WO2022170803A1

WO2022170803A1 - Electroplating solution for steel substrate direct cyanide-free plating under strong acidic conditions, and preparation method therefor

Info

Publication number: WO2022170803A1
Application number: PCT/CN2021/131270
Authority: WO
Inventors: 张志梁
Original assignee: 张志梁
Priority date: 2021-02-10
Filing date: 2021-11-17
Publication date: 2022-08-18
Also published as: CN112899738A; CN112899738B

Abstract

An electroplating solution for steel substrate direct cyanide-free plating under strong acidic conditions, comprising the following components: 50-250 g/L of a main salt, 30-100 g/L of a compound adsorbent, 1-5 g/L of an additive, and 160-300 g/L of a strong acid composition. The synergistic action of the compound adsorbent, the additive and the strong acid composition produces an effect of 1+1 being greater than 2, the speed of an "iron-copper replacement reaction" under strong acidic conditions is effectively inhibited, a steel substrate forms an elemental copper layer with a firm binding force at the moment of contact with the acidic plating solution, and the sulfuric acid content is 150-250 g/L. The present invention overcomes the technical problem that the stronger the acidity, the looser the plating layer, and the plating layer is still firm when reaching 300 μm.

Description

A direct cyanide-free copper-plating electroplating solution for iron and steel matrix under strong acid conditions and preparation method thereof

technical field

The invention belongs to the technical field of electroplating, and in particular relates to a direct cyanide-free copper-plating electroplating solution for a steel substrate under strong acid conditions and an electroplating method.

Background technique

Since the advent of electroplating technology for more than 100 years, direct acid copper plating on steel substrates has been regarded as a "forbidden area" by peers and is considered unfeasible. According to the metal activity sequence table: K, Na, Ca, Mg, Al, Zn, Fe, Sn, Pb, (H), Cu, Hg, Ag, Pt, Au, after the steel substrate workpiece enters the acid copper plating solution The substitution reaction will take place instantaneously: Fe+CuSO ₄ =Cu+FeSO ₄ generates a substitution copper layer with extremely poor loose bonding force. In general, the higher the acid content in the copper plating solution, the faster the replacement reaction, the rougher and more porous the copper plating layer, and the worse the bonding force. Direct copper plating of steel parts in strong acid conditions has always been regarded as a forbidden area in the industry and is considered unfeasible.

In order to obtain a good coating adhesion, the direct copper plating on the steel substrates at home and abroad adopts the alkaline highly toxic cyanide copper plating process (because cyanide is the best complexing agent in the metal electrodeposition process). However, cyanide is extremely toxic, and 0.2 grams can be fatal in an instant. A little carelessness in production, storage, transportation, and use will lead to unimaginable consequences. It seriously pollutes the environment and endangers human health, and brings huge security risks to the society. The elimination of highly toxic cyanide electroplating is not only the vision of the industry, but also the responsibility of the government. In the 1970s in my country, there was a climax of eliminating the highly toxic cyanide electroplating, and some results were also achieved, but it was basically a galvanizing process. However, in the field of copper plating, there is nothing good to say. Acid copper has the problem of replacing the copper layer. Most of the cyanide-free alkali copper is gradually eliminated and faded out of the industry due to poor technology. This led to the resurgence of highly toxic cyanide electroplating after the 1980s and 1990s. Not only China, but also the iron and steel substrates of developed countries in the world are directly plated with copper, and the traditional highly toxic cyanidation process is still used.

In order to solve this problem and realize cyanide-free copper plating, it is necessary to solve the two major technical problems of substitution reaction and passivation at the same time. It is necessary to effectively suppress the replacement reaction rate of copper and iron and to ensure the passivation film formed in the air after the pretreatment of the steel substrate. It can be dissolved instantly when entering the plating solution, so as to ensure the strong bonding force of the plating layer. CN104975311A discloses a direct cyanide-free copper plating solution and process on a steel substrate. The plating solution does not contain cyanide, and copper is directly plated on the steel substrate under acidic conditions. It has reached the national standard of GB/5270-2005. However, this method simply reduces the potential of copper ions in the plating solution through complexing agents, and inhibits the substitution reaction to improve the binding force, but cannot completely inhibit the substitution reaction of copper and iron under acidic conditions. There is no bonding force between copper and the steel substrate and the subsequent coating. Due to the inclusion of cuprous oxide in the copper plating layer, although the bonding force can reach the national standard, the bonding force is not the best, and the thickness of the coating is only 30μm. Therefore, this method is only suitable for high-quality steel substrates, but in large-scale production, there are various inclusions in steel parts, which make the bonding force of the copper-plated layer poor, resulting in relatively single copper-plated products. CN111321436A discloses a cyanide-free copper-plating solution auxiliary and copper-plating solution, which utilizes the combination of complexing agent and copper ions to form copper complex ions to reduce the potential of copper ions and suppress the replacement reaction speed. At the same time, the strong activation ability of perchloric acid, hydrofluoric acid and hydrochloric acid is used to make the passivation film of the steel substrate dissolve instantly in the plating solution. Rapid dissolution of even dense stainless steel passivation films. It not only inhibits the replacement reaction rate, but also solves the passivation problem well, and greatly improves the bonding force of the coating. The copper-plated layer has strong bonding force, and the coating layer of 150 μm is firmly up to GB5270-2005, but when the coating layer exceeds 200 μm, peeling occurs, which limits the application range of copper-plated products.

SUMMARY OF THE INVENTION

The invention provides a direct cyanide-free copper-plating electroplating solution for iron and steel substrates under strong acid conditions and a preparation method thereof. The electroplating solution is composed of copper salt, compound adsorbent, additives and strong acid. The effect of 1+1 is greater than 2, which can effectively inhibit the "iron-copper replacement reaction" speed under strong acid conditions, so that the iron and steel substrate forms a solid copper layer with strong binding force at the moment of contact with the acid plating solution instead of loose copper dendritic oxidation. Cuprous, and this layer of elemental copper has a strong bond with the substrate. The replacement reaction with binding force is carried out at the same time as the copper electroplating, so that a dense copper layer is quickly formed on the surface of the substrate, which isolates the contact between the acidic plating solution and the substrate, so that the replacement reaction stops quickly, thereby ensuring that the copper plating layer has a strong bonding force. It completely overcomes the technical problem that the higher the acid content, the worse the bonding force of the copper-plated layer. The copper-plated layer has super strong bonding force, which not only meets the national standard of GB/T 5270-2005, but also has a wider range of applications. Most steel substrates are Direct acid copper plating is possible.

The present invention is achieved through the following technical solutions:

A direct cyanide-free copper-plating electroplating solution for iron and steel substrates under strong acid conditions, in terms of weight fraction, comprises the following components: main salt 50-250g/L, compound adsorbent 30-100g/L, additives 0.1-5g/L, Strong acid composition 160-300g/L.

Described main salt is copper chloride, copper carbonate, copper sulfate, copper hydroxide;

Described compound adsorbent is halide, and the mixture of one or more in ammoniacal liquor, phenyl thiourea, diphenyl thiourea, ethylene thiourea, cucurbituril, ferric sulfate, wherein halide 20- 50g/L, ammonia water 20-100g/L, urea compound 0.3-2g/L; the halide is alkali metal halide or ammonium halide.

The composite adsorbent is adsorbed on the surface of the cathode, which can reduce the copper ion potential of the electric double layer at the cathode interface, effectively inhibit the speed of the replacement reaction, inhibit the side reaction of hydrogen evolution, and make the replacement reaction form a dense elemental copper layer with good binding force. Rapid electrodeposition of copper plating on the dense but not loose elemental copper layer, replacement and electroplating are carried out at the same time. Because the electrochemical deposition of copper layer is very fast, when the rapidly deposited dense copper layer reaches a certain thickness, the contact between the acid plating solution and the steel substrate is isolated, and the replacement reaction is quickly stopped. Thus, the obtained copper layer has strong bonding force. The addition of ammonia water makes the adsorption reversibility of the composite adsorbent, which effectively avoids the excessive inclusion of the adsorbent in the coating during the electrodeposition process.

The additive is preferably a mixture of one or more of urotropine, ascorbic acid, aliphatic amine polyoxyethylene ether, alkylphenol polyoxyethylene ether, and polyethylene glycol; the additive is an antioxidant substance, which can be relatively The oxidation of new ecological copper is well controlled, because new ecological copper has high reactivity and can quickly undergo redox reaction with divalent cupric ions to form cuprous oxide, which has been oxidized into oxide before entering the steel surface lattice. Cuprous and cuprous oxide have no adhesion to the substrate and subsequent coatings. Therefore, the addition of antioxidant substances is very important to form a copper layer instead of a cuprous oxide layer on the surface of the substrate, and to improve the bonding force. At the same time, antioxidants generate more complex substances through the bridging effect of divalent copper ions, which increases the adsorption effect of the adsorbent and better inhibits the replacement reaction rate.

The strong acid composition is a mixture of sulfuric acid and formic acid, and the content in the electroplating solution is 150-250g/L of sulfuric acid and 10-50g/L of formic acid; under normal circumstances, the higher the acid content in the copper-plating solution, the faster the replacement reaction. The rougher and more porous the copper plating layer, the worse the bonding force. In the bath containing compound adsorbent, due to the synergistic effect of sulfuric acid, formic acid and compound adsorbent, the higher the sulfuric acid content, the stronger the adsorption effect and the better the binding force. The optimum sulfuric acid content is 150-250g/L. produced unexpected effects. Strong acids can form complexes with certain stability constants with copper ions and iron ions. At the beginning of the replacement reaction, under the synergy of the adsorbent, the strong acid and the iron ions dissolved by corrosion form a viscous multi-ligand complex mucosa on the working surface of the cathode. Inhibit the corrosion of sulfuric acid to the iron matrix, thereby improving the adhesion of the coating. Formic acid has a certain reducibility, which can not only form a mucous membrane with the dissolved iron ions after mixing with sulfuric acid, slow down the replacement reaction speed, but also accelerate the deposition speed of copper ions on the cathode surface. The amount of sulfuric acid in the copper-plating bath of the present invention is 150-250g/L, which belongs to the strong acid bath, and is far higher than the content of 20-80g/L disclosed in CN104975311A and 50-120g/L disclosed in CN111321436. The technical problem that the stronger the acidity is, the looser the coating will be, and in these two patents, sulfuric acid is mainly used in the electroplating solution to increase the conductivity of the electroplating solution, preventing the hydrolysis of copper salt and improving the crystallization of the coating, but it does not have the effect of adsorption.

The invention also discloses the preparation method of the above-mentioned cyanide-free copper plating solution, comprising the following steps:

(1) pure water of 1/2 volume of calculated amount is added to the container;

(2) adding the main salt and stirring until dissolved; adding the strong acid composition under stirring; then adding the compound adsorbent for stirring and dissolving, and then adding the additive for stirring and dissolving.

(3) Add the remaining pure water to the working volume and stir evenly to carry out electroplating.

The invention also discloses a direct cyanide-free copper plating method for a steel substrate under strong acid conditions, comprising the following steps:

The iron and steel substrates are sequentially subjected to degreasing, pickling, and activation treatments, and then placed in an electroplating tank for electroplating, and the copper-plating treatment of the iron and steel substrates is completed in the above-mentioned electroplating solution.

The above-mentioned technical scheme of the present invention has the following advantages compared with the prior art:

The invention abandons the traditional complex theory, and finds another way to produce the effect of 1+1 greater than 2 through the synergistic effect of compound adsorbents, additives and strong acids, effectively suppressing the iron-copper replacement reaction speed under strong acid conditions, so that the iron and steel substrates are in contact with acid plating. The liquid instantly forms a solid copper layer with strong bonding force instead of a loose copper dendritic cuprous oxide, and this layer of simple copper layer has a strong bonding force with the substrate. The composite adsorbent adsorbed on the cathode surface can reduce the copper ion potential of the cathode interface electric double layer, change the copper ion concentration in the electric double layer, and inhibit the discharge precipitation of copper ions, thereby effectively inhibiting the speed of the replacement reaction and inhibiting the side reaction of hydrogen evolution. At the same time, the oxidation resistance of the additive can be used to better control the oxidation of new ecological copper, preventing the formation of cuprous oxide with poor binding force, and at the same time, the antioxidant substances can generate more complex substances through the bridging effect of divalent copper ions. The adsorption effect of the adsorbent is increased, and the displacement reaction rate is better suppressed. The strong acid composition can quickly dissolve the passive film of the steel matrix and form a complex with a certain stability constant with copper ions and iron ions. At the beginning of the displacement reaction, under the synergy of the compound adsorbent, a viscous multi-ligand complex is formed on the cathode working surface with the dissolved iron ions, and the mucous membrane adsorbs the cathode surface, which makes the thermal movement of ions difficult, the thickness of the dispersion layer decreases, and the double The structure of the electric layer is compact, which can effectively slow down the replacement reaction rate of copper and iron as a barrier layer, and at the same time can inhibit the corrosion of sulfuric acid to the iron matrix, thereby improving the bonding force of the coating. This CN104975311A is completely different from the sulfuric acid disclosed in CN111321436A in the electroplating solution, and the sulfuric acid has no adsorption properties. The thickness of the plating layer can only reach 30 μm and 150 μm, while the thickness of copper plating in the electroplating solution of the present invention can reach 300 μm.

The electroplating solution disclosed by the invention can replace the highly toxic cyanide copper plating in the field of copper plating on steel substrates, and relieve the serious threat caused by the highly toxic cyanide to operators and the environment. It solves the defects of the current non-cyanide-free alkaline copper plating due to the lack of activation ability, the bonding force is not strong, the current is not large, and the copper plating speed is slow. After electroplating enterprises use the electroplating solution, the electroplating wastewater does not contain cyanide, which can reduce the cost of wastewater treatment and reduce sewage discharge. Because the electroplating solution is a strong acid electroplating solution, the small resistance can reduce the electroplating voltage and save a lot of electric energy.

Detailed ways

In order to better understand the present invention, the present invention will be described in detail below with specific reference to the embodiments.

Example 1

A direct cyanide-free copper-plating electroplating solution for iron and steel substrates under strong acid conditions, the components and contents are shown in Table 1;

The preparation method of the electroplating solution comprises the following steps:

Take 1/2 volume of pure water, add copper sulfate to it and stir to dissolve, then add strong acid to it under constant stirring, then add compound adsorbent and additives in turn and stir evenly, add the remaining pure water to the required volume After the copper plating solution is obtained, electroplating can be performed.

Table 1 is the electroplating solution of embodiment 1:

组分与操作条件Components and Operating Conditions	含量g/LContentg/L
氯化铜copper chloride	100100
硫酸sulfuric acid	200200
甲酸Formic acid	2020
苯基硫脲Phenylthiourea	0.30.3
氯化铵Ammonium chloride	3030
氨水ammonia	7070
乌洛托品Urotropine	11
脂肪胺聚氧乙烯醚Fatty amine polyoxyethylene ether	0.20.2

极电流密度(A/dm ²) Electrode current density (A/dm ² )	22
电镀时间(min)Plating time (min)	1010
温度/℃temperature/℃	室温room temperature
阳极anode	磷铜Phosphor Bronze
搅拌方法Stirring method	空气搅拌及阴极移动Air Stirring and Cathode Movement

Electroplating method: The steel test piece is subjected to degreasing, pickling, and activation treatment in sequence, and then placed in an electroplating tank for electroplating. The current density is set to 2A/dm ² , and electroplating is performed at room temperature for 10 minutes to complete the copper plating treatment of steel. After observation, it was found that the crystals of the copper plating layer after electroplating were fine and bright.

Binding force test: Test according to GB/T 5270-2005 national standard:

(1) Bending test: The copper-plated steel test piece is repeatedly bent to break, the copper-plated layer does not have bubbling or peeling, and the copper layer at the fracture does not peel off.

(2) Cross-cut test: Use a hard steel knife to draw a square with a side length of 1 mm, and draw it to the base of the test piece, and the copper-plated layer does not fall off.

(3) Thermal vibration test: Put the copper-plated steel test piece into a heating furnace and heat it to 250°C, and then put it into cold water to quench it, and the copper-plated layer has no bubbling and flake peeling.

After bending test, cross-cut test and thermal vibration test, the copper-plated layer has no bubbling, peeling, peeling off, and the bonding strength reaches the national standard of GB/T 5270-2005.

Example 2

A direct cyanide-free copper-plating electroplating solution for iron and steel substrates under strong acid conditions, the components and contents are shown in Table 2;

The preparation method of the electroplating solution includes the following steps: taking 1/2 volume of pure water, adding copper sulfate to it, stirring and dissolving it, adding strong acid to the tool under constant stirring, and then adding compound adsorbents and additives in sequence and stirring Evenly, add the remaining amount of pure water to the required volume to obtain a copper plating solution, and then electroplating can be performed.

The copper plating solution of table 2 embodiment 2:

组分与操作条件Components and Operating Conditions	含量g/LContentg/L
硫酸铜copper sulfate	100100
硫酸sulfuric acid	150150
甲酸Formic acid	3030

葫芦脲Cucurbituril	22
氨水ammonia	2020
溴化铵Ammonium Bromide	3030
抗坏血酸ascorbic acid	11
聚乙二醇polyethylene glycol	0.30.3
阴极电流密度(A/dm ²) Cathode current density (A/dm ² )	33
电镀时间(min)Plating time (min)	1010
温度/℃temperature/℃	室温room temperature
阳极anode	磷铜Phosphor Bronze
搅拌方法Stirring method	空气搅拌及阴极移动Air Stirring and Cathode Movement

Electroplating method: The steel test piece is subjected to degreasing, pickling, and activation treatment in sequence, and then placed in an electroplating tank for electroplating. The current density is set to 3A/dm ² , and electroplating is performed at room temperature for 10 minutes to complete the copper plating treatment of steel. After observation, it was found that the crystals of the copper plating layer after electroplating were fine and bright.

Binding force test: Test according to GB/T 5270-2005 national standard:

After bending test, cross-cut test and thermal vibration test, the copper-plated layer has no bubbling, peeling, peeling off, and the bonding force reaches the national standard of GB/T 5270-2005.

Example 3

A direct cyanide-free copper-plating electroplating solution for iron and steel substrates under a strong acid condition, the components and contents are shown in Table 3;

The copper plating solution of table 3 embodiment 3:

Binding force test: Test according to GB/T 5270-2005 national standard:

Example 4

Table 4 is the electroplating solution of embodiment 4:

Binding force test: Test according to GB/T 5270-2005 national standard:

(3) Thermal vibration test: Put the copper-plated steel test piece into a heating furnace and heat it to 250°C, then put it into cold water to quench it, and the copper-plated layer is free of bubbling and sheet-like peeling.

Comparative ratio

In the process of electroplating technology research and development, the bonding force is often judged by thickening the high-hardness and high-stress coating to make a comparative test. The thicker the coating, the greater the shear stress generated during the bending test, and the easier the coating is to peel, bubble and peel.

Electroplating with the electroplating solution of Examples 1-4 disclosed in CN104975311A, when the coating is 30 μm, the bending test bonding force is well detected, when the coating is 100 μm, the bending coating is partially peeled, and when the coating is 150 μm, the coating is peeled and the steel substrate is completely peeled off. .

Electroplating with the electroplating solutions of Examples 1-8 disclosed in CN111321436A, when the coating layer is 200 μm, the bending coating begins to peel, and when the coating is 300 μm, the peeling of the bending coating and the steel substrate are completely peeled off.

Electroplating with the electroplating solution disclosed in this application, when the coating layer is 30 μm, the bending test bonding force detection meets the standard, when the coating layer is 100 μm, the bending coating bonding force is firm, and when the coating layer is 150 μm, the bending coating and the steel substrate are firm. When the coating layer is 300μm, the coating layer and the steel substrate have no cracking, peeling and peeling phenomenon in the bending test, and the bonding force is firm. It is illustrated that electroplating by the electroplating solution of the present invention overcomes the technical problem of insufficient binding force caused by the stronger cuprous oxide and acidity in the prior art. The results are shown in Table 6.

Table 6 Comparison of bonding force of coating bending test

	30μm30μm	100μm100μm	150μm150μm	200μm200μm	300μm300μm
CN104975311ACN104975311A	牢固firm	部分起皮partially peeled	起皮peeling	剥离peel off	剥离peel off
CN111321436ACN111321436A	牢固firm	牢固firm	牢固firm	起皮peeling	剥离peel off
本申请this application	牢固firm	牢固firm	牢固firm	牢固firm	牢固firm

Claims

A direct cyanide-free copper plating solution for iron and steel substrates under strong acid conditions, comprising the following components: main salt 50-250g/L, compound adsorbent 30-100g/L, additives 1-5g/L, strong acid composition 160- 300g/L.
The electroplating solution according to claim 1, wherein the compound adsorbent is a mixture of halide, ammonia water and urea compound.
The electroplating solution according to claim 2, wherein the urea compound is phenylthiourea, diphenylthiourea, ethylenethiourea or cucurbituril.
The electroplating solution according to claim 1, wherein the additive is preferably a mixture of one or more of urotropine, ascorbic acid, aliphatic amine polyoxyethylene ether, alkylphenol polyoxyethylene ether, and polyethylene glycol .
The electroplating solution according to claim 1, wherein the main salt is copper chloride, copper carbonate, copper sulfate, and copper hydroxide.
The electroplating solution according to claim 1, wherein the content of the compound adsorbent in the electroplating solution is 20-50g/L of halides, 20-100g/L of ammonia water, and 0.3-2g/L of urea compounds; The halide is an alkali metal halide or an ammonium halide.
The electroplating solution according to claim 1, wherein the strong acid composition is a mixture of sulfuric acid and formic acid.
The electroplating solution according to claim 1, wherein the content of the strong acid composition in the electroplating solution is 150-250 g/L of sulfuric acid and 10-50 g/L of formic acid.
The preparation method of the direct cyanide-free copper-plating electroplating solution for iron and steel matrix under the strong acid condition of claim 1, comprises the steps:

(1) pure water of 1/2 volume of the calculated amount is added to the container;

(2) adding main salt, stirring to dissolve; adding strong acid composition under stirring; then adding compound adsorbent to stirring and dissolving, then adding additive to stirring and dissolving;

(3) Add the remaining pure water to the working volume and stir evenly to implement electroplating.
A direct cyanide-free copper plating method for a steel substrate under strong acid conditions, comprising the following steps:

The steel substrate is sequentially subjected to degreasing, pickling and activation treatment, and then placed in an electroplating tank for electroplating, and the electroplating solution used is the electroplating solution described in any one of claims 1-8.