JP3219003B2 - Surface treatment agent for steel and surface treated steel - Google Patents

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 paint for steel materials, and a rust layer (hereinafter referred to as "weather resistant and stable") which has a protective effect even in severe atmospheric corrosion environment due to the influence of salt such as coastal areas. Rust), and a surface-treated steel material coated with the same.

[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 weather-resistant steels, but they form rust (hereinafter referred to as weather-resistant rust) that protects against corrosion in a few years outdoors, and so-called corrosion-resistant treatment work such as painting is unnecessary. Maintenance-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 occur during the period, which is not only undesirable in appearance but also causes It still has the problem of causing environmental pollution. In particular, in the environment where sea salt particles fly, not only this tendency is remarkable, but also weather resistant rust is not formed.

Regarding this problem, see, for example,
As described in No. 142088, a surface treatment method for forming a phosphate film has been proposed.

[0005]

However, the content of the treatment is complicated, for example, it is necessary to perform an appropriate pre-treatment before forming a phosphate film, and when welding of steel material is necessary, it is necessary to add a pre-treatment to the welded portion. There is a problem that it is not easy to apply the treatment and it is difficult to apply it to a building structure. In addition, there remains a question as to how weather-resistant rust is formed by this method in an atmosphere corrosive environment in which salt comes in.

Accordingly, an object of the present invention is to provide a weather-resistant and stable rust on a steel material surface at an early stage by applying it to a surface or a rust layer of a so-called rust-forming steel material such as a low-alloy steel such as a weather-resistant steel or an ordinary steel. It is an object of the present invention to provide a surface treatment agent capable of forming a surface treatment, and to provide a surface-treated steel material coated with the surface treatment agent.

[0007]

The inventors of the present invention have analyzed stable rust formed by exposing for more than 20 years and found that weather-resistant stable rust was α- (Fe, Cr) OOH (hereinafter referred to as chromium goethite). ) Was clarified to be composed of a dense set of fine crystals consisting of: For this reason, in order to protect the steel material, in order to generate weatherable stable rust early and suppress the generation of floating rust and flowing rust, it is important to promote the generation of dense chromium goethite. I learned.

As a specific method for solving the above-mentioned problems, the present inventors have applied an organic resin paint containing an appropriate amount of chromium sulfate to the surface of a steel material or a rust layer of the steel material, thereby preventing the occurrence of flow rust and the like. A method for early formation of stable rust with weather resistance was developed.

Therefore, the invention according to claim 1 of the present invention, which has solved the above-mentioned problems, is applied to a surface of a steel material or a rust layer.
Sulfuric acid as an essential component for forming the chromium goethite layer
Aluminum sulfate containing 1% by mass or more and less than 15% by mass of chromium
It is a surface treatment agent for a steel material, which is an organic resin paint containing no lithium .

[0010] The invention according to claim 2 is characterized in that the steel surface or
Must be applied to the rust layer to form a chrome goethite layer
Contains 1% by mass or more and less than 15% by mass of chromium sulfate as a component
And coated with an organic resin paint that does not contain aluminum sulfate.
A surface-treated steel material characterized by being covered .

[0011]

The present invention will be described below in detail.

(1) Meaning of Chromium Sulfate If the structure of rust is dense, it is easy to physically block the atmospheric corrosion environment, and the elution of Fe ions, which is a fundamental cause of floating rust and flowing rust, is reduced. 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. Therefore, it is necessary to form a dense and continuous rust layer.

Chromium sulfate becomes chromium ion and sulfate ion when water permeates into the film and reaches the film / steel interface. Sulfate ions and moisture corrode the steel to form iron ions. The chromium ions have an effect of converting the iron ions to chromium goethite, which is a main component of weatherable stable rust. Further, it is considered that sulfate ions are involved not only in the acceleration of initial iron ion generation but also in the fine and dense denaturation of stable rust.

In order to obtain this effect even in a severe corrosive environment where salt content comes in, it is necessary to add 1% by mass or more of chromium sulfate to the paint. By adding 1% by mass or more of chromium sulfate, the coating according to the present invention is applied, and when a steel material having a dried coating film on the surface is placed in an atmospheric corrosive environment, the weather-resistant stable rust generated early is The effect of suppressing permeation of corrosive anions is exhibited. The reason why the upper limit of the addition amount is limited to less than 15% by mass is that if the addition amount is 15% by mass or more, the effect of suppressing the corrosive anion permeation of the generated weather-resistant and stable rust is reduced, thereby preventing corrosion in a severe corrosive environment. This is because the action cannot be guaranteed. Here, the mass ratio of chromium sulfate means the ratio to the paint solid content excluding volatile components such as water and solvent.

(2) Organic resin The organic resin forms a barrier to the surface of the steel material by the coating, generates weather-resistant stable rust on the surface of the underlying steel material, prevents the bleeding of iron ions, and prevents the generation of flowing rust. I do.

In the present invention, the organic resin used is not particularly limited, and may be an epoxy resin, a urethane resin, a vinyl resin, a polyester resin, an acrylic resin,
Alkyd resin, phthalic acid resin and the like can be exemplified. In addition, the above resin is converted into a paint and the coating is carried out. However, there is no particular problem whether it is a solvent-based paint or an aqueous paint.

In the coating composition of the present invention, in addition to the essential chromium sulfate, coloring pigments such as red iron oxide, titanium dioxide, carbon black and phthalocyanine blue; Pigment, chromium oxide, zinc chromate, lead chromate,
Rust prevention pigments such as basic lead sulfate, other thixotropic agents, dispersants,
Conventional additives such as antioxidants can be included.

When used, it is needless to say that the viscosity is adjusted to a level suitable for the coating operation with an appropriate amount of solvent or water, and the solvent or water evaporates by natural drying after coating. It is considered that a part of the moisture also contributes to the stable rust formation reaction of weather resistance.

Further, iron sulfate, copper sulfate, nickel sulfate, phosphoric acid or the like or an aqueous solution thereof may be added, which is rather preferable. Iron ions, copper ions, nickel ions or phosphoric acid have the effect of promoting the formation of chromium goethite when coexisting with chromium ions.

Here, if the above-mentioned paint has a thickness of 5 to 150 μm after being dried and solidified, the supply balance of chromium ions and iron ions is optimal in the stage of forming weather-resistant and stable rust. It is thick.

(3) Formation of Coating The above-mentioned paint can be applied by a conventional method such as air spray, airless spray or brushing as in a normal coating method, so that it can be applied to any place. It is. In addition, since the effect can be obtained by one coating operation, the cost is also excellent. Furthermore, since on-site painting is possible, it is possible to cope with on-site steel materials after processing such as cutting and welding, and steel materials having rust on the surface.

After the stable rust is formed, the corrosion rate of the steel material becomes extremely low, so that the upper layer can be further coated with a colored coating. The effect of extending the life of the colored coating film can also be expected as compared with the case of coating with.

The steel material to be coated with the present coating material is not particularly limited in steel type, and may be a common steel, a low alloy steel such as a weather-resistant steel, or a material that generates so-called rust. It does not matter.

Even if some external force acts on the protective rust layer thus generated and cracks are generated or peeled off, if chromium sulfate remains in the coating film of the healthy part, the rust layer is soundly damaged at the damaged part. Needless to say, there is a supply of chromium sulfate from the part, and the self-healing performance of generating the weather-resistant stable rust again can be expected.

[0025]

EXAMPLES The chemical compositions of the two kinds of test steels used in the examples of the present invention are shown in Table 1, and the two kinds of pretreatment methods for steel materials are shown in Table 2. Table 3 shows various base resin compositions used for the paint.
The dimensions of the test piece were 150 × 70 × 3.2 mm.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

Tables 4 and 5 show the preparation conditions and test results of the samples.

[0030]

[Table 4]

[0031]

[Table 5]

In preparing the sample, a coating material having a viscosity (measured by a B-type viscometer) of 200 to 1000 CPS was prepared by adding an appropriate amount of a solvent to the resin / additive compounding composition shown in Tables 4 and 5, and air was prepared. Coated by spray painting. This sample test piece is placed horizontally and the raw powder of artificial seawater is 1 m.
Under the same conditions of spraying on the upper surface of the test piece every day so as to obtain g / dm ² , it was exposed to the coastal area of Naoetsu City, Niigata Prefecture, 100 m from the coast, for one year.

At the time of evaluation, the residual film and rust were removed, the weight was measured, and the corrosion weight was measured by subtracting from the previously measured weight of the steel material before coating. In Tables 4 and 5, the average corrosion weight loss on one side, which is half the measured corrosion weight loss, is shown. Further, for the sample after exposure, the cross section of the generated rust was subjected to structural analysis by Raman spectroscopy and elemental analysis in rust was performed to confirm the presence or absence of a chromium goethite layer.

As a result, in Examples 1 to 23, generation of flowing rust was not recognized, corrosion loss was small, and it was recognized that weather-resistant stable rust was formed on the base steel surface portion. In particular, Examples 15 to 2 were compared with those using chromium sulfate alone.
The combination of copper sulfate and nickel sulfate etc. in 3,
Due to the synergistic effect, corrosion weight loss tends to be low. As can be seen in Examples 8, 20 to 23, a sufficient effect was also observed when the composition was applied after forming the rust layer.

On the other hand, as shown in Comparative Examples 24 to 35, when the addition amount of chromium sulfate is out of the appropriate range, the formation of weather-resistant stable rust is insufficient and the corrosion weight loss is large.

[0036]

As described above, the organic resin paint according to the present invention containing 1% by mass or more and less than 15% by mass of chromium sulfate,
By coating and drying this on steel, it is possible to quickly form a weather-resistant stable rust layer on the steel surface without causing floating or flowing rust such as red rust and yellow rust even in severe atmospheric corrosion environments. Excellent corrosion resistance can be ensured. It is a very useful treating agent because it exerts its effects even in the sea salt particle flying environment near the coast, which is a particularly severe corrosive environment.

When this paint is applied to steel for civil engineering or building structures, it is possible to form weatherable and stable rust at an early stage without floating or flowing rust such as red rust and yellow rust. It is expected that maintenance related to anticorrosion will be unnecessary, and will greatly contribute to the enhancement of social capital.

────────────────────────────────────────────────── (5) References JP-A-8-13158 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86 B05D 7 / 14

Claims (2)

(57) [Claims] 1. A chromium coating applied to the surface of a steel material or a rust layer.
Chromium sulfate is one of the essential components for forming the goethite layer.
Not less than 15% by mass and containing aluminum sulfate
A surface treatment agent for steel materials, which is an organic resin paint . 2. A method for coating a steel material on a surface or a rust layer,
Chromium sulfate as an essential component to form
1 mass% or more and less than 15 mass%, containing aluminum sulfate
A surface-treated steel material characterized by being coated with an organic resin paint not containing .