CN105200468A - Bolt surface corrosion prevention method - Google Patents

Abstract

The invention discloses a bolt surface corrosion prevention method. The method comprises procedures as follows: a bolt is subjected to surface treatment including degreasing, deoiling and oxidation film removal with a conventional method; anode activation is performed on an ionic liquid, and the oxidation film on the surface of the bolt is completely removed; the ionic liquid is subjected to electro-deposition, an aluminum-manganese plating is formed, the bolt is subjected to constant-current electro-deposition with a barrel plating method, an aluminum-manganese alloy plating is formed, a plating solution comprises a bis-substituted imidazolium chloride-aluminum chloride type ionic liquid and manganese salt, a two-electrode system is adopted, the bolt is taken as a working electrode, a metal Al plate is taken as a counter electrode, the anodic current density is 6-20 mA/cm<2>, and the plating time is 0.5-2 h. With the adoption of the method, the bolt can have a clean surface without an oxidation layer in advance, the aluminum-manganese alloy plating is obtained through electro-deposition in a barrel plating manner, a process is simple, the operation is convenient, the energy consumption is low, no pollution is produced to the environment, platings are uniformly distributed on the part surface and well combined with the surface, higher corrosion resistance performance is achieved, batch production can be realized, and a wide application prospect is achieved.

Description

A method for anti-corrosion of bolt surface

technical field

The invention relates to a metal surface anticorrosion method, in particular to a method for electroplating an aluminum-manganese alloy anticorrosion coating on the surface of a bolt by using an ionic liquid, and belongs to the field of electrochemical surface treatment.

Background technique

Bolts are widely used in construction, home appliances, automobiles, and petrochemical industries. However, under some extremely harsh conditions, such as marine environments, the surface of bolts is prone to electrochemical reactions, resulting in rust and corrosion. Rusty carbon steel bolts reduce the structural strength quickly, which directly affects the safety and reliability of the equipment. Moreover, during the regular maintenance process, the corroded bolts are very easy to slip due to the decrease in the strength of the angular structure, and sometimes they have to be disassembled by violent destruction, which increases the labor intensity and engineering cost in the production and maintenance process. Therefore, it is necessary to carry out surface treatment on traditional bolts to improve their anti-corrosion performance.

At present, the most widely used surface treatment method is anti-corrosion plating, which deposits a corrosion-resistant layer on the surface of the bolt through electrochemical reaction to improve the overall corrosion resistance of the bolt. However, the material of the bolt workpiece itself is usually easy to oxidize. During storage, the surface is prone to oxidation reaction to form an oxide film, and the oxide film layer is difficult to completely remove. Even if the oxide layer on the surface is removed by physical grinding, when the grinding is finished, it is very easy to re-oxidize under the action of oxygen and moisture in the air, so that a re-oxidation layer is formed on the surface of the bolt. If the coating is carried out without completely removing the oxide layer, the resulting coating will be very poorly bonded to the substrate.

Taking the hot-dip galvanizing that is commonly used at present as an example, when the surface of the bolt is anti-corrosion by hot-dip galvanizing, due to the existence of an oxide layer on the surface of the bolt substrate, the bonding strength between the galvanized layer and the bolt substrate is low, and local peeling is prone to occur. Moreover, the galvanized layer is used as a cathodic protective layer. Once the galvanized layer is cracked, the exposed bolt base will accelerate corrosion, which is difficult to meet the actual use requirements of bolts in some special occasions.

Therefore, before the bolts are electroplated, pretreatment is required to remove the oxide layer on the surface of the bolts and improve the adhesion of the electroplating deposit. The existing conventional pretreatment processes include: degreasing and dipping, pre-copper plating, nickel flash plating, etc. However, the bolt workpieces pretreated by these processes cannot meet the requirements of adhesion after electroplating. Due to the gap barrier characteristics of the bolt itself, the oxide layer in the gap on the surface of the bolt during the chemical pretreatment process is not easy to peel off in conventional treatment. It is very urgent to seek new pretreatment methods to improve the bonding force between the coating and the bolt matrix.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings existing in the prior art, and to provide a method for barrel-plating an aluminum-manganese alloy coating on the surface of a bolt by using an ionic liquid.

The purpose of the present invention is achieved through the following technical solutions, adopting ionic liquid to coat the aluminum-manganese alloy on the surface of the bolt:

A method for anti-corrosion of a bolt surface, comprising the steps of:

Step (1) Degreasing and pickling: Put the bolts in the electrolyte, electrolytically degrease, put the electrolytically degreased bolts into the pickling solution, and pickle to remove the oxides on the surface of the bolt matrix.

Step (2) Anode activation: Put the bolts into the activation solution to remove the plating.

Step (3) Ionic liquid electrodeposition: immerse the bolts treated in steps (1) and (2) in an electroplating solution for constant current electrodeposition treatment. The electroplating solution is composed of disubstituted imidazolium chloride-aluminum chloride type ionic liquid and manganese salt. The disubstituted imidazolium chloride-aluminum chloride type ionic liquid is composed of disubstituted imidazolium chloride and AlCl3 in a molar ratio of ₁ :1.5-2, and the ionic liquid is Lewis acidic. The manganese salt concentration in the electroplating solution is 0.1-0.5 mol/L. A two-electrode system is adopted, with the bolt as the working electrode and the metal aluminum as the counter electrode. The temperature of the plating solution is 20-40°C, preferably 20-30°C, such as 25°C, the anode current density is 6-20mA/cm ² , and the plating time is 0.5h-2h.

The bolt of the present invention undergoes appropriate pretreatment first, and the grease, dirt and oxide layer on the surface are fully removed for a second time, and the bonding force between the surface of the bolt base and the electroplating layer is good, and it is not easy to fall off. During the electroplating process, the aluminum-manganese coating is electroplated on the bolt under the condition of constant current. During the electroplating process, as the aluminum ions on the aluminum electrode dissolve into the electrolyte, the aluminum-manganese alloy layer is rapidly deposited on the surface of the bolt. Moreover, the concentration of manganese ions in the electroplating solution is suitable, the proportion of aluminum and manganese in the deposited aluminum-manganese deposition layer is in the optimal range, the formed coating has good surface strength and outstanding corrosion resistance.

Preferably, the manganese salt concentration in the electroplating solution is 0.1-0.3 mol/L.

Preferably, the electroplating operation is performed in an inert gas atmosphere. In the surface anticorrosion treatment process of the present invention, electrolytic degreasing, pickling and anodic activation are carried out on the surface of the bolt in advance, and there is no oxide layer on the surface of the bolt, and the activity is extremely high, and it is easy to react with oxygen and water vapor in the air to form an oxide layer again. Therefore, inert atmosphere protection is used to improve the quality assurance of electroplating.

Preferably, the plating method is barrel plating with a rotation speed of 10-20r/min. Barrel plating equipment is used to carry out in a vacuum glove box, wherein the rotating speed of barrel plating is 10-20r/min. The use of barrel plating has the characteristics of high production efficiency, uniform coating, and good quality. Especially for the bolt objects treated by the present invention, it can well overcome the problem of poor control of the uniformity of the coating of various parts of the bolt special-shaped structure.

In the bolt electrolytic degreasing process described in step (1) of the present invention, the electrolyte is an alkaline degreasing solution comprising: sodium hydroxide 20-60g/L, sodium carbonate 20-40g/L, trisodium phosphate 5-15g /L; The treatment step is to use the bolt workpiece as the cathode, put it into the electrolyte at a temperature of 50-90°C, apply a current density of 2-10mA/cm ² , and electrolytically degrease for 20s-2min. In the process of electrolytic degreasing, an alkaline degreasing solution is used for electrolysis. Electrolysis produces tiny bubbles that adhere to the metal surface and push the grease on the surface of the bolt to separate from the surface. The alkaline solution has good solubility for grease and can Promotes the efficiency of electrolytic degreasing. During the process of electrolytic degreasing, the current density is controlled at a low level, and the time of electrolytic degreasing is also short. There is no major interference to the bolt itself, which can well ensure that the bolt itself does not lose strength during the electrolytic degreasing process. .

In the bolt pickling process described in the step (1) of the present invention, the pickling solution is one or more of dilute hydrochloric acid, dilute sulfuric acid, dilute nitric acid, its mass concentration is 5-10%, and the pickling time is 20s -2min. Dilute acid solutions are used in pickling, and the mass concentration is controlled at a low level. Its corrosive power is average, and it has a corrosive effect on the oxides on the metal surface, but it does not have a strong corrosive effect on the non-oxidized part of the metal. Selective sample surface treatment is achieved.

The anode activation solution described in step ( ₂ ) of the present invention is AlCl in the ionic liquid system that organic salt forms, and wherein organic salt is disubstituted imidazole chloride, and the molar ratio of aluminum trichloride and organic salt is 0.5～4: 1. Anodic activation, also known as deplating, uses the same principle as electroplating to place the workpiece on the anode and use current to dissolve part of the metal ions on the surface of the bolt workpiece into the solution, remove the oxide layer in the tiny gap structure on the surface of the bolt, and make the surface of the bolt The oxide layer of each part is completely removed, and the surface has good activity, which provides reliable conditions for surface anti-corrosion treatment.

The activation parameters of the ionic liquid in step (2) of the present invention are as follows: the anode is a bolt workpiece, the cathode is a stainless steel plate, the temperature of the activation solution is 15-80°C, the activation current density is 2-10mA/cm ² , and the activation time is 2-8min. During the anode activation process, the temperature of the activation solution is controlled at a relatively low and suitable level, which not only ensures the conduction of the current in the ionic liquid and the ions on the workpiece on the anode are plated off under the action of the current, but also prevents the bolt from being over-activated and over-activated. Much ion exfoliation.

Further, the anode activation is carried out in an atmosphere protected by inert gas. After anodic activation, the oxide layer on the surface of the bolt workpiece is completely removed, and the metal components are completely exposed. Due to the high activity of metal iron, it is easy to be oxidized by the action of oxygen molecules and water molecules in the air, so the atmosphere protected by inert gas is used. Anodic activation can ensure the quality of anodic activation.

The electroplating solution in the ionic liquid electrodeposition described in the step ( ₃ ) of the present invention is a system composed of AlCl and an organic salt, wherein the organic salt is a disubstituted imidazole chloride, and its molar ratio is 1.5～2:1, and the ionic liquid is Lewis acid. The selection of Lewis acidic ionic liquid can promote the deposition rate of Al-Mn on the bolt surface during the electroplating process, improve the deposition morphology of Al-Mn, and have a synergistic effect on the formation of a uniform coating structure on the bolt surface.

The parameters of the ionic liquid electrodeposition described in step (3) of the present invention are as follows: a two-electrode system is adopted, the anode is an aluminum plate, and the cathode is a bolt workpiece processed through the steps (1) (2), and the bath temperature is 25° C. The anode current density is 6-20mA/cm ² , and the plating time is 0.5h-2h.

Steps (2) and (3) of the present invention all adopt barrel plating equipment and are carried out in a vacuum glove box, wherein the rotating speed of barrel plating is 10-20r/min. That is, in the process of anodic activation, barrel plating equipment is also used. In this way, the workpiece can be homogenized in the process of anodic activation, ensuring that all parts of the bolt can be well activated, and the aluminum deposited by subsequent electroplating The uniform adhesion of each part of the manganese layer provides a good guarantee.

Compared with the prior art, the present invention has the following beneficial effects:

1. The process of the present invention adopts ionic liquid anodic activation, and anodic activation is to use electrolysis to further remove the oxide film on the surface of the substrate sample to obtain a microscopically rough surface, which is conducive to enhancing the bonding force between the coating and the substrate obtained by subsequent electrodeposition.

2. The present invention adopts an ionic liquid electrodeposition process, which is suitable for electrodeposition of active metals and alloys, and the coating obtained in an anhydrous and oxygen-free environment has high density and high purity, no hydrogen embrittlement, the process can be operated at room temperature, and is highly environmentally friendly.

3. The aluminum-manganese alloy coating obtained in the present invention has extremely excellent corrosion resistance, and can be used as a sacrificial anode coating, which greatly improves the corrosion resistance of bolts.

4. The barrel plating equipment adopted in the present invention is suitable for batch plating of special-shaped small parts, and the obtained coating, especially the coating around the thread, is uniform and dense, which solves the problems of conventional rack plating well.

Description of drawings:

FIG. 1 is a macroscopic view of a bolt after electroplating an AlMn coating in Example 1. FIG.

Fig. 2 is the SEM picture of the bolt after electroplating AlMn coating in embodiment 1.

FIG. 3 is a cross-sectional SEM diagram of the crest of the external thread of the bolt after electroplating the AlMn coating in Example 1. FIG.

Fig. 4 is a macroscopic view of samples of carbon steel and AlMn-plated bolts in Example 1 after 10 days of salt spray test.

FIG. 5 is a macroscopic view of a bolt after electroplating an AlMn coating in Example 2. FIG.

Fig. 6 is the SEM image of the bolt after electroplating AlMn coating in embodiment 2.

Detailed ways

The present invention will be further described in detail below in conjunction with test examples and specific embodiments. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

The present invention will be further described below in conjunction with specific embodiment

Embodiment 1 In 45# bolt surface ionic liquid electrodeposition aluminum-manganese alloy coating, concrete steps are as follows:

(1): Use one-step degreasing method to degrease and degrease 45# bolts. The degreasing agent is sodium hydroxide 20g/L, sodium carbonate 10g/L, trisodium phosphate 15g/L and the rest of deionized water. Put the 45# bolt workpiece as the cathode, and the 304 stainless steel plate as the anode, put it into the electrolyte at a temperature of 60°C, apply a current density of 10mA/cm ² , and electrolytically degrease for 30s. Subsequently, the 45# bolt workpiece that has been electrolytically degreased is immersed in 20% HCl and cleaned for 5 minutes to preliminarily remove the oxide film on the surface of the substrate.

(2) The above-mentioned 45# bolts processed through the steps are immersed in the activation solution to carry out anodic activation treatment, with the 45# bolt workpiece as the anode, and the Al plate (purity 99.9wt%) as the cathode; the activation solution is prepared by the following method: A small amount of anhydrous aluminum chloride is added to disubstituted imidazole chloride (1-ethyl-3-methylimidazole chloride) several times to form a disubstituted imidazole chloride-aluminum chloride type ionic liquid at room temperature. The molar ratio of disubstituted imidazolium chloride to AlCl ₃ is 1:0.5, and the ionic liquid is Lewis basic; the applied activation current density is 6mA/cm ² , the activation time is 4min, and the rotational speed of barrel plating is 10r/min.

After the anodic activation treatment, rinse the 45# bolt in the activation solution for 3 times; finally wipe it with absorbent cotton until the surface of the substrate reveals a metallic luster.

(3) Electrodeposit the aluminum-manganese alloy coating on the surface of the 45# bolts pretreated by the above steps, and immerse the 45# bolts after the surface pretreatment in the plating solution in an argon-protected glove box for constant current electroplating. Deposition treatment: a two-electrode system is adopted, with the 45# bolt that has been pretreated on the surface as the cathode (working electrode), and the metal Al sheet with a purity of 99.9wt% as the anode (counter electrode), and the temperature of the plating solution is 25 ° C. The current density at the working electrode is 6mA/cm ² ; the electrodeposition time is 2h. Among them, the preparation method of the plating solution is as follows: a small amount of anhydrous aluminum chloride is added to 1-methyl-3-ethyl imidazole chloride several times, and a disubstituted imidazole chloride (EMIC)-aluminum chloride type is formed at room temperature. The ionic liquid, the molar ratio of 1-methyl-3-ethyl imidazolium chloride and AlCl ₃ is 1:2, then weigh a certain amount of anhydrous MnCl2 solid powder and add it to the AlCl ₃ -EMIC ionic liquid, where the concentration of MnCl2 is 0.15mol/L.

Steps (2) and (3) of the present invention all adopt barrel plating equipment, carried out in a vacuum glove box, and the rotating speed of barrel plating is 10r/min.

In the bolt workpiece obtained through the above electrodeposition process, it can be seen macroscopically that the surface of the bolt is covered with a layer of Al-Mn coating as shown in Figure 1, and the coating is uniform, dense and free of voids. A scanning electron microscope (SEM) was used to observe the surface morphology of the aluminum-manganese coating on the surface of the 45# bolt (as shown in Figure 2). The coating is dense without holes and consists of micron-scale nodular structures, showing amorphous morphology. According to EDS analysis, the Mn content on the surface of the coating is 20.3at%.

Figure 3 is a cross-sectional SEM image of the crest of the external thread of the bolt. The aluminum-manganese coating is evenly coated on the bolt substrate, with a thickness of about 10 μm, and the bonding force between the coating and the substrate is very good.

The corrosion resistance of the samples was tested, and the 45# steel bolts began to appear rust spots after 5 hours of salt spray test, while the carbon steel bolts coated with aluminum and manganese did not appear rust spots after 240 hours. Figure 4 is a macroscopic view of the sample after the ten-day salt spray test.

Embodiment 2: ionic liquid electrodeposits aluminum-manganese alloy coating on the surface of 304 stainless steel bolts, the specific steps are as follows:

(1): Use one-step degreasing method to degrease and degrease 304 stainless steel bolts. The degreasing agent is sodium hydroxide 30g/L, sodium carbonate 30g/L, trisodium phosphate 5g/L and the rest of deionized water. The 304 stainless steel bolt workpiece is used as the cathode, and the 304 stainless steel plate is used as the anode, put into the electrolyte at a temperature of 60°C, apply a current density of 5mA/cm ² , and electrolytically degrease for 1min. Subsequently, the 304 stainless steel bolt workpiece that has been electrolytically degreased is immersed in 10% HCl and cleaned for 10 minutes to initially remove the oxide film on the surface of the substrate.

(2) The above-mentioned 304 stainless steel bolts processed through the steps are immersed in the activation solution to carry out anodic activation treatment, with the 304 stainless steel bolt workpiece as the anode, and the Al plate (purity 99.9wt%) as the cathode; the activation solution is prepared by the following method: A small amount of anhydrous aluminum chloride is added to disubstituted imidazole chloride (1-ethyl-3-methylimidazole chloride) several times to form a disubstituted imidazole chloride-aluminum chloride type ionic liquid at room temperature. The molar ratio of disubstituted imidazolium chloride to AlCl ₃ is 1:0.8, and the ionic liquid is Lewis basic; the applied activation current density is 2mA/cm ² , the activation time is 8min, and the rotational speed of barrel plating is 20r/min.

After the anodic activation treatment, rinse the 304 stainless steel bolts in the activation solution for 3 times; finally wipe them with absorbent cotton until the surface of the substrate reveals a metallic luster.

(3) Electrodeposit the aluminum-manganese alloy coating on the surface of the 304 stainless steel bolts that have been pretreated in the above steps. In an argon-protected glove box, immerse the 304 stainless steel bolts after the surface pretreatment in the plating solution for constant current electroplating. Deposition treatment: a two-electrode system is adopted, with the 304 stainless steel bolts that have been pretreated on the surface as the cathode (working electrode), and the metal Al sheet with a purity of 99.9wt% as the anode (counter electrode), and the temperature of the plating solution is 25 ° C. The current density at the working electrode is 10mA/cm ² ; the electrodeposition time is 60min. Wherein, the preparation method of the plating solution is as follows: a small amount of anhydrous aluminum chloride is added to 1-methyl-3-ethyl imidazole chloride several times, and a disubstituted imidazole chloride-aluminum chloride type ionic liquid is formed at room temperature. The molar ratio of 1-methyl- ₃ -ethylimidazolium chloride and AlCl3 is 1:2, then weigh a certain amount of anhydrous MnCl2 solid powder and add it to the AlCl3 _- EMIC ionic liquid, where the concentration of MnCl2 is 0.2mol /L.

Steps (2) and (3) of the present invention all adopt barrel plating equipment, and carry out in a vacuum glove box, and the rotating speed of barrel plating is 20r/min.

In the bolt workpiece obtained through the above electrodeposition process, it can be seen macroscopically that the surface of the bolt is covered with a layer of aluminum-manganese coating, and the coating is uniform, dense and free of voids (as shown in Figure 5). A scanning electron microscope (SEM) was used to observe the surface morphology of the aluminum-manganese coating on the surface of 304 stainless steel bolts (as shown in Figure 6). The coating is dense and without holes, and consists of micron-sized nodular structures with a diameter of less than 5 μm, showing an amorphous morphology. feature. According to EDS analysis, the Mn content on the surface of the coating is 29at%.

Example 3-6

The 304 stainless steel bolt workpiece was treated with the same pretreatment method as in Example 2, and then the surface deposition electroplating was performed using the same electroplating method. There are only some differences in the temperature and composition ratio of the ionic liquid during the electroplating process, the current density and time of electroplating, etc., see Table 1 below for details.

Table 1

*The composition ratio is the molar ratio of 1-methyl-3-ethylimidazole chloride and AlCl3

It can be seen from the above examples that when the current density is controlled at 6-10mA/cm ² and the ratio of aluminum trichloride and EMIC in the selected ionic liquid is 1-2:1, when the concentration of MnCl ₂ is 0.2-0.3mol/L, the obtained The coating is amorphous. When the concentration of MnCl2 is 0.1mol/L, 20mA/ ^cm2 large current electroplating can get the coating of crystal phase. When the current density is controlled at 6-10mA/cm ² , AlCl ₃ :EMIC=1～2:1, and the concentration of MnCl ₂ is 0.1-0.5mol/L, the obtained coating is amorphous Al-Mn, which has High hardness, corrosion resistance, etc., is an ideal coating.

Embodiment 7-8 and comparative example 9-10

Use the same pretreatment method as in Example 1 for 45# bolts, and then use the same electroplating method for surface deposition electroplating. There are only some differences in the temperature and composition ratio of the ionic liquid during the electroplating process, the current density and time of electroplating, etc., see Table 2 below for details.

Table 2

**The ingredient ratio is the molar ratio of 1-methyl-3-ethylimidazole chloride and AlCl3.

Claims (10)

1. A bolt surface anti-corrosion method, comprising the steps of: Step (1) Degreasing and pickling: Put the bolts in the electrolyte, electrolytically degrease, put the electrolytically degreased bolts into the pickling solution, and pickle to remove the oxides on the surface of the bolt matrix; Step (2) Anode activation: Put the bolts into the activation solution to remove the plating; Step (3) Ionic liquid electrodeposition: immerse the bolts treated in steps (1) and (2) in the electroplating solution for constant current electrodeposition treatment; the electroplating solution is composed of disubstituted imidazolium chloride-aluminum chloride ionic liquid and manganese salt; the disubstituted imidazolium chloride-aluminum chloride type ionic liquid is composed of disubstituted imidazolium chloride and AlCl according to a molar ratio of ₁ :1.5~2, and the ionic liquid is Lewis acidic; the electroplating solution The concentration of manganese salt is 0.1~0.3mol/L; a two-electrode system is adopted, with bolts as the working electrode and metal aluminum as the counter electrode; the temperature of the plating solution is 20~40°C, and the anode current density is 6-20mA/cm ² . Plating time is 0.5h-2h. 2. The bolt surface anticorrosion method according to claim 1, characterized in that the electroplating operation is carried out in an inert gas atmosphere. 3. The anti-corrosion method for the bolt surface according to claim 1, characterized in that, the plating method is barrel plating, and the rotation speed is 10-20r/min. 4. The anti-corrosion method for bolt surface according to claim 1, characterized in that, in the electrolytic degreasing process of bolts described in step (1), the electrolyte is an alkaline degreasing liquid comprising: sodium hydroxide 20-60g/ L, sodium carbonate 20-40g/L, trisodium phosphate 5-15g/L. 5. The anti-corrosion method for bolt surface according to claim 1, characterized in that step (1) is to use the bolt workpiece as the cathode, put it into the electrolyte at a temperature of 50-90°C, and apply a current density of 2-10mA/ cm2, electrolytic degreasing 20s-2min. 6. The bolt surface anticorrosion method according to claim 1, characterized in that, in the bolt pickling process described in step (1), the pickling solution is one or a combination of dilute hydrochloric acid, dilute sulfuric acid, dilute nitric acid more than one species. 7. The bolt surface anticorrosion method according to claim 1, characterized in that the mass concentration of the pickling solution is 5-10%, and the pickling time is 20s-2min. 8. The bolt surface anticorrosion method according to claim 1, characterized in that the ionic liquid anode activation solution in step ( ₂ ) is a system composed of AlCl and organic salts, wherein the organic salts are disubstituted imidazole chlorides , the molar ratio of aluminum trichloride and organic salt is 0.5~4:1. 9. The bolt surface anticorrosion method according to claim 1, characterized in that the activation parameters of the ionic liquid in step (2) are as follows: the anode is a bolt workpiece, the cathode is a stainless steel plate, the temperature of the activation solution is 15-80°C, and the activation temperature is 15-80°C. The current density is 2-10mA/cm2, and the activation time is 2-8min. 10. The bolt surface anticorrosion method according to claim 1, characterized in that the electroplating solution in the ionic liquid electrodeposition described in step (3) is a system composed of AlCl ₃ and organic salts, wherein the organic salts are disubstituted Imidazole chloride has a molar ratio of 1.5~2:1, and the ionic liquid is Lewis acidic.