KR100435422B1 - A COATING COMPOSITION FOR ANTI-CORROSION CONTAINING TiO2 AND Zn AND A METHOD FOR FORMING COATING BY USING THEM - Google Patents

Abstract

The present invention relates to a corrosion resistant coating composition containing titanium dioxide and zinc and a method for forming a corrosion resistant coating on a steel sheet using the same, comprising a pigment, an inorganic silicate solvent and a sulfuric acid solution in which a titanium dioxide: zinc powder is mixed at a weight ratio of 1: 0.01-0.05. Titanium dioxide has an average particle diameter of 30-70 nm, zinc powder has an average particle diameter of 1-5 μm, and the mixed pigment of solvent: titanium dioxide and zinc powder is mixed in a 1: 0.5-1 weight ratio and sulfuric acid is a paint composition. Corrosion-resistant coating composition of 0.1-0.2% by weight based on the total weight and using it to coat the dry coating thickness to 5-20㎛ and then dried at room temperature to form a corrosion-resistant coating layer on a steel sheet.

The coating layer formed of the coating composition of the present invention prevents the corrosion of the material metal steel sheet by photocathode as well as antibacterial, antifouling and deodorizing effect by the photocatalytic action of titanium dioxide. The zinc powder improves the flexibility of the coating layer and the adhesion to the material metal.

Description

Corrosion-resistant coating composition containing titanium dioxide and zinc and a method for forming a corrosion-resistant coating using the same {A COATING COMPOSITION FOR ANTI-CORROSION CONTAINING TiO2 AND Zn AND A METHOD FOR FORMING COATING BY USING THEM}

The present invention relates to a corrosion resistant coating composition containing titanium dioxide and zinc and a method for forming a corrosion resistant film on a steel sheet using the same. More specifically, the present invention relates to a coating composition excellent in corrosion resistance by a cathode method by photoelectrons emitted from titanium dioxide and a method of forming a corrosion resistant film on a steel sheet using the same.

Titanium dioxide (TiO ₂ ) is a photocatalyst, which acts as a photocatalyst in which photoelectron is emitted from titanium when ultraviolet (UV) radiation is applied thereto.

The band gap energy of titanium dioxide is 3.2eV (λ390nm), and when titanium dioxide is irradiated with a wavelength of 390nm or less emitted by a general ultraviolet lamp, photons and holes are excited and some photoelectrons are exposed to sunlight. Is known to occur. Photoelectrics and holes in the excited state exhibit antibacterial, organic substance decomposition and deodorizing effects by the ambient atmosphere and continuous redox reactions, and titanium dioxide is used in various fields such as antibacterial, antifouling and deodorizing.

Coating methods for applying titanium dioxide to metal materials include sol-gel coating, thermal spray coating, chemical vapor deposition, and paint coating.

The sol-gel coating method is to dip a material into a solution containing titanium ions. Due to its nature, a sol-gel coating method requires a process of heating a coated steel sheet at about 300 to 500 ° C after deposition, and also has a coating thickness of 0.1 for a single deposition. In order to form a uniform coating layer with a thin film of about μm, it is cumbersome to repeat the 3-4 deposition process and the heating process.

Korean Patent Application No. 93-014226 discloses a process of hydrothermally treating titanium sulfate or titanium dioxide fine particles at 100 ° C. or higher to produce a titanium oxide film. However, due to the post-coating heating process, the size of the titanium oxide coating is limited to the size of the heating furnace.

Japanese Patent JP-006172 discloses a method of mixing titanium dioxide particles with NiCr metal particles and melting and scattering them with a high temperature flame using a thermal spraying machine to form a coating layer, but this method requires a high temperature of about 1000 ° C. or more. do.

Japanese Patent JP-0071137 discloses a method of forming a titanium oxide coating layer using a chemical vacuum deposition method, but has a disadvantage that the size of the coating is very limited when the coating is performed in a vacuum atmosphere.

International patent PCT / JP1997 / 04559 discloses a method of forming an acrylic modified silicone resin as a first coating layer on a material and forming a titanium oxide layer using colloidal silica-based titanium dioxide as a second coating layer thereon. There is no mention of temperature in the production of titanium coating layer and the manufacturing process is complicated by using two layers.

In addition, in the conventional metal coating method using titanium dioxide, there is no disclosure regarding the long-term corrosion resistance of the metal material by titanium dioxide.

Further, if the heat treatment step when TiO ₂ coating, is a number of elements of the material spread on a plate layer of the n- type TiO ₂ enters into the TiO ₂ thus it reduces the photoelectron emission effect upon UV irradiation.

Accordingly, an object of the present invention is to provide a corrosion-resistant paint composition in which the corrosion of the metal sheet is prevented for a long time by a cathode method by the photoelectrons emitted from titanium dioxide.

Another object of the present invention is to provide a corrosion resistant paint composition having excellent adhesion between the coating layer and the material metal.

Still another object of the present invention is to provide a corrosion resistant paint composition capable of forming a coating layer on a steel sheet at room temperature.

Furthermore, another object of the present invention is to provide a method of forming a corrosion resistant coating on a steel sheet using the corrosion resistant paint composition of the present invention.

1 is a side cross-sectional view of a steel sheet having a coating layer showing the anticorrosive principle of the steel sheet by the corrosion-resistant coating formed of the paint composition of the present invention.

Brief description of the main parts of the drawing

1 .... Steel plate 2 .... Coating film layer

According to one aspect of the invention,

Titanium dioxide: zinc powder is composed of 1: 0.01-0.05 weight ratio of pigment, inorganic silicate solvent and sulfuric acid solution, titanium dioxide has an average particle diameter of 30-70nm and zinc powder has an average particle diameter of 1-5㎛. The mixed pigment of the solvent: titanium dioxide and zinc powder is mixed in a 1: 0.5-1 weight ratio, and sulfuric acid is provided with a corrosion-resistant coating composition having 0.1-0.2% by weight based on the total weight of the coating composition.

According to another aspect of the present invention,

Provided is a method for forming a corrosion resistant coating layer on a steel sheet by coating the corrosion resistant paint composition of the present invention on a metal steel sheet to a dry coating thickness of 5-20㎛ and dried at room temperature.

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

Steel sheet having a coating formed of a corrosion-resistant coating composition according to the present invention is a negative electrode protection function by the photoelectrons emitted from the titanium dioxide contained in the coating during ultraviolet irradiation to prevent metal corrosion for a long time.

In addition, zinc is bound to the silicate solvent structure by acid catalysis of zinc particles and sulfuric acid, thereby providing flexibility to the coating layer, thereby preventing cracking of the coating layer, and increasing adhesion of the material metal and durability of the coating layer.

Corrosion of metals is an electrochemical phenomenon caused by the movement of electrons and ions. As the anticorrosive method, a cathode method that electrochemically changes the potential of metal in the negative direction such as a galvanized steel sheet is mainly used.

When ultraviolet rays are irradiated to the coating film containing the titanium dioxide of the present invention, electrons in the titanium dioxide-containing coating film layer are excited by the ultraviolet rays to generate holes (e-h pair generation). Subsequently, electrons and holes are separated by charge repulsion, and the separated electrons move to the material steel sheet (electron diffusion) to exhibit a cathodic protection effect on the material steel sheet.

At this time, the movement of the electrons to the material steel plate by the electron diffusion is an important step of the photocathode protection method is dependent on the electron mobility of the titanium dioxide coating layer and the interfacial phenomenon of the coating layer / material steel sheet. Therefore, the titanium oxide coating layer should have conductivity.

In addition, when the impurity content is large, the mobility of the excited photoelectrons to the material metal is deteriorated, and the negative electrode protection effect is lowered.

When a film is formed on a steel sheet using a titanium dioxide-containing composition, when a separate heat treatment process is performed, various elements of the raw material steel sheet diffuse into the titanium dioxide-containing film layer and act as impurities in the film layer. Therefore, in order to prevent the diffusion of various elements of the raw metal into the coating layer during the coating process, the coating layer should be formed at room temperature without a separate heat treatment process when forming the coating layer.

In addition, if there is a heating step in the manufacturing process there is a variation in the performance of the coating and therefore there is a problem that is not applicable to large steel structures.

In the present invention, corrosion of a metal sheet such as electrons sacrificing the steel sheet is prevented by the photoelectrons generated by the radiation irradiated thereto using a room temperature dry type titanium oxide-containing paint composition.

The paint composition having excellent corrosion resistance and adhesion to a raw metal is composed of titanium dioxide and zinc powder, an inorganic silicate solvent, and sulfuric acid as pigments.

Titanium dioxide acts as a photocatalyst that emits photoelectrons when irradiated with UV light, and the excited photoelectrons cause continuous oxidation and reduction reactions with the surrounding atmosphere as shown in Chemical Formula 1 below to exhibit antibacterial, organic decomposition and deodorization effects as well as cathodic protection effects. .

Photocathode protection of TiO ₂

TiO ₂ ----> ne ^-

2H ₂ O + 4h ⁺ ---> O ₂ + 4H ⁺ (oxidation reaction)

_{^{O 2 + 4h + + 4e -}} ---> 2H 2 O ( reduction)

Titanium dioxide has an average particle diameter of 30-70 nm. Titanium dioxide having a particle diameter of 30 nm or less is difficult to apply because it is difficult to manufacture substantially, and when titanium dioxide having a particle diameter of 70 nm or more is used, the surface area of titanium dioxide is reduced, which is ineffective for photocatalytic action.

As the zinc, zinc powder having an average particle diameter of 1-5 탆 is used. Zinc having a particle diameter of less than 1 μm is practically difficult to apply and cannot be applied. Forming a thin film having a thickness of at least 5 μm as a coating composition according to the present invention, if the size of the zinc particles is large, the zinc particles are exposed out of the coating layer and are defective in the coating layer. The smaller the particles of the zinc powder has the advantage of wider reaction area with the inorganic silicate solution.

Zinc binds to the silicate structure as shown in Equation 2 below to give flexibility to the coating layer to prevent the coating layer from cracking or peeling from the material metal.

[Si-O-Zn-O-Si] _n

The titanium dioxide particles and the zinc powder are mixed with titanium dioxide particles: zinc powder in a ratio of 1: 0.01-0.05 by weight. If the content of zinc powder in the pigment is too small, there is no effect of increasing the coating strength and adhesion to the coating / material metal, and if the content of zinc powder is too large, the photoelectron emission effect of the coating layer is reduced.

As the solvent, an inorganic silicate is used. It functions to form a coating and also acts as a binder and imparts conductivity to the coating layer. In other words, the silicate solvent serves to help the photoelectrons generated by the photocatalytic action of titanium dioxide to move to the material steel sheet. As the inorganic silicate solvent, a liquid silicate solution in which the silicate is dissolved in a solvent is used so that the solvent is easily mixed with the pigment. More specifically, about 20-30% of the silicate solution is used. When the concentration of the silicate solution is less than 20%, the coating capacity is easily broken due to a decrease in binding capacity, and when the concentration of the silicate solution is 30% or more, it is difficult to exert a photocatalytic action due to a small amount of titanium dioxide.

As the silicate solution, a general organic solvent used for forming a coating film may be used as the solvent. For example, the solvent includes organic solvents such as alcohol, acetate, and xylene.

Pigments (hereinafter, referred to as 'mixed pigments') in which the inorganic silicate solvent, titanium dioxide and zinc powder are mixed are mixed in a 1: 0.5-1 weight ratio. If the amount of silicate solution as a solvent is too large, the relative amount of pigment per unit volume is difficult to exhibit photocatalytic action and photocathodic protection performance. If the amount of solvent is too small, pores in the film are large and moisture, oxygen and other corrosive ions are easily coated. It penetrates into and the coating film strength is weakened, so the coating film is brittle, so the durability of the coating film is lowered.

Sulfuric acid promotes drying of the coating film by acid catalysis while helping to form SiO ₂ network. Sulfuric acid is added at 0.1-0.2% by weight based on the total weight of the coating composition. When sulfuric acid is added at 0.1% by weight or less, there is no acid catalyst action and there is no effect of promoting the drying of the coating film. When the sulfuric acid is added at 0.2% by weight or more, cracking occurs in the coating film after forming the dry coating film.

Furthermore, an extender pigment may be added to the paint composition to reinforce the strength of the coating film and to prevent flow during coating. As an extender pigment, aluminum oxide, potassium carbonate, mica (Si), or the like may be used alone or in combination. The extender pigment is added in an amount of 5-10% by weight based on the weight of the paint composition. If it is added in excess of 10% by weight, the anticorrosive performance may be reduced.

By coating the coating composition of the present invention on the metal surface, a film is formed on the metal steel sheet without a separate heat treatment process, and the steel sheet having such a coating layer is required for antimicrobial, organic substance decomposition, and devolatilization effects, which are conventional titanium dioxide photocatalytic coating applications. Not only can it be used in the field but also corrosion of metal is prevented by cathodic protection action by photoelectron excited in titanium dioxide.

The coating film layer formed of the coating composition of the present invention on the metal surface is coated so that the coating thickness is 5-20 μm, preferably 5-10 μm when dried. When the thickness of the dry coating layer is less than 5 μm, the coating layer is so thin that it is difficult to form a complete coating layer on the metal sheet. Therefore, the durability is lowered and the amount of titanium dioxide is also low, which lowers the corrosion resistance. When the thickness of the dry coating film layer is 20㎛ or more, the coating film layer is so thick that the conductivity and corrosion resistance of the coating layer and the metal material are degraded, and the photocatalytic effect of ultraviolet rays does not affect the thickness of 20㎛ or more.

Furthermore, when the coating film is formed using the coating composition, the coating film is formed by drying at room temperature, that is, about 10-30 ° C. without a separate heat treatment process.

In the present invention, since the coating film is formed at room temperature without a separate heat treatment process as described above, atoms of the base metal do not diffuse into the coating film layer, and thus, impurities are not contained in the titanium dioxide coating layer and impurities when the photoelectron moves to the material steel sheet by photocatalytic action. Since there is no interference by, it shows excellent conductivity and cathodic protection.

Figure 1 is a side cross-sectional view showing the anticorrosive principle of the corrosion-resistant coated steel sheet according to the present invention. The coating film layer containing the titanium dioxide pigment formed on the steel sheet according to the present invention prevents corrosion of the steel sheet by the sacrificial method (cathode protection) as shown in FIG.

That is, when ultraviolet rays are irradiated to the coating film containing titanium dioxide, electrons in the titanium dioxide-containing coating film layer are excited by the ultraviolet rays, and then the electrons and holes are separated by the surface repulsion action, and the separated electrons move to the material steel sheet. It shows a cathodic protection effect on the steel sheet.

Furthermore, the film coating layer containing titanium dioxide and zinc according to the present invention has excellent adhesion between the coating layer and the metal material without causing cracks in the coating layer for a long time because fine zinc particles are bonded to the silicate structure to impart flexibility to the coating layer.

Photoelectron excitation from titanium dioxide is generated not only by ultraviolet light but also by natural light such as sunlight.

Hereinafter, the present invention will be described in detail through examples.

Example 1

To the coating composition was prepared in the composition of Table 1 and spray-coated to 436 stainless steel at about 25 ℃ room temperature to form a coating layer having a thickness of 10㎛ dry coating film. Sulfuric acid was added to each of the paint compositions of Inventive Examples 1-3 and Comparative Examples at 0.15% by weight based on the total weight of the paint composition.

Paint Ingredients Inventive Example 1 Inventive Example 2 Inventive Example 3 Comparative example Mixed weight ratio of pigment TiO ₂ Particles ^{* 1} One One One One Zinc powder (particle size 1-5㎛) 0.01 0.02 0.04 - Pigment in dry coating: Mixing weight ratio of solvent Whole pigment 0.5 0.74 0.9 0.74 Silicate solvent One One One One

* Titanium dioxide powder (average particle size 50nm) of product number P-25 manufactured by DEGUSA

Then, the anticorrosive performance of the titanium dioxide-containing coating film by the photocathodic protection reaction was evaluated by measuring the natural potential of the coated steel sheet with a standard electrode (SCE) device when irradiated with ultraviolet rays and when not irradiated with ultraviolet rays.

In order to compare the natural potential with and without ultraviolet rays, the natural potential of the steel sheet with the coating film layer when the ultraviolet rays were irradiated using the natural potential and the 160 watt mercury bulb with the external light blocked. It was measured and the results are shown in Table 2 below.

Natural potential measurement result Specimen Classification No UV (vs. SCE) mV UV irradiation (vs. SCE) mV Inventive Example 1 -75 -545 Inventive Example 2 -123 -590 Inventive Example 3 -159 -550 Comparative example -53 -590

In addition, after drying for 30 days, the coating film layer and the material metal peeling and the presence of cracking of the coating layer was visually observed and the results are shown in Table 3 below.

Psalter Inventive Example 1 Inventive Example 2 Inventive Example 3 Comparative example Drying after 30 days of coating layer O ◎ ◎ ×

◎: No coating layer peeling phenomenon and very good

O: No coating layer peeling phenomenon

X: coating layer peeling

As shown in Tables 2 and 3, a coating layer was formed of a photocatalyst anticorrosive coating composition containing titanium dioxide and zinc, thereby forming an excellent coating layer without peeling of the coating layer even after 30 days of drying. It has a natural potential of, so that it can effectively protect the negative electrode of the steel sheet, it can be seen that the corrosion resistance and coating properties of the steel products in the long term is excellent.

On the other hand, in the comparative example in which only titanium dioxide was used as the pigment, the photocathode protection of the steel sheet was excellent, but the coating layer was peeled off after a long time after drying.

The coating layer formed of the coating composition of the present invention prevents the corrosion of the material metal steel sheet by photocathode as well as antibacterial, antifouling and deodorizing effect by the photocatalytic action of titanium dioxide. In addition, the zinc powder improves the flexibility of the coating layer and adhesion to the raw metal.

Claims (3)

Titanium dioxide: zinc powder is composed of 1: 0.01-0.05 weight ratio of pigment, inorganic silicate solvent and sulfuric acid solution, titanium dioxide has an average particle diameter of 30-70nm and zinc powder has an average particle diameter of 1-5㎛. , The solvent: titanium dioxide and zinc powder mixed pigment is mixed in a 1: 0.5-1 weight ratio and sulfuric acid is 0.1-0.2% by weight based on the total weight of the paint composition of the corrosion-resistant paint composition. The paint composition according to claim 1, wherein the corrosion resistant paint composition comprises 5-10% by weight of a extender pigment selected from aluminum oxide, potassium carbonate and mica based on the total weight of the paint composition. A method of forming a corrosion resistant coating layer on a steel sheet by coating the corrosion resistant paint composition of claim 1 or 2 on a metal steel sheet to a dry coating thickness of 5-20㎛ and dried at room temperature.