JP2884941B2 - Steel material excellent in weather resistance and method of forming rust layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a new method of surface treatment of steel, causing the processing steel material and the rust covered with the highly stable and corrosion resistance in an atmospheric environment rust surface generated promote the steel surface It is about the method.

[0002]

2. Description of the Related Art In general, corrosion resistance in the atmosphere can be improved by adding elements such as P, Cu, Cr, and Ni to steel. These low-alloy steels are called corrosion-resistant steels. In a few years outdoors, they form rust that protects against corrosion (hereinafter referred to as weather-resistant rust), and so-called maintenance that eliminates the need for corrosion-resistant treatment such as painting. Free steel.

However, since it takes several years before weather-resistant rust is formed, floating rust such as red rust and yellow rust and flowing rust are generated during the period, which is not only externally favorable but also causes It still has the problem of causing environmental pollution.

Regarding this problem, see, for example,
As shown in No. 142088, a surface treatment method for forming a phosphate film has been proposed. However, it is necessary to perform an appropriate pre-treatment before forming a phosphate film, and the content of the treatment is complicated, and when welding of a steel material is necessary, it is not easy to apply a treatment to a welded portion. It is difficult to apply to building structures.

[0005] Conventionally, surface treatment methods such as applying a coating film on the surface of weather-resistant steel or forming a phosphate film and then applying a coating have been carried out. Are slowed down, and the coating film itself deteriorates and the appearance is significantly impaired.

Further, even in weather-resistant steel such as a coastal zone, there are many environments in which formation of weather-resistant rust is difficult, and the fact is that weather-resistant rust is not formed even by performing the above-described treatment.

[0007]

The main object of the present invention is to provide a rust layer which is stable in an atmospheric corrosive environment by a simple treatment, has a high anticorrosion property, and suppresses the generation of floating rust such as red rust and yellow rust and flowing rust. And to provide a treated steel material covered with a rust layer with high weather resistance as a material for construction or the like.

[0008]

The present inventors have SUMMARY OF THE INVENTION may, after coating Cr, Cu, P, the aqueous solution containing Ni ions rust layer of the steel material surface or steel, OH rust layer of the steel surface ^-
It has been found that the stability of the rust layer to the atmospheric corrosion environment is enhanced and the corrosion resistance thereof is enhanced by supplying the rust layer to an environment exceeding pH 7.

An aqueous solution containing one or more of Fe, P, Cu and Ni ions in an aqueous solution of chromium (III) ions and / or copper (II) ions has an appropriate amount α.
-It was also found that by adding FeOOH powder and applying it to the surface of steel or to the rust layer of steel, the corrosion resistance of the rust layer formed in the atmospheric corrosion environment and the rust layer already formed can be enhanced. did. That is, the present invention is as follows.

<First Invention> Cr and C in which almost all of the steel surface is 0.3% by weight or more
α-F containing one or more of u, P and Ni
A treated steel excellent in weather resistance, which is covered with a rust layer composed of eOOH.

<Second invention> An aqueous solution containing 0.2 to 12.0% by weight of chromium (III) ion and 0.3 to
After applying at least one aqueous solution containing 7.0% by weight of copper (II) ions, OH ^- is supplied to the rust layer formed on the surface of the steel material to obtain an environment having a pH of more than 7, and the α-FeO
A method for forming a rust layer having excellent weather resistance, wherein conditions for forming a rust layer composed of OH are given .

<Third Invention> An aqueous solution containing 0.2 to 12.0% by weight of chromium (III) ion and 0.3 to
Mixing of at least one aqueous solution containing 7.0% by weight of copper (II) ions with an aqueous solution containing 0.1 to 10.0% by weight of one or more of Fe, P and Ni ions After applying the aqueous solution, OH ^- is supplied to the rust layer formed on the surface of the steel material so that the environment exceeds pH 7 , and α-Fe
A method for forming a rust layer having excellent weather resistance, which provides conditions for forming a rust layer composed of OOH .

<Fourth Invention> An aqueous solution containing 0.2 to 12.0% by weight of chromium (III) ion and 0.3 to 7.0% by weight of copper ( II) 0.0 of the sum of at least one of the aqueous solutions containing ions
A method for forming a rust layer having excellent weather resistance, which comprises applying a mixed solution with α-FeOOH powder having a weight of 0.5 to 2 times.

<Fifth Invention> An aqueous solution containing 0.2 to 12.0% by weight of chromium (III) ion and 0.3 to 7.0% by weight of copper ( II) at least one aqueous solution containing ions, Fe,
One or more of P and Ni ions are 0.1
Aqueous solution containing 0.1 to 10.0% by weight, and α-Fe having 0.005 to 2 times the weight of the mixed aqueous solution.
A method for forming a rust layer having excellent weather resistance, which comprises applying a mixed solution with OOH powder.

Before using the steel material of the present invention as a building structure, the surface of Cr, Cu,
Cr or Cu having a surface of 0.3% by weight or more according to the treatment method of the present invention for a steel material covered by containing one or more of P and Ni, and a steel material already used as a building structure. , P, and Ni, and a steel material having an α-FeOOH layer containing one or more of them. Further, the rust layer formed on the surface of the steel material before the treatment is a precipitation type coating formed by corrosion involving an aqueous solution, and does not include an oxide scale or the like formed during hot working. Also, the rust layer is easily formed by outdoor exposure to the atmosphere,
By artificially placing the steel surface in a dry and wet environment using various aqueous solutions repeatedly, it is formed early according to the frequency. Each treatment method may be performed by supplying an aqueous solution containing various ions, and the treatment can be performed by any method such as air spray, airless spray, or brush coating as in the case of a normal coating method.

[0016]

The present invention will be described below in detail. If the rust is chemically stable in an atmospheric corrosion environment, the electrochemical reaction accompanying the rust phase transformation and dissolution is suppressed. Furthermore, if chemically stable rust is physically dense, structural defects such as cracks and voids are unlikely to be generated, preventing oxygen, water and even corrosive substances in the atmosphere from entering. It is easy to shut off the atmospheric corrosion environment and reduces the elution of Fe ions, which is a fundamental cause of floating rust and flow rust.

The present inventors have described in the following analysis and investigation results.
As described above, almost all of the steel surface is composed of α-FeOOH , a final product compound that is stable in a normal atmospheric corrosion environment.
If the α-FeOOH rust contains Cr, Cu, P, and Ni in the rust layer, the weather resistance of the steel becomes extremely good, and particularly, the sea salt particle resistance is excellent. I found However, the steel referred to in the present invention does not include those that do not generate so-called rust, which is a normal precipitation type coating such as stainless steel and Ni-based alloy, and mainly refers to low alloy steel such as weathering steel and carbon steel.

(1) An aqueous solution containing 0.2 to 12.0% by weight of chromium (III) ion (hereinafter, all percentages are by weight), 0.3 to 7.0% of copper (II) ) Apply one or both of the aqueous solutions containing ions.If the steel structure is dense, it is easy to physically block the atmospheric corrosion environment, and the elution of Fe ions, which is the fundamental cause of floating rust and flow rust To reduce However, if there are cracks or pores in the rust, it becomes a supply path for water or oxygen, and the corrosion resistance of the rust is reduced. The effect of applying the aqueous solution containing chromium (III) ions and the aqueous solution containing copper (II) ions is to make the formed rust dense and have a structure with few cracks and pores. For this purpose, an aqueous solution containing chromium (III) ions at a concentration of 0.2% or more or an aqueous solution containing copper (II) ions at a concentration of 0.3% or more is required. If the chromium (III) ion concentration exceeds 12.0% or the copper (II) ion concentration exceeds 7.0%, the effect is saturated and economically disadvantageous. 0.2-1
2.0%, and the range of the copper (II) ion concentration is set to 0.3 to 7.0.
%.

Since sulphate ions are also effective in growing α-FeOOH, it is better to use chromium (III) sulphate or copper (II) sulphate when using chromium (III) ions and copper (II) ions. Especially effective.

(2) Means of ion addition Fe, P, and Ni ions are replaced by chromium (III) ions or copper ions.
(II) The effect is further enhanced by adding it to the ion-containing aqueous solution, and the interface structure between rust and steel is densified, and the rust particles themselves are densified. For that, Fe,
One or more of P and Ni ions must be contained in the aqueous solution in an amount of 0.1% or more, and preferably two or more ions are added. However, 10.0
%, The effect saturates and becomes economically disadvantageous. Therefore, the range of the added ion concentration is limited to 0.1 to 10.0%.

[0021] (3) in the rust layer OH ^- rust layer of meaning steel surface be environment than was pH7 supplies OH ^- The purpose of the environment in excess of supplying pH7 and was eluted from the steel Fe The early conversion of ions into environmentally stable α-FeOOH or the conversion of already formed rust layers into stable α-FeOOH. For this purpose, for example, Na
It can be easily realized by applying an OH aqueous solution. In addition,
It goes without saying that the same effect can be expected even if another alkaline aqueous solution such as an aqueous ammonia solution or a KOH aqueous solution is used. It is sufficient that the pH exceeds 7 at the time of the treatment, but it is particularly preferable that the pH be 9 to 14 in order to convert the initially generated rust layer to α-FeOOH at an early stage. However, from the viewpoint of improving the working environment, it is possible to select a treatment in a neutral environment even if the rusting is slightly delayed.

In addition, this treatment is performed for Cr, such as weather-resistant steel,
Particularly effective for low alloy steel containing Cu, P, Ni, etc.,
It is also effective for carbon steel.

(4) Meaning of addition of α-FeOOH powder The purpose of adding α-FeOOH is that α-FeOOH is chemically stable in an atmospheric corrosion environment and does not undergo phase transformation or dissolution.
The purpose is to cover the steel material surface with FeOOH.

This suppresses the electrochemical reaction accompanying the phase transformation and dissolution of the rust layer. Further, by adding an aqueous solution containing chromium (III) ions or copper (II) ions to such a chemically stable rust layer, the interface structure between rust and steel is made dense, and Fe, P, By adding Ni ions to make the rust particles themselves dense, subsequent structural defects such as cracks and voids are unlikely to occur, which also prevents the entry of oxygen, water, or corrosive substances in the atmosphere. As a result, the atmospheric corrosion environment is easily shut off, and the elution of Fe ions, which is a fundamental cause of floating rust and flow rust, is reduced.

To obtain this effect, it is necessary to add α-FeOOH powder having a weight of 0.005 times or more of the aqueous solution to be applied to the steel material. Further, when more than twice the amount of α-FeOOH is added, the effect is not only saturated, but also after the treatment is completed, the saturated α-FeOOH falls off the steel material surface and causes contamination of the surroundings.
The range of the amount of FeOOH added was limited to 0.005 to 2 times the mass of the aqueous solution applied to the steel material.

(5) Treatment All of the above treatment liquids can be applied by any method such as air spraying, airless spraying or brush coating as in the usual application method. It is. Further, it is desirable to repeat the application a plurality of times after the application is allowed to stand and dry.
It is effective even in one application operation and is economically excellent.
Furthermore, since on-site painting is possible, cutting steel materials on-site,
It can respond even after processing such as welding.

[0027]

The effects of the present invention will be described below in detail with reference to examples. <Example 1> Table 1 shows the chemical components of the test steel used in the examples of the present invention. Tables 2 to 7 show the composition of the applied treatment liquid and the treatment method.
Shown in Tables 2 to 6 show the pretreatment liquids, and Table 7 shows the treatment liquids applied to the test steels of Nos. 1 to 39 after the pretreatment. The dimensions of the test piece were 150 mm × 60 mm × 3 mm, and the surface before the treatment was polished with emery paper and buffed to be a mirror surface.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

[0033]

[Table 6]

[0034]

[Table 7]

Each of the test pieces subjected to the above treatment was exposed to a coastal area in Kitakyushu City, Fukuoka Prefecture (5 m from the sea) in an atmospheric corrosion environment for 300 days under the same conditions. As a result, in any of the tests, Examples 1 to 14, 18 to 31, 3
With treatment liquids A, B, C and D in Table 7 of Tables 4 to 39, flow rust was very small and the surface tone was uniform black-brown. On the other hand, in the case of using Comparative Examples 15 to 17, 32, and 33 and the treatment liquid E, much more flow rust was confirmed, and the color tone of the surface was reddish brown, and red rust was distributed in a dot-like manner.

Further, as a result of investigating the constituents in the rust layer and investigating the distribution thereof by X-ray diffraction, Fourier transform infrared spectroscopy and microscopic laser Raman spectroscopy, Examples 1 to 14, A of 18-31, 34-39,
B, C, and D tend to be less when the pH is low, but almost all are composed of α-FeOOH.

On the other hand, the comparative examples 15 to 17, 32,
33 and the processing solution E, about 15% was α-Fe
OOH, others are β-FeOOH and γ-FeOO
It can be said that H is present in substantially equal amounts, and that each is generally present in the rust layer. Further, as a result of examining the element distribution state in the rust layer by EPMA, Examples 1 to 14, 18 to 3
In A, B, C and D of 1, 34 to 39, supplied Cr, C
u, P, and Ni were concentrated by 0.3% or more over the entire area of the rust layer.
On the other hand, when Comparative Examples 15 to 17, 32, and 33 and the treatment liquid E were used, the presence of Cr, Cu, P, and Ni in the rust layer was slightly scattered in the case of the weather-resistant steel. Was rarely observed.

Tables 8 and 9 show the thickness reduction of each test piece after the treatment.

[0039]

[Table 8]

[0040]

[Table 9]

Regardless of the exposure period, in any of the tests, the reduction in the sheet thickness of the present invention example was suppressed to almost half or less compared with the comparative example, and the rust protection property of the present invention was reduced. It is thought that it was increased by the processing. In addition, Cr, C
Although it is inferior to the effect on weathering steel containing elements effective in forming weathering rust such as u, P, Ni, etc., the method of the present invention can also be applied to ordinary steel to provide a highly corrosion-resistant rust layer in an atmospheric corrosion environment. Are formed early.

<Example 2> The chemical components of the test steel used in the examples of the present invention are the same as the components used as the weathering steel (a) shown in Table 1 in Example 1. . Tables 10 to 15 show the compositions and treatment methods of the applied treatment liquids.
Shown in The dimensions of the test piece were 150 × 60 × 3 mm, and the surface before the treatment was polished with emery paper and buffed to be a mirror surface.

[0043]

[Table 10]

[0044]

[Table 11]

[0045]

[Table 12]

[0046]

[Table 13]

[0047]

[Table 14]

[0048]

[Table 15]

Under the same conditions, the test pieces subjected to the above treatments were placed in an industrial zone in Amagasaki City, Hyogo Prefecture at a distance of 4 km from the coast, for test numbers 41 to 56 and 66 to 81 for 70 days and 3 days.
35 days, 57-65, 82-90 are 100 days and 36
Exposure was for 5 days. As a result, in any of the tests, Examples 41 to 53, 57 to 63 and 66 to 78, 82 of the present invention.
At ~ 88, the flow rust was very small. On the other hand, in Comparative Examples 54 to 56, 64, 65, 79 to 81, 89 and 90, much more flow rust was confirmed. Also, EPM
As a result of investigating the distribution of the main elements in the rust layer by A, the effective elements in the treatment liquid were concentrated in Examples 41-53, 57-63 and 66-78, 82-88 of the present invention in any of the tests. It is considered that rust cracking is small and weather resistant rust is formed. On the other hand, Comparative Examples 55, 56, 65,
At 80, 81 and 90, the concentration of the effective element is slight, and it can be said that the concentration is inferior in the density.

Table 16 shows the thickness reduction of each test piece after treatment.
19. Regardless of the exposure period, 54-5 of Comparative Examples
Inventive Examples 41 to 53, 57 to 63 and 66 to 7 in comparison with 6, 64, 65, 79 to 81 and 89, 90.
In the case of 8, 82 to 88, the reduction in plate thickness was suppressed to about half or less, and it is considered that the rust protection was enhanced by the application of the treatment liquid of the present invention.

[0051]

[Table 16]

[0052]

[Table 17]

[0053]

[Table 18]

[0054]

[Table 19]

[0055]

As described above, the steel material treated according to the present invention has a high corrosion resistance and stable corrosion in an atmospheric corrosive environment in which almost no floating rust such as red rust or yellow rust or flow rust is generated after the treatment. A rust layer can be formed. In particular, it is possible to provide a treated steel material having good corrosion resistance in a coastal zone, which has been a problem in the past, and having excellent sea salt particle resistance. In addition, since the treatment is easy and can be performed anywhere, it is possible to produce a stable rust-covered steel material with high anticorrosion properties in an atmospheric corrosion environment at a factory, and also to apply on-site painting. It is possible to cope after the processing such as cutting and welding of steel material on site.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-11739 (JP, A) JP-A-55-76078 (JP, A) JP-A-64-55389 (JP, A) 142088 (JP, A) JP-A-50-77236 (JP, A) JP-A-62-260866 (JP, A) JP-A-55-97478 (JP, A) JP-A-62-103373 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C23C 22/00-22/86

Claims (5)

(57) [Claims] The steel surface is covered with a rust layer composed of α-FeOOH containing one or more of Cr, Cu, P, and Ni in an amount of 0.3% by weight or more. Treated steel with excellent weather resistance. 2. The method according to claim 1, wherein the surface of the steel material or the rust layer of the steel material has a thickness of 0.2 to 0.2%.
After applying at least one of an aqueous solution containing 12.0% by weight of chromium (III) ions and an aqueous solution containing 0.3 to 7.0% by weight of copper (II) ions, the rust formed on the steel material surface is reduced. Supply OH ^- to the bed to make the environment more than pH 7 ,
A method for forming a rust layer having excellent weather resistance, which provides conditions for forming a rust layer composed of α-FeOOH . 3. The method according to claim 1, wherein the surface of the steel material or the rust layer of the steel material has a thickness of 0.2%.
At least one of an aqueous solution containing chromium (III) ions of 0.1 to 12.0% by weight and an aqueous solution containing copper (II) ions of 0.3 to 7.0% by weight; 0.1 to 10.0% by weight of one or more types
OH ^- is supplied to the rust layer formed on the steel surface after applying the mixed aqueous solution with the aqueous solution containing
Then, conditions for forming a rust layer composed of α-FeOOH were given.
Method of forming a weather-resistant excellent rust layer, characterized in that that. 4. The method according to claim 1, wherein the surface of the steel material or the rust layer of the steel material has a thickness of 0.2%.
0.005 to 2 times the weight of the sum of at least one of an aqueous solution containing chromium (III) ions and an aqueous solution containing 0.3 to 7.0% by weight copper (II) ions. A method for forming a rust layer having excellent weather resistance, which comprises applying a mixed solution with α-FeOOH powder having the following. 5. The method according to claim 5, wherein the surface of the steel material or the rust layer of the steel material has a thickness of 0.2%.
At least one of an aqueous solution containing chromium (III) ions of 0.1 to 12.0% by weight and an aqueous solution containing copper (II) ions of 0.3 to 7.0% by weight; 0.1 to 10.0% by weight of one or more types
And a mixed aqueous solution with an aqueous solution containing 0.1 wt.
A method for forming a rust layer excellent in weather resistance, which comprises applying a mixed solution with α-FeOOH powder having a weight of 005 to 2 times.