solution composition and preparation process, improve the density, uniformity and adhesion of the coating, thereby significantly improving the corrosion resistance of the bolt and extending its service life. Summary of the invention

[0005] Based on the deficiencies in the prior art, the present invention discloses a corrosion-resistant bolt surface treatment process, which improves the element composition of the zinc coating layer and forms a dense zinc coating on the bolt surface to enhance the corrosion resistance.

[0006] The present invention includes the following technical solutions:

[0007] A corrosion-resistant bolt surface treatment process, the process comprising forming a dense zinc coating on the surface of the bolt, wherein the zinc coating is prepared by a hot-dip galvanizing method to enhance the corrosion resistance of the bolt;

[0008] The hot-dip galvanizing bath contains the following alloying elements in percentage by mass: Mg: 0.2-0.25%; Cu: 0.05%-0.1%; Si: 0.01%-0.03%; Mn: 0.02%-0.05%; Sn: 0.03%-0.07%; Ti: 0.01-0.02%; Y: 0.05-0.08%; Nd: 0.01-0.02%; Sb: 0.03-0.07%; Ir: 0.05-0.1%; the balance is Zn and unavoidable impurities.

[0009] Furthermore, in the above-mentioned corrosion-resistant bolt surface treatment process, the hot-dip galvanizing bath contains the following alloy element components in mass percentage, Mg: 0.23%; Cu: 0.075%; Si: 0.02%; Mn: 0.035%; Sn: 0.05%; Ti: 0.015%; Y: 0.06%; Nd: 0.015%; Sb: 0.05%; Ir: 0.075%; the balance is Zn and unavoidable impurities.

[0010] Furthermore, in the above-mentioned corrosion-resistant bolt surface treatment process, the hot-dip galvanizing bath is prepared by the following process:

[0011] 1) Use a high-precision electronic scale to accurately weigh each alloy element according to its mass percentage content;

[0012] 2) Mix the weighed alloying elements thoroughly in a dry, clean container to ensure that the distribution of each element is uniform;

[0013] 3) Use a graphite crucible or ceramic furnace to ensure that the inside of the furnace is clean and free of impurities, and preheat the furnace to 550-600℃;

[0014] 4) Add an appropriate amount of zinc base material to the furnace, and after it is completely melted, adjust the furnace temperature to 750-800℃;

[0015] 5) Slowly add the alloying elements in batches until they are evenly mixed. After each batch is added, gently stir the plating solution with a stirrer to ensure that the alloying elements are evenly distributed and dissolve faster;

[0016] 6) After all the alloying elements are added and dissolved, add an appropriate amount of deoxidizer and slag remover to remove oxygen and impurities in the plating solution. At the same time, maintain a stirring speed of 100-200rpm to promote the deoxidation and slag removal process;

[0017] 7) Use a spectrometer to analyze the composition of the plating solution to ensure that the content of each alloy element meets the predetermined requirements;

[0018] 8) Keep the plating solution at 500-550℃ for 6-10h to allow the alloy elements to fully diffuse and homogenize, while reducing bubbles and impurities in the plating solution;

[0019] 9) Using a filter to filter the plating solution to remove suspended particles and tiny impurities therein to obtain the hot-dip galvanizing plating solution.

[0020] Furthermore, the above-mentioned corrosion-resistant bolt surface treatment process comprises the following steps:

[0021] S1. Pre-plating treatment

[0022] S11 skim:

[0023] Use chemical degreasing or water-based metal degreasing cleaning agent to degrease the bolts so that they are completely wetted;

[0024] S12 pickling:

[0025] Use hydrochloric acid pickling process to remove rust and oxides on the surface of bolts;

[0026] S13 Washable:

[0027] Water washing removes the residual acid and iron salt on the bolt surface to prepare for the subsequent plating treatment;

[0028] S14 plating aid:

[0029] Soak the bolt in a plating agent to assist plating;

[0030] drying:

[0031] Dry the bolts at 120℃-180℃;

[0032] S2, hot dip galvanizing

[0033] S21 Galvanized:

[0034] The dried bolts are immersed in molten hot-dip galvanizing solution for galvanizing;

[0035] S3, post-plating treatment

[0036] S31 Cooling:

[0037] Use air cooling or water cooling to quickly cool down the bolts;

[0038] S32 passivation:

[0039] Passivation using chromates;

[0040] S33 finishing:

[0041] Use physical means to remove excess zinc and zinc nodules on the bolt surface;

[0042] Get corrosion-resistant bolts.

[0043] During the galvanizing process, this process uses molten hot-dip galvanizing solution for galvanizing. By precisely controlling the composition and temperature of the plating solution, as well as reasonable stirring and heat preservation and standing time, the coating can be evenly and densely attached to the bolt surface. In addition, the cooling, passivation and finishing steps in the post-plating treatment also further improve the corrosion resistance and appearance quality of the coating. In particular, the passivation treatment further enhances the corrosion resistance of the coating by forming a passivation film on the surface of the coating, enabling it to maintain good performance for a long time in harsh environments.

[0044] Furthermore, in the above-mentioned corrosion-resistant bolt surface treatment process, in the S14 plating aid, the plating aid is calculated by weight and includes 100 parts of zinc chloride, 50 parts of ammonium chloride, 5 parts of iminoacetic acid, 15 parts of wetting agent, 5 parts of silicon, 3 parts of sulfur, 3 parts of phosphorus, and 500 parts of water.

[0045] Furthermore, in the above-mentioned corrosion-resistant bolt surface treatment process, the plating aid is prepared by the following steps:

[0046] I. Add zinc chloride and ammonium chloride solid raw materials into water, heat to 50-60°C and stir until completely dissolved;

[0047] II. Add iminoacetic acid and continue stirring to mix evenly;

[0048] III. Add a wetting agent and trace elements such as silicon, sulfur and phosphorus to ensure that they are fully dispersed in the solution to obtain the plating aid.

[0049] Furthermore, in the above-mentioned corrosion-resistant bolt surface treatment process, in the S14 plating assistance, the plating assistance time is 3-5 minutes.

[0050] Pre-plating treatment includes degreasing, pickling, washing and plating aids, which can completely remove oil, rust and oxides on the bolt surface, providing a clean and activated substrate surface for subsequent galvanizing. In particular, the use of plating aids not only promotes the bonding between the coating and the substrate, but also improves the uniformity and density of the coating. The synergistic effect of zinc chloride, ammonium chloride, iminoacetic acid and other components in the plating aid makes the plating aid effect more significant. At the same time, the precise control of the plating aid time also ensures the stability and consistency of the plating aid effect.

[0051] The invention also discloses a corrosion-resistant bolt which is processed by the above-mentioned surface treatment process.

[0052] Compared with the prior art, the present invention has the following outstanding beneficial effects:

[0053] The corrosion-resistant bolt surface treatment process of the present invention significantly improves the corrosion resistance of the bolt through a series of carefully designed steps and optimized alloy element ratios, and has many beneficial effects.

[0054] First, this process forms a dense zinc coating on the surface of the bolt, which not only has excellent anti-corrosion properties, but also effectively isolates the bolt substrate from direct contact with the corrosive medium, thereby greatly extending the service life of the bolt. In particular, the alloy elements in the plating solution, such as Mg, Cu, Si, Mn, Sn, Ti, Y, Nd, Sb, Ir, etc., through precisely controlled ratios and refined preparation processes, enable the coating to maintain high density while also having good corrosion resistance and adhesion. The addition of these alloy elements not only enhances the hardness and wear resistance of the coating, but also further improves the corrosion resistance of the coating by forming a dense oxide or compound layer.

[0055] In summary, the corrosion-resistant bolt surface treatment process of the present invention has many beneficial effects. It not only significantly improves the corrosion resistance of the bolts and prolongs the service life, but also improves the density, uniformity and adhesion of the coating by optimizing the composition of the plating solution and the preparation process. In addition, the process also has the advantages of simple operation, low cost, environmental protection and pollution-free, which meets the needs of modern industry for high quality, high efficiency and low energy consumption. Therefore, the corrosion-resistant bolt surface treatment process of the present invention has broad application prospects and important economic value in the fields of machinery manufacturing, automobile manufacturing, marine engineering, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a comparative test of the bonding strength of Examples 1-3 and Comparative Examples 1-5. DETAILED DESCRIPTION

[0057] A corrosion-resistant bolt surface treatment process, the process comprising forming a dense zinc coating on the surface of the bolt, wherein the zinc coating is prepared by a hot-dip galvanizing method to enhance the corrosion resistance of the bolt;

[0058] The hot-dip galvanizing bath contains the following alloying elements in percentage by mass: Mg: 0.2-0.25%; Cu: 0.05%-0.1%; Si: 0.01%-0.03%; Mn: 0.02%-0.05%; Sn: 0.03%-0.07%; Ti: 0.01-0.02%; Y: 0.05-0.08%; Nd: 0.01-0.02%; Sb: 0.03-0.07%; Ir: 0.05-0.1%; the balance is Zn and unavoidable impurities.

[0059] The hot-dip galvanizing bath is prepared by the following process:

[0060] 1) Use a high-precision electronic scale to accurately weigh each alloy element according to its mass percentage content;

[0061] 2) Mix the weighed alloying elements thoroughly in a dry, clean container to ensure that the distribution of each element is uniform;

[0062] 3) Use a graphite crucible or ceramic furnace to ensure that the inside of the furnace is clean and free of impurities, and preheat the furnace to 550-600℃;

[0063] 4) Add an appropriate amount of zinc base material to the furnace, and after it is completely melted, adjust the furnace temperature to 750-800℃;

[0064] 5) Slowly add the alloying elements in batches until they are evenly mixed. After each batch is added, gently stir the plating solution with a stirrer to ensure that the alloying elements are evenly distributed and dissolve faster;

[0065] 6) After all the alloying elements are added and dissolved, add an appropriate amount of deoxidizer and slag remover to remove oxygen and impurities in the plating solution. At the same time, maintain a stirring speed of 100-200rpm to promote the deoxidation and slag removal process;

[0066] 7) Use a spectrometer to analyze the composition of the plating solution to ensure that the content of each alloy element meets the predetermined requirements;

[0067] 8) Keep the plating solution at 500-550℃ for 6-10h to allow the alloy elements to fully diffuse and homogenize, while reducing bubbles and impurities in the plating solution;

[0068] 9) Using a filter to filter the plating solution to remove suspended particles and tiny impurities therein to obtain the hot-dip galvanizing plating solution.

[0069] The above-mentioned corrosion-resistant bolt surface treatment process is characterized by comprising the following steps:

[0070] S1. Pre-plating treatment

[0071] S11 skim:

[0072] Use chemical degreasing or water-based metal degreasing cleaning agent to degrease the bolts so that they are completely wetted;

[0073] S12 pickling:

[0074] Use hydrochloric acid pickling process to remove rust and oxides on the surface of bolts;

[0075] S13 Washable:

[0076] Water washing removes the residual acid and iron salt on the bolt surface to prepare for the subsequent plating treatment;

[0077] S14 plating aid:

[0078] Soak the bolt in a plating agent to assist plating;

[0079] drying:

[0080] Dry the bolts at 120℃-180℃;

[0081] S2, hot dip galvanizing

[0082] S21 Galvanized:

[0083] The dried bolts are immersed in molten hot-dip galvanizing solution for galvanizing;

[0084] S3, post-plating treatment

[0085] S31 Cooling:

[0086] Use air cooling or water cooling to quickly cool down the bolts;

[0087] S32 passivation:

[0088] Passivation using chromates;

[0089] S33 finishing:

[0090] Use physical means to remove excess zinc and zinc nodules on the bolt surface;

[0091] Get corrosion-resistant bolts.

[0092] In the S14 plating aid, the plating aid is calculated by weight and includes 100 parts of zinc chloride, 50 parts of ammonium chloride, 5 parts of iminoacetic acid, 15 parts of wetting agent, 5 parts of silicon, 3 parts of sulfur, 3 parts of phosphorus, and 500 parts of water.

[0093] The plating aid is prepared by the following steps:

[0094] I. Add zinc chloride and ammonium chloride solid raw materials into water, heat to 50-60°C and stir until completely dissolved;

[0095] II. Add iminoacetic acid and continue stirring to mix evenly;

[0096] III. Add a wetting agent and trace elements such as silicon, sulfur and phosphorus to ensure that they are fully dispersed in the solution to obtain the plating aid.

[0097] In the S14 plating assistance process, the plating assistance time is 3-5 minutes.

[0098] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0099] Example 1

[0100] A corrosion-resistant bolt surface treatment process, the process comprising forming a dense zinc coating on the surface of the bolt, wherein the zinc coating is prepared by a hot-dip galvanizing method to enhance the corrosion resistance of the bolt;

[0101] The hot-dip galvanizing bath contains the following alloying element components in mass percentage: Mg: 0.2%; Cu: 0.05%; Si: 0.01%; Mn: 0.02%; Sn: 0.03%; Ti: 0.01%; Y: 0.05%; Nd: 0.01%; Sb: 0.03%; Ir: 0.05%; the balance is Zn and unavoidable impurities.

[0102] The hot-dip galvanizing bath is prepared by the following process:

[0103] 1) Use a high-precision electronic scale to accurately weigh each alloy element according to its mass percentage content;

[0104] 2) Mix the weighed alloying elements thoroughly in a dry, clean container to ensure that the distribution of each element is uniform;

[0105] 3) Use a graphite crucible or ceramic furnace to ensure that the inside of the furnace is clean and free of impurities, and preheat the furnace to 550-600℃;

[0106] 4) Add an appropriate amount of zinc base material to the furnace, and after it is completely melted, adjust the furnace temperature to 750-800℃;

[0107] 5) Slowly add the alloying elements in batches until they are evenly mixed. After each batch is added, gently stir the plating solution with a stirrer to ensure that the alloying elements are evenly distributed and dissolve faster;

[0108] 6) After all the alloying elements are added and dissolved, add an appropriate amount of deoxidizer and slag remover to remove oxygen and impurities in the plating solution. At the same time, maintain a stirring speed of 100-200rpm to promote the deoxidation and slag removal process;

[0109] 7) Use a spectrometer to analyze the composition of the plating solution to ensure that the content of each alloy element meets the predetermined requirements;

[0110] 8) Keep the plating solution at 500-550℃ for 6-10h to allow the alloy elements to fully diffuse and homogenize, while reducing bubbles and impurities in the plating solution;

[0111] 9) Using a filter to filter the plating solution to remove suspended particles and tiny impurities therein to obtain the hot-dip galvanizing plating solution.

[0112] The above-mentioned corrosion-resistant bolt surface treatment process is characterized by comprising the following steps:

[0113] S1. Pre-plating treatment

[0114] S11 skim:

[0115] Use chemical degreasing or water-based metal degreasing cleaning agent to degrease the bolts so that they are completely wetted;

[0116] S12 pickling:

[0117] Use hydrochloric acid pickling process to remove rust and oxides on the surface of bolts;

[0118] S13 Washable:

[0119] Water washing removes the residual acid and iron salt on the bolt surface to prepare for the subsequent plating treatment;

[0120] S14 plating aid:

[0121] Soak the bolt in a plating agent to assist plating;

[0122] drying:

[0123] Dry the bolts at 120℃-180℃;

[0124] S2, hot dip galvanizing

[0125] S21 Galvanized:

[0126] The dried bolts are immersed in molten hot-dip galvanizing solution for galvanizing;

[0127] S3, post-plating treatment

[0128] S31 Cooling:

[0129] Use air cooling or water cooling to quickly cool down the bolts;

[0130] S32 passivation:

[0131] Passivation using chromates;

[0132] S33 finishing:

[0133] Use physical means to remove excess zinc and zinc nodules on the bolt surface;

[0134] Get corrosion-resistant bolts.

[0135] In the S14 plating aid, the plating aid is calculated by weight and includes 100 parts of zinc chloride, 50 parts of ammonium chloride, 5 parts of iminoacetic acid, 15 parts of wetting agent, 5 parts of silicon, 3 parts of sulfur, 3 parts of phosphorus, and 500 parts of water.

[0136] The plating aid is prepared by the following steps:

[0137] I. Add zinc chloride and ammonium chloride solid raw materials into water, heat to 50-60°C and stir until completely dissolved;

[0138] II. Add iminoacetic acid and continue stirring to mix evenly;

[0139] III. Add a wetting agent and trace elements such as silicon, sulfur and phosphorus to ensure that they are fully dispersed in the solution to obtain the plating aid.

[0140] In the S14 plating assistance process, the plating assistance time is 3-5 minutes.

[0141] Example 2

[0142] A corrosion-resistant bolt surface treatment process, the process comprising forming a dense zinc coating on the surface of the bolt, wherein the zinc coating is prepared by a hot-dip galvanizing method to enhance the corrosion resistance of the bolt;

[0143] The hot-dip galvanizing bath contains the following alloying elements in percentage by mass: Mg: 0.23%;

[0144] Cu: 0.075%; Si: 0.02%; Mn: 0.035%; Sn: 0.05%; Ti: 0.015%; Y: 0.06%; Nd: 0.015%; Sb: 0.05%; Ir: 0.075%; the balance is Zn and inevitable impurities.

[0145] The hot-dip galvanizing bath is prepared by the following process:

[0146] 1) Use a high-precision electronic scale to accurately weigh each alloy element according to its mass percentage content;

[0147] 2) Mix the weighed alloying elements thoroughly in a dry, clean container to ensure that the distribution of each element is uniform;

[0148] 3) Use a graphite crucible or ceramic furnace to ensure that the inside of the furnace is clean and free of impurities, and preheat the furnace to 550-600℃;

[0149] 4) Add an appropriate amount of zinc base material to the furnace, and after it is completely melted, adjust the furnace temperature to 750-800℃;

[0150] 5) Slowly add the alloying elements in batches until they are evenly mixed. After each batch is added, gently stir the plating solution with a stirrer to ensure that the alloying elements are evenly distributed and dissolve faster;

[0151] 6) After all the alloying elements are added and dissolved, add an appropriate amount of deoxidizer and slag remover to remove oxygen and impurities in the plating solution. At the same time, maintain a stirring speed of 100-200rpm to promote the deoxidation and slag removal process;

[0152] 7) Use a spectrometer to analyze the composition of the plating solution to ensure that the content of each alloy element meets the predetermined requirements;

[0153] 8) Keep the plating solution at 500-550℃ for 6-10h to allow the alloy elements to fully diffuse and homogenize, while reducing bubbles and impurities in the plating solution;

[0154] 9) Using a filter to filter the plating solution to remove suspended particles and tiny impurities therein to obtain the hot-dip galvanizing plating solution.

[0155] The above-mentioned corrosion-resistant bolt surface treatment process is characterized by comprising the following steps:

[0156] S1. Pre-plating treatment

[0157] S11 skim:

[0158] Use chemical degreasing or water-based metal degreasing cleaning agent to degrease the bolts so that they are completely wetted;

[0159] S12 pickling:

[0160] Use hydrochloric acid pickling process to remove rust and oxides on the surface of bolts;

[0161] S13 Washable:

[0162] Water washing removes the residual acid and iron salt on the bolt surface to prepare for the subsequent plating treatment;

[0163] S14 plating aid:

[0164] Soak the bolt in a plating agent to assist plating;

[0165] drying:

[0166] Dry the bolts at 120℃-180℃;

[0167] S2, hot dip galvanizing

[0168] S21 Galvanized:

[0169] The dried bolts are immersed in molten hot-dip galvanizing solution for galvanizing;

[0170] S3, post-plating treatment

[0171] S31 Cooling:

[0172] Use air cooling or water cooling to quickly cool down the bolts;

[0173] S32 passivation:

[0174] Passivation using chromates;

[0175] S33 finishing:

[0176] Use physical means to remove excess zinc and zinc nodules on the bolt surface;

[0177] Get corrosion-resistant bolts.

[0178] In the S14 plating aid, the plating aid is calculated by weight and includes 100 parts of zinc chloride, 50 parts of ammonium chloride, 5 parts of iminoacetic acid, 15 parts of wetting agent, 5 parts of silicon, 3 parts of sulfur, 3 parts of phosphorus, and 500 parts of water.

[0179] The plating aid is prepared by the following steps:

[0180] I. Add zinc chloride and ammonium chloride solid raw materials into water, heat to 50-60°C and stir until completely dissolved;

[0181] II. Add iminoacetic acid and continue stirring to mix evenly;

[0182] III. Add a wetting agent and trace elements such as silicon, sulfur and phosphorus to ensure that they are fully dispersed in the solution to obtain the plating aid.

[0183] In the S14 plating assistance process, the plating assistance time is 3-5 minutes.

[0184] Example 3

[0185] A corrosion-resistant bolt surface treatment process, the process comprising forming a dense zinc coating on the surface of the bolt, wherein the zinc coating is prepared by a hot-dip galvanizing method to enhance the corrosion resistance of the bolt;

[0186] The hot-dip galvanizing bath contains the following alloying element components in mass percentage: Mg: 0.25%; Cu: 0.1%; Si: 0.03%; Mn: 0.05%; Sn: 0.07%; Ti: 0.02%; Y: 0.08%; Nd: 0.02%; Sb: 0.07%; Ir: 0.1%; the balance is Zn and unavoidable impurities.

[0187] The hot-dip galvanizing bath is prepared by the following process:

[0188] 1) Use a high-precision electronic scale to accurately weigh each alloy element according to its mass percentage content;

[0189] 2) Mix the weighed alloying elements thoroughly in a dry, clean container to ensure that the distribution of each element is uniform;

[0190] 3) Use a graphite crucible or ceramic furnace to ensure that the inside of the furnace is clean and free of impurities, and preheat the furnace to 550-600℃;

[0191] 4) Add an appropriate amount of zinc base material to the furnace, and after it is completely melted, adjust the furnace temperature to 750-800℃;

[0192] 5) Slowly add the alloying elements in batches until they are evenly mixed. After each batch is added, gently stir the plating solution with a stirrer to ensure that the alloying elements are evenly distributed and dissolve faster;

[0193] 6) After all the alloying elements are added and dissolved, add an appropriate amount of deoxidizer and slag remover to remove oxygen and impurities in the plating solution. At the same time, maintain a stirring speed of 100-200rpm to promote the deoxidation and slag removal process;

[0194] 7) Use a spectrometer to analyze the composition of the plating solution to ensure that the content of each alloy element meets the predetermined requirements;

[0195] 8) Keep the plating solution at 500-550℃ for 6-10h to allow the alloy elements to fully diffuse and homogenize, while reducing bubbles and impurities in the plating solution;

[0196] 9) Using a filter to filter the plating solution to remove suspended particles and tiny impurities therein to obtain the hot-dip galvanizing plating solution.

[0197] The above-mentioned corrosion-resistant bolt surface treatment process is characterized by comprising the following steps:

[0198] S1. Pre-plating treatment

[0199] S11 skim:

[0200] Use chemical degreasing or water-based metal degreasing cleaning agent to degrease the bolts so that they are completely wetted;

[0201] S12 pickling:

[0202] Use hydrochloric acid pickling process to remove rust and oxides on the surface of bolts;

[0203] S13 Washable:

[0204] Water washing removes the residual acid and iron salt on the bolt surface to prepare for the subsequent plating treatment;

[0205] S14 plating aid:

[0206] Soak the bolt in a plating agent to assist plating;

[0207] drying:

[0208] Dry the bolts at 120℃-180℃;

[0209] S2, hot dip galvanizing

[0210] S21 Galvanized:

[0211] The dried bolts are immersed in molten hot-dip galvanizing solution for galvanizing;

[0212] S3, post-plating treatment

[0213] S31 Cooling:

[0214] Use air cooling or water cooling to quickly cool down the bolts;

[0215] S32 passivation:

[0216] Passivation using chromates;

[0217] S33 finishing:

[0218] Use physical means to remove excess zinc and zinc nodules on the bolt surface;

[0219] Get corrosion-resistant bolts.

[0220] In the S14 plating aid, the plating aid is calculated by weight and includes 100 parts of zinc chloride, 50 parts of ammonium chloride, 5 parts of iminoacetic acid, 15 parts of wetting agent, 5 parts of silicon, 3 parts of sulfur, 3 parts of phosphorus, and 500 parts of water.

[0221] The plating aid is prepared by the following steps:

[0222] I. Add zinc chloride and ammonium chloride solid raw materials into water, heat to 50-60°C and stir until completely dissolved;

[0223] II. Add iminoacetic acid and continue stirring to mix evenly;

[0224] III. Add a wetting agent and trace elements such as silicon, sulfur and phosphorus to ensure that they are fully dispersed in the solution to obtain the plating aid.

[0225] In the S14 plating assistance process, the plating assistance time is 3-5 minutes.

[0226] Comparative Example 1

[0227] Compared with Example 2, the hot-dip galvanizing bath of this comparative example does not contain Cu: 0.075%, that is:

[0228] The hot-dip galvanizing bath contains the following alloying elements in percentage by mass: Mg: 0.23%;

[0229] Si: 0.02%; Mn: 0.035%; Sn: 0.05%; Ti: 0.015%; Y: 0.06%; Nd: 0.015%; Sb: 0.05%; Ir: 0.075%; the balance is Zn and inevitable impurities.

[0230] The rest is the same as Example 2.

[0231] Comparative Example 2

[0232] Compared with Example 2, Al is used instead of Mg in the hot-dip galvanizing bath of this comparative example, that is,

[0233] The hot-dip galvanizing bath contains the following alloying element components in mass percentage: Al: 0.23%; Cu: 0.075%; Si: 0.02%; Mn: 0.035%; Sn: 0.05%; Ti: 0.015%; Y: 0.06%; Nd: 0.015%; Sb: 0.05%; Ir: 0.075%; the balance is Zn and unavoidable impurities.

[0234] The rest is the same as Example 2.

[0235] Comparative Example 3

[0236] Compared with Example 2, the hot-dip galvanizing bath of this comparative example uses Al instead of Mg, and does not contain Cu: 0.075%, that is:

[0237] The hot-dip galvanizing bath contains the following alloying element components in mass percentage: Al: 0.23%; Si: 0.02%; Mn: 0.035%; Sn: 0.05%; Ti: 0.015%; Y: 0.06%; Nd: 0.015%; Sb: 0.05%; Ir: 0.075%; the balance is Zn and unavoidable impurities.

[0238] The rest is the same as Example 2.

[0239] Comparative Example 4

[0240] This comparative example does not include S14 plating aid, and the rest is the same as Example 2

[0241] Comparative Example 5

[0242] In this comparative example, S14 plating aid does not contain 5 parts of silicon, 3 parts of sulfur and 3 parts of phosphorus, and the rest is the same as Example 2.

[0243] Test Case

[0244] Corrosion resistance test:

[0245] The test used 45 steel 8th grade nuts for surface treatment, and used the treatment processes of Examples 1-3 and Comparative Examples 1-5, and compared the anti-corrosion effects of the above processes by salt spray test. The specific standard reference was GB / T10125-2012 "Artificial Atmosphere Corrosion Test Salt Spray Test" to test the corrosion-resistant bolts of the examples and comparative examples. The corrosion-resistant bolts were subjected to a salt spray test using a 6% mass percent acetic acid solution, and the corrosion-resistant bolts were observed after 500h, 750h, and 1000h of the salt spray test.

[0246] Plating bonding ability test:

[0247] The following test method is used to determine the bonding strength between the anticorrosive coating and the surface of the corrosion-resistant bolt: the materials of the bolts of Examples 1-3 and Comparative Examples 1-5 are made into discs with a diameter of 20 mm and a thickness of 2 mm, and then the anticorrosive surface treatment is performed using the same process as in Examples 1-3 and Comparative Examples 1-5 to obtain the test specimens. The bonding strength test of the above test specimens is performed with reference to GB / T5210-2006 "Adhesion Test of Color Paint and Clear Coat by Pull-Off Method".

[0248] The results are shown in Table 1 and Figure 1 Shown

[0249] The results are shown in Table 1

[0250] 500h 750h 1000h Bonding strengthMpa Example 1 No obvious rust No obvious rust No obvious rust 55 Example 2 No obvious rust No obvious rust No obvious rust 58 Example 3 No obvious rust No obvious rust No obvious rust 53 Comparative Example 1 No obvious rust Visible rust Visible rust 53 Comparative Example 2 Visible rust Visible rust Moderate rust 54 Comparative Example 3 Moderate rust Moderate rust Obvious rust 56 Comparative Example 4 No obvious rust No obvious rust No obvious rust 37 Comparative Example 5 No obvious rust No obvious rust No obvious rust 42

[0251] It can be seen that after using the treatment process of the present invention, the anti-corrosion ability of the bolts is greatly improved, especially using the Mg+Cu additive solution, the bolts can be handled for 1000h salt spray test without obvious corrosion, relatively speaking, using the Al or Al+Cu solution, they will rust after 750h test. Further, by comparing the bonding strength MPa, it can be found that after using the plating aid described in the present invention, the bonding strength is improved by more than 20%, so that the coating has good corrosion resistance and adhesion while maintaining high density.

[0252] The above are only a few preferred embodiments of the present invention, which are described in a more specific and detailed manner, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A corrosion-resistant bolt surface treatment process, characterized in that: The process includes forming a dense zinc coating on the surface of the bolt, wherein the zinc coating is prepared by a hot-dip galvanizing method to enhance the corrosion resistance of the bolt; The hot-dip galvanizing bath contains the following alloying elements in percentage by mass: Mg: 0.2%-0.25%; Cu: 0.05%-0.1%; Si: 0.01%-0.03%; Mn: 0.02%-0.05%; Sn: 0.03%-0.07%; Ti: 0.01%-0.02%; Y：0.05%-0.08％； Nd: 0.01%-0.02%; Sb: 0.03%-0.07%; Ir: 0.05%-0.1%; the balance is Zn and inevitable impurities.

2. A corrosion-resistant bolt surface treatment process according to claim 1, characterized in that: The hot-dip galvanizing bath contains the following alloying elements in percentage by mass: Mg: 0.23%; Cu: 0.075%; Si: 0.02%; Mn: 0.035%; Sn: 0.05%; Ti: 0.015%; Y: 0.06%; Nd: 0.015%; Sb: 0.05%; Ir: 0.075%; the balance is Zn and inevitable impurities.

3. A corrosion-resistant bolt surface treatment process according to claim 1, characterized in that: The hot-dip galvanizing bath is prepared by the following process: 1) Use a high-precision electronic scale to accurately weigh each alloy element according to its mass percentage content; 2) Mix the weighed alloying elements thoroughly in a dry, clean container to ensure that the distribution of each element is uniform; 3) Use a graphite crucible or ceramic furnace to ensure that the inside of the furnace is clean and free of impurities, and preheat the furnace to 550-600℃; 4) Add an appropriate amount of zinc base material to the furnace, and after it is completely melted, adjust the furnace temperature to 750-800℃; 5) Slowly add the alloying elements in batches until they are evenly mixed. After each batch is added, gently stir the plating solution with a stirrer to ensure that the alloying elements are evenly distributed and dissolve faster; 6) After all the alloying elements are added and dissolved, add appropriate amount of deoxidizer and slag remover to remove oxygen and impurities in the plating solution. At the same time, maintain a stirring speed of 100-200rpm to promote the deoxidation and slag removal process; 7) Use a spectrometer to analyze the composition of the plating solution to ensure that the content of each alloy element meets the predetermined requirements; 8) Keep the plating solution at 500-550℃ for 6-10 hours to allow the alloy elements to fully diffuse and homogenize, while reducing bubbles and impurities in the plating solution; 9) Using a filter to filter the plating solution to remove suspended particles and tiny impurities therein to obtain the hot-dip galvanizing plating solution.

4. A corrosion-resistant bolt surface treatment process according to claim 1, characterized in that: The following steps are involved: S1. Pre-plating treatment S11 skim: Use chemical degreasing or water-based metal degreasing cleaning agent to degrease the bolts so that they are completely wetted; S12 pickling: Use hydrochloric acid pickling process to remove rust and oxides on the surface of bolts; S13 Washable: Water washing removes the residual acid and iron salt on the bolt surface to prepare for the subsequent plating treatment; S14 plating aid: Soak the bolt in a plating agent to assist plating; drying: Dry the bolts at 120℃-180℃; S2, hot dip galvanizing S21 Galvanized: The dried bolts are immersed in molten hot-dip galvanizing solution for galvanizing; S3, post-plating treatment S31 Cooling: Use air cooling or water cooling to quickly cool down the bolts; S32 passivation: Passivation using chromates; S33 finishing: Use physical means to remove excess zinc and zinc nodules on the bolt surface; Get corrosion-resistant bolts.

5. A corrosion-resistant bolt surface treatment process according to claim 4, characterized in that: In the S14 plating aid, the plating aid is calculated by weight and includes 100 parts of zinc chloride, 50 parts of ammonium chloride, 5 parts of iminoacetic acid, 15 parts of wetting agent, 5 parts of silicon, 3 parts of sulfur, 3 parts of phosphorus, and 500 parts of water.

6. A corrosion-resistant bolt surface treatment process according to claim 5, characterized in that: The plating aid is prepared by the following steps: I. Add zinc chloride and ammonium chloride solid raw materials into water, heat to 50-60°C and stir until completely dissolved; II. Add iminoacetic acid and continue stirring to mix evenly; III. Add a wetting agent and trace elements such as silicon, sulfur and phosphorus to ensure that they are fully dispersed in the solution to obtain the plating aid.

7. A corrosion-resistant bolt surface treatment process according to claim 4, characterized in that: In the S14 plating assistance process, the plating assistance time is 3-5 minutes.

8. A corrosion-resistant bolt, characterized in that: The surface is treated by the surface treatment process as described in any one of claims 1 to 7.

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