CN104294327B - A kind of ionic liquid electrolytic solution and the method for preparing bright aluminum coating with the electrolytic solution - Google Patents

Abstract

An ionic liquid electrolyte and a method for preparing a bright aluminum coating by using the electrolyte mainly solve the problems of unsuitable viscosity and conductivity of an ionic liquid for preparing a bright aluminum coating in the prior art. The electrolyte is composed of ionic liquid, anhydrous aluminum halide salt and additives, the molar ratio of the ionic liquid to the anhydrous aluminum halide salt is 1:1.5-2.0, and the molar ratio of the ionic liquid to the additive is 1:0.1- 4. The method for preparing a bright aluminum coating with the electrolyte is as follows: first, the electrolysis device is placed in an atmosphere of nitrogen or argon at normal pressure, anhydrous and oxygen-free, and the ionic liquid electrolyte is added. The density is 1-10A/dm ² , electrolysis is carried out under the condition of adjusting the tank pressure to obtain a mirror glossy aluminum coating. After the additive is added to the ionic liquid electrolyte used in the preparation of the bright aluminum coating in the invention, the pressure of the electrolytic tank is reduced, and the viscosity and conductivity of the ionic liquid are improved, thereby obtaining the bright aluminum coating of electrodeposition.

Description

A kind of ionic liquid electrolytic solution and the method for preparing bright aluminum coating with the electrolytic solution

technical field

The invention relates to an ionic liquid electrolyte and a method for preparing a bright aluminum coating by using the electrolyte, belonging to the field of electroplating.

Background technique

Since aluminum is a cathode metal whose electrode potential is more negative than that of hydrogen, aluminum electrolysis in water system cannot be realized, and high-temperature molten salt electrolysis aluminum technology has high temperature and cannot directly obtain solid aluminum. The emergence and application of low-temperature electrolytic aluminum technology provides the possibility to directly obtain solid aluminum products by electrolysis. Electrolytic aluminum in low temperature non-aqueous system mainly includes organic solvent system, molten salt system and ionic liquid system. In comparison, the advantages of the ionic liquid system are that it has a wide temperature range, high electrical conductivity and a wide electrochemical window, less side reactions, non-volatile, and non-flammable. At present, there are many research papers and patents on the use of ionic liquid system electrodeposition to obtain metal aluminum or aluminum alloys. The cations of the system mainly involve imidazolium salts, pyridinium salts, pyrrole salts, piperidine salts, quaternary ammonium salts, dimethyl sulfone, etc. Anions include halogen anions, tetrafluoroborate, [N(CF ₃ SO ₂ ) ₂ ] ^- and the like. Chloroaluminate system is the most used in the research of electrodeposited aluminum. Its good physical and chemical properties, low viscosity and electrolysis temperature provide an ideal room temperature reaction medium for electrolytic aluminum, and become the preferred electrolyte system for low-temperature electrolytic aluminum. . Even so, the electrodeposition of aluminum in the chloroaluminate system still shows an interface-controlled process of concentration polarization, and problems such as loose coating and dendrites appear. Obtaining a dense and bright aluminum coating can not only improve the exquisite appearance of the electroplating parts, but also increase its protective performance to the substrate, which has always been one of the important directions of electroplating aluminum research. For the chloroaluminate electrolytic aluminum system, increasing the electrochemical reaction polarization of the deposition surface or reducing the concentration polarization of the electrolyte are two effective ways to obtain dense and smooth aluminum coatings. Although properly increasing the electrodeposition temperature can reduce the viscosity of the ionic liquid and accelerate the ion diffusion rate, the accelerated gradient of the chemical reaction on the electrode surface is greater than the accelerated gradient of the ion migration, thereby aggravating the concentration polarization. Thermal instability, this method is not advisable. Chinese patent CN101760758A, while electrodepositing aluminum, makes the electrolytic cell centrifugally rotate to generate a supergravity field, strengthens the convection and diffusion process, can refine the crystal grains, and avoid the production of dendrite aluminum, but the production equipment has high requirements and belongs to special conditions. field of metal electrodeposition. U.S. Patent US2013168258A1 uses organic solvents with a dielectric constant less than or equal to 8, such as hexane, toluene, diethyl ether, ethyl acetate, etc., to improve the conductivity of the electrolyte and obtain a continuous and uniform aluminum coating, but these organic solvents are prone to Flammable and explosive, increasing the danger of application. US Patent US20120006688A1 uses the following three types of compounds as additives, R ³ N ⁺ (R ⁴ ) ₃ Hal ^- , R ⁵ SO ₃ ^- M ⁺ , in the process of electrolysis of aluminum in various types of ionic liquids, a flat and dense aluminum coating can be obtained, and no additives are mentioned for the conductivity of the electrolyte , The effect of viscosity. Chinese patent CN103849911A adds 0.5-15g/L pyridine derivatives to generate adsorption on the electrode surface to increase the chemical polarization of the electrode surface, thereby obtaining a bright aluminum coating, but at the same time it also increases the cell pressure and reduces the current density. Although various bright or uniform aluminum coating technologies have their own characteristics and applicability, we still need to continue to explore new methods and technologies to obtain excellent aluminum coatings.

In addition, ethanol, acetone and other solvents are often used in the final finishing and cleaning of the obtained electroplating products or electroplating equipment, but these solutions are not only flammable and explosive, but also bond with the active aluminum ions in the electrolyte, resulting in product cleaning. It is not clean, and the viscosity of the cleaning solution increases, so that it is too thick to be used. A solvent or cleaning agent that does not interact with the anions and cations of the chloroaluminate system is needed.

Contents of the invention

The present invention aims at solving the above problems, proposes a kind of ionic liquid electrolytic solution and the method for preparing bright aluminum coating with this electrolytic solution, this ionic liquid electrolytic solution has added auxiliary in ionic liquid-anhydrous aluminum halide salt AlX ₃ system The addition of additives and additives improves the viscosity and conductivity of the ionic liquid, thereby obtaining bright aluminum coatings for electrodeposition. The additives can also be used for dilution of chloroaluminic acid-type electroplating aluminum electrolytes, product cleaning, etc. Waste liquids can be collected after distillation reuse.

To achieve the above object, the present invention adopts the following technical solutions:

An ionic liquid electrolyte, consisting of an ionic liquid, anhydrous aluminum halide salt (AlX ₃ ) and an auxiliary agent; the cations of the above-mentioned ionic liquid are imidazoles, pyridines, quaternary ammoniums, quaternary phosphoniums, pyrroles, and piperidines Classes, morpholines or dimethyl sulfone or their mixtures, the anion is halogen, the X of the above-mentioned anhydrous aluminum halide salt (AlX ₃ ) is Cl, Br or I, and the above-mentioned auxiliary agent is a halogenated alkyl, which is dichloromethane, three Chloromethane, dibromomethane, haloethane or their isomers.

The molar ratio of the ionic liquid to the anhydrous aluminum halide salt is 1:1.5-2.0, and the molar ratio of the ionic liquid to the auxiliary agent is 1:0.1-4.

The above-mentioned ionic liquid electrolyte is prepared by mixing the ionic liquid with anhydrous aluminum halide salt (AlX ₃ ) Mix according to the above molar ratio, and then add the auxiliary agent in the above molar ratio to the mixed solution.

The method for preparing a bright aluminum coating with the electrolytic solution comprises the following steps: firstly, the electrolytic device is placed in a nitrogen or argon environment atmosphere of anhydrous and oxygen-free at normal pressure, the water content and the oxygen content are both ≤ 5‰, and the In the above electrolysis device, the ionic liquid is mixed with the anhydrous aluminum halide salt (AlX ₃ ) in molar ratio, and then the auxiliary agent in the molar ratio is added to the mixed solution, and the anode is made of active anode pure aluminum or inert anode glassy carbon, The cathode is a conductive metal substrate. At an electrolysis temperature of 10-30°C, the active anode is pure aluminum, the tank voltage control range is 0.5-1.5V, and the inert anode glassy carbon is used. The tank voltage control range is 2.5-4.0V, and the current density is 1-10A/dm ² Under certain conditions, electrolysis is carried out for 3-20 minutes to obtain a mirror-glossy aluminum coating.

The method for preparing a bright aluminum coating with the electrolyte, its specific implementation steps are as follows:

a. Place the electrolysis device in a water-free and oxygen-free nitrogen or argon atmosphere at normal pressure, and the water content and oxygen content are both ≤5‰;

b. Take the various components of the above-mentioned ionic liquid electrolyte according to the molar ratio, first mix the ionic liquid and anhydrous aluminum halide salt into the electrolytic device evenly, and then add additives to it, the anode can be active anode pure aluminum or inert anode glass Carbon, the cathode is a conductive metal substrate, such as polished copper, titanium, stainless steel, zinc and other metals or their alloys, the pole distance is 5-30mm; if an inert anode is used, the content of anhydrous aluminum halide salt varies with The deposition of aluminum and the production of simple halogen will gradually decrease, and it is best to supplement at any time to maintain the progress of electrolysis and the quality of aluminum deposition.

c. The electrolysis temperature should be controlled below the boiling point of the additive, between 10-30°C. The active anode pure aluminum tank pressure control range is 0.5-1.5V, and the inert anode glassy carbon tank pressure control range is 2.5-4.0V. Perform electrolysis under the condition of density ^1-10A /dm2 to obtain bright aluminum coating;

d. Take out the aluminum plated sheet of the above-mentioned bright aluminum coating, put it into the above-mentioned additives and wash it three times, dry it naturally, seal it up, and use the additives that have been used many times to concentrate distillation and purification for reuse.

The beneficial effects of the present invention are: the auxiliary agent in the ionic liquid electrolyte of the present invention improves the viscosity and conductivity of the ionic liquid, thereby obtaining an electrodeposited bright aluminum coating, and can be used for dilution and cleaning of the ionic liquid electrolyte. Using room temperature chloroaluminate-type ionic liquid, adding an appropriate amount of electrolyte additives to prepare the electrolyte, the addition of additives can greatly reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and reduce concentration polarization Effects such as roughness and dendrites on the deposited layer. This additive can also be used for dilution of chloroaluminic acid-type electroplating aluminum electrolyte, product cleaning, etc., and the waste liquid can be reused after being collected by distillation. The additives are low-toxic, non-flammable, easy to use and low in price.

In addition, after the additive is added to the ionic liquid electrolyte, the pressure of the electrolytic cell is reduced, which greatly increases the current density during electrolysis, shortens the electroplating time to obtain the same thickness of aluminum coating, and makes the grains of aluminum deposition fine and smooth, which can reach Mirror-like luster, the obtained aluminum deposit has a decorative and protective effect.

Instructions attached

Fig. 1 carries out the bright coating picture that electrolysis obtains when 1-methyl-3 butyl imidazolium chloride salt among the present invention and dichloromethane mol ratio 1:3;

Fig. 2 is the SEM image of the aluminum coating that does not add dichloromethane when the electrolysis of the present invention passes electricity 16.2C;

Fig. 3 is the SEM image of the aluminum-plated surface after adding dichloromethane by 1-methyl-3 butylimidazolium chloride salt ([BMIM]Cl) and dichloromethane 1:3 mol ratio when the electrolysis electricity of the present invention is 16.2C;

Fig. 4 is the influence of the dichloromethane content in the ionic liquid electrolyte of the present invention on conductivity;

Fig. 5 is the effect of the dichloromethane content in the ionic liquid electrolyte in the present invention on the viscosity.

detailed description

Example 1

A kind of ionic liquid electrolyte, is made up of ionic liquid, anhydrous aluminum halide salt AlX ₃ and auxiliary agent; Above-mentioned ionic liquid and anhydrous aluminum halide salt AlX ₃ are 1-methyl-3 butyl imidazolium chloride salt ([BMIM] Cl) and anhydrous AlCl ₃ , the above auxiliary agent is dichloromethane;

Described 1-methyl-3 butylimidazolium chloride salt ([BMIM]Cl) and anhydrous AlCl _The molar ratio is 1:2,1-methyl-3 butylimidazole chloride salt ([BMIM]Cl) and The molar ratio of dichloromethane is 1:3.

The method for preparing a bright aluminum coating with the electrolytic solution comprises the following steps: firstly, the electrolytic device is placed in an atmosphere of nitrogen or argon gas at normal pressure, anhydrous and oxygen-free, and the water content and oxygen content are both ≤ 5‰, and press The above-mentioned molar ratio takes each component of the above-mentioned ionic liquid electrolyte and places them in the above-mentioned electrolysis device. The anode is made of active anode pure aluminum or inert anode glassy carbon, and the cathode is a conductive metal substrate. Then, electrolysis is carried out to obtain a specular glossy aluminum coating.

The method for preparing a bright aluminum coating with the electrolytic solution, its specific implementation steps are as follows:

First of all, in an anhydrous and oxygen-free nitrogen or argon atmosphere at normal pressure (both water content and oxygen content ≤ 5‰), you can choose to use a glove box. According to the above molar ratio, each component of the above-mentioned ionic liquid electrolyte is placed in the electrolysis device, and the ionic liquid electrolyte is prepared. The conductivity is 2.7 times higher than that before the addition of the auxiliary agent, and the viscosity is 6 times lower than that before the addition of the auxiliary agent. The ground and polished copper sheet was used as the cathode, and the high-purity aluminum sheet was used as the anode. The distance between the two electrodes was kept at 10mm, and the temperature was controlled at 30°C. Using a stabilized DC power supply and adjusting the cell voltage to 0.6v, the current density can reach 2.5A/dm ² , which is 10 times higher than before adding additives. Electroplating for 10 minutes to obtain a mirror glossy aluminum coating. As shown in Figure 1, the area inside the white wireframe is a bright aluminized sheet, and the mapped text pattern can be seen to show the visual degree of specular gloss. Scan the aluminum-plated sheet obtained by electroplating with a scanning electron microscope, as shown in Figure 2-3. Under the same magnification (20,000 times), Figure 2 is the microscopic appearance of the aluminum-plated surface without adding dichloromethane, with large grains. The surface is rough. Figure 3 shows the microscopic morphology of the aluminum-plated surface after adding dichloromethane at a molar ratio of 1-methyl-3-butylimidazolium chloride ([BMIM]Cl) to dichloromethane at 1:3. The particles are obviously fine chemical, smooth.

Take out the aluminum-plated sheet, wash it three times in dichloromethane, dry it naturally, and seal it up. The cleaning agent that has been used many times is concentrated and purified by distillation for reuse.

Example 2

A kind of ionic liquid electrolyte, is made up of ionic liquid, anhydrous aluminum halide salt AlX ₃ and auxiliary agent; Above-mentioned ionic liquid and anhydrous aluminum halide salt AlX ₃ are 1-methyl-3 ethyl imidazolium chloride salt ([EMIM] Cl) and anhydrous AlCl ₃ , the above auxiliary agent is dichloromethane;

Described 1-methyl-3 ethylimidazolium chloride salt ([EMIM]Cl) and anhydrous AlCl _The molar ratio is 1:2,1-methyl-3 ethylimidazole chloride salt ([EMIM]Cl) and The molar ratio of dichloromethane is 1:3.

The method for preparing a bright aluminum coating with the electrolytic solution comprises the following steps: firstly, the electrolytic device is placed in an atmosphere of nitrogen or argon gas at normal pressure, anhydrous and oxygen-free, and the water content and oxygen content are both ≤ 5‰, and press The above-mentioned molar ratio takes each component of the above-mentioned ionic liquid electrolyte and places them in the above-mentioned electrolysis device. The anode is made of active anode pure aluminum or inert anode glassy carbon, and the cathode is a conductive metal substrate. Then, electrolysis is carried out to obtain a specular glossy aluminum coating.

The method for preparing a bright aluminum coating with the electrolytic solution, its specific implementation steps are as follows:

First of all, in an anhydrous and oxygen-free nitrogen or argon atmosphere at normal pressure (both water content and oxygen content ≤ 5‰), you can choose to use a glove box. According to the above molar ratio, each component of the above-mentioned ionic liquid electrolyte is placed in the electrolysis device, and the ionic liquid electrolyte is prepared. The conductivity is 2.5 times that before the addition of the auxiliary agent, and the viscosity is 5.1 times lower than that before the addition of the auxiliary agent. The ground and polished copper sheet is used as the cathode, and the inert electrode glassy carbon is used as the anode. The distance between the two electrodes is kept at 10mm, and the temperature is controlled at 30°C. Using a stabilized DC power supply and adjusting the cell voltage to 3.0v, the current density can reach 5A/dm ² , which is 8 times higher than that before adding additives. Electroplating for 5 minutes to obtain a mirror glossy aluminum coating. Take out the aluminum-plated sheet, wash it three times in dichloromethane, dry it naturally, and seal it up. The cleaning agent that has been used many times is concentrated and purified by distillation for reuse.

Example 3

A kind of ionic liquid electrolyte, is made up of ionic liquid, anhydrous aluminum halide salt AlX ₃ and auxiliary agent; Above-mentioned ionic liquid and anhydrous aluminum halide salt AlX ₃ are 1-methyl-3 butyl imidazolium chloride salt ([BMIM] Cl) and anhydrous AlCl ₃ , the above auxiliary agent is chloroform.

Described 1-methyl-3 butylimidazolium chloride salt ([BMIM]Cl) and anhydrous AlCl _The molar ratio is 1:2,1-methyl-3 butylimidazole chloride salt ([BMIM]Cl) and The molar ratio of chloroform is 1:3.

The method for preparing a bright aluminum coating with the electrolytic solution comprises the following steps: firstly, the electrolytic device is placed in an atmosphere of nitrogen or argon gas at normal pressure, anhydrous and oxygen-free, and the water content and oxygen content are both ≤ 5‰, and press The above-mentioned molar ratio takes each component of the above-mentioned ionic liquid electrolyte and places them in the above-mentioned electrolysis device. The anode is made of active anode pure aluminum or inert anode glassy carbon, and the cathode is a conductive metal substrate. Then, electrolysis is carried out to obtain a specular glossy aluminum coating.

The method for preparing a bright aluminum coating with the electrolytic solution, its specific implementation steps are as follows:

First of all, in an anhydrous and oxygen-free nitrogen or argon atmosphere at normal pressure (both water content and oxygen content ≤ 5‰), you can choose to use a glove box. According to the above molar ratio, the components of the above-mentioned ionic liquid electrolyte are placed in the electrolysis device, and the ionic liquid electrolyte is prepared. The conductivity is 1.6 times that before the addition of the auxiliary agent, and the viscosity is 42% lower than that before the addition of the auxiliary agent. The polished copper sheet is used as the cathode, and the high-purity aluminum sheet is used as the anode. The distance between the two electrodes is kept at 10mm, and the temperature is controlled at 20°C. Using the pulse electroplating power supply and adjusting the tank voltage to 0.7v, the current density can reach 1.2A/dm ² , which is 10 times higher than before adding additives. Electroplating for 20 minutes to obtain a silver-white aluminum coating. Take out the aluminum-plated sheet, wash it three times in chloroform, dry it naturally, and seal it up. The cleaning agent that has been used many times is concentrated and purified by distillation for reuse.

The addition of the additive can greatly reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and reduce the impact of concentration polarization on the deposition layer such as roughness and dendrites. As shown in Figure 4, with [BMIM]Cl as the base number, methylene chloride accounts for the molar number of [BMIM]Cl in the range of 0-77.6%. With the increase of methylene chloride in the amount added, the conductivity of the electrolyte increases; two After methyl chloride accounts for [BMIM]Cl moles greater than 77.6%, the conductivity of the electrolyte gradually decreases as the amount of dichloromethane added increases; as shown in Figure 5, with [BMIM]Cl as the base, dichloromethane accounts for [ BMIM] Cl molar number in the range of 0-80%, with the increase of methylene chloride added, the viscosity of the electrolyte decreased gradually.

Claims (4)

1. an ionic liquid electrolyte, is characterized in that, is made up of ionic liquid, anhydrous aluminum halide salt AlX ₃ and auxiliary agent; The cation of above-mentioned ionic liquid is imidazoles, pyridines, quaternary ammoniums, quaternary phosphoniums, pyrrole Classes, piperidines, morpholines or dimethyl sulfone or their mixtures, the anion is a halogen, the X of the above-mentioned anhydrous aluminum halide salt AlX ₃ is Cl, Br or I, the above-mentioned auxiliary agent is a haloalkane, and the haloalkane is Dichloromethane, chloroform, methylene bromide, haloethane or their isomers; the mol ratio of the ionic liquid to anhydrous aluminum halide salt is 1:1.5-2.0, the ratio of ionic liquid and auxiliary agent The molar ratio is 1:0.1-4. 2. a kind of ionic liquid electrolytic solution as claimed in claim 1, is characterized in that, the preparation of described ionic liquid electrolytic solution is in the nitrogen or argon environment atmosphere of normal pressure anhydrous oxygen-free, water content, oxygen content Under the condition that both are ≤5‰, the ionic liquid and the anhydrous aluminum halide salt AlX ₃ are mixed according to the molar ratio, and then the additives in the molar ratio are added to the mixed liquid. 3. prepare the method for bright aluminum coating with the described ionic liquid electrolytic solution of claim 1 or 2, it is characterized in that, at first electrolytic device is placed in the nitrogen or argon ambient atmosphere of normal pressure anhydrous and oxygen-free, water content, Oxygen content ≤ 5‰, the ionic liquid and anhydrous aluminum halide salt AlX ₃ are mixed in molar ratio in the above electrolysis device, and then the auxiliary agent in the molar ratio above is added to the mixed solution, and the anode adopts active anode pure aluminum Or inert anode glassy carbon, the cathode is a conductive metal substrate, at an electrolysis temperature of 10-30°C, the active anode pure aluminum tank voltage control range is 0.5-1.5V, and the inert anode glassy carbon tank voltage control range is 2.5-4.0V, and the current density Under the condition of 1-10A/dm ² , electrolysis is then carried out to obtain a mirror glossy aluminum coating. 4. the method for preparing bright aluminum coating with ionic liquid electrolyte as claimed in claim 3, its concrete realization steps are as follows: a. Place the electrolysis device in a water-free and oxygen-free nitrogen or argon atmosphere at normal pressure, and the water content and oxygen content are both ≤5‰; b. Take the various components of the ionic liquid electrolyte according to the molar ratio, first mix the ionic liquid and anhydrous aluminum halide salt into the electrolysis device evenly, and then add additives to it, the anode can be active anode pure aluminum or inert anode glass Carbon, the cathode is a conductive metal substrate, and the conductive metal substrate is a polished copper sheet, titanium sheet, stainless steel sheet, zinc sheet or their alloys, and the pole distance is 5-30mm; c. The electrolysis temperature should be controlled below the boiling point of the additive, between 10-30°C. The active anode pure aluminum tank pressure control range is 0.5-1.5V, and the inert anode glassy carbon tank pressure control range is 2.5-4.0V. Under the condition of density ^1-10A /dm2, carry out electrolysis for 3-20min to obtain bright aluminum coating; d. Take out the aluminum plated sheet of the above-mentioned bright aluminum coating, put it into the above-mentioned additives and wash it three times, dry it naturally, seal it up, and use the additives that have been used many times to concentrate distillation and purification for reuse.