Method for preparing nickel electrolyte and its use in electroplating methods

Abstract

The present invention relates to a nickel plating bath. The present invention also relates to the use of a nickel plating bath in an electroplating method, particularly in the production of nickel-plated substrates for electrical applications such as batteries and electrolytic cells.

Description

[Technical Field]

[0001] The present invention relates to a nickel plating bath comprising an aqueous nickel electrolyte and a method for preparing such an electrolyte. Furthermore, the present invention relates to the use of the electrolyte for producing nickel-plated substrates, particularly nickel-plated substrates for electrical applications such as batteries and electrolytic cells. [Background technology]

[0002] The world faces enormous challenges in terms of environmental change. A significant reduction in greenhouse gas emissions is needed to mitigate climate change. One of these greenhouse gases is carbon dioxide, which is released during the combustion of fossil fuels. The main users of fossil fuels are the transportation sector, particularly the automotive sector. One way to reduce fossil fuel consumption is through the electrification of the automotive sector, which would mean a significant increase in the energy storage capacity of vehicles to have the desired range to make electric vehicles attractive as an alternative to vehicles with internal combustion engines. Another way to reduce consumption is through a transition to an economy based on hydrogen as a fuel rather than fossil fuels.

[0003] Both electrification of the transportation sector and the option of a hydrogen-fuel-based economy require access to large quantities of nickel-plated steel. This nickel-plated steel is used in batteries to protect them from corrosion or to function as part of the electrical circuits within the batteries. Nickel-plated steel is also used in hydrogen production in electrolytic cells.

[0004] Depending on the application or type of battery, steel substrates, typically supplied in the form of (coiled) strips or sheets, are plated on one or both main surfaces ("top" and "bottom") of the steel substrate. Most batteries, including battery components in the automotive sector, have a cylindrical or prismatic shape, and the material for battery cans is usually a steel strip or sheet substrate with nickel coating on one or both sides. This nickel coating is typically applied by an electroplating process in a continuous electroplating line.

[0005] From the perspective of the environmental challenges mentioned above, the demand for nickel-plated steel will increase. Current production of nickel-plated steel is expected to be insufficient to meet this increasing demand, requiring further production capacity. The scale of current production lines for nickel-plated steel does not match the anticipated demand and cannot be easily increased by augmenting existing capacity based on existing plating technology.

[0006] Nickel-plated steel strips or sheets are typically produced by plating a nickel layer onto the strip or sheet using a sulfate-based, chloride-based, or sulfamate-based electroplating bath. In electroplating, nickel ions are consumed at the cathode. This can be done by replenishing nickel by adding fresh electrolyte to the plating cell. The continuous addition of fresh electrolyte is expensive and requires careful storage of large quantities of these chemicals. A further problem with nickel plating baths is that the maximum usable current density during plating limits their usefulness for high-speed electroplating methods. An alternative is to generate nickel ions for deposition at the anode. That is, the anode is made from nickel in some metallic form, for example, nickel pellets stacked in an inert titanium basket to ensure good electrical contact between each pellet. The dissolution of nickel anode material into the plating bath is a limiting factor in nickel electroplating of this type of steel substrate, thereby limiting the production capacity of such plating lines. European Patent Application Publication No. 0892087(A2) discloses an electroplating of a nickel layer based on a nickel salt, and also discloses the option of using a soluble nickel anode.

[0007] The problem with using all current standard nickel plating electrolytes is that they do not readily allow for scale-up. Most electrolytes contain chlorides that produce toxic chlorine at the anode, or the electrolyte has limited conductivity that limits the rate of nickel deposition, or electrolytes such as sulfamate electrolytes decompose. [Overview of the project] [Problems that the invention aims to solve]

[0008] One object of the present invention is to provide a method for preparing an aqueous solution containing nickel ions that can be used as an electrolyte in a nickel electroplating method.

[0009] Another object of the present invention is to provide an electrolytic solution that avoids the generation of toxic or environmentally harmful by-products such as chlorine or undesirable metal ions.

[0010] Yet another object of the present invention is to provide a method for preparing an aqueous solution containing nickel ions that can be used as an electrolytic solution in a continuous high-speed nickel electroplating method.

[0011] Yet another object of the present invention is to provide an apparatus for using an electrolytic solution in a continuous high-speed nickel electroplating method.

Means for Solving the Problems

[0012] This object is achieved (a) nickel (metal), (b) methanesulfonic acid, and (c) an oxygen-releasing compound by a process of combining in an aqueous solution comprising a method for preparing a nickel plating bath.

Embodiments for Carrying Out the Invention

[0013] The nickel plating bath is understood to be an aqueous solution containing nickel ions (Ni 2+ ) for electroplating nickel onto a metal substrate. The plating bath can also be referred to as an electrolytic solution or an electroplating bath. An example of a nickel plating bath or electrolytic solution is an aqueous solution of nickel methanesulfonate.

[0014] In the context of the present invention, an oxygen-releasing compound is a chemical compound that can dissolve in an aqueous solution. This compound releases oxygen. Without being bound by the following theory, it is presumed that the released oxygen is not molecular oxygen (O2), but so-called active oxygen or atomic oxygen. Then, the oxygen can react with other compounds in the aqueous solution to form a nickel plating bath. This reaction is preferably an exothermic reaction.

[0015] In a preferred embodiment of the present invention, the method for preparing a nickel plating bath is as follows: (a) Nickel (metal), (b) Methanesulfonic acid, (c) Hydrogen peroxide and / or ozone The process includes the step of combining the elements in an aqueous solution.

[0016] In another embodiment of the present invention, the method for preparing a nickel plating bath is: (a) Nickel (metal), (b) Methanesulfonic acid, (c) Ozone The process includes the step of combining the elements in an aqueous solution.

[0017] In another embodiment of the present invention, the method for preparing a nickel plating bath is: (a) Nickel (metal), (b) Methanesulfonic acid, (c) Sodium perborate The process includes the step of combining the elements in an aqueous solution.

[0018] Nickel methanesulfonate solution has the advantage of having extremely high conductivity and enabling a high deposition rate in electroplating methods for preparing nickel coatings.

[0019] A simple method for preparing a nickel methanesulfonic acid solution would be to dissolve nickel metal (nickel(metal)) in methanesulfonic acid. However, nickel is not soluble in methanesulfonic acid. Surprisingly, however, nickel is very quickly and cleanly dissolved in an aqueous methanesulfonic acid solution by reactive oxygen species released by oxygen-releasing compounds such as hydrogen peroxide (H2O2), ozone (O3), or sodium perborate (NaH2BO4), resulting in the formation of nickel ions (Ni 2+ It is oxidized to ).

[0020] Surprisingly, an oxidation method using a suitable oxygen-releasing compound was found to be remarkably fast and clean in its preparation of nickel methanesulfonate from metallic nickel in water.

[0021] The temperature of the solution or water also affects the dissolution rate of nickel metal. The solution temperature has been found to be preferably between 20°C and 80°C. Dissolution is particularly fast at temperatures above 40°C, for example, between 50°C and 70°C. The appropriate maximum dissolution temperature is 68°C. Preferably, the temperature is between 55°C and 65°C. To avoid misunderstanding, it should be noted that the solution or water temperature refers to the temperature during the preparation of the nickel methanesulfonate solution.

[0022] The following intermediate reaction occurs between hydrogen peroxide and nickel: Ni(metal)+H2O2→NiO+H2O (1)

[0023] NiO is an intermediate reaction product that dissolves immediately in methanesulfonic acid. The total reaction is as follows: Ni (metal)+H2O2+2CH3SO3H→Ni 2+ +2CH3SO3 - +2H2O (2)

[0024] The following reaction occurs between ozone and nickel: Ni (metal) + O3 → NiO + O2↑ (gas) (3)

[0025] The total reaction is as follows: Ni (metal)+O3+2CH3SO3H→Ni 2+ +2CH3SO3 - +O2↑(gas)+H2O (4)

[0026] Sodium perborate undergoes hydrolysis upon contact with water, producing hydrogen peroxide (H2O2) which reacts as shown in formula (1). Boric acid (B(OH)3) may also be produced as a result of the hydrolysis.

[0027] As can be seen from equation (2) above, only water is produced as a byproduct, while in equation (4), O2 and water are produced as byproducts. The reaction can be accelerated by increasing the surface area of ​​metallic nickel, for example by using smaller pellets, thinner strips, or nickel powder, and by raising the temperature of the aqueous solution. The advantage of using hydrogen peroxide as the oxygen-releasing compound is that it is available as a liquid and is therefore easier to handle than gaseous ozone. Ozone is added preferably as a gas, preferably by bubbling ozone gas through an aqueous solution.

[0028] Furthermore, surprisingly, the addition of boric acid and / or taurine was found to significantly increase the maximum current density that can be used in nickel plating methods when using these nickel plating baths. The use of sodium perborate as an oxygen-releasing compound may already provide boric acid to the solution.

[0029] From a practical standpoint, the use of hydrogen peroxide and / or ozone is preferred because it produces a pure nickel methanesulfonate solution without generating boric acid in the solution. This is advantageous when a nickel methanesulfonate solution with only taurine added (and no boric acid) is selected.

[0030] A nickel plating bath suitable for nickel electroplating can be prepared by adding various compounds to a nickel methanesulfonic acid solution. These compounds may, but are not limited to, buffers, brighteners, and stress control agents. The addition of these compounds, their effects, and the appropriate amounts to be added are well known in the art.

[0031] The reaction of hydrogen peroxide or ozone with nickel is 100% efficient because both react to form water or oxygen, without producing undesirable, toxic, or environmentally harmful by-products such as chlorine. The method according to the invention results in a nickel plating bath that does not contain compounds that can cause the formation of toxic or environmentally harmful by-products such as chlorine or bromine, or undesirable metal ions.

[0032] Furthermore, the dissolution of nickel in an acidic aqueous solution of methanesulfonic acid containing hydrogen peroxide and / or ozone is very fast, so this method is useful in combination with high-speed continuous electroplating methods.

[0033] The method according to the invention has the great advantage that the amount of nickel required for the production of a nickel methanesulfonate solution as an electrolyte is much less in terms of volume than alternative solutions.

[0034] For example, 1000 kg of metallic nickel has a volume of 112.2 dm 3 whereas the equivalent amount of nickel from nickel carbonate has a volume of 460.6 dm 3 When using nickel carbonate as the nickel source, a volume 4.5 times larger has to be handled. Furthermore, the handling, transport, and storage of salts are more difficult than for metallic nickel from a safety and hygiene point of view and from a logistics point of view. These compounds have been identified as potentially carcinogenic and toxic compounds (see, for example, www.ilo.org for nickel carbonate and nickel(II) oxide). Therefore, the costs and safety risks associated with this method are higher than those of the method according to the invention.

[0035] With appropriate safety precautions, the production mechanism of a nickel methanesulfonate solution based on nickel carbonate (NiCO3), nickel hydroxide (Ni(OH)2) or NiO is as follows: NiCO3 + 2CH3SO3H → Ni 2+ + 2CH3SO3 - + H2CO3(5) Next, H2CO3 → H2O + CO2 (gas) (5a) Ni(OH)2 + 2CH3SO3H → Ni 2+ +2CH3SO3 - +2H2O (6) NiO + 2CH3SO3H → Ni2 + +2CH3SO3 - +H2O (7)

[0036] However, compared to the method according to the present invention, this is more cumbersome from the standpoint of safety and health, handling, and cost.

[0037] In one embodiment, the method for preparing a nickel plating bath (aqueous solution of nickel methanesulfonate) according to the present invention is as follows: (a) Nickel (metal), (b) Methanesulfonic acid, (c) Hydrogen peroxide and / or ozone The process includes the step of combining these in an aqueous solution to obtain an aqueous solution of nickel methanesulfonate.

[0038] This means combining nickel, methanesulfonic acid, and hydrogen peroxide, or nickel, methanesulfonic acid, and ozone, or nickel, methanesulfonic acid, hydrogen peroxide, and ozone in an aqueous solution for the reaction; that is, reacting these components in an aqueous solution.

[0039] The aqueous solution is preferably water, or an aqueous solution of one or two of the other components (a), (b), and (c). The water may be distilled water, demineralized water, or simply tap water. The order in which components (a), (b), and (c) are added is arbitrary. This means, for example, adding methanesulfonic acid and hydrogen peroxide to water, or combining methanesulfonic acid and hydrogen peroxide as an aqueous solution and then adding nickel to the resulting aqueous solution. Alternatively, as an example, nickel may be added to water or one of components (b) or (c), and the remaining components may be added to the resulting aqueous solution. When components (a), (b), and (c) are combined, they react with each other. Nickel reacts with hydrogen peroxide and / or ozone to form Ni 2+ Oxidized into an ion, the methanesulfonate anion becomes Ni 2+ It forms a counterion for an ion.

[0040] When sodium perborate is used, the conditions of the aqueous solution must be favorable for the hydrolysis of the perborate to hydrogen peroxide and boric acid. This hydrolysis is accelerated by higher temperatures in the aqueous solution. Sodium perborate rapidly releases oxygen at temperatures above 55°C. To activate it at lower temperatures (40°C to 55°C), a suitable activator may be used.

[0041] Nickel is added as a metal, and its form may be arbitrary. To enhance the dissolution of nickel into water by oxidation with hydrogen peroxide and / or ozone, the surface area of ​​the nickel should be as large as possible. In a preferred embodiment of the present invention, the nickel is in the form of metal pellets or metal powder. The average size of the pellets or powder particles is preferably less than 10 mm, more preferably less than 5 mm, even more preferably less than 1 mm, even more preferably less than 0.1 mm, and most preferably 0.001 mm to 0.1 mm. When using thin strips of nickel, the thickness of the strip is preferably less than 1 mm, even more preferably less than 0.1 mm, and most preferably 0.001 mm to 0.1 mm. An advantage of using nickel as a metal is that the raw material is easy to store and requires little space. Storing nickel metal does not pose any safety problems.

[0042] The present invention is also embodied in a nickel plating bath or electrolyte obtained by the method of the present invention described above.

[0043] In one embodiment, the nickel plating bath is placed in water. (a) Nickel methanesulfonate in concentrations of 26 g / L to 316 g / L (b) 10 g / L to 100 g / L of boric acid and / or 10 g / L to 70 g / L of taurine It consists of including.

[0044] In a preferred embodiment, the nickel plating bath is in water, (a) Nickel methanesulfonate in concentrations of 26 g / L to 285 g / L (b) 10 g / L to 100 g / L of boric acid and / or 10 g / L to 70 g / L of taurine It consists of including.

[0045] The temperature of the solution or water also affects the dissolution rate of nickel metal. The solution temperature has been found to be preferably between 20°C and 80°C. Dissolution is particularly fast at temperatures above 40°C, for example, between 50°C and 70°C. The appropriate maximum dissolution temperature is 68°C. Preferably, the temperature is between 55°C and 65°C.

[0046] The precise dissolution rate of metallic nickel in solution depends on the precise composition and temperature of the solution and can be easily determined using simple laboratory methods. The dissolution rate of nickel is approximately 0.05 kg / m³ when nickel is added to a solution at 60°C (the solution is prepared from 80 g / L of 30% H₂O₂ and 129 g / L of 70% methanesulfonic acid solution). 2 ·min ~ approx. 0.2kg / m 2 It was found to be within the range of minutes. For explanation, the dissolution rate of nickel was set to 0.1 kg / m³. 2 Assuming a dissolution time of approximately 5 mm, the dissolution time for 1 kg of nickel pellets is approximately 150 minutes. For an average particle size of 0.5 mm, the dissolution time is approximately 15 minutes, and for an average particle size of 0.01 mm, the dissolution time for 1 kg of particles is approximately 20 seconds.

[0047] The concentration of hydrogen peroxide in the solution is preferably 4% to 15% by weight of H2O2, more preferably 7% to 12% by weight of H2O2, and most preferably 8% to 10% by weight of H2O2, based on the total weight of the solution. The total weight of the solution includes water, hydrogen peroxide, and methanesulfonic acid, but does not contain nickel metal. The concentration of methanesulfonic acid is preferably 15% to 35% by weight, more preferably 20% to 30% by weight of methanesulfonic acid, based on the total weight of the solution. These concentrations provide a high dissolution rate for nickel.

[0048] In a preferred embodiment of the present invention, the molar ratio of methanesulfonic acid to hydrogen peroxide in the solution is 2:(0.90~1.10), preferably 2:(0.95~1.05), more preferably 2:(0.98~1.02), and most preferably 2:(0.995~1.005).

[0049] Nickel can be added in excess, but it is preferable to add it in stoichiometric amounts. The molar ratio of nickel:methanesulfonic acid:hydrogen peroxide is preferably (0.90~1.10):2:(0.90~1.10), more preferably (0.95~1.05):2:(0.95~1.05), even more preferably (0.98~1.02):2:(0.98~1.02), and most preferably (0.995~1.005):2:(0.995~1.005). Ozone is added as a gas until the above amounts given for hydrogen peroxide have reacted.

[0050] Even if the molar ratio of nickel:methanesulfonic acid:hydrogen peroxide or ozone is exactly 1:2:1, the chemical reaction is never complete, and the solution may still contain trace amounts of hydrogen peroxide or ozone. However, the inventors have found that these trace components do not significantly affect the plating properties or the properties or composition of the nickel plating layer.

[0051] The nickel plating bath according to the present invention has been found to be particularly useful for preparing an electrolyte used in nickel electroplating methods, especially high-speed nickel electroplating methods.

[0052] Therefore, the present invention also, (a) Nickel, (b) Methanesulfonic acid, (c) Oxygen-releasing compounds The present invention relates to a nickel plating bath obtained by a method comprising the step of combining in water or an aqueous solution to obtain an aqueous solution of nickel methanesulfonate. The oxygen-releasing compound may be hydrogen peroxide, ozone, sodium perborate, or a combination thereof.

[0053] The nickel methanesulfonate aqueous solution obtained by the method of the present invention is preferably 10 -6 % by weight to 0.1% by weight of hydrogen peroxide and / or 10 -6 Ozone at a concentration of % by weight to 0.01% by weight, comfortably within 10°C.-5 % by weight to 0.05% by weight of hydrogen peroxide and / or 10 -5 The solution contains an aqueous solution of nickel methanesulfonate containing 0% to 0.005% by weight of ozone. The pH is preferably 1 to 4. More preferably, the pH is less than 3. Even more preferably, the pH is 1.5 to 2.5, and most preferably 1.6 to 2.2.

[0054] The present invention further relates to the use of a nickel plating bath according to the present invention in a nickel electroplating method. This use is the use of a nickel plating bath as an electrolyte in a method for preparing a nickel coating, particularly a method for preparing a nickel coating by electroplating an article, preferably a steel sheet. Electroplating is also known as electrodeposition or electrochemical plating (galvanic coating).

[0055] In a preferred embodiment of such use, an aqueous solution of nickel methanesulfonate is used to prepare an electrolyte for high-speed nickel electroplating, preferably electroplating using a dimensionally stable anode. Such a dimensionally stable anode is preferably made from a metal oxide, more preferably a mixture of metal oxides, for example on a titanium support. The metal oxides are preferably iridium oxide, osmium oxide, ruthenium oxide, rhodium oxide, palladium oxide, platinum oxide, or mixtures thereof.

[0056] When using an aqueous nickel methanesulfonate solution as a nickel plating bath, the current flow rate is approximately 100 A / dm². 2 The maximum current density (amperes per square decimeter) is possible. Surprisingly, in the study of the present invention, the addition of boric acid (H3BO3) and / or taurine (2-aminoethylsulfonic acid) makes the usable maximum current density 140 A / dm 2 It was found that the current density could be increased to this level, but in an aqueous solution of nickel methanesulfonate without the addition of boric acid or taurine, the maximum current density mentioned above was approximately 100 A / dm². 2 This improves the efficiency and usefulness of this nickel plating bath for high-speed plating methods.

[0057] Therefore, the present invention also applies to water, (a) Nickel methanesulfonate in concentrations of 26 g / L to 316 g / L (b) 10 g / L to 100 g / L of boric acid and / or 10 g / L to 70 g / L of taurine The present invention relates to a nickel plating bath for electroplating nickel, comprising the following:

[0058] This means that the nickel plating bath preferably contains 26 g / L to 316 g / L of nickel methanesulfonate prepared by the method according to the present invention, 10 g / L to 100 g / L of boric acid and / or 10 g / L to 70 g / L of taurine, with the remainder being water. The nickel plating bath may additionally contain typical electrolytic additives.

[0059] In a preferred embodiment, the nickel plating bath is in water, (a) Nickel methanesulfonate in concentrations of 26 g / L to 285 g / L (b) 10 g / L to 100 g / L of boric acid and / or 10 g / L to 70 g / L of taurine It consists of including.

[0060] The nickel plating bath according to the present invention comprises 26 g / L to 316 g / L of nickel methanesulfonate, preferably 26 g / L to 285 g / L of nickel methanesulfonate, more preferably 80 g / L to 200 g / L of nickel methanesulfonate, and even more preferably 105 g / L to 160 g / L of nickel methanesulfonate. The above given amounts of nickel methanesulfonate correspond to about 10 g / L to 120 g / L of nickel dissolved in ionic form, preferably about 10 g / L to 110 g / L, more preferably about 30 g / L to 75 g / L, and even more preferably about 40 g / L to 60 g / L of nickel.

[0061] The amount of boric acid in the nickel plating bath according to the present invention is 10 g / L to 100 g / L of boric acid, preferably 30 g / L to 70 g / L of boric acid, and more preferably 40 g / L to 60 g / L of boric acid. The amount of taurine according to the preferred embodiment is 10 g / L to 70 g / L of taurine, preferably 30 g / L to 60 g / L of taurine, and more preferably 40 g / L to 60 g / L of taurine.

[0062] The above quantities can be combined in any combination. This is because a preferred embodiment of the present invention is, for example, In the water, (a) Nickel methanesulfonate in concentrations of 26 g / L to 316 g / L (b) 30 g / L to 70 g / L of boric acid and / or 30 g / L to 60 g / L of taurine A nickel plating bath comprising, In the water, (a) Nickel methanesulfonate in concentrations of 80 g / L to 285 g / L (b) 10 g / L to 100 g / L of boric acid and / or 10 g / L to 70 g / L of taurine A nickel plating bath comprising, In the water, (a) Nickel methanesulfonate in concentrations of 80 g / L to 200 g / L (b) 10 g / L to 100 g / L of boric acid and / or 10 g / L to 70 g / L of taurine This means that the nickel plating bath contains [a specific substance].

[0063] Both boric acid and taurine act as buffering and complexing agents. Taurine is biodegradable and therefore preferable from an environmental standpoint. A preferred embodiment of the present invention comprises taurine as component (b).

[0064] Another preferred embodiment of the present invention is the use of a nickel plating bath according to the present invention in a nickel electroplating method.

[0065] The present invention also relates to the use of a nickel plating bath according to the present invention in a nickel electroplating method, preferably nickel electroplating on steel, and more preferably nickel electroplating on a steel sheet. A preferred embodiment of the present invention is the use of a nickel plating bath according to the present invention for manufacturing a battery case or electrolytic cell component. This method comprises nickel electroplating a steel sheet and then using the resulting steel sheet having a nickel layer on its surface to manufacture a battery case. This use may include, among other known steps, cutting the nickel-coated steel sheet and shaping the sheet.

[0066] The nickel-plated steel sheets manufactured in this manner can be used for other applications and are not necessarily limited to battery or electrolytic cell components.

[0067] In the nickel plating bath used according to the present invention, i.e., in the electroplating method, the temperature of the nickel plating bath in the nickel electroplating method is preferably 40°C to 70°C, more preferably 50°C to 60°C. The pH is preferably 1 to 4, more preferably 1 to 3. The pH is preferably 1 to 4. More preferably the pH is less than 3. Even more preferably the pH is 1.5 to 2.5, and most preferably 1.6 to 2.2.

[0068] The present invention also relates to a nickel electroplating method, wherein nickel is electrodeposited onto an article, preferably a steel sheet or steel strip, in a nickel plating bath manufactured according to the present invention. The current density is preferably 40 A / dm 2 ~140A / dm 2 The temperature of the plating bath is as described above.

[0069] The substrate used for nickel-plated metal substrates in batteries and electrolytic cells is typically low-carbon steel strips. These strips are manufactured by cold rolling. While strips are usually supplied in coil form, they may also be cut into smaller pieces called sheets. Wide coils may be slit into narrower strips and then recoiled or cut into sheets.

[0070] In plating methods, it is preferable to plate strips rather than individual sheets. The productivity of the plating method is much higher and it can be carried out in a continuous plating line. Steel strips are very hard after cold rolling and usually need to be annealed to soften or recrystallize the microstructure of the steel in order to enable further processing such as deep drawing for manufacturing batteries. Annealing can be carried out before or after nickel plating. If plating is carried out after annealing, a nickel layer is formed on the steel substrate. If plating is carried out before annealing, nickel begins to diffuse into the steel substrate and iron begins to diffuse into the nickel layer. The degree of interdiffusion can vary depending on the thickness of the nickel layer, the annealing temperature, the annealing time, and the annealing method (batch annealing or continuous annealing). If the annealing temperature is not very high or the annealing time is very short, the degree of diffusion may be very limited (so-called shallow annealing). In this method, the surface of the nickel layer is still nickel only, but a diffusion layer is formed at the nickel-steel interface. The longer the annealing time, the thinner the nickel plating, and the higher the annealing temperature, the more nickel and iron intermix until iron begins to migrate to the surface of the plating layer. In some applications, this is very important, and a 1:1 Ni:Fe value on the surface is often reported. The choice of annealing temperature and time also depends on the desired microstructure of the steel substrate after annealing. Post-treatment (in any order) of the annealed and plated strips may be performed, for example, temper rolling or tension leveling. This heat treatment can be carried out in several ways, such as batch annealing, continuous annealing, normalizing, and flash annealing. All heat treatments impart specific desired mechanical properties to the heat-treated material. The main differences between heat treatments are the heating rate, the maximum temperature, and the duration at this maximum temperature. Heating can be carried out by gas flame, electric heating, or any other method to raise the temperature of the nickel-plated steel base in a controlled manner.

[0071] Figure 8 shows a series of nickel-plated steel (Fe) substrates, with a schematic cross-sectional structure on the left and a schematic diagram of nickel concentration on the right, where the left side of the graph represents the surface. Figure 8a shows a nickel-plated steel strip with no diffusion. This is a steel substrate plated with a nickel layer after annealing of the steel substrate or without any annealing of the substrate. Figure 8b shows a nickel-plated steel strip that has undergone light annealing. Diffusion of nickel into the steel substrate and iron into the nickel layer is minimal, and the iron has not yet reached the surface. The surface of the nickel-plated layer is still 100% nickel. Figure 8c shows a nickel-plated steel strip that has undergone stronger annealing. Diffusion of nickel into the steel substrate and iron into the nickel layer is considerably more extensive, and the iron has reached the surface. The surface of the plated layer is approximately 70% Ni and 30% Fe. The Fe content at the surface increases as the annealing (time or temperature) becomes stronger or as the nickel layer becomes thinner. The surface composition can be controlled by controlling the annealing and the thickness of the plating layer. [Examples]

[0072] The following embodiments provide preferred embodiments of the present invention and further illustrate the present invention.

[0073] Example 1 A nickel methanesulfonic acid solution (nickel plating bath) was prepared by immersing a 50 x 50 mm nickel sheet in a mixture of 80 g of 30 wt% H2O2 and 192 g of 70 wt% methanesulfonic acid solution at 60°C. The nickel content was 0.1 kg / m². 2 Approximately 0.01 g / cm³ per minute 2 It dissolves at a rate of [number] minutes.

[0074] The nickel sheet was removed when the concentration reached 50 g / L of Ni. The resulting solution contained only nickel methanesulfonate and trace amounts of H2O2. This solution was used in a nickel electroplating method using a rotating cylinder electrode on a black plate (low-carbon cold-rolled steel). This rotating cylinder approach allows for accurate simulation of industrial plating methods and conditions.

[0075] The experimental conditions were as follows: ·Current density: 10A / dm 2 , 20A / dm 2 , 40A / dm 2 , 60A / dm 2 , 80A / dm 2 and 100A / dm 2 Plating time: 10 seconds • Cylinder rotation speed: 400 rpm (revolutions per minute), which is equivalent to a line speed of 100 m / min. Temperature: 50°C and 60°C ·Anode / cathode spacing: 15mm

[0076] The above conditions resulted in a highly efficient nickel coating on steel (efficiency exceeding 90% was achievable). These experiments demonstrate that the solution according to the present invention can be efficiently used in a high-speed nickel electroplating method.

[0077] Example 2 The maximum current density that can be used in the nickel plating bath of Example 1 is approximately 100 A / dm². 2 In Example 1, boric acid was added to the plating bath in amounts of 15 g / L, 30 g / L, and 45 g / L, and electroplating was performed at T=60°C, 400 rpm, and t=10 seconds. The maximum current was 140 A / dm 2 Current densities up to [value missing] were possible, and the nickel layer obtained on the steel sheet exhibited excellent appearance across the entire range of current densities.

[0078] Example 3 Adhesion Test Nickel electroplating was performed using the above nickel plating baths, with and without boric acid, at line speeds of 75 m / min to 150 m / min, plating times of 5 seconds, 10 seconds, and 20 seconds, hydrogen peroxide concentrations of 0 wt%, 0.1 wt%, and 0.5 wt%, and temperatures of 35°C, 40°C, 50°C, 60°C, and 70°C. The current density was 100 A / dm². 2 The samples were subjected to adhesion tests (NEN EN ISO 2409:2013, Erichsen-Dohm test, 5 mm, followed by adhesive tape (cross-cut test (Gitterschnitt test))). No samples showed delamination.

[0079] Example 4 Taurine added The maximum current density that can be used in the nickel plating bath of Example 1 is approximately 100 A / dm². 2 In Example 1, 30 g / L of taurine was added to the plating bath, and electroplating was performed at T=60°C, 400 rpm, and t=10 seconds. The maximum current was 140 A / dm 2 This current density was possible, and the nickel layer obtained on the steel sheet had excellent appearance across the entire range of current densities.

[0080] The present invention will be illustrated with the following non-limiting drawings. [Brief explanation of the drawing]

[0081] [Figure 1] Figure 1 shows the relationship between nickel pellet diameter (mm) and the dissolution time (minutes) of 1 kg of nickel pellets, assuming a nickel dissolution rate of 0.1 kg / m2·min. [Figure 2] Figure 2 shows the relationship between the rotational speed (RCE) of a rotating cylinder electrode and the line speed of an industrial plating line. [Figure 3]Figure 3 shows the thickness (μm) of the nickel layer deposited from a nickel methanesulfonate solution containing 100 g / L Ni at 60°C and RCE 400 rpm as a function of current density (A / dm2) for different deposition times (5 seconds (5s) (lower curve), 10 seconds (10s), and 20 seconds (20s) (upper curve)). [Figure 4] Figure 4 shows the thickness (μm) of the nickel layer deposited from a nickel methanesulfonate solution containing 50 g / L Ni and 30 g / L boric acid at 60°C for a plating time of 10 seconds, as a function of current density (A / dm2), for different rotational speeds of the RCE (i.e., different coating line speeds). [Figure 5] Figure 5 shows the effect of boric acid concentration on the plating layer thickness under a 400 rpm condition for 15 g / L (upper curve), 30 g / L, and 45 g / L boric acid (lower curve), as a function of current density (A / dm2) under a plating time of 10 seconds. [Figure 6] Figure 6 shows the plating efficiency of a nickel methanesulfonate solution containing 50 g / L Ni and 30 g / L boric acid as a function of pH. The plating efficiency increases sharply from less than 50% when the pH is below 1 to over 70% when the pH is above 1. At pH values ​​of 1.5 or higher, even higher efficiencies exceeding 90% are obtained (for clarification, a higher pH value means a lower acidity of the solution). [Figure 7] Figure 7 shows the impression of the quality of the plated layers obtained at different current densities under the conditions of a plating temperature of 60°C and a plating time of 10 seconds for the nickel methanesulfonate solution obtained by the method according to the present invention. All show excellent visual appearance. [Figure 8] Figure 8 shows a series of nickel-plated steel (Fe) substrates at various stages of diffusion annealing as described herein. [Figure 9]Figure 9 shows an apparatus consisting of one or more dissolution tanks (D) for dissolving metallic nickel in methanesulfonic acid. One or more buffer tanks (B) can be used to store the nickel methanesulfonic acid bath for convenient storage or to fine-tune the bath composition by adding boric acid or taurine and other necessary additives as desired. From these buffer tanks, the solution can be pumped to plating cells (only two cells are shown here, but more may be used). In a continuous plating method, a coil of metal substrate can be unwound and fed into the plating cells for plating, and then the plated substrate can be wound into a coil again for further processing. Pre-treatment or post-treatment of plated strips, such as washing or annealing of cold-rolled strips (before or after plating), is not shown. Piping, pumps, and plating peripheral equipment are also not shown. Furthermore, means of supplying nickel metal and other necessary chemicals are not shown.

Claims

1. A method for preparing a nickel plating bath, (a) Nickel (metal), (b) Methanesulfonic acid, and (c) Oxygen-releasing compounds A method comprising the step of combining in an aqueous solution.

2. The method described above is (a) Nickel (metal), (b) Methanesulfonic acid, and (c) Hydrogen peroxide and / or ozone The method according to claim 1, comprising the step of combining in an aqueous solution.

3. The following intermediate reaction: a) Ni (metal) + H ２ O ２ →NiO+H ２ O (1) In formula (1), NiO is an intermediate reaction product that dissolves immediately in methanesulfonic acid, and the total reaction is as follows: Ni (metal) + H ２ O ２ + 2CH ３ SO ３ H → Ni ２＋ + 2CH ３ SO ３ － + 2H ２ O (2), or b) Ni (metal) + O ３ →NiO+O ２ ↑ (gas) (3) In equation (3), NiO is an intermediate reaction product that dissolves immediately in methanesulfonic acid, and the total reaction is as follows: Ni (metal) + O ３ +2CH ３ SO ３ H→Ni ２＋ +2CH ３ SO ３ － +O ２ ↑ (gas) + H ２ O (4), The method according to claim 2, wherein the following occurs, thereby generating an aqueous solution of nickel methanesulfonate.

4. The method according to any one of claims 1 to 3, characterized in that the temperature of the aqueous solution is 20°C to 80°C, preferably 50°C to 70°C.

5. The method according to any one of claims 1 to 4, characterized in that the concentration of hydrogen peroxide is 4% to 15% by weight, based on the total weight of the solution, and / or the concentration of methanesulfonic acid is 15% to 25% by weight, based on the total weight of the solution.

6. The method according to any one of claims 1 to 5, characterized in that methanesulfonic acid and / or hydrogen peroxide are used in the form of an aqueous solution.

7. The method according to any one of claims 1 to 6, characterized in that nickel (metal) is used in the form of metal pellets or metal powder.

8. The method according to claim 7, characterized in that the average size of the pellets or the average size of the powder particles is less than 10 mm, preferably 0.001 mm to 1 mm.

9. The method according to any one of claims 1 to 8, characterized in that the molar ratio of methanesulfonic acid to hydrogen peroxide is 2:(0.95 to 1.05), preferably 2:(0.98 to 1.02).

10. A nickel plating bath obtained by the method according to any one of claims 1 to 9.

11. The nickel plating bath according to claim 10, characterized in that the nickel plating bath further contains 10 g / L to 100 g / L of boric acid and / or 10 g / L to 70 g / L of taurine.

12. The nickel plating bath is in water, Nickel methanesulfonate in concentrations of 26 g / L to 316 g / L, 10 g / L to 100 g / L of boric acid and / or 10 g / L to 70 g / L of taurine A nickel plating bath according to claim 10 or 11, comprising the above.

13. The nickel plating bath is in water, Nickel methanesulfonate in concentrations of 80 g / L to 200 g / L, 30 g / L to 70 g / L of boric acid and / or 30 g / L to 60 g / L of taurine A nickel plating bath according to claim 12, comprising the above.

14. The nickel plating bath is in water, Nickel methanesulfonate in concentrations of 80 g / L to 200 g / L, and 30g / L to 60g / L of taurine A nickel plating bath according to claim 12 or 13, comprising the above.

15. The use of a nickel plating bath according to any one of claims 9 to 14, preferably in a nickel electroplating method, and preferably in a nickel electroplating method for steel strips or steel sheets, and preferably in a continuous electroplating method.

16. Use of the nickel plating bath according to claim 15 for producing nickel-plated substrates, particularly nickel-plated substrates for electrical applications such as batteries and electrolytic cells.

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