KR100482209B1 - Coating Paint For Coated Steel With Superior Corrosion Resistance And Method For Manufacturing Coated Steel Using The Coating Paint - Google Patents

Abstract

The present invention relates to coated steel having excellent corrosion resistance, and is coated on the surface of steel materials such as weather resistant steel and ordinary steel or covered with a rust layer, so that not only a solid corrosion layer can be formed at an early stage even in a strict corrosion environment, It is an object of the present invention to provide a coating coating for coating steel having excellent corrosion resistance, which can perform surface treatment with excellent economy, and a coating steel having excellent corrosion resistance using the same.

The present invention has a total amount of one or two or more selected from the group consisting of sulfates and phosphoric acids of metals having a dissolution amount in calcium nitrate and 100 g of water at 1 ° C. or less at 5 ° C .: 0.2 to 60% by weight (% by weight after dry solidification) and organic Resin: 40-99.8 wt%

(Weight% after dry solidification), and the content of the calcium nitrate is 0.1 to 30% by weight (weight% after dry solidification), a coating material for coating steel having excellent corrosion resistance, and a method for producing coated steel having excellent corrosion resistance using the same. To that point.

Description

Coating paint for coated steel with excellent corrosion resistance and manufacturing method using coated steel {Coating Paint For Coated Steel With Superior Corrosion Resistance And Method For Manufacturing Coated Steel Using The Coating Paint}

The present invention relates to a coated steel having excellent corrosion resistance, and more specifically, a rust layer (highly stable rust layer, hereinafter referred to as a high antirust layer) having an extremely high protection against an atmospheric corrosion environment can be formed on the steel surface early. The present invention relates to a coating material for coating steel having excellent corrosion resistance and a method for producing coated steel having excellent corrosion resistance using the same.

Generally, the corrosion resistance in air | atmosphere can be improved by adding a small amount of elements, such as P, Cu, Cr, and Ni, to steel. Such low alloy steels are called weather resistant steels, and they have a protective rust (hereinafter referred to as protective rust) formed by corrosion after several years in the outdoors, and do not require anti-corrosion work such as painting afterwards. It is a so-called maintenance free river.

However, it takes a long time of about 10 years or more to form protective rust, and red or yellow peeled rust and spilled rust are generated by the initial corrosion, which is not aesthetically unfavorable, and damage such as reduction of plate thickness due to corrosion is notable. have.

In particular, in a salt particle scattering environment, this tendency is remarkable and becomes a problem, and in the case of a large amount of scattering salts, there is a problem that protective rust does not form even after a long period of time.

In addition, if the amount of protective molten arsenate is somewhat high, the function of protecting the steel is deteriorated, and the upper limit of the amount of arsenic acid salt for protecting the steel shows an extremely low value.

In connection with the above problem, Japanese Patent Laid-Open No. 1-124088 proposes to solve by a surface treatment method for forming a phosphate film.

However, in the case of the above-described method, the contents of the treatment are complicated, such as the need for appropriate pretreatment before forming the phosphate film, and if the welding of steel is required, the treatment in the weld is not easy. There are problems such as difficulty in application to structures and the like.

In addition, Japanese Patent Application Laid-Open No. 53-22530 proposes a method of forming protective rust while suppressing initial corrosion by resin coating.

However, this method has a problem that not only the suppression of the initial corrosion is insufficient in a corrosive environment, but also the generation of protective rust is slow.

In addition, Japanese Laid-Open Patent Application No. 56-33911 proposes a method using two-layer coating.

In this method, the initial corrosion can be suppressed, but since the corrosion resistance is too high, it takes too long to form protective rust, and there is a problem in poor workability.

In addition, in the above-described conventional techniques, it has been pointed out that the problem is that the formation of protective rust is difficult in a strict corrosive environment, such as an environment having a large amount of scattering salts, and the corrosion resistance is insufficient.

MEANS TO SOLVE THE PROBLEM The present inventors made the research and experiment in order to solve the various problems of the prior art, and based on the result, this invention is made to the surface of steel materials, such as weather-resistant steel and a common steel, or the surface of steel covered with a rust layer. As a result of the coating, it is possible to provide a corrosion resistant coating coating having excellent corrosion resistance, which can not only form a high-rust rust layer at an early stage even in a strict corrosion environment, but also can perform a surface treatment with excellent workability and economic efficiency, and a method of manufacturing a coating steel having excellent corrosion resistance using the same. This is the purpose.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention has a total amount of one or two or more selected from the group consisting of sulfates and phosphoric acids of metals having a dissolution amount in calcium nitrate and 100 g of water at 1 ° C. or less at 5 ° C .: 0.2 to 60% by weight (% by weight after dry solidification) and organic Resin: 40-99.8% by weight (% by weight after dry solidification), and the calcium nitrate content is 0.1-30% by weight (% by weight after dry solidification). .

In addition, the present invention is a total amount of one or two or more selected from the group consisting of sulfate and phosphoric acid of a metal having a dissolution amount in calcium nitrate and 100 g of water at 1 ° C. or less at 5 ° C .: 0.2 to 60% by weight (% by weight after dry solidification) And organic resin: 40 to 99.8 wt% (wt% after solidification), and the calcium nitrate content is 0.1 to 30 wt% (wt% after solidification). The present invention relates to a method for producing a coated steel excellent in corrosion resistance by coating a steel surface or a steel surface covered with a rust layer so as to have a dry film thickness of 1 to 200 µm.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

As a result of repeating the study, the inventors have found out from the investigation of steel materials corroded for over 100 years that the corrosion resistance of the rust layer is extremely high when the sulfate and calcium ions are simultaneously contained in the rust layer. From this, it was found that it is important to actively supply sulfate and calcium ions to the steel surface for the early generation of the solid antirust layer.

Further, as a result of repeating the intensive studies, as a specific method to solve the above problems, an appropriate amount of calcium nitrate and an appropriate amount of sulfate or phosphoric acid alone or two or more kinds of organic resins having a certain degree of solubility in water are mixed. By coating a coating liquid on a steel surface or on a steel surface covered with a rust layer, it was found that a solid corrosion prevention layer was formed early with subsequent corrosion of the steel.

The present invention is made based on the results of the above study.

Hereinafter, the reason for addition of each component in the present invention and the reason for numerical limitation on the component range thereof will be described.

(1) calcium nitrate

When the corrosion resistance of the rust layer is low, since the rust layer contains voids and the like, the density of the rust layer is low and the permeation of various corrosive substances such as water and oxygen existing in the external corrosive environment to the steel surface cannot be suppressed. That is, in order to form a solid antirust system, it is necessary to improve the compactness of a rust layer.

Calcium nitrate is one of the well soluble in water among calcium salts which are mainly poorly soluble in water. For this reason, when moisture is supplied to the coated steel surface in a corrosive environment, calcium nitrate present in the coated coating film dissociates into nitrate ions and calcium ions.

The calcium ions produced in this way react with the sulfate ions formed by dissociating the metal sulphate added in the coating film in the same manner to form calcium sulphate which is poorly soluble in water. This calcium sulfate has a densifying effect of the rust layer by filling the voids in the rust layer mainly composed of iron oxyhydroxide and iron oxide formed by the corrosion reaction in parallel.

The effects of calcium ions are exhibited not only by reaction with sulfate ions but also by reaction with phosphate ions to produce calcium phosphate. In other words, the effect of calcium nitrate is to combine with sulfate ions or phosphate ions present at the same time to form a poorly soluble salt in the water, the salt densify the rust layer by filling the pores in the rust layer, water and oxygen from the outside environment, It is a main effect to suppress the penetration of a material which significantly accelerates corrosion of steel such as salt and sulfurous acid gas through the rust layer. At the same time, sulfate ions produced by dissociation accelerate the elution of iron, the very early corrosion of steel, and have an effect of forming a rust layer early.

In order to obtain the above effect, it is necessary to contain at least 0.1% by weight of calcium nitrate in the coating paint.

However, if the content exceeds 30% by weight, the coating paint becomes very vulnerable after drying, and calcium nitrate is present in the coating film in the form of droplets to dissolve when water is supplied and pinholes are applied to the coating film. Corrosion is significantly accelerated by creating shape defects.

Therefore, it is preferable to limit the addition amount of calcium nitrate to 0.1-30 weight%.

(2) sulfate and phosphoric acid of metals

The dissolution amount of metal in 100g of water in sulfate is more than 1g at 5 ℃ and dissociates into metal ion and sulfate ion when water is supplied at room temperature. As described above, the dissociated sulfate ions react with the calcium ions to form calcium sulfate, which is poorly soluble in water, to fill the pores of the rust layer mainly composed of iron oxyhydroxide and iron oxide produced by the corrosion reaction of steel. Thereby, the density of a rust layer improves and corrosion resistance improves. Since this effect is also exerted by the calcium phosphate formed by the reaction of calcium ions and phosphate ions, it can be achieved even if phosphoric acid and calcium nitrate are added simultaneously without the addition of metal sulfate. Therefore, phosphoric acid was selected as one of the number of choices of the compound which can be added simultaneously with calcium nitrate.

The reason why the amount of metal dissolved in 100 g of water in sulphate is limited to 1 g or more at 5 ° C. is lower than that, so that water may be supplied by rainfall and condensation in a normal atmospheric corrosion environment, especially at a low temperature in winter. This is because the amount of metal ions and sulfate ions necessary for obtaining the above-mentioned effects are not produced.

Examples of the sulfate having such a function include aluminum sulfate, nickel sulfate, cobalt sulfate, chromium sulfate, copper sulfate, and iron sulfate.

In addition, metal ions generated by dissociation have an effect of densifying iron oxyhydroxide and iron oxide constituting the rust layer.

The dissolution amount of the metal sulfate in 100 g of water was selected at least 1 g at 5 ° C. and at least one selected from phosphoric acid, and the lower limit of the total amount including calcium nitrate at 0.2% by weight is expected to be lower than this. Because it is not exercised. The upper limit of the total amount is 60% by weight because the organic resin becomes very fragile after drying, and thus the above effect is not obtained by the collapse or weathering of the coating film before the solid corrosion protection layer is formed.

(3) coating coating film

In the present invention, the coating coating film keeps calcium nitrate, metal sulfate, and phosphoric acid, which are effective in the early formation of a high anticorrosive layer, on the steel surface, thereby preventing the release of these substances with rainfall and condensation until the effect is exerted. It has a role to stop.

In addition, the barrier effect of appropriately suppressing the permeation of the substance which accelerates the corrosion from the outside to the steel surface until the formation of the anticorrosive rust layer is one of the roles of the coating film.

In the present invention, the coating film is limited to a dry film thickness of 1 to 200 μm, and the barrier effect is low at a thickness thinner than 1 μm, and it is not possible to completely prevent the outflow of iron ions generated by corrosion of the steel, and therefore it is not rusted from the steel surface. This is because an outflow rust flowing out to the outside is produced, and the active ingredient of calcium nitrate and metal sulfate or phosphoric acid added at the same time is also leaked out and the effect of the active ingredient is not obtained. In addition, permeation of chlorine ions in the environment of flying sea salt particles leads to excessive corrosion and inhibits the solid corrosion protection layer.

On the other hand, when the dry film thickness exceeds 200 µm, not only is it economically disadvantageous, but the corrosion barrier effect on the inner metal salt layer is too large, and it takes too long to form a solid antirust layer on the metal surface. Prior to the formation of the solid rust layer, the dry film thickness should be 200 µm or less, since if the film is dropped due to an impact or the like, significant corrosion may proceed from the portion without the effect of the organic resin film.

The organic resin used in the present invention is not particularly limited, and epoxy resins, urethane resins, vinyl resins, butyral resins, butal acid resins and the like can be used.

Moreover, although the said resin is made into a paint and it coats, there is no problem even if it uses a solvent-based paint or an aqueous paint.

In the present invention, in addition to organic resins, calcium nitrates, sulfates of metals and phosphoric acid, conventional additives such as coloring pigments such as bengala, sieving pigments such as silica, rust preventive pigments such as zinc chromic acid, dispersing agents and antioxidants Can be included The anti-corrosive pigment may be added in the sense of anticorrosive control when used in a place where corrosion environment is very strict, but the amount of the anti-corrosive pigment is preferably 10% by weight or less so that the anticorrosive property is not too good.

In the present invention, the concentrations of calcium nitrate, sulfates of metals, phosphoric acid and other additives in the coating paints indicate the concentrations after dry solidification. Prior to coating, a suitable amount of solvent or water is adjusted to a viscosity suitable for the painting operation. The solvent or water is evaporated by natural drying after coating to form a coating film having a desired dry film thickness.

Since the coating paint of the present invention can be coated by a common method such as an air spray, airless spray, or roller in the same way as a conventional coating method, it can be applied regardless of the place. In addition, it is economical because the effect is obtained by one painting work. Furthermore, since local painting is possible, it is possible to cope with after machining such as cutting and welding of steel in the field.

Further, the steel used in the present invention is not particularly limited to steel grades and may be ordinary steel or weather resistant steel.

That is, the rust formed in ordinary steel by the action of calcium nitrate and metal sulfate or phosphoric acid in the coated coating film of the present invention can finally be transformed into a chemically stable and dense high anticorrosive rust layer to exhibit high corrosion resistance.

However, when cracks and peelings occur for some reason in the solid corrosion layer produced in this way, it is preferable to use weather resistant steel because the self-repairing ability of the solid steel to generate the solid corrosion layer again is impaired.

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

Example

Table 1 shows the chemical composition of the test steel used in this Example, Table 2 shows the pretreatment conditions of the test piece, and Table 3 shows the resin system using the organic resin of the coating material.

The test piece was 200 mm x 100 mm x 3.5 mm in size, and in the case of pretreatment X, the surface was removed from the mill scale by shot blast before coating. In the case of pretreatment Y, the coating process was performed after removing the rust which was easily removed from the rust formed by the air exposure beforehand with a wire brush.

Chemical composition (% by weight) C Si Mn P S Al N Cr Ni Cu ① Weather resistant steel 0.09 0.21 0.65 0.03 0.004 0.01 0.003 0.40 0.15 0.32 ② ordinary steel 0.10 0.11 0.34 0, .005 0.004 0.02 0.002 0.01 0.01 0.01

X Shot blast Y 60-day exposure at the same exposure site as the exposure test to form a rust layer

sign A B C D Resin type Vinyl Butyral Resin Epoxy resin Urethane Resin Butal Acid Resin

After pretreatment of the test steel having the chemical composition of Table 1 under one pretreatment condition of Table 2, using a resin of Table 3 to prepare a coating paint under the conditions shown in Tables 4 to 12 The exposure test was performed by coating the test steel surface pretreated as above with the film thicknesses of Tables 4 to 12, and the results are shown in Tables 4 to 12, respectively.

The sulfate of the metal used in the present examples is aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), nickel sulfate (NiSO ₄ ), cobalt sulfate (CoSO ₄ ), chromium sulfate (CrSO ₄ ), and copper sulfate (CuSO ₄ ). Here, the same effect can be expected because it is easily reduced to cobalt sulfate using second cobalt sulfate instead of cobalt sulfate (CoSO ₄ ).

An appropriate amount of solvent was added to the resin / additive formulation to prepare a paint having a viscosity (measured to type B viscometer) of 200 to 1000 CPS, and was coated by air spray coating. This coated steel test piece was exposed to the coastal zone of Fukui Prefecture, Japan, which was located 10m from the coast under the same conditions, for two years. The exposure to this salt is 1.10 mdd (mg / dm ² / day), which is a very severe corrosive environment. After the exposure, the test piece was removed from the mixed aqueous solution composed of ammonium citrate and a small amount of corrosion inhibitor solution, and the amount of thickness reduction of the test piece was obtained during the exposure test period by comparing the weight of the base iron only with the weight before exposure.

In the case of pretreatment Y, the same amount of plate thickness reduction in the period exposed to produce a rust layer was calculated using a separate specimen, and the corrosion thickness reduction of the specimen during the exposure test period was calculated based on the value. .

In addition, the presence or absence of the formation of a rust layer was confirmed by cross-sectional observation by a scanning electron microscope, and the result was shown.

As shown in Tables 4 to 10 below, in Examples 1 to 76 of the present invention, the formation of the rust layer was recognized, and although the corrosion reaction of the steel proceeded, it can be seen that the plate thickness decrease was very slight. In other words, the rust layer produced in Examples 1 to 76 of the present invention was found to be a solid antirust layer having high anticorrosiveness even in a very severe corrosive environment. In particular, compared with the use of sulphate and phosphate alone, the addition of them in combination shows that the anticorrosive property of the rust layer is higher due to the synergistic effect, and the amount of reduction in plate thickness is particularly low.

On the other hand, as shown in Table 11 and Table 12, in Comparative Examples 77-96, the addition amount of sulfate and phosphoric acid of calcium nitrate, metal having a moderate solubility in water is outside the proper range, or coating coating thickness is appropriate. If it is outside the range, it turns out that a solid corrosion prevention layer is not formed and a large corrosion reduction amount is shown also when a rust layer is formed.

Therefore, it turned out clearly that a solid corrosion prevention layer is not produced in a comparative example.

** Numerical value of coating coating composition is% by weight

** The presence or absence of rust formation is determined by the presence of rust formation when rust is observed when the cross section near the surface of the test steel is observed 50,000 times under the scanning electron microscope.

** Numerical value of coating coating composition is% by weight

** The presence or absence of rust formation is determined by the presence of rust formation when rust is observed when the cross section near the surface of the test steel is observed 50,000 times under the scanning electron microscope.

** Numerical value of coating coating composition is% by weight

** The presence or absence of rust formation is determined by the presence of rust formation when rust is observed when the cross section near the surface of the test steel is observed 50,000 times under the scanning electron microscope.

** Numerical value of coating coating composition is% by weight

** The presence or absence of rust formation is determined by the presence of rust formation when rust is observed when the cross section near the surface of the test steel is observed 50,000 times under the scanning electron microscope.

** Numerical value of coating coating composition is% by weight

** The presence or absence of rust formation is determined by the presence of rust formation when rust is observed when the cross section near the surface of the test steel is observed 50,000 times under the scanning electron microscope.

** Numerical value of coating coating composition is% by weight

** The presence or absence of rust formation is determined by the presence of rust formation when rust is observed when the cross section near the surface of the test steel is observed 50,000 times under the scanning electron microscope.

** Numerical value of coating coating composition is% by weight

** The presence or absence of rust formation is determined by the presence of rust formation when rust is observed when the cross section near the surface of the test steel is observed 50,000 times under the scanning electron microscope.

** Numerical value of coating coating composition is% by weight

** The presence or absence of rust formation is determined by the presence of rust formation when rust is observed when the cross section near the surface of the test steel is observed 50,000 times under the scanning electron microscope.

** Numerical value of coating coating composition is% by weight

** The presence or absence of rust formation is determined by the presence of rust formation when rust is observed when the cross section near the surface of the test steel is observed 50,000 times under the scanning electron microscope.

As described above, the present invention provides a unique coating steel coating paint and a method for producing a coating steel having excellent corrosion resistance using the coating material, thereby providing a corrosion resistance capable of forming a solid antirust layer at an early stage even in a strict corrosion environment such as a large amount of arsenate. Not only can this excellent coated steel sheet be provided, but also has excellent workability and economical efficiency in surface treatment, and can be widely applied to steel materials. Therefore, maintenance on the method of steel materials becomes unnecessary, and thus social capital It is expected to contribute to the improvement.

Claims (8)

The total amount of one or two or more selected from the group consisting of sulfates and phosphoric acids of metals having a dissolution amount in calcium nitrate and 100 g of water at 1 ° C. or less at 5 ° C .: 0.2 to 60% by weight (% by weight after dry solidification) and organic resin: 40 -99.8% by weight (% by weight after dry solidification), and the content of the calcium nitrate is 0.1-30% by weight (% by weight after dry solidification) coating coating for coating steel with excellent corrosion resistance The coating coating for coating steel with excellent corrosion resistance according to claim 1, wherein the sulfate is at least one selected from the group consisting of aluminum sulfate, nickel sulfate, cobalt sulfate, chromium sulfate, copper sulfate, and iron sulfate. The coating coating for coating steel with excellent corrosion resistance according to claim 1 or 2, wherein the organic resin is one selected from the group consisting of an epoxy resin, a urethane resin, a vinyl resin, a butyral resin and a butal acid resin. The coating coating for coating steel with excellent corrosion resistance according to claim 1 or 2, further comprising one or more additives selected from the group consisting of colored pigments, extender pigments, rust preventive pigments, dispersants, and antioxidants. The coating paint for coating steel with excellent corrosion resistance according to claim 3, wherein one or more additives selected from the group consisting of colored pigments, extender pigments, rust preventive pigments, dispersants, and antioxidants are further added. The coating material for coating steel with excellent corrosion resistance according to claim 4, wherein the amount of the antirust pigment is 10% by weight or less. The coating material for coating steel with excellent corrosion resistance according to claim 5, wherein the amount of the antirust pigment is 10% by weight or less. The method for producing coated steel with excellent corrosion resistance, characterized by coating the coated coating for coating steel according to any one of claims 1 to 7, on a steel surface or a steel surface covered with a rust layer so as to have a dry film thickness of 1 µm to 200 µm.