JPH07207455A - Surface treatment for steel excellent in weather resistance - Google Patents

Abstract

PURPOSE:To produce weather-resistant rust which is stable in an atmospheric environment without producing unstable rust such as red rust, yellow rust and flaky rust by a simple treatment. CONSTITUTION:An aluminum-copper soln. containing at least one of 1.030.0 mass% aluminum sulfate and 1.0-17.0 mass% copper sulfate (II) is applied on the surface or on a rust layer of a steel material. Or, one or more kinds of phosphoric acid, Fe(II), Fe(III), Cr(III), and Ni ions are added to the aluminum- copper soln. so that the soln. contains 0.1-10 mass% ions and is applied. Or, alpha-FeOOH powder is added to the aluminum-copper soln. or ion-added soln. by 0.005-2 times mass as the mass of the soln. and then applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new surface treatment method for steel products, and more particularly to a method for growing a layer of rust having a protective action against atmospheric corrosion environment, so-called weathering rust, on the surface of steel products in a short period of time. .

[0002]

2. Description of the Related Art Generally, by adding elements such as P, Cu, Cr and Ni to steel, corrosion resistance in the atmosphere can be improved. These low alloy steels are called weather resistant steels, but they form rust that protects against corrosion (hereinafter referred to as weather resistant rust) in the outdoors for several years, and the so-called corrosion-resistant treatment work such as painting is unnecessary thereafter. Maintenance-free steel.

However, since it takes several years until the weather-resistant rust is formed, floating rust such as red rust and yellow rust and flow rust occur during the period until then, which is not only preferable in appearance but also the surrounding environment. The problem remains that it also causes environmental pollution.

[0004]

[Problems to be Solved by the Invention]
For example, as shown in Japanese Patent Application Laid-Open No. 1-142088, a surface treatment method for forming a phosphate film has been proposed. However, the content of the treatment is complicated, such as the need to perform an appropriate pretreatment before forming the phosphate coating,
Further, when welding of steel materials is required, it is not easy to process the welded portion, and it is difficult to apply it to a building structure.

Therefore, the main object of the present invention is to produce stable weather-resistant rust against atmospheric corrosive environment by simple treatment, with almost no floating rust such as red rust or yellow rust or flow rust. is there.

[0006]

The first invention for solving the above-mentioned problems is to provide a surface of a steel material or a rust layer of a steel material,
1.0 to 30.0 mass% aluminum sulfate and 1.
The point where an aqueous solution containing at least one of copper (II) sulfate of 0 to 17.0 mass% is applied is its constitution.

In the second aspect of the present invention, 1.0 to 30.0% by mass of aluminum sulfate and 1.0 to 17.0% by mass of copper (II) sulfate are formed on the surface of the steel material or the rust layer of the steel material. At least one of the above, and phosphoric acid, Fe (II), Fe (I
The point is to apply an aqueous solution containing one or two or more of II), Cr (III), and Ni ions in a total mass% of 0.1 to 10 mass%.

Further, according to the third aspect of the present invention, 1.0 to 30.0% by mass of aluminum sulfate and 1.0 to 17.0% by mass of copper (II) sulfate are provided on the surface of the steel material or the rust layer of the steel material. In an aqueous solution containing at least one of
The point of applying an aqueous solution obtained by adding 5 to 2 times the mass of α-FeOOH is its constitution.

According to the fourth aspect of the present invention, 1.0 to 30.0% by mass of aluminum sulfate and 1.0 to 17.0% by mass of copper (II) sulfate are provided on the surface of the steel material or the rust layer of the steel material. At least one of them, and phosphoric acid, Fe (II), Fe (I
II), Cr (III), and Ni ions in an aqueous solution containing one or two or more of them in an amount of 0.1 to 10% by mass based on their total mass%, and an α content of 0.005 to 2 times the mass. -F
The point of applying an aqueous solution obtained by adding eOOH is its constitution.

[0010]

The action of each substance used in the present invention will be described below. (1) Aluminum sulphate and copper (II) sulphate If the structure of weathering rust is dense, it is easy to block the atmospheric corrosive environment, and Fe is the fundamental cause of floating rust and flow rust.
Reduces elution of ions. On the other hand, however, if there are cracks or pores in the weather-resistant rust, they serve as a supply path for water and oxygen, and the corrosion resistance of the weather-resistant rust decreases.

When an aqueous solution containing at least one of aluminum sulfate and copper (II) sulfate (hereinafter referred to as "aluminum-copper aqueous solution") is applied to the surface of the steel material or the rust layer of the steel material, it is thermodynamically stable and electrochemical. A rust layer is formed which is difficult to reduce. Also, the rust layer is composed of extremely fine crystals, and the adhesion between rust particles is improved,
The structure is dense and stable, and has few cracks and pores. Therefore, the supply route of water and oxygen can be cut off, the elution of Fe ions, which is the fundamental cause of floating rust and flow rust, can be reduced, and the atmospheric corrosive environment can be blocked very well.

In order to obtain the effect of the present invention,
The aluminum-copper aqueous solution is aluminum sulfate having a concentration of 1.0% by mass or more and copper (II) sulfate having a concentration of 1.0% by mass or more.
At least one of the above is required. In addition, 30.
Even if it exceeds 0% by mass and 17.0% by mass, the effect is saturated, it is economically disadvantageous, and there is a possibility that crystals may be precipitated because the solubility is exceeded.
It was limited to 0.0% by mass and 1.0 to 17.0% by mass.

(2) Fe, phosphoric acid, Cr, Ni ions Fe, phosphoric acid, Cr, Ni ions make the interface structure between rust and steel dense and improve the adhesion between rust particles. is there. Therefore, an aqueous solution formed by adding one or more of each of these ions to the aforementioned aluminum-copper aqueous solution (hereinafter referred to as an ion-added aqueous solution)
Is applied to the surface of the steel material or the rust layer of the steel material, a rust layer having a more precise and stable structure is obtained, and the effect when the aluminum-copper aqueous solution is applied is further improved.

The sulfate ion is thermodynamically stable α-
Since it is effective for growing FeOOH, it is particularly preferable to use these ions as sulfates like aluminum sulfate and copper (II) sulfate shown in (1).

In order to obtain the effects of the present invention, the amount of each ion added must be 0.1% by mass or more of one or more of Fe, phosphoric acid, Cr and Ni ions. Yes, it is preferable to add two or more kinds. However, if the addition amount exceeds 10% by mass, the effect is saturated and it is economically disadvantageous. Therefore, the range of the added ion concentration is limited to 0.1 to 10% by mass.

(3) α-FeOOH powder α-FeOOH is a main constituent compound of a stable rust layer having high anticorrosion property formed by long-term exposure of weathering steel, and chemically chemically in a normal atmospheric corrosive environment. It is stable and does not undergo phase transformation or dissolution. Therefore, when α-FeOOH powder is added to an aluminum-copper aqueous solution or an ion-added aqueous solution, stable α-FeOOH can mainly coat the surface of the steel material, and α-FeOOH is not only formed but also added α-FeOOH. As a result, extremely fine rust particles are formed by using as a core, further improving the rust denseness.

Therefore, the electrochemical reaction due to the phase transformation and dissolution of the rust layer is suppressed, and such a stable rust layer becomes physically dense, so that after that, structural problems such as cracks and voids occur. Defects are less likely to occur, and it also prevents the ingress of oxygen, water, or corrosive substances in the atmosphere. As a result, it is easy to shut off the atmospheric corrosive environment, and the Fe ion which is the fundamental cause of floating rust and flow rust. Elution can be further reduced.

In order to obtain the effect of the present invention,
It is necessary to add to the aqueous solution 0.005 times or more the mass of the aqueous solution to which α-FeOOH is added.
On the other hand, even if α-FeOOH is added more than twice as much as the aqueous solution to be added, the effect is not only saturated, but also excess α-FeOOH falls off from the surface of the steel after the treatment, which causes contamination of the surroundings. Therefore, the range of the addition amount of α-FeOOH is limited to 0.005 to 2 times the mass% of the aqueous solution.

The treatment liquid described above can be applied by any method such as air spraying, airless spraying or brush coating as in the ordinary coating method, so that the application can be performed anywhere. Further, it is desirable to apply the coating a plurality of times each time it rains, but it is also economical because it is effective even if it is applied once. Furthermore, since it can be painted on-site, it can be used even after processing such as cutting and welding steel materials on-site. Further, the target steel material is not limited to the weather resistant steel, as long as it is a steel material that generates rust in a normal atmospheric corrosion environment, for example, low alloy steel and carbon steel etc. are also listed as the target steel material of the present invention. .

[0020]

EXAMPLES Hereinafter, experimental examples of the present invention will be shown, and the effects of the present invention and the limiting conditions of each substance will be described in detail based on the experimental examples. <Experimental example 1> The experiment was performed by the following procedure. The surface of a test steel piece consisting of the chemical components shown in Table 1 and having a size of 150 × 60 × 3 mm ³ was mirror-polished by polishing with emery paper and buffing. Table 2 to Table 14 show this test piece on the surface of the test piece which was exposed to the test piece for 30 days at a point 50 m from the coast in Naoetsu City, Niigata Prefecture, and a rust layer was formed on the surface. The treatment liquid having the composition was applied, dried and then applied again three times to produce rusted steel. On the other hand, bare steel was also produced by directly applying the treatment liquids having the compositions shown in Tables 2 to 14 to the above test steel pieces.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

[Table 5]

[0026]

[Table 6]

[0027]

[Table 7]

[0028]

[Table 8]

[0029]

[Table 9]

[0030]

[Table 10]

[0031]

[Table 11]

[0032]

[Table 12]

[0033]

[Table 13]

[0034]

[Table 14]

Under the same conditions, each test piece subjected to the above treatment was exposed for 365 days at a position 50 m from the coast in Naoetsu City, Niigata Prefecture, in an atmospheric corrosive environment. As a result, in bare steel and rusted steel, almost no flow rust was observed in the test numbers 1-128 of the present invention, whereas in the test numbers 129-137 of the comparative example, A large amount of flow rust was confirmed.

Further, as a result of investigating the distribution of main elements in rust by EPMA, in any of the test numbers of bare steel and rusted steel, in the test numbers 1-128 of the present invention, the effective elements in the treatment liquid Is concentrated, and it is considered that weather resistant steel is formed with little rust cracking. On the other hand, in the test numbers 129 to 137 which are comparative examples, the concentration of the effective element is small and it can be said that the denseness is inferior.

Next, Tables 15 to 19 show the amount of reduction in plate thickness after exposure of each test steel piece.

[0038]

[Table 15]

[0039]

[Table 16]

[0040]

[Table 17]

[0041]

[Table 18]

[0042]

[Table 19]

According to Tables 15 to 19, when comparing the sheet thickness reduction amounts of test numbers 1-128, which are examples of the present invention, with the sheet thickness reduction amounts of test numbers 129-137, which are comparative examples, the present invention is shown. It can be seen that the sheet thickness reduction amount of the example is suppressed to half or less of the sheet thickness reduction amount of the comparative example. That is, it is considered that the protection property against weather-resistant rust was further enhanced by applying the treatment liquid according to the present invention.

The addition of α-FeOOH was carried out according to the test numbers 27 and 138, 38 and 139, 49 and 140, 60 and 1.
As is clear from a comparison of Nos. 41, 82 and 142, respectively, the mass% of α-FeOO exceeds twice that of the aqueous solution.
Even if H is added, the effect is saturated.

[0045]

As described above, according to the present invention, by simple treatment, floating rust such as red rust or yellow rust or flow rust is hardly generated, and stable weather-resistant rust is generated in an atmospheric corrosive environment. It becomes possible to do.

Claims (4)

[Claims] 1. The surface of steel material or the rust layer of steel material, 1.0
~ 30.0 mass% aluminum sulphate and 1.0-1
A method for surface treatment of steel material having excellent weather resistance, which comprises applying an aqueous solution containing at least one of 7.0% by mass of copper (II) sulfate. 2. The surface of the steel material or the rust layer of the steel material, 1.0
~ 30.0 mass% aluminum sulphate and 1.0-1
7.0 mass% of at least one of copper (II) sulfate, and phosphoric acid, Fe (II), Fe (III), Cr (III),
A surface treatment method for a steel material having excellent weather resistance, which comprises applying an aqueous solution containing one or more of Ni ions in an amount of 0.1 to 10% by mass based on the total mass of the Ni ions. 3. The surface of the steel material or the rust layer of the steel material, 1.0
~ 30.0 mass% aluminum sulphate and 1.0-1
An aqueous solution containing at least one of 7.0% by mass of copper (II) sulfate and an α-FeOOH mass of 0.005 to 2 times the mass of the aqueous solution is applied. A method for surface treatment of steel having excellent weather resistance. 4. The surface of the steel material or the rust layer of the steel material, 1.0
~ 30.0 mass% aluminum sulphate and 1.0-1
At least one of 7.0 mass% copper (II) sulfate, and phosphoric acid, Fe (II), Fe (III), Cr (III), Ni
An aqueous solution containing one or two or more kinds of ions in an amount of 0.1 to 10% by mass in total, and adding α-FeOOH in an amount of 0.005 to 2 times the mass of the aqueous solution. A surface treatment method for a steel material having excellent weather resistance, which comprises applying an aqueous solution.