JP2005336432A - Coating for steel material and steel material having excellent corrosion resistance and rust preventing property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosion-resistant coating and a corrosion-resistant steel material stably exhibiting excellent corrosion resistance and rust preventing properties. <P>SOLUTION: The coating for a steel material having the excellent corrosion resistance and rust preventing properties comprises 0.1-10.0 mass% of Mg and further the balance containing an alloy metal flake consisting essentially of Zn. The thickness of the alloy metal flake is ≤5 μm and the average particle diameter of the major axis is 1-50 μm. The steel material is coated with the coating and has the excellent corrosion resistance and rust preventing properties and ≤300 μm film thickness of the coating on the steel material surface after drying. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a corrosion-resistant paint and a corrosion-resistant steel material coated with the same, and more particularly to a corrosion-resistant paint and a corrosion-resistant steel material that exhibit excellent corrosion resistance and rust resistance when applied to the surface of various steel materials.

As anti-corrosion measures for steel materials used in ships, industrial machinery, vehicles, chemical industrial facilities, buildings, bridges, etc. and their production, etc., zinc powder is used as a pigment, organic materials and inorganic materials are used as vehicles (liquid Zinc rich paint with the composition of binder component is mainly used. Zinc rich paint is mainly used as an undercoat for short-term rust prevention and heavy anticorrosion coating, and the feature of the anticorrosion mechanism is the sacrificial anticorrosion action of zinc powder contained in the coating film. However, since the anticorrosion performance of the zinc rich paint coating depends strongly on the sacrificial anticorrosive action of zinc powder as described above, depending on the use environment, the disappearance rate of zinc is large and the protective action against steel materials cannot be maintained for a long time. There is a case.
Therefore, measures such as increasing the content of zinc powder in the coating film and increasing the film thickness have been taken. However, the adhesion to the steel surface is reduced, the coating cracks, or the paint is used during painting operations. Such as sagging is likely to occur, and workability during cutting and welding is greatly reduced, and it is difficult to achieve both the anticorrosion performance of the coating film and the physical properties and workability.

  Therefore, development of a high-performance zinc rich paint that retains the advantages of the conventional zinc rich paint and exhibits sacrificial anticorrosive action for a long period of time is expected, and various proposals have been made so far. For example, in (Patent Document 1) and (Patent Document 2), zinc-rich paint containing Zn-Mg alloy powder in addition to zinc powder is used. In (Patent Document 3), Zn-Mg alloy is used in addition to zinc powder. A zinc rich paint containing powder and Mn powder has been proposed.

Furthermore, (Patent Document 4) showed the long-life anticorrosion performance of Zn— (5 to 15%) Mg alloy powder in paint. The long life corrosion performance of the Zn-Mg alloy powder composed of (Patent Document 5), the metal structure Zn and MgZn ₂ was shown. On the other hand, in (Patent Document 6), although it is a Zn—Mg—Al hot-dip plated layer, the metallographic structure of the plated layer is composed of Zn and Mg ₂ Zn ₁₁ than that composed of Zn and MgZn _2. Furthermore, it was shown that it was excellent in corrosion resistance.

Further, in (Patent Document 7), the metal powder is composed of a Zn phase and a Zn—Mg alloy (Zn—Mg eutectic or intermetallic compound) phase alone, and further a metal phase of a solid solution of Zn and Mg. When the paint containing the material is converted into a paint, the corrosion resistance is excellent, and the larger the amount of the solid solution, the better the corrosion resistance and the rust resistance, and depending on the mixed state of the metal structure of these powders, At the same time, it was found that the performance development was unstable and sufficient corrosion resistance could not be obtained. Furthermore, “Zn powder”, “Zn-Mg alloy powder” and “Mg in Zn were solidified in the coating film components. It was found that sufficient anticorrosive properties can be obtained when each of the “melted metal powder” is mixed as particles, and a metal powder containing 0.3 to 6% by mass of Mg and the balance of Zn as a main component is used as a vehicle. Mixed with (liquid binder component) The composition of this metal powder is mainly composed of three types of Zn phase, Zn-Mg alloy phase and Zn and Mg solid solution phase, and these are mixed in the paint as powder particles respectively. A corrosion-resistant paint characterized by the following is disclosed.
JP 59-52645 A JP 59-167249 A JP 59-198142 A Japanese Unexamined Patent Publication No. 1-311178 JP-A-2-73932 JP-A-8-60324 JP 2000-80309 A

However, it is a paint obtained by mixing a metal powder mainly composed of Zn with a Mg content of 0.3 to 6% by mass and the balance as a main component in a vehicle (liquid binder component), and the structure of the metal powder is Zn-Mg alloy powders, etc., mainly composed of three phases, a Zn phase and a Zn-Mg alloy phase and a solid solution phase of Zn and Mg, are mixed in the paint as powder particles, respectively. However, in order to secure sufficient anticorrosion properties, it is necessary to control the mixed state of the metal structure. Therefore, there are great restrictions on the production method and economy, and further improvements are required.
Therefore, in view of such a current situation, an object of the present invention is to provide a corrosion-resistant paint and a corrosion-resistant steel material that stably exhibit corrosion resistance and rust resistance superior to those of the conventional art.

The gist of the present invention is as follows.
(1) A paint containing alloy metal flakes containing 0.1 to 10.0% by mass of Mg and the balance being Zn as a main component, the alloy metal flakes having a thickness of 5 μm or less and a long axis A steel coating material excellent in corrosion resistance and rust prevention, characterized by having an average particle size of 1 to 50 μm.
(2) A paint containing 0.1 to 10% by mass of Mg, 0.1 to 10% of Al, and the balance containing alloy metal flakes mainly composed of Zn, the alloy metal flakes The coating material for steel materials excellent in corrosion resistance and rust prevention, characterized in that the thickness is 5 μm or less and the average particle size of the major axis is 1 to 50 μm.
(3) Corrosion resistance and rust prevention, characterized in that the steel material is coated with the paint according to (1) or (2), and the thickness of the paint on the surface of the steel material after drying is 300 μm or less. Excellent steel material.

  The paint of the present invention and the steel material coated with the paint exhibit corrosion and rust prevention properties superior to those of conventional products. Therefore, it can be suitably used as an anti-corrosion measure for steel materials used in ships, industrial machines, vehicles, chemical industrial facilities, buildings, structures such as bridges, and the production thereof.

  In order to solve the problem, the present inventors have studied the alloy powder in a spherical form of Zn and Mg. As a result, the metal powder is composed of a Zn phase and a Zn-Mg alloy (Zn-Mg eutectic or intermetallic compound) phase. Furthermore, when a coating containing a metal phase of a solid solution of Zn and Mg is formed into a paint, the corrosion resistance is excellent, and the greater the amount of the solid solution, the better the corrosion resistance and rust resistance. It was reconfirmed that depending on the mixed state of the tissue, the performance expression was unstable and could not be obtained with sufficient corrosion resistance.

  Therefore, as a result of repeated research on alloy powder conditions that can be made into paints to obtain sufficient anticorrosion properties, depending on the mixed state of the metal structure of the above powder, performance development is unstable and sufficient anticorrosion properties cannot be obtained continuously Even so, by making the above spherical alloy powder into a flat flake shape by rolling, a more excellent anticorrosion property can be stably obtained compared to the conventional case, and in order to obtain a sufficient anticorrosion property The present invention has been completed by finding that the component range of the necessary alloy powder is remarkably expanded as compared with the prior art.

Hereinafter, embodiments of the present invention will be described in detail.
The Mg content in the metal powder is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, with the balance being composed of metal powder mainly composed of Zn. If the Mg concentration is less than 0.1% by mass, the effect of improving the corrosion resistance by Mg is reduced, and if it exceeds 10% by mass, the effect is saturated and the economic efficiency is lowered. Moreover, although content of Zn which is a remainder is not specified in particular, it is usually contained about 90-99.9 mass% normally.
Furthermore, in the present invention, it is preferable to add Al in the metal powder in addition to the above components. In the case where alloy flakes are formed by the addition of Al, even more excellent anticorrosion properties can be stably obtained as compared with the conventional case, but if less than 0.1% by mass, the effect is not required, and 10% by mass. The effect is saturated even if added in excess of.

  As a method for producing the metal powder, a metal material having an Mg concentration of 0.1 to 10% by mass (usually appropriately containing Mg-containing Zn ingot, pure Zn or pure Mg for fine adjustment, and further pure Al) The metal powder can be produced by heating and melting and treating by a volatilization method (evaporation coagulation method), an atomization method (spraying method) or the like, which is a general-purpose powder production method. In order to obtain an alloy powder with a more uniform composition, it is manufactured by an atomizing method (spraying method) that does not require consideration of differences in boiling point between Mg solid solution phase, Zn-Mg intermetallic compound phase and Zn phase generated during cooling. Is preferred. In these production methods, there are very small amounts of inevitable impurities. The primary particles thus obtained can be made into alloy flakes using methods such as roll rolling, ball milling, and bead milling.

If the thickness of the alloy flakes exceeds 5 μm, it may occur that even more excellent anticorrosive properties cannot be stably obtained as compared to the conventional case. Therefore, it is important that the thickness of the metal flakes be 5 μm or less. When more stable anticorrosion and coating workability are desired, the thickness is desirably 2 μm or less. The lower limit of the thickness of the metal flakes is preferably 0.05 μm from the viewpoint of paintability.
In addition, if the average particle size of the major axis of the metal flakes is less than 1 μm, there may be cases where even more excellent anticorrosive properties cannot be stably obtained compared to the conventional case. Therefore, the average particle size exceeds 1 μm and the average particle size exceeds 50 μm. And 50 μm or less because of nozzle clogging during spray coating.

Such metal powder is mixed with a vehicle (liquid binder) to form a paint. In this case, the vehicle includes alkyl silicate, alkali silicate, epoxy resin, urethane resin, phenoxy resin, polyester resin, and other zinc rich. The liquid binder currently used for the paint can be used. The type of paint may be either an emulsion type or a solvent type. However, hydrolyzed ethyl silicate (a kind of alkyl silicate) dissolved in a high-boiling solvent is preferable in order to maximize the corrosion resistance.
Further, other usual additives can be added as long as the corrosion resistance is not impaired, and when used as an anticorrosive undercoat, a third component such as boron may be added in order to improve the adhesion as a top coat.

The mixing ratio of the metal powder and the liquid binder is such that the metal powder is 60 to 90% by mass, preferably 70 to 80% by mass, and the liquid binder is 10 to 40% by mass, preferably, in order to maximize the corrosion resistance. It is preferable to mix 20-30 mass% uniformly. The paint obtained by such mixing is applied to a steel plate or the like. When an inorganic binder such as an alkali silicate or an alkyl silicate is used for coating, it is more desirable to adjust the substrate to some extent in order to ensure adhesion with a steel material or a steel plate. Although it may be processed and applied with a hand tool or a power tool, it is preferably applied after blasting in order to ensure higher adhesion.
When using an organic binder such as epoxy resin, urethane resin, phenoxy resin, polyester resin, etc., it may be applied directly to steel plate or steel material, but the surface may be blasted beforehand, phosphate treatment, If it is applied after chromate treatment, a coated steel sheet with better corrosion resistance can be obtained.

  By various methods as described above, a steel material coated with the paint of the present invention can be obtained. As the coating thickness of the coated steel material increases, the corrosion resistance increases. However, in order to prevent cracking and sagging, the coating thickness after drying should be 300 μm or less, preferably 5 to 100 μm. preferable. The coating film thus formed exhibits high corrosion resistance.

  In the present invention, there are many unclear points as to why the metal flakes having the composition and shape described above exhibit high corrosion resistance, but the following may be considered. The three phases of Zn phase, Zn-Mg alloy phase, and solid solution phase of Zn and Mg are non-uniformly distributed inside and outside the particles by being treated by a volatilization method (evaporation solidification method), an atomization method (spray method), or the like. By subjecting this to flake rolling, the uniformity or non-uniformity of the surface exposure rate of each of the three phases of the Zn phase, the Zn-Mg alloy phase, and the solid solution phase of Zn and Mg is further increased. Compared to the past, the stability and stability of the effect is significantly improved, and at the same time, the alloy powder component range necessary for obtaining sufficient corrosion resistance has been expanded. It is considered a thing.

Specific examples of the present invention will be described below.
[Example 1]
Table 1 shows the composition at the time of preparing the primary alloy powder of the alloy flakes prepared, the average flake thickness after flake rolling, and the average flake major axis length. Ethyl silicate was used as a paint binder, and various paints were prepared by mixing 75% by mass of the alloy powder shown in Table 1 and 25% by mass of the binder.
Using these paints, various samples in which a 15 μm coating film was formed on the surface of a shot-blasted steel sheet having a width of 50 mm, a length of 150 mm, and a thickness of 4 mm were prepared.
The surface of the coating film was immersed in a 3% by mass NaCl solution at room temperature, and the period (time) during which the potential was maintained below the anticorrosion potential of −0.78 V was evaluated based on the silver-silver chloride electrode. The results are shown in Table 2.
As is clear from the results in Table 2, the retention period below the anticorrosion potential of the paint using the alloy flakes of the present invention is longer than that of other comparative paints and is extremely excellent in long-term anticorrosion performance. Understand.

[Example 2]
Using the same paint as used in Example 1 above, various samples were prepared in which a 15 μm coating film was formed on the surface of a shot blasted steel plate having a width of 50 mm, a length of 150 mm, and a thickness of 4 mm. The surface of the prepared sample was cross-cut and the anticorrosion performance of each sample was evaluated according to the time until red rust occurred in an SST (salt spray test) environment based on JIS Z 2371. The results are also shown in Table 2.
As is clear from the results in Table 2, it can be seen that the paint using the alloy flakes of the present invention has a longer red rust occurrence time than other comparative paints and is extremely excellent in corrosion resistance and rust prevention.

Claims (3)

A paint containing 0.1 to 10.0% by mass of Mg, and the balance containing alloy metal flakes containing Zn as a main component, the alloy metal flakes having a thickness of 5 μm or less and a long axis average particle size A steel coating material excellent in corrosion resistance and rust prevention, characterized in that is 1 to 50 μm. A coating containing alloy metal flakes containing 0.1 to 10.0% by mass of Mg, 0.1 to 10% Al, and the balance of Zn as a main component, the thickness of the alloy metal flakes Is a coating material for steel material excellent in corrosion resistance and rust prevention, characterized in that the average particle size of the major axis is 1 to 50 μm. A steel material coated with the coating material according to claim 1 or 2, wherein the coating material on the surface of the steel material has a thickness after drying of 300 µm or less, and is an iron and steel material excellent in corrosion resistance and rust prevention.