CN119287369B - High-strength corrosion-resistant chromeplated bolt and preparation method thereof - Google Patents
High-strength corrosion-resistant chromeplated bolt and preparation method thereof Download PDFInfo
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Abstract
The application relates to the field of metal surface treatment, and particularly discloses a high-strength corrosion-resistant chromeplate bolt and a preparation method thereof, wherein the preparation method comprises the following steps of S1, pretreatment, S2, intermediate layer treatment, namely, coating mixed powder of LaNi5 alloy powder and nickel powder on the surface of the pretreated bolt by adopting a plasma spraying technology to form an intermediate layer, S3, chromeplating, namely, placing the bolt subjected to the intermediate layer treatment in an electroplating chromeplate solution added with a trivalent chromeplate source and a stabilizer for electroplating, S4, post-treatment, and sequentially carrying out water washing, drying and dehydrogenation treatment on the bolt subjected to the electroplating in the step S3 to prepare the chromeplate bolt.
Description
Technical Field
The application relates to the technical field of metal surface treatment, in particular to a high-strength corrosion-resistant chromeplated bolt and a preparation method thereof.
Background
The chromed bolt is a fastener which is formed by plating a layer of chromium on the surface of the bolt through an electroplating process so as to enhance the corrosion resistance and the attractive appearance of the bolt. The chromed bolt can keep better corrosion resistance in severe environment, is not easy to rust and corrode, has smooth and bright surface after chromed, is rich in metal texture, and has longer service life due to better wear resistance and corrosion resistance.
The aircraft can try various adverse circumstances such as high temperature, high humidity, salt fog etc. in the flight in-process, and chromed bolt can effectively resist the erosion of these environmental factors by virtue of its excellent corrosion resistance to extension bolt's life guarantees the safe operation of aircraft, and in aviation field, the bolt needs to bear huge pulling force and shearing force moreover, and chromed bolt's chromed layer has very high hardness and wearability, can show the mechanical properties that promotes the bolt, ensures aircraft's structural integrity and stability.
Along with the continuous development of aviation technology, the application field of the chromed bolt is also expanding continuously, and besides the traditional aircraft structural connection, the chromed bolt is also widely applied to the fields of the assembly of aeroengines, the connection of avionics systems and the like.
However, the traditional chromium plating process of the bolt adopts hexavalent chromium for chromium plating, the use of hexavalent chromium causes potential threat to the environment and human health, so that the development of a more environment-friendly high-strength corrosion-resistant chromium plating technology is required, the environment-friendly chromium plating technology adopting trivalent chromium to replace hexavalent chromium is gradually raised in recent years, but the quality of a plating layer of a chromium plating layer obtained by adopting trivalent chromium as a chromium plating liquid is required to be improved at present, and the aviation chromium plating bolt has higher requirements on the strength and corrosion resistance thereof, and a new solution is required to be provided for the bolt with the higher requirement on the plating layer quality so as to meet the requirements.
Disclosure of Invention
In order to take trivalent chromium as a chromium plating solution and have higher strength and corrosion resistance to a plating layer obtained by chromium plating of a bolt so as to meet high requirements, the application provides a high-strength corrosion-resistant chromium plated bolt and a preparation method thereof.
In a first aspect, the application provides a method for preparing a high-strength corrosion-resistant chromeplated bolt, which adopts the following technical scheme:
A preparation method of a high-strength corrosion-resistant chromeplated bolt comprises the following steps:
S1, preprocessing, namely cleaning a bolt, removing oil and then washing the bolt with water;
S2, carrying out intermediate layer treatment, namely coating mixed powder of LaNi5 alloy powder and nickel powder on the surface of the pretreated bolt by adopting a plasma spraying technology to form an intermediate layer;
S3, chromium plating, namely placing the bolt treated by the middle layer in the step S2 into an electroplating chromium solution added with a trivalent chromium source and a stabilizer for electroplating;
S4, post-treatment, namely sequentially performing water washing, drying and dehydrogenation treatment on the bolt electroplated in the step S3 to obtain the chromed bolt.
According to the technical scheme, the quality of the chromium plating layer formed by electroplating with the trivalent chromium plating solution is poor, on one hand, the trivalent chromium plating solution is poor in stability and is easy to convert into hexavalent chromium, so that the stability of the electroplating solution and the quality of a plating layer are affected, and on the other hand, hydrogen is generated in the electroplating process due to the existence of the trivalent chromium plating solution and the electroplating chromium solution, the hydrogen is absorbed by the bolts in the electrochemical reaction process, hydrogen atoms absorbed by the bolts can diffuse in metal and gather at defects such as inclusions or cracks, the gathered hydrogen atoms are recombined into hydrogen molecules, high pressure is formed at the defects, and along with the continuous diffusion and gathering, a hydrogen embrittlement phenomenon finally occurs, the bonding strength is reduced, and the corrosion resistance and the strength are also affected.
Therefore, on the one hand, the stability is added in the chromium electroplating solution to improve the stability of trivalent chromium solution, on the other hand, after the bolt is subjected to cleaning and degreasing pretreatment, firstly, an intermediate layer is formed on the surface by spraying LaNi5 (AB 5 type) alloy powder through plasma, wherein the LaNi5 alloy powder takes Ni as a main metal element, la is a rare earth element, the rare earth metal in the formation of the intermediate layer can react with hydrogen to generate rare earth hydride, so that the initial hydrogen storage is realized, the hydrogen absorption of a bolt matrix in the chromium plating process is reduced, the probability of hydrogen embrittlement caused by the penetration of the hydrogen into the bolt is reduced, and then the hydrogen removal treatment is performed at the later stage to remove the stored hydrogen in the alloy powder, so that the quality of a plating layer is poor due to the hydrogen embrittlement phenomenon is fundamentally reduced, the quality of the plating layer is improved, the LaNi5 alloy intermediate layer has good corrosion resistance, the corrosion resistance of the overall plating layer can be further improved, the bonding strength between the bolt and the chromium plating layer can be further improved by adopting a plasma spraying means, the plating layer is prevented from peeling, and finally, the obtained layer through the method has high strength, the corrosion resistance and better bonding strength and meets the high-strength requirement of the plating layer.
Optionally, the adding mass ratio of the LaNi5 alloy powder to the nickel powder is 1 (1.2-1.5).
By adopting the technical scheme, the prior aviation bolt is mainly made of titanium alloy or high-strength steel, particularly high-strength steel, and has better corrosion resistance and high temperature resistance because of relatively stable chemical property of nickel, and the surface activity of the nickel is lower than that of carbon steel, so that trivalent chromium is better combined with nickel base in the electroplating process of trivalent chromium, and therefore, when LaNi5 alloy powder and nickel powder are selected as an intermediate layer in the application, the LaNi5 alloy powder is used as rare earth hydrogen storage alloy powder, so that the hydrogen embrittlement phenomenon is solved, the problem that the bonding strength of the prior trivalent chromium electroplating technology and a base material is weak is solved, the hydrogen embrittlement phenomenon is reduced, and the corrosion resistance and the strength performance of the chromium-plated bolt are obviously improved by forming the intermediate layer between chromium-plated layers.
Optionally, the nickel powder is spherical nickel powder and spindly spherical nickel powder with the mass ratio of 1 (0.6-0.8) and the particle size of 20-30 nm.
By adopting the technical scheme, the surface of the spinned spherical nickel powder is covered with the spinned structure with nanometer size, which is favorable for enhancing the adhesiveness with the base layer and the chrome plating layer and enhancing the bonding strength, while the surface of the spherical nickel powder is smooth and easy to disperse, which is favorable for forming a uniform coating in the electroplating process, and the spherical nickel powder can provide good wettability and is favorable for spreading and bonding the chrome plating layer on the middle layer.
Optionally, in the step S2, in the plasma spraying process, the spraying distance is 50-100mm, the spraying power is 15-25kw, the spraying speed is 120-150mm/S, and the spraying thickness is 250-300nm.
By adopting the technical scheme, the bonding strength between the middle layer and the bolt and the chromium coating and the comprehensive performance of the formed comprehensive coating are better through controlling the parameters.
Optionally, the chromium electroplating solution in the step S3 includes the following raw materials:
30-70g/L trivalent chromium salt, 0.1-0.2g/L stabilizer, 30-50g/L complexing agent, 120-150g/L conductive salt and 50-80g/L buffer.
By adopting the technical scheme, trivalent chromium ions are provided by the trivalent chromium salt, the conductivity of the plating solution is improved by the conductive eye, the pH value of the plating solution can be maintained by adding the buffering agent to meet the electroplating requirement, the complexing agent can form a complexing effect with the trivalent chromium salt, inert trivalent chromium is converted into an easy-to-deposit complex with higher electric activity, the quality of a plating layer is improved, the stabilizer can prevent the trivalent chromium from being oxidized into hexavalent chromium, and hexavalent chromium in the plating solution is reduced into trivalent chromium, so that the stability of the plating solution is improved, and the quality of the plating layer is improved.
Optionally, the trivalent chromium salt is chromium sulfate, the conductive salt is one or more of sodium sulfate, potassium sulfate and ammonium sulfate, the buffer is one or more of boric acid, aluminum sulfate and citric acid, and the complexing agent is one or two of glycolic acid and citric acid;
The stabilizer at least comprises one or more of sodium sulfite, neutral amino acid, methanol, sodium hypophosphite and ferrous sulfate.
Optionally, the stabilizer is selected from sodium sulfite, neutral amino acid and PAMAM in a mass ratio of 1 (1.2-1.5) (0.1-0.2).
According to the technical scheme, the stabilizer disclosed by the application takes sodium sulfite and neutral amino acid as main materials, a small amount of PAMAM is added, on one hand, sodium sulfite can form a complex with trivalent chromium ions to further stabilize the chromium ions in the plating solution and prevent the chromium ions from being oxidized into hexavalent chromium, the sodium sulfite is used as a strong reducing agent to effectively inhibit and reduce the generation of hexavalent chromium in the plating solution, the neutral amino acid can form stable complexation with trivalent chromium ions and play a role in buffering the pH of the plating solution, the wettability of the plating solution can be increased, the PAMAM can be spread on the surface of an intermediate layer more easily, a small amount of PAMAM not only has good complexation capability and can form a stable complex with trivalent chromium, but also has excellent dispersion performance, can be used as an interface fusion agent to form a more uniform and stable plating solution, the quality of a plating layer is improved, a small amount of nitrogen element is introduced into a chromium plating layer, the nitrogen element can form nitride with the chromium element to further improve the corrosion resistance and the plating layer, and the plating layer quality is improved.
Optionally, the neutral amino acid is one or more of glycine, glutamic acid and alanine.
Optionally, the chromium electroplating solution is prepared by the following method:
dissolving trivalent chromium salt in water, adding a buffering agent, mixing and stirring, adding a complexing agent, stirring at 50-70 ℃ for 30-50min, adding a conductive salt and a stabilizing agent, stirring for 2-4h, regulating the pH value of the plating solution to 2.5-4.5, continuously stirring for 2-3h, and standing to obtain the chromium electroplating solution.
Optionally, when the chromium electroplating solution is prepared, the conductive salt is added, and 0.05-0.1g/L of sodium methyldisulfonate is also added.
By adopting the technical scheme, the sodium methyldisulfonate is used as the chromium plating brightening agent, so that the deposition speed of hard chromium is obviously improved, the current efficiency in the electroplating process is improved by more than 25%, and the bright chromium layer is formed, and the hardness and corrosion resistance are improved.
Optionally, during the chrome plating process, the electroplating temperature is 45-60 ℃.
Optionally, direct current plating is adopted for chrome plating, and the current density during plating is 1-3A/dm2.
By adopting the technical scheme, the plating quality is improved by controlling the plating temperature and the current density.
Optionally, pulse current is firstly adopted for electroplating for 20-30min and then direct current electroplating is continued, the pulse frequency is 2500-3000Hz, the pulse duty ratio is 20-40% and the current density is 5-10A/dm2 during pulse electroplating.
By adopting the technical scheme, the application firstly adopts pulse plating to form a plating layer on the middle layer, utilizes the rapid change of current in the pulse plating process to generate impact force, is beneficial to increasing the bonding force between the plating layer and the middle layer, simultaneously adopts pulse plating to reduce the defects of pores, cracks and the like in the plating layer, then carries out direct current plating, has more controllable plating thickness, forms a more compact and uniform plating layer by the pulse plating, can shorten the plating time, obviously improves the final plating quality, and finally adopts the combination of the pulse plating and the direct current plating to obviously improve the bonding strength of a chromium plating layer and the middle layer, obviously improves the plating quality such as corrosion resistance and the like, finally forms the middle layer by plasma spraying after acidification in the application, solves the bonding strength defect between the current trivalent chromium plating layer and a bolt base layer by the pulse plating, and improves the service life of the plating.
Optionally, the operation of the dehydrogenation in step S4 is as follows:
and (3) preserving the temperature of the chromed bolt at 130-150 ℃ for 60-90min.
Through adopting above-mentioned technical scheme, the bolt after will chromeplating is toasted the processing of above-mentioned temperature and is carried out the release and get rid of the hydrogen element in the rare earth alloy in the intermediate level, improves hardness, intensity and the corrosion resistance of bolt.
In a second aspect, the application provides a high-strength corrosion-resistant chromeplated bolt, which adopts the following technical scheme:
a high strength corrosion resistant chromed bolt is prepared by a method such as a high strength corrosion resistant chromed bolt.
By adopting the technical scheme, the chromeplated bolt prepared by the method has more excellent strength and corrosion resistance, and meets the high requirement of aviation bolts.
In summary, the application has the following beneficial effects:
1. According to the application, on one hand, stability is added in the chromium electroplating solution to improve the stability of the trivalent chromium solution, on the other hand, after the bolt is subjected to cleaning and degreasing pretreatment, an intermediate layer is formed on the surface by spraying LaNi5 (AB 5) alloy powder through plasma, the LaNi5 alloy powder takes Ni as a main metal element, la is a rare earth element, the rare earth metal in the formation of the intermediate layer can react with hydrogen to generate rare earth hydride, so that initial hydrogen storage is realized, the hydrogen absorption of a bolt matrix in the chromium plating process is reduced, the probability of hydrogen permeation into the bolt is reduced, hydrogen embrittlement is caused, and then hydrogen removal treatment is performed in the later stage to remove the stored hydrogen in the alloy powder, so that poor plating quality caused by the hydrogen embrittlement is fundamentally reduced, and the plating quality is improved;
2. When the LaNi5 alloy powder and the nickel powder are selected as the intermediate layer in the application, the LaNi5 alloy powder is used as the rare earth hydrogen storage alloy powder, which is helpful for solving the problem of hydrogen embrittlement, and the addition of the nickel powder is helpful for improving the problem of weak bonding strength between the existing trivalent chromium electroplating technology and the base material, and is also helpful for reducing the occurrence of the hydrogen embrittlement; and the bonding strength between the bolt and the chromium coating can be improved by adopting a plasma spraying means, the peeling of the coating is prevented, and finally the chromium coating obtained by the method provided by the application has high strength, better corrosion resistance and better coating bonding, and meets the requirement of higher requirement of high strength and corrosion resistance.
Detailed Description
The present application will be described in further detail with reference to the following examples, which are not to be construed as limiting the scope of the application, and the raw materials used in the following examples, unless otherwise specified, are commercially available.
The bolt base material in the following examples is a 30CrMnSiA alloy steel bolt.
In the following examples, lanthanum-nickel alloy powder LaNi5 of Baotou, which is a lanthanum-nickel alloy powder of New Material science and technology Co., ltd, wherein La content is 32.1% and Ni content is 67.9%.
Example 1
A preparation method of a high-strength corrosion-resistant chromeplated bolt comprises the following steps:
S1, preprocessing, namely primarily cleaning a bolt by deionized water to remove dust and impurities on the surface, degreasing by an alkaline cleaning agent, performing acid cleaning activation in a dilute sulfuric acid solution with the mass concentration of 20% for 15min, and then drying after washing;
s2, carrying out intermediate layer treatment, namely mixing LaNi5 alloy powder and nickel powder according to the mass ratio of 1:1.3 to obtain mixed powder, and then coating the mixed powder of the LaNi5 alloy powder and the nickel powder on the surface of the pretreated bolt by adopting a plasma spraying technology to form an intermediate layer, wherein the specific parameters of plasma spraying are that the spraying distance is 80mm, the spraying power is 20kw, the spraying speed is 130mm/S, and the spraying thickness is 280nm, wherein the nickel powder is spherical nickel powder and thorn spherical nickel powder with the particle size of 20-30nm and the mass ratio of 1:0.7;
s3, chromium plating, namely preparing an electroplating chromium liquid, namely preparing materials according to 50g/L trivalent chromium salt, 0.15g/L stabilizer, 40g/L complexing agent, 130g/L conductive salt, 65g/L buffering agent and 0.08g/L sodium methyldisulfonate brightening agent;
Dissolving trivalent chromium salt in water, adding a buffering agent, mixing and stirring, adding a complexing agent, stirring at 60 ℃ for 40min, adding a conductive salt, a stabilizing agent and a brightening agent, stirring for 3h, adjusting the pH of the plating solution to 3, continuously stirring for 2.5h, and standing to obtain an electroplating chromium solution;
Wherein, the trivalent chromium salt is chromium sulfate, the conductive salt is sodium sulfate, the buffering agent is boric acid, the complexing agent is glycolic acid, the stabilizing agent is sodium sulfite, neutral amino acid and PAMAM with the mass ratio of 1:1.3:0.15, and the neutral amino acid is glutamic acid;
Placing the bolt subjected to the interlayer treatment in the step S2 into the obtained chromium electroplating solution for electroplating, wherein the electroplating temperature is 50 ℃, and the direct current electroplating is performed by taking a graphite rod as an anode, and the current density during electroplating is 2A/dm < 2 >;
S4, post-treatment, namely sequentially performing water washing, drying and dehydrogenation treatment on the bolt electroplated in the step S3, wherein the dehydrogenation treatment is performed by keeping the temperature of the bolt subjected to chromium plating at 140 ℃ for 70 minutes, and then cooling to obtain the chromium plated bolt.
Example 2
A preparation method of a high-strength corrosion-resistant chromeplated bolt comprises the following steps:
S1, preprocessing, namely primarily cleaning a bolt by deionized water to remove dust and impurities on the surface, degreasing by an alkaline cleaning agent, performing acid cleaning activation in a dilute sulfuric acid solution with the mass concentration of 20% for 10min, and then drying after washing;
S2, carrying out intermediate layer treatment, namely mixing LaNi5 alloy powder and nickel powder according to the mass ratio of 1:1.2 to obtain mixed powder, and then coating the mixed powder of the LaNi5 alloy powder and the nickel powder on the surface of the pretreated bolt by adopting a plasma spraying technology to form an intermediate layer, wherein the specific parameters of plasma spraying are that the spraying distance is 50mm, the spraying power is 15kw, the spraying speed is 120mm/S, and the spraying thickness is 250nm, wherein the nickel powder is spherical nickel powder and spiny spherical nickel powder with the particle size of 20nm and the mass ratio of 1:0.6;
S3, chromium plating, namely preparing chromium electroplating solution, namely preparing materials according to 30g/L trivalent chromium salt, 0.1g/L stabilizer, 30g/L complexing agent, 120g/L conductive salt, 50g/L buffer and 0.05g/L sodium methyldisulfonate brightening agent;
Dissolving trivalent chromium salt in water, adding a buffering agent, mixing and stirring, then adding a complexing agent, stirring at 50 ℃ for 50min, adding a conductive salt, a stabilizing agent and a brightening agent, stirring for 2h, adjusting the pH of the plating solution to 2.5, continuously stirring for 2h, and standing to obtain an electroplating chromium solution;
Wherein, the trivalent chromium salt is chromium sulfate, the conductive salt is ammonium sulfate, the buffering agent is boric acid and aluminum sulfate with the mass ratio of 1:1, the complexing agent is glycolic acid, the stabilizer is sodium sulfite, neutral amino acid and PAMAM with the mass ratio of 1:1.2:0.1, and the neutral amino acid is glycine;
placing the bolt subjected to the interlayer treatment in the step S2 into the obtained chromium electroplating solution for electroplating, wherein the electroplating temperature is 45 ℃, and the direct current electroplating is performed by taking a graphite rod as an anode, and the current density during electroplating is 3A/dm2;
s4, post-treatment, namely sequentially performing water washing, drying and dehydrogenation treatment on the bolt electroplated in the step S3, wherein the dehydrogenation treatment is performed by preserving heat of the bolt subjected to chromium plating at 130 ℃ for 90 minutes, and then cooling to obtain the chromium plated bolt.
Example 3
A preparation method of a high-strength corrosion-resistant chromeplated bolt comprises the following steps:
S1, preprocessing, namely primarily cleaning a bolt by deionized water to remove dust and impurities on the surface, degreasing by an alkaline cleaning agent, performing acid cleaning activation in a dilute sulfuric acid solution with the mass concentration of 20% for 20min, and then drying after washing;
S2, carrying out intermediate layer treatment, namely mixing LaNi5 alloy powder and nickel powder according to the mass ratio of 1:1.5 to obtain mixed powder, and then coating the mixed powder of the LaNi5 alloy powder and the nickel powder on the surface of the pretreated bolt by adopting a plasma spraying technology to form an intermediate layer, wherein the specific parameters of plasma spraying are that the spraying distance is 100mm, the spraying power is 25kw, the spraying speed is 150mm/S, and the spraying thickness is 300nm, wherein the nickel powder is spherical nickel powder and thorn spherical nickel powder with the particle size of 20-30nm and the mass ratio of 1:0.8;
s3, chromium plating, namely preparing an electroplating chromium liquid, namely preparing materials according to 70g/L trivalent chromium salt, 0.2g/L stabilizer, 50g/L complexing agent, 150g/L conductive salt, 80g/L buffering agent and 0.1g/L sodium methyldisulfonate brightening agent;
Dissolving trivalent chromium salt in water, adding a buffering agent, mixing and stirring, adding a complexing agent, stirring at 70 ℃ for 30min, adding a conductive salt, a stabilizing agent and a brightening agent, stirring for 4h, adjusting the pH of the plating solution to be 4.5, continuously stirring for 3h, and standing to obtain an electroplating chromium solution;
Wherein, the trivalent chromium salt is chromium sulfate, the conductive salt is sodium sulfate, the buffering agent is boric acid, the complexing agent is glycolic acid, the stabilizer is sodium sulfite, neutral amino acid and PAMAM with the mass ratio of 1:1.5:0.2, and the neutral amino acid is alanine;
Placing the bolt subjected to the interlayer treatment in the step S2 into the obtained chromium electroplating solution for electroplating, wherein the electroplating temperature is 60 ℃, and the direct current electroplating is performed by taking a graphite rod as an anode, and the current density during electroplating is 1A/dm2;
S4, post-treatment, namely sequentially performing water washing, drying and dehydrogenation treatment on the bolt electroplated in the step S3, wherein the dehydrogenation treatment is performed by keeping the temperature of the bolt subjected to chromium plating at 150 ℃ for 60 minutes, and then cooling to obtain the chromium plated bolt.
Example 4
A preparation method of a high-strength corrosion-resistant chromed bolt is carried out according to the method in the embodiment 1, except that sodium sulfite is adopted as a stabilizer.
Example 5
A preparation method of a high-strength corrosion-resistant chromeplated bolt is carried out according to the method in the embodiment 1, and is different in that sodium sulfite and glutamic acid with the mass ratio of 1:1.3 are adopted as stabilizers.
Example 6
A preparation method of a high-strength corrosion-resistant chromeplated bolt is carried out according to the method in the embodiment 1, and is different in that all nickel powder in the step S2 is spherical nickel powder.
Example 7
A preparation method of a high-strength corrosion-resistant chromeplated bolt is carried out according to the method in the embodiment 1, and is characterized in that square wave pulse current is firstly adopted for electroplating for 25min and then direct current electroplating is continued in the step S3, the pulse frequency is 2800Hz, the pulse duty ratio is 30%, and the current density is 8A/dm2 in the pulse electroplating.
Example 8
A preparation method of a high-strength corrosion-resistant chromeplated bolt is carried out according to the method in the embodiment 1, and is characterized in that square wave pulse current is firstly adopted for electroplating for 20-30min in the step S3, then direct current electroplating is continued, the pulse frequency is 3000Hz, the pulse duty ratio is 20%, and the current density is 5A/dm2 in the pulse electroplating.
Example 9
A preparation method of a high-strength corrosion-resistant chromeplated bolt is carried out according to the method in the embodiment 1, and is characterized in that square wave pulse current is firstly adopted for electroplating for 20-30min in the step S3, then direct current electroplating is continued, the pulse frequency is 2500Hz, the pulse duty ratio is 40%, and the current density is 10A/dm2 in the pulse electroplating.
Example 10
A method for preparing a high-strength corrosion-resistant chromed bolt was carried out in the same manner as in example 7, except that the pulse frequency of the pulse current was 2000Hz.
Comparative example 1
A method for preparing a high-strength corrosion-resistant chromed bolt is carried out according to the method in the embodiment 1, except that the treatment of the step S2 is not carried out, and the bolt pretreated in the step S1 is directly subjected to the chromed operation in the step S3.
Comparative example 2
A preparation method of a high-strength corrosion-resistant chromeplated bolt is carried out according to the method in the embodiment 1, except that the LaNi5 alloy powder in the step S2 is replaced by nickel powder in an equivalent amount to form a nickel-based intermediate layer.
Comparative example 3
A preparation method of a high-strength corrosion-resistant chromeplated bolt is carried out according to the method in the embodiment 1, except that nickel powder is replaced by Lani5 alloy powder in an equivalent amount in the step S2 to form an alloy intermediate layer.
Comparative example 4
A preparation method of a high-strength corrosion-resistant chromeplated bolt is carried out according to the method in the embodiment 1, except that a stabilizer is not added in the chromium electroplating solution in the step S3.
Performance detection
The chromed bolts of the examples and comparative examples of the present application were finally chromed to a thickness of 6 μm by controlling the plating time, and then the chromed bolts of the examples and comparative examples of the present application were subjected to hardness and corrosion resistance test, wherein the corrosion resistance test was a copper ion accelerated salt spray test (CASS test) at 50 ℃ and a salt spray solution of 5% by mass concentration and a copper chloride doped with 10% by mass of sodium chloride, and the time when the test pieces showed corrosion spots, rust or bubble phenomenon was observed.
Table 1:
Continuing with table 1:
Referring to the test results in table 1 above, the hardness of the chromed bolts produced in examples 1-3 of the present application was above 600, the chromed bolts obtained had better strength, and corrosion resistance did not appear in the copper ion accelerated salt spray test for 78 hours or more, such as corrosion spots, red rust, etc., and it can be seen that the bonding force between the plating layer and the bolt substrate in the present application was better. And combining the detection results of the embodiment 1, the embodiment 4 and the embodiment 5 again, it can be seen that when PAMAM is not added in the stabilizer, the quality of the final coating is reduced, the stabilizer is helpful to maintain the stability of trivalent chromium, so that a more uniform and compact coating is formed, the quality of the coating is improved, the combination with the bolt base material is better, when the detection result of the embodiment 6 is combined again, the combination force between the coating and the base material is obviously reduced when the spherical nickel powder is fully selected as the nickel powder in the middle layer, the final corrosion resistance is also reduced, and when the detection result of the embodiment 7-9 is combined again, the pulse plating is performed first and then the direct current plating is performed in the step S3, the combination force of the final coating is better, and the corrosion resistance is better. And in combination with the detection result of the embodiment 10, the bonding force between the coating and the substrate is affected when the pulse current frequency is low, and the corrosion resistance is also reduced to a small extent, so that the coating quality is affected.
Referring to the results of the test of example 1 and comparative example 1, it can be seen that the bonding force between the plating layer and the substrate is significantly reduced and the corrosion resistance is also reduced when the intermediate layer treatment in step S2 is not performed, and referring to the test results of comparative example 2 and comparative example 3, the bonding property between the plating layer and the substrate is reduced and the quality of the plating layer is also reduced when the intermediate layer is a single nickel layer or an alloy layer, and the quality of the plating layer is reduced when the stabilizer is not added to the chrome plating solution in combination with the test result of comparative example 4.
The present embodiment is only for explanation of the present application and is not to be construed as limiting the present application, and modifications to the present embodiment, which may not creatively contribute to the present application as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present application.
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| CN102899681A (en) * | 2012-10-26 | 2013-01-30 | 华侨大学 | Porous nickel composite electrode, electroplating solution and preparation method of porous nickel composite electrode |
| CN105018973A (en) * | 2014-11-27 | 2015-11-04 | 太仓市金鹿电镀有限公司 | Environment-friendly electroplating liquid and electroplating process |
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