KR100976787B1 - Zinc plated steel having iron flash plating film thereon and composition of bath of iron flash plating and method for manufacturing the zinc plated steel - Google Patents

Abstract

The present invention is a technique for reinforcing the characteristics of the plating film of the galvanized steel sheet. Disclosed is a railway gold technology and a railway gold film formed by a pretreatment process for improving the characteristics of an electrogalvanized film. In general, in the electro zinc plating process of the steel sheet, as a pretreatment process for improving the coating characteristics of the electro zinc plating, after the nickel flash (Flash) plating is performed, the electro zinc plating is finally performed thereon. Rather than plating, a relatively cheap railroad train is implemented. Conventionally, an electrogalvanized steel sheet excellent in corrosion resistance, adhesion and concealability obtained by applying nickel flash plating is obtained by the iron flash plating technique according to the present invention.

The present invention is excellent in corrosion resistance, adhesiveness and concealability composed of a conventional railroad gold layer having a rail thickness of 0.01 µm or more as a lower layer, and an electrogalvanized layer having a zinc plating thickness of 2 µm or more as an upper layer. Disclosed are an iron flash plated coating on a base plate capable of producing a galvanized steel sheet and a method for producing the plating solution.

Electro galvanized steel sheet, nickel flash plating, iron flash plating, electro zinc plating pretreatment

Description

(Zinc plated steel having iron flash plating film thereon and composition of bath of iron flash plating and method as rail plating solution and rail gold solution as base plating solution for manufacturing galvanized steel sheet) for manufacturing the zinc plated steel}

The present invention relates to a new pretreatment process of an electrogalvanized steel sheet used as a structural material for automobiles, home appliances, and building materials. Specifically, the galvanized film of the conventional galvanized steel sheet has excellent hiding power, adhesion and corrosion resistance. It is a technique to replace nickel flash plating, which is a pretreatment process performed to have a). Plating technology according to the present invention is a new base plating process with high economical efficiency, and relates to an iron flash plating process and an iron flash plating film used by the iron flash plating process used in the iron flash plating process and the iron flash plating process.

Steel plate is widely used in structural materials such as automobiles, home appliances, and building materials because of its excellent mechanical strength, good workability, and abundant resources. However, the steel plate itself is extremely poor in corrosion resistance, and its surface is mainly galvanized to extend its lifespan. .

In general, the corrosion resistance of galvanizing is about 2 years in the industrial zone, when the thickness of the plating itself without post-treatment is 0.025 mm, until the red rust, which is the corrosion of the base metal, is generated. Are reported to be about three years old and about five years in rural areas, which may be further reduced depending on the environment. Galvanized steel sheet, which is widely used for building materials, uses hot dip galvanizing and its plating adhesion amount reaches 40g / m ² or more, but when used as a non-painting material, corrosion resistance is not great. Moreover, in hot dip galvanizing, plating is performed by immersing the steel plate in a high temperature galvanizing bath of 400 ° C. or higher, thus affecting the mechanical properties of the steel sheet, thereby limiting the selection of the steel sheet.

On the other hand, the corrosion protection ability to protect iron is generally better the thicker the galvanized thickness, but the high corrosion resistance to the steel sheet alone is limited and uneconomical, so the back of the chromate after galvanization etc. The process of increasing the corrosion resistance is selected through the treatment process, and in recent years, research on a new plating technology, such as electro-galvanizing technology, to obtain high corrosion resistance with less zinc adhesion amount has been conducted. As a result, the galvanized steel sheet having a relatively low amount of zinc compared to hot dip plating can be used more appropriately for products requiring high corrosion resistance and high sealing property in automobiles, home appliances, and building materials. Electro-zinc plating usually has a plating thickness of 0.005 mm to 0.025 mm, but the economic thickness is about 0.008 mm-0.013 mm.

However, the problem of lowering the corrosion resistance of such a thin zinc plated film of the galvanized steel sheet can be compensated by the surface treatment such as chromate. Since the concealment force is lowered, defects existing on the original surface of the base steel appear on the plating film after plating, and as a result, surface defects such as stains and ridge marks are visually confirmed, resulting in smoothness of the plating surface. It causes harm to beauty.

That is, in general, the steel sheet for electro-galvanizing is manufactured through a multi-stage pretreatment process such as degreasing, rinsing, electrolytic degreasing, pickling, and rinsing, followed by electro-galvanizing, but the physical surface of the base iron is bad and In the case of various kinds of impurities, the adhesion between the base iron and the galvanized film is not only worsened, but also causes a state in which plating is not performed. As shown in FIG. 1A, the surface can be easily visually confirmed after plating. The aesthetics of the surface of the galvanized steel sheet are greatly impaired, such as a trace or scratches left. The thinner the galvanized film is, the more serious this poor plating occurs.

As one of the prior arts to solve the problem of surface defects including the problem of visual damage of the galvanized steel sheet obtained by electro-galvanizing, the technique currently used effectively is nickel thin plating called so-called nickel flash plating before electro zinc plating. Will be done first. This nickel flash plating not only smoothes the surface of the base iron, but also electro-galvanizes it by first plating a thin film of nickel on the surface of the base iron with various impurities. By blocking the bleeding phenomenon to obtain a beautiful galvanized film.

Nickel flash plating is based on nickel plating in principle. Nickel plating is widely used as a base plating of chromium plating in addition to being used for the purpose of anticorrosion and decoration by plating steel and copper. Nickel plating is also most widely used in the current plating varieties due to its good color, relatively little discoloration, moderate hardness, and good mechanical properties. Such nickel plating is mainly manufactured by electroplating in a plating bath using nickel sulfate, nickel chloride, and sulfamic acid, in addition to a watt bath, a hard bath, and a sulfamic acid bath.

However, nickel plating has to go through a difficult process such as adjusting the acidity (pH) and the cathode current density of the plating bath, and it requires a separate pollution prevention facility and expense for the wastewater treatment of the plating bath. In some cases, there is a case in which the complete concealment characteristic for which the under plating is to be achieved may not be achieved depending on the composition of the plating solution, plating conditions, and the like. In the actual nickel flash plating process, when the content of the Fe component in the composition of the plating solution reaches 500 ppm, the nickel flash plating is not made well, and when the amount reaches 1000 ppm, the degree is very serious. In addition, as shown in FIG. 2B, a large crack may occur in the nickel plated layer due to the large internal stress of the nickel plated layer, which may cause deterioration of corrosion resistance and poor adhesion to the zinc plated layer. .

As described above, as a pretreatment of the electro-zinc plating process, nickel flash plating is effectively used to obtain a smooth plating surface by concealing it when the degree of physical and chemical defects on the surface of the iron material is severe. However, this nickel flash plating has such a high hiding effect, but sometimes the hiding power is lowered due to the physical and chemical properties of the nickel plating itself, and it is difficult to operate conditions. It is becoming a decisive factor to increase the manufacturing cost of steel sheet. For this reason, there is a need for an effective alternative to nickel flash plating.

Korean Patent Laid-Open Publication No. 1992-0021742 discloses a technique for improving lubricity, corrosion resistance and paintability by using an electrogalvanized layer formed on the surface of a steel sheet and a zinc-cobalt alloy electroplated layer formed thereon. have. This application technology is expected to give the advantage of surface defect removal that surpasses the effect of nickel flash plating, but the problem of increasing the manufacturing cost of the galvanized steel sheet, which is a fundamental disadvantage of nickel flash plating, is not solved due to the use of cobalt metal. .

In addition, Korean Patent Laid-Open Publication No. 195-0018678 proposes to use a chloride plating bath to improve surface characteristics such as surface glossiness of galvanized steel sheet.

In addition, Korean Patent No. 311796 relates to the manufacture of flash-plated steel sheet for hot-dip galvanized steel sheet, which is applied on the hot-dip galvanized steel sheet by vacuum evaporation instead of electroplating. By applying Fe-metal, and controlling the temperature of the material during deposition, the process is simple, the process for producing zinc alloyed galvanized steel sheet with excellent phosphate treatment and electrodeposition coating property and excellent corrosion resistance. It is starting.

Japanese Patent Application Laid-Open No. 57-171692 discloses a technique of forming a Ni diffusion layer in a steel by forming a Ni coating layer on a steel sheet and heating it in a non-oxidizing atmosphere to perform Zn-Ni alloy plating on the steel sheet. In the course of corrosion, however, after the loss of the plating layer or the corrosion product, the Ni-Fe diffusion layer certainly contributes to the improvement of corrosion resistance, but the effect is insufficient. The reason is considered as follows. That is, since the surface state of the steel sheet is stabilized by the presence of the Ni-Fe diffusion layer, the origin of corrosion is suppressed, but once the corrosion of the underlying iron begins, the density of the corrosion product is not high. Moisture or oxygen contributing to the product easily penetrates the product and cannot inhibit the progress of melting. Therefore, the present invention may be a solution to replace nickel flash plating, but does not solve the problem of economics, which is one of the objects of the present invention, in using nickel materials.

In general, the underlying plating process is to provide a leveling effect on the substrate to smooth the surface and improve the gloss. In Korean Patent Laid-Open No. 1999-0070721, the plating technique is omitted. In other words, the base metal is pretreated in the order of cutting polishing, polishing polishing, pickling, alkaline sonication and electrolytic degreasing, and then electroplated with the metal to be coated directly on the surface of the base metal without plating. Direct plating method is proposed to prevent discoloration and corrosion. This invention differs from the present invention in that it is a direct plating method without underplating, and is limited to those suitable for metals such as gold, silver, rhodium, palladium, and thus does not correspond to a galvanized steel sheet.

The present invention is effective in imparting high concealment characteristics of the zinc plated coating as a conventional pretreatment, but in connection with the disadvantages of the nickel flash plating process and the uneconomical disadvantage of increasing manufacturing cost, As a pretreatment process that can replace nickel flash plating, iron flash plating process and railway gold film obtained by this iron flash plating process are proposed.

The process principle of the iron flash plating of the present invention is based on the railway gold plating process. Railroad gold has been used mainly in electric poles, such as printing plates, since the late 19th century through attempts to obtain high-purity iron by electrolysis, and the most commonly used in the plating field is embossing plating. The main purpose was to strengthen the surface by industrial chromium plating after embossing with railway gold, but it was also applied to metals such as aluminum, beryllium and uranium. These are used for special purposes, and there are many examples of rail surface treatment and other surface treatments. For example, since it can harden | cure by carburizing or nitriding, and can also attach a corrosion-resistant colored film by the blackening method, railway gold is unexpectedly widely used for a special use.

Commonly used railway gold is an acid bath plating using ferrous iron, which is roughly divided into five types: ferrous sulfate bath, ferric chloride bath, mixed bath of both, ferrous boride bath, and sulfone ferrous bath. On the other hand, as a ferric bath, a bath in which triethanolamine or EDTA is added as an alkaline bath has been reported, but there is no report of practical use. Cheil is easily oxidized, and ferric iron increases in the bath. If the amount is less than 0.5 g / l, it may be effective to prevent uniform electrodeposition or pit occurrence as in the case of ferrous chloride bath, but if the amount is more than several g / l It is generally black and has a black-gray plating with high electrodeposition stress, and causes pits and tingling. These shortcomings of railroads make it impossible to replace the nickel flash plating process. Therefore, the prevention of the oxidation of the bath to suppress the production of ferric iron is an important point in railway abstinence management.

Next to Cheil, the main components of the bath are salts, which are conductive additives to improve conductivity. In ferrous chloride baths, calcium chloride, potassium chloride, sodium chloride, ammonium chloride, and ferrous sulfate are ammonium sulfate. Each is used. In addition, boric acid is mainly used in ferrous sulfate bath or mixed bath as a buffer of pH. In addition, as various types of precipitation aids used to refine the crystals of the electrodeposited material, or to prevent them from being soft and not filled, it is attempted to add chlorides such as manganese, aluminum and beryllium to the ferric chloride bath, and aluminum sulfate to the ferrous sulfate bath, respectively. It is becoming. Besides these, organic compounds such as surfactants, glycerin, dextrin, and saccharin are used in the ferrous sulfate bath.

The ferrous sulfate bath is generally plated at a low temperature of about room temperature, and has a low pH bath and a high pH bath. All are based on ammonium ferrous sulfate, and the bath temperature is 25 ^° C. Ferric hydroxide precipitates at a pH of about 3.5 and ferric hydroxide precipitates at a pH of about 6.0. Thus, in low pH baths ferric iron increases in the bath without producing precipitation of iron. On the other hand, in the high pH bath, ferric precipitates, so that harm caused by ferric iron can be avoided. Since ferrous iron is easily oxidized in a bath temperature of 60 ^° C., a high pH bath cannot be used and a low pH bath should be used. It is a drawback that the railroad in this bath is easy to produce pits or cracks, and is sold out.

Since chloride has a high solubility, it is possible to make the bath highly concentrated and to improve the conductivity of the bath so that the plating is carried out at a high current density. However, due to the high bath temperature, there is a drawback to 90 ^° C. However, there are baths to be plated at 40 ^° C. or lower like electroplating baths, but they are special as ferrous chloride baths. Whereas the rail gold of the ferrous sulfate bath is black-grey, and is susceptible to cracks, pits, streak traces, etc., the plating of the high temperature ferrous chloride bath reveals the color of the clean metallic iron that appears white, and the grains are rough, It is uniform in size, free of cracks and pits, and has an unknown feature.

Ferrous borohydride bath is a bath containing fluoride. Van der Horst baths are cast iron oxides, and they can be classified as fluoride baths because they also contain ferrous boride as an additive or composition. In both cases, chloride is added in the composition, and the temperature of the bath is about 60 ^° C., which is intermediate between the ferric chloride bath and the ferrous sulfate bath. In general, the characteristics of the iron fluoride bath plating are more similar to those of the iron sulfate bath than the ferric chloride bath.

Railway gold by sulfamic acid bath is mainly composed of iron sulfamate and sulfamic acid, and glycerin is added. Formalin or hydroquinone is used as a reducing agent, and ammonium sulfamate is added as a buffer. Recently, alloy plating of iron-cobalt, iron-zinc, iron-nickel, etc. has been studied based on sulfamic acid railroad gold.

These railroads are generally macroscopic irregularities, rough surfaces, cracks or pits, and various defects, but they are characterized by small stress in electrodeposites. Research is underway to solve this problem and the results have been proposed. However, these studies have been conducted only for electric poles or other special purposes, and researches to improve the surface characteristics of electrogalvanized steel sheets, in particular, can replace nickel flash plating, which is a conventional pretreatment process. It has never been proposed or studied as a process.

The present inventors tried to make a case that the composition of the conventional railway gold or the composition of the other railway gold proposed for the study can replace the nickel flash plating which is performed by the pretreatment process in the manufacture of the conventional galvanized steel sheet. It has been found that it is impossible to obtain electro zinc plating and its coating having excellent plating properties, including high hiding power obtained by conventional nickel flash plating, by using any existing railway gold and its plating solution composition. In order to achieve iron flash plating, it was found that the railroad's decision-making organization had to be radically different from the existing ones to achieve its purpose.

The reason is that the plating film made of flash plating is very thin and the bivalent iron ions (Fe ²⁺ ), which are the main components of the railway value, are unstable and easily oxidized to trivalent iron ions (Fe ³⁺ ).

In addition, it takes a long time to galvanize a body with a large plating area, such as a galvanized steel sheet. During this long time galvanizing, a thin film of railroad is easily melted and oxidized, and part of it turns into a black iron oxide film. This reduces the quality of galvanizing. In addition, the plated film made of oxidized iron may have a so-called unplated state in which the galvanization is not locally electrodeposited because the conductivity is sharply lowered than that of the pure iron film. It is easily broken due to low hardness, or a plated film having a very low adhesion of the plated film is formed. In addition, the instability of the bivalent iron ions (Fe ²⁺ ) is directly connected to the stability of the liquid, which reduces the stability of the liquid causes a serious problem in the storage of the plating solution in the plating factory.

The structure of the iron flash plating to be proposed in the present invention is formed in the form of covering the surface of the base iron, it can be expected a hiding power such as nickel flash plating if it can block the oxidation of bivalent iron in the plating solution.

In principle, the railway gold solution contains a complexing agent that gives a function to maintain the stability of the plating solution itself and an antioxidant for preventing the oxidation of divalent Fe into trivalent Fe in the solution. In some cases, since the component contained as a complexing agent may also serve as an oxidizing agent, in such a case, it may be omitted to include only the complexing agent and to add a separate oxidizing agent. However, if the complexing agent can also serve as an oxidant, a separate oxidant may be added.

As described above, nickel flash plating, which is generally performed as a pretreatment process of the electro zinc plating process, is effectively used for the purpose of obtaining a smooth and beautiful electro zinc plating surface by concealing the physical and chemical defects present on the surface of the iron sheet. However, nickel flash plating sometimes has a lower hiding power due to the physical and chemical properties of the nickel plating itself, and nickel plating electrodeposition is affected by the presence of iron in the nickel flash plating solution. It is difficult and, above all, nickel and its compounds have a disadvantage that the manufacturing cost of the galvanized steel sheet is a factor that increases the cost.

Therefore, an economical alternative is required while being able to sufficiently replace the function of nickel flash plating, and the present invention responds to such a request, and it is possible to replace nickel flash plating, which is performed as a pretreatment process of the conventional electro zinc plating process. To provide iron flash plating processes and compositions for rail coatings thereof, i.e., in the amount of base metal applied to the manufacture of electrogalvanized steel sheets, the same level of hiding power as that used for nickel-plated underplating used up to now, An object of the present invention is to provide an iron flash plating solution having excellent adhesion and corrosion resistance, and an iron flash plating solution composition capable of forming the plating coating.

According to the present invention, a composition of a railway amount that can substitute for the role of nickel flash plating is based on 1 L of an iron flash plating solution to be prepared. First, the content of iron in an appropriate salt containing iron ions is 5 to 300 g. It consists of an aqueous solution containing the amount of salt. Second, in order to increase the conductivity of the iron flash plating solution, 5 ~ 250g of one or more conductive salts in addition to the iron flash plating composition as an electric conduction aid, third, 0.1 ~ 250g of an antioxidant for preventing oxidation of iron ions in the solution is added. Should be. Fourth, as a precipitation aid for smoothly performing the electrodeposition process of iron flash plating according to the type of railway gold flash, a stress reducing agent for controlling viscosity and stress of the plating solution is 0.1 to 50 g, and impurities in the solution as the plating process proceeds. 0.1 to 50 g of the vaccinating agent having a function of suppressing the increase should be added, and fifthly, it has a dense crystal structure of the iron flash coating film after the iron flash plating, and a leveling agent for imparting smoothness and moisture. As a surface improver, 0.1 to 50 g should be added. Finally, the iron flash plating solution consisting of the above various components maintains the stability of the iron flash plating solution, such as preventing the deterioration of the plating solution due to the physicochemical reaction between the components, and blocking the deterioration of stability due to long-term use and storage. The iron flash plating solution of the present invention comprises a complexing agent of 0.5 to 250 g as a stabilizer for the purpose.

In addition, the base rail gold layer forming method according to the present invention,

Dipping the iron plated body made of iron in a plating composition solution consisting of an aqueous solution containing a salt containing 5 to 300 g of the salt containing iron ions based on a total of 1 L of the prepared iron flash plating solution;

A step of flowing a current 1.0 to 200 ASD (ampere per square decimeter) to the plated body to form a base rail gold layer having a thickness of 0.01㎛ or more.

An electrogalvanized steel sheet can finally be produced by plating zinc on the underlying plated layer formed by execution in this step.

FIG. 4 is a railway gold coating formed using the railway gold composition proposed in the present invention. As can be seen in the figures of FIGS. 4 (b) and 2 (b), the nickel plating coating and the bone of the nickel flash plating are shown. The rail gold coating of the iron flash plating proposed in the present invention has a similar structure, and in both cases of FIGS. 3 (b) and 5 (b), similar effects are obtained by pre-treatment plating for improving the surface of zinc plating. As can be seen, it can be seen that the above object of the present invention has been achieved.

Therefore, by replacing the nickel flash plating which is performed as a pretreatment process of the conventional electrogalvanizing process, the iron electroplating process using the composition for rail gold coating according to the present invention and an iron flash plating process using the composition, the economical cost of the conventional galvanized steel sheet As the base plating liquid used in the manufacture, an iron flash plating film for electro-zinc plating having excellent hiding power, adhesion and corrosion resistance equal to or higher than nickel flash plating can be obtained.

The present invention is a method of manufacturing an electro-galvanized steel sheet, the surface of the pickled and rinsed steel sheet is subjected to Fe plating so that the plating film thickness is 0.01㎛ or more, instead of nickel flash plating, and then electro-galvanized by a conventional method The effect of obtaining the electro-galvanized steel sheet excellent in the plating adhesiveness provided is provided.

On the other hand, iron is a major component of the plating solution, iron itself is a substance that is easy to flow in the entire galvanizing process, unlike the conventional nickel flash plating, iron components must be controlled by blemishes. In the present invention, it is possible to maintain the chemical stability of the plating liquid by treating the iron component, which was not easy to control when treated as an impurity, as the main constituent of the plating liquid.

Hereinafter, the present invention will be described in more detail.

The iron metal of the iron coating of the present invention is supplied in an appropriate salt form, and examples of the salt are iron chloride tetrahydrate, iron sulafate7 hydrate, iron boric fluoride, and ferrous ammonium sulfate 6. Sulfuric acid salts, ammonium salts, chloride salts, boric acid salts and the like may be used, such as iron ammonium sulfate 6 hydrate, iron sulfamate, iron formate, and the like, and plating compositions may be used. It may be reacted with a suitable conductive salt in advance before being added to. The concentration of the iron metal in the composition is 5 to 300 g, preferably 100 g, based on 1 L of the iron flash plating solution to be produced.

If the concentration of ferrous metal in 1 liter of iron flash plating solution is higher than 300g, the current efficiency is too high, so that plating of high current part takes place and the activity of metal is also increased, which causes metal crystals to precipitate on the plating surface, resulting in uneven plating surface. When the concentration of the ferrous metal is lower than 5 g, the current efficiency is low and plating is not easily performed at low current sites, and pin holes or pits are easily generated on the plating surface.

In order to maintain the conductivity of the plating solution based on the solution, addition of a conductive salt as a conductivity aid is required, which should be appropriately selected according to the type of ferrous metal salt, and include sulfate salts, ammonium salts, boric acid salts, and fluoride salts. And the like can be used. Examples include ammonium sulfate, ammonium chloride, borax, ammonium phosphate, potassium sulfate, potassium chloride, sodium chloride, ammonium fluoride or mixtures thereof. Since the conductive salt must be well combined with the metal, it must be sufficiently reacted with the metal, in which case it is added after reacting separately with the metal. The concentration of the conductive salt is adjusted to 5 to 250 g based on 100 g of iron concentration in 1 L of the iron flash plating solution, preferably 50 to 200 g.

If the concentration of the conductive salt is higher than 250g, the current efficiency is increased to cause cracking or uneven plating of the metal particles due to the high internal stress of the plating layer formed on the plating of the high current portion. If the concentration of the conductive salt is lower than 5 g, the plating of the low current portion is performed. It does not work well, and surface lubricity, corrosion resistance, adhesiveness, etc. are inferior.

In iron flash plating, bivalent iron ions in the plating solution are oxidized to trivalent iron, which is a fatal problem of railway gold. Antioxidants to prevent this phenomenon are very important components. This can be imparted with benzoic acid, ethylene diamine + citric acid system, aminoacetic acid, benzelsulfonate, 4-oxo-pentanoic acid or mixtures thereof which can be used as the following complexing agents. As used above, the amount of antioxidant used may be added in an amount of 0.1 to 250 g based on 100 g of the iron component in the iron flash plating solution, and preferably 2 to 150 g. If the amount of antioxidant is added below 0.1 g, the possibility of partial oxidation increases, and if it is added more than 250 g, the effect of antioxidant is not a problem, but the stress of the plating solution is increased or the stability of the liquid is reduced. .

The above members are the basic constituents of the iron flash plating solution, and in order to express the function of the iron flash plating solution replacing the conventional nickel flash plating, the functions of precipitation aids such as stress reducing agent and vacancy agent are required. Do. As the stress reducing agent, 0.1 to 50 g of tridecyloxy poly (ethyleneoxy) ethanol (III), N- (3-hydroxybutyllimen-P-sulfanylic acid, diisodecylphthalate, or a mixture thereof is added. It is preferable to use 5 to 30 g When the stress reducing agent is added to 0.1 g or less, the viscosity of the plating liquid is too high, so that the current conduction efficiency during plating or the stress of the railway gold layer is severely cracked and pits occur. In the case of the above addition, the plating liquid becomes turbid or the equilibrium of the plating liquid is easily broken due to the excessive amount of organic matter, and the plating surface also becomes narrow in the current range, so that both high current and low current are not plated, or pin holes and pits are severely generated. As a precipitation aid, the vacancy is used by 0.1-50 g of ethyleneimine, etc., and is preferably produced by adding 5-30 g. When used in 0.1g or less, the trace components present in the plating solution continuously remain in the plating solution as the electrodeposition reaction proceeds. Heavy impurities increase and eventually lead to poor iron flash plating.This vaccinating agent has little effect on plating when used in excess of 50g, but it is an expensive chemical, which leads to an increase in production cost. It is enough to use only the minimum required amount.

As described above, the surface improver densifies the structure of the electrodeposited railway gold, suppresses the gas generation at the anode, and makes the electrodeposition process smooth by providing a uniform electron supply during the electrodeposition reaction at the cathode. As the surface improving agent, anionic surfactants such as 2-methoxy-1-naphthaldehyde, ethylene glycol, polyethylene glycol, monolauryl ether, polyimine, and ethylene diamine are used. Preferably, nonionic surfactants are used. good. Or mixtures thereof. The surface improver is used in an amount of 0.1 to 50 g based on 100 g of the iron component in 1 L of the iron flash plating solution, and preferably 2 to 30 g is added. The amount of surface improving agent added is less than 0.1g, and the structure of railway gold coating is soft and gloss-free. When it is used over 50g, it does not affect the electrodeposition reaction itself like the vacancy agent, but the manufacture of plating solution because the chemical price is high The cost will rise.

Finally, the iron metal component and the conductive salt can be reacted well in the railroad money, and the complexing agent that increases the stability of the iron ion in the plating solution and also imparts the effect that iron ion is not easily oxidized is properly selected and used. It is preferable. Examples of the complexing agent include gluconic acid, ethylene diamine + citric acid system, aminoacetic acid, benzelsulfonate, 4-oxo-pentanoic acid or a mixture thereof. The amount of the complexing agent to be used is about 0.5 to 250g, preferably 3 to 150g based on 100g of the iron content in 1L of the iron flash plating solution.

When the concentration of the complexing agent is higher than 250g or lower than 0.5g based on the amount of iron in 100g, not only the plating surface defect but also the equilibrium of the plating solution is broken, and the life of the plating solution is shortened.

The iron flash plating composition according to the present invention uses a conductive salt and a complexing agent as an appropriate conduction aid according to the type of metal salt, so that the plating is uniform even when used for a long time because of excellent stability and very insensitive to impurities.

Hereinafter, in performing iron flash plating using the iron flash plating solution of the composition of the present invention, the reason for numerical limitation of plating conditions will be described in detail.

In the iron flash plating method according to the present invention, the plating solution has a pH of 1.0 or less, the plating surface is dark and semi-gloss, and the color of the plating solution is 1.0-6.0 since the surface color becomes yellow. It is desirable to limit.

When the temperature of the plating solution is 15 ° C. or lower, the color of the plating layer is dark and the adhesion of the plating layer is inferior, and peeling occurs. When the temperature of the plating layer is 90 ° C. or higher, the plating stripe is severe and the gloss of the plating layer is lost. It is preferable to plate at a temperature range of 15-90 ° C.

It is preferable to apply a current so that the current density is 1.0 to 200 ASD when the railroad is in accordance with the present invention. The reason is that when the applied current density value is 1.0ASD or less, the coating grains coarsen and the coating film adhesion is deteriorated. This is because edge burning occurs and operation is difficult.

Hereinafter, the present invention will be described in more detail with reference to Comparative Examples and Examples.

 Comparative Example 1

For comparative evaluation of the results of the iron flash plating of the present invention, first, only zinc plating performed after the conventional nickel flash plating was separately performed, and the state of the zinc plating film was examined.

First of all, after the pretreatment process that is generally performed in the existing electrogalvanizing, the iron is first subjected to the first chemical degreasing process and then washed, followed by electrolytic degreasing, pickling and washing. The galvanizing bath in the electrogalvanizing process, which is performed in the existing galvanizing steel sheet manufacturing process, is a sulfuric acid bath. Accordingly, in the following Comparative Examples and Examples, electrogalvanization was performed in a sulfuric acid bath, and the bath property was used as an aqueous solution containing 420 g of zinc sulfate, 23 g of ammonium sulfate, and 12 g of sulfuric acid based on 1 L of the plating solution. . The bath temperature was 55 ^o C and the current density was 70 ASD. Electro zinc plating result according to Comparative Example 1 As shown in Figure 1a, the surface of pure electro zinc plating without pre-plating such as nickel flash plating protrudes from the surface of the zinc plating surface defects, stains, etc. can confirm. It can be seen from the electron micrograph (photographing the galvanized film at 4000 times magnification) of FIG. 1B that the cause of the film formation is that the crystal grains formed as a result of zinc plating electrodeposition are so fine and upright that the stress between tissues is insufficient. have. For this reason, pre-plating processes such as nickel flash plating before electro zinc plating are necessary.

Comparative Example 2

For comparative evaluation of the results of the iron flash plating of the present invention, the state of the nickel plated film formed in the conventional nickel flash plating process was investigated. First, the following pretreatment process, which is generally performed in conventional electrogalvanization, was carried out. In other words, the iron is first washed through the first chemical degreasing process, followed by the electrolytic degreasing, pickling and washing. In Comparative Example 2, the bath property of the nickel flash plating process was used as an aqueous solution of 300 g of nickel sulfate, 27 g of boric acid, and 3 g of sulfuric acid in 1 L of the nickel flash plating solution. The temperature of the bath was maintained at 55 ^o C and the current density was 70 ASD. As a result of nickel flash plating, as shown in FIG. 2A, it can be seen that the nickel flash plating film was smoothly plated without surface defects, stains, etc. existing on the same surface as the electrogalvanized film. In addition, as shown in the electron micrograph of FIG. 2B, the nickel plated film has a strong interstitial stress of crystal grains, and thus it may be confirmed that minute cracks appear on the film. The cracks formed due to the high stress between grains may be a cause of deterioration of corrosion resistance, but the zinc coating formed on the film is smoothed, and impurities, stains, etc. existing on the substrate are prevented from being formed, thereby forming a beautiful zinc plated film. To be.

Comparative Example 3

For comparative evaluation of the results of the iron flash plating of the present invention, nickel flash plating was carried out under the conditions of the conventional nickel flash plating process and zinc plating was carried out to investigate the state of the final galvanized film.

First, the following pretreatment is performed in the existing electro zinc plating. So Ji-cheol first goes through the first chemical degreasing process and then washes, followed by electrolytic degreasing, pickling and washing. In <Comparative Example 3>, the bath properties and process conditions of the nickel flash plating process are those in <Comparative Example 2>, and the bath properties and process conditions of the electro-zinc plating process are those of the zinc plating performed in <Comparative Example 1>. Condition. Nickel flash plating and electro galvanized zinc coating film as shown in Figure 3a, although the top surface is a galvanized film, as shown in Figure 1a, unlike the surface of the plate, as shown in Fig. It did not protrude. In the electron micrograph (4000 times magnification) of FIG. 3B, the final plating film is a zinc film, but the electrodeposited crystal grains are completely different forms and cover the surface of the base metal with the shape of crystal grains having directional spreading on the surface of the substrate. Able to know. Therefore, the coating of the iron flash plating to be proposed in the present invention can also achieve the object of the invention if it has similar characteristics to the galvanized coating film subjected to the nickel flash plating.

&Lt; Example 1 >

Railway gold of the present invention first proceeded after the pre-treatment process is performed in the existing electro zinc plating. That is, So Ji-cheol first goes through the first chemical degreasing process and then washes, followed by electrolytic degreasing, pickling and washing. Based on the amount of ferrous sulfate in which the iron content in ferrous sulfate is 100 g in 1 L of the prepared iron flash plating solution, the steel sheet undergoing such a pretreatment process is 100 g of sodium sulfate as a conductive salt, 20 g of benzoic acid as an antioxidant, and solution stabilization. 150 g of gluconic acid as a complexing agent, 30 g of ethylene glycol as a leveling agent for imparting surface smoothness during the plating reaction, 20 g of benzoic acid as an antioxidant of iron ions in solution, and an agent for suppressing the increase of impurities in the plating solution. As an example, iron flash plating is performed in a plating bath composed of 50 g of ethyleneimine and 20 g of tridecyloxy poly (ethyleneoxy) ethanol (III) as a stress reducing agent. At this time, a bath temperature of 35 ^o C, pH 2.3, and a current density of 70 ASD were applied. Under the above conditions, it was confirmed that the rail money of the present invention is electrodeposited. The steel plated specimens were washed with water and then galvanized according to the electrogalvanization process of sulfuric acid bath which is commonly used in the manufacturing process of electrogalvanized steel sheet. Zinc plating carried out in the present invention is the same conditions as the zinc plating process presented in <Comparative Example 1>.

<Example 2>

The pretreatment process for the railroad proceeded in the same manner as illustrated in <Example 1>. The steel sheet after the pretreatment process is 150 g of gluconic acid as a complexing agent to stabilize ammonium chloride as a conductive salt based on the amount of ferrous chloride in which iron content in iron chloride is 100 g in 1 L of the prepared iron flash plating solution. , 50 g of polyethylene glycol (molecular weight 600) as a leveling agent, 20 g of benzoic acid as an antioxidant of iron ions in solution, 50 g of ethyleneimine as a vacancy, and 20 g of tridecyloxy poly (ethyleneoxy) ethanol (III) as a stress reducing agent Iron flash plating is performed in a plating bath consisting of: At this time, a bath temperature of 45 ^o C, pH 2.5, and a current density of 70 ASD were applied. Under the above conditions, it was confirmed that the railroad train as intended in the present invention was electrodeposited. It was confirmed that the railway funds were electrodeposited. The rail-plated specimens were rinsed and then galvanized according to a conventional electrolytic zinc plating process. The zinc plating was carried out in a sulfuric acid bath as in <Example 1>, and the conditions were the same as in <Example 1>. After galvanizing, washing with water and drying were carried out to investigate the properties of the plating film.

<Example 3>

The pretreatment process for the railway funds was carried out in the same manner as illustrated in Example 1. The steel sheet after the pretreatment process is 200 g of sulfamic acid as a conductive salt and 150 g of gluconic acid as a complexing agent for stabilizing the solution, based on the amount of iron sulfamate in which the iron content of iron is 100 g in the iron flash plating solution. Plating bath composed of 30 g of ethylene glycol as a leveling agent, 20 g of benzoic acid as an antioxidant of iron ions in solution, 50 g of ethyleneimine as a vacancy, and 20 g of tridecyloxy poly (ethyleneoxy) ethanol (III) as a stress reducing agent The iron flash plating is carried out at. The bath temperature 50 ^o C, pH 2.6, current density 70 ASD was applied. Under the above conditions, it was confirmed that the rail money of the present invention is electrodeposited. The rail-plated specimens were rinsed and then galvanized according to a conventional electrolytic zinc plating process. The zinc plating was carried out in a sulfuric acid bath as in <Example 1>, and the conditions were the same as in <Example 1>. After galvanizing, washing with water and drying were carried out to investigate the properties of the plating film.

<Example 4>

The pretreatment process for the railway funds was carried out in the same manner as illustrated in Example 1. The steel sheet subjected to the pretreatment process is based on the amount of iron fluoride in which iron content of iron fluoride is 100 g in 1 L of the prepared iron flash plating solution, 150 g of ammonium fluoride as a conductive salt, and 150 g of gluconic acid as a complexing agent to stabilize the solution. Plating bath composed of 30 g of ethylene diamine as a leveling agent, 10 g of benzoic acid as an antioxidant of iron ions in solution, 50 g of ethyleneimine as a vacancy, and 20 g of tridecyloxy poly (ethyleneoxy) ethanol (III) as a stress reducing agent. The iron flash plating is carried out at. At this time, a bath temperature of 55 ^o C, pH 2.6, current density 70 ASD was applied. Under the above conditions, it was confirmed that the rail money of the present invention is electrodeposited. The rail-plated specimens were rinsed and then galvanized according to a conventional electrolytic zinc plating process. The zinc plating was carried out in a sulfuric acid bath as in <Example 1>, and the conditions were the same as in <Example 1>. After galvanizing, washing with water and drying were carried out to investigate the properties of the plating film.

<Example 5>

The pretreatment process for the railway funds was carried out in the same manner as illustrated in Example 1. The steel sheet after the pretreatment process is based on the amount of iron formic acid in which the content of iron in iron formic acid is 100 g in 1 L of the prepared iron flash plating solution, 200 g of sodium formate as a conductive salt, and 150 g of gluconic acid as a complexing agent, as a leveling agent. Rail gold is applied in a plating bath composed of 30 g of ethylenediamine, 50 g of ethylene imine as a vacancy, and 20 g of tridecyloxy poly (ethyleneoxy) ethanol (III) as a stress reducing agent, with a bath temperature of 50, pH 2.5 and current density. 70 ASD was applied. Under the above conditions, it can be confirmed that the railroad funds of the present invention are electrodeposited. The rail-plated specimens were rinsed and then galvanized according to a conventional electrolytic zinc plating process. The zinc plating was carried out in a sulfuric acid bath as in <Example 4>, and the conditions were the same as in <Example 1>. After galvanizing, washing with water and drying were carried out to investigate the properties of the plating film.

Corrosion resistance, adhesiveness and paintability of the specimen prepared according to the present invention prepared in <Comparative Example 3> and the nickel flash plating of <Examples 1 to 5> were determined, and the specific results are shown in Table 1 below. Indicated. Here, the corrosion resistance was evaluated by the time of occurrence of red blue water when spraying 5% saline, and the adhesiveness was evaluated by the tape test after the 180 degree bending test.

TABLE 1

Table 1. Properties of Galvanized Film after Iron Flash Plating

Corrosion Resistance (min)

Plating adhesion
Paintability
Remarks
Comparative Example 3
230
○
◎

Nickel Flash Plating
Example 1

270
○
◎
Iron Flash Plating
(Ferrous sulfate)
Example 2

290
○
◎
Iron Flash Plating
(1st movie)
Example 3

220
○
◎
Iron Flash Plating
(Sulfamate)
Example 4

230
○
◎
Iron Flash Plating
(Iron fluoride)
Example 5

250
○
◎ l
Iron Flash Plating
(Forged Iron)

(1) Corrosion resistance: Red blue time: 5% or more of the total surface area

(2) Plating adhesion: The damage condition of the plating film at the bend end was observed by the 180 degree bending test, and the following criteria were evaluated.

○ The degree of damage or microcracks

△ When large crack is generated or peeling of plating piece is confirmed

× When plating peeling occurs extensively

(3) Paintability: After coating and electrodeposition coating the plated steel sheet under normal conditions, the film adhesion was evaluated by cross-cut and tape test.

◎-No peeling occurs at all.

○-Peeling partially occurs but area of peeling part is less than 5% of the whole.

(Triangle | delta)-Peeling partial occurs but area of a peeling part is less than 50% of the whole.

X-Peeling occurs at an area of 50% or more of the whole.

As shown in Table 1, the inventive examples (Examples 1-5) can be seen to exhibit the characteristics of corrosion resistance, adhesion and paintability according to or better than the comparative example.

As described above, the present invention provides an automobile, home appliance, and the like by providing a function of the base plating effective in producing an electro-galvanized steel sheet excellent in corrosion resistance, adhesion and paintability by the iron base plating process for providing a railway gold film In the structural material for building materials, there is an effect that can be appropriately used in place of the nickel flash plating process used in the pre-treatment process of electro-zinc plating, which requires high corrosion resistance, adhesion and paintability.

FIG. 1A is a micrograph (magnification × 50) of a pure galvanized film coated on base iron, and FIG. 1B is an electron scanning micrograph (magnification × 4000) of a pure galvanized film coated on base iron.

FIG. 2A is a micrograph (magnification × 50) of a pure nickel flash plating film, and FIG. 2B is an electron scanning micrograph (magnification × 4000) of a pure nickel flash plating film.

3A is a micrograph (magnification × 50) of a nickel-plated galvanized film after nickel flash plating;

3B is an electron scanning micrograph (magnification × 4000) of the nickel-plated galvanized film.

4A is a micrograph (magnification × 50) of a pure iron flash plated film, and FIG. 4B is an electron scanning micrograph (magnification × 4000) of a pure iron flash plated film.

5a is a micrograph (magnification × 50) of a galvanized film after iron flash plating,

5B is an electron scanning micrograph (magnification x 4000) of the galvanized film after iron flash plating.

Claims (18)

 In the manufacturing process of electro-galvanized steel sheet, before the electro-galvanization, it is a railway gold solution used as a base plating solution for the base steel which is a pretreatment process, With iron-containing salts: A conductive salt for increasing the conductivity of the railway gold solution; A complexing agent for stabilizing the railway gold solution; An antioxidant for preventing oxidation of iron ions contained in the salt containing iron; A surface improving agent (leveling agent) for smoothing the railway gold film coated on the base steel; And, Vacancy agents (precipitation aids); And Railroad gold solution comprising a stress reducing agent The method according to claim 1, The iron metal concentration of the iron-containing salt is a railway gold solution, characterized in that it contains 5 ~ 300g of 1L of the iron flash plating solution prepared The method according to claim 2, The salt containing iron is at least one of ferrous sulfate, ferrous ammonium sulfate, ferrous chloride, iron sulfamate, iron fluoride, ferrous borate and iron formate. The method according to claim 1, The iron metal concentration of the salt containing iron is 5 ~ 300g in 1L of iron flash plating solution, the concentration of the conductive salt is 5 ~ 250g based on 100g iron concentration in the plating solution, the amount of complexing agent for plating solution stabilization is iron flash plating solution 0.5 ~ 250g per 1l, the amount of antioxidant is 0.1 ~ 250g per 1l of the iron flash plating solution, the amount of surface improving agent (leveling agent), stress reducing agent, vacancy is 0.1 ~ 50g per 1l of iron flash plating solution, respectively Railway gold solution. The method according to claim 1, The conductive salt is sodium sulfate, ammonium sulfate, ammonium chloride, sodium chloride, sulfamic acid, ammonium fluoride, sodium formic acid, ammonium formate, any one of the railroad gold solution. The method according to claim 1, The railway gold solution stabilizing complexing agent is at least one of gluconic acid, EDTA, sodium alkanoic acid, citric acid, tartaric acid, diopionate ester, alkyl cresol, thiourea, imidazole. The method according to claim 1, The iron ions antioxidant is a rail gold solution, characterized in that the benzoic acid. The method according to claim 1, The surface improving agent (leveling agent) for smoothing the railway gold film is at least one of 2-methoxy-1-naphthaldehyde, ethylene glycol, polyethylene glycol, monolauryl ether, polyimine, ethylene diamine Railway gold solution. The method according to claim 1, The vacancy is a railway gold solution, characterized in that the ethylene imine. The method according to claim 1, The stress reducing agent is any one of tridecyloxy poly (ethyleneoxy) ethanol (III), N- (3-hydroxybutyl lime-P-sulfanylic acid, diisodecyl phthalate or a mixture thereof. Railway gold solution characterized by. The method according to claim 1, The iron-containing salt is at least one of ferrous sulfate, ferrous ammonium sulfate, ferrous chloride, iron sulfate, iron fluoride, ferrous borate and iron formate, and the concentration of the metal in the iron-containing salt is iron flash plated. 5-300 g / l in 1 liter of solution; The rail gold solution stabilizing complexing agent is any one of benzoic acid, ethylene diamine + citric acid, amino acetic acid, benzelsulfonate, 4-oxo-pentanoic acid or a mixture thereof, and the amount of the complexing agent for plating solution stabilization is iron flash. 0.5-250 g of 1 L of plating solution; The antioxidant of iron ion is benzoic acid and the amount of antioxidant of iron ion is 0.1-250 g in 1 liter of iron flash plating solution; The surface improving agent is at least one of 2-methoxy-1-naphthaldehyde, ethylene glycol, polyethylene glycol, monolauryl ether, polyimine, and ethylene diamine, and the amount of the surface improving agent is 0.1- in 1 L of the iron flash plating solution. 50 g; The vacancy is ethyleneimine and its amount is 0.1-50 g in 1 L of the iron flash plating solution; And, The stress reducing agent is any one of tridecyloxy poly (ethyleneoxy) ethanol (III), N- (3-hydroxybutyllimene-P-sulfanylic acid, diisodecylphthalate or a mixture thereof. The amount of the stress reducing agent is a rail gold solution, characterized in that 0.1 ~ 50g in 1ℓ of iron flash plating solution delete delete delete delete delete delete delete

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