JPH0621273B2 - Rust-stabilized surface treatment method for weathering steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention suppresses reddish brown rust and flaky red rust that occur when weathering steel is used in the atmosphere, and at the same time prevents rusting on the weathering steel surface. TECHNICAL FIELD The present invention relates to a rust stabilizing treatment method for weather-resistant steel for promoting the formation of a film (referred to as stable rust) having properties.

[Conventional technology]

Weather-resistant steel reduces P, Cu,
A low-alloy steel with a small amount of alloy elements such as Cr, Ni, Si, and Mo added. This alloy steel is a film called stable rust that has a dense and protective surface when exposed to the naked air for a long period of time. To prevent corrosion of the steel itself. Therefore, in recent years, the use of weather resistant steel has been expanded as a maintenance-free material for buildings or structures.

The above-mentioned stable rust is generated by the action of the above-mentioned alloying elements contained in the weather-resistant steel, thereby producing a product which imparts special corrosion resistance which is amorphized inside the formed red rust. It is formed. This red rust has a composition in which the above-mentioned alloying elements are concentrated in rust composed of oxides of Fe ³⁺ and Fe ²⁺ .

There is also a problem with weather resistant steels having such characteristics. For example, during the initial stage until the formation of the above stable rust, usually 1 to 3 years, remarkable reddish brown rust juice and flaky peelable rust (floating rust) are generated, which may contaminate passersby or However, it has the drawback that it can contaminate the surfaces of buildings and structures, and that it is difficult to form stable rust in places where the environment is bad.

Therefore, as a means to protect from the above-mentioned undesired floating rust formation and corrosion until the stable rust formation of structures and buildings made of weather resistant steel, means such as spin coating and lining were taken. Since these methods depend on the corrosion resistance of the surface coating formed by them, protect the steel underneath when these coatings are destroyed or scratched. Cannot be repaired and repair is required.

As an alternative to the above-mentioned method, there is known a method in which a weather-resistant steel is subjected to a chemical conversion treatment, and further, a Rucker coating and other various organic coatings are formed on the weather resistant steel. Since chemical treatment is required, workability at the site is difficult, high-speed treatment is problematic, and it is economically disadvantageous.

Therefore, a method for stabilizing the rust itself of the weather resistant steel, that is, a rust stabilizing treatment method has been proposed (for example, Japanese Patent Publication No. 53-225).
No. 30, JP-B-56-33991, JP-B-58-17
833, Japanese Patent Publication No. 58-39915). These methods are methods in which the weather-resistant steel is applied with a treatment liquid whose main component is butyral resin containing iron oxide, various metal simple substances and metal compounds, phosphoric acid and the like. These methods are methods which, once applied to the surface of the weather resistant steel, can prevent initial floating rust, shorten the period for forming stable rust, and require almost no subsequent maintenance.

[Problems to be solved by the invention]

However, even with the rust stabilization treatment method described above, it is possible to sufficiently prevent the formation of floating rust and rust liquor in a place where the corrosive environment is severe, such as a floodgate, bridge, or marine structure where there is constant dew condensation. It turns out that there are things I can't do.

Therefore, the present invention is an improvement of the above-mentioned rust-stabilized surface treatment method, that is, even under a severe corrosive environment, the adhesion to the surface of the weather-resistant steel is excellent in one treatment, and the stable rust-forming property is good and dense. It is another object of the present invention to provide a method capable of economically forming a surface coating excellent in weather resistance.

[Means for solving problems]

The present invention is 0.1-10 wt% of one or more compounds of P, Cu, Cr, Ni, Si and Mo, 1-20 wt% of Fe ₂ O ₃ + Fe _3.
Rust stability of weather resistant steel coated with a coating solution containing O ₄ , 0.1 to 10% by weight of phosphoric acid and 10 to 40% by weight of bisphenol-based epoxy resin, the remainder being a solvent and a coating auxiliary agent. Surface treatment method.

The present invention further uses a coating liquid containing 0.1 to 2% by weight of one or more of a chelating agent and a coupling agent.

The compounds of P, Cu, Cr, Ni, Si and Mo used in the present invention include, for example, oxides, hydroxides, carbonates and phosphates, which may be used in the form of one kind or a mixture of two or more kinds. Can be used. Halogen compounds such as chlorides and sulfates are not preferable because they accelerate corrosion of the weather resistant steel and accelerate deterioration of the coating film for treatment. The addition range of these metal compounds is set to 0.1 to 10% by weight if the amount is less than 0.1% by weight, the rust stabilizing effect described below is not exhibited, and
Even if it exceeds 0% by weight, there is no change in the time until fine stable rust is formed, and accordingly, there is no effect of adding more than 10% by weight.

The range of addition of the mixture of Fe ₂ O ₃ and Fe ₃ O ₄ used in the present invention is from 1 to
The amount of 20% by weight is not preferable because if it is less than 1% by weight, the effects described later cannot be obtained, and if it exceeds 20% by weight, the coating film becomes brittle and may cause peeling. The mixing ratio of Fe ₂ O ₃ and Fe ₃ O ₄ may be arbitrary.

As the phosphoric acid used in the present invention, various forms of phosphoric acid such as metaphosphoric acid, pyrophosphoric acid, orthophosphoric acid, triphosphoric acid and tetraphosphoric acid can be used. These are used in the range of 0.1 to 10% by weight. If it is less than 0.1% by weight, the function and effect described later cannot be obtained, and if it exceeds 10% by weight, the coating film becomes sticky and the adhesion to weather resistant steel is adversely affected, which is not preferable.

The bisphenol-based epoxy resin used in the present invention is generally a repeating unit represented by the following general formula. Consisting of two or more epoxy groups in the molecule, the molecular weight is 5,000 to 200,000, and the hydroxyl group content is about 0.3.
It is preferably 5 equivalents / 100 g. Molecular weight 5000
If it is less than this, a tough coating film cannot be generally obtained, which is not preferable. If the molecular weight exceeds 200,000, the coating film becomes brittle and cracks easily occur, which is not preferable. Such epoxy resins are available on the market, for example, PKHH (registered trademark) manufactured by Union Carbide and Carbon Corporation, Epicoat (registered trademark) manufactured by Ciel Chemical Co., Ltd., Epicron (registered trademark) manufactured by Dainippon Ink and Chemicals, Inc. ). These resins are used in the range of 10-40% by weight. If it is less than 10% by weight, the coating film performance is deteriorated and the desired coating film performance cannot be obtained.
If it exceeds, the formation of stable rust of the weather resistant steel is delayed, which is not preferable.

The coating liquid used in the present invention is formed by completely or partially dissolving each of the above-mentioned components in a suitable solvent. Solvents that can be used include diacetone alcohol, acetone, toluene, methyl ethyl ketone, cyclohexanone, cellosolve acetate and the like, and these are used alone or in the form of a mixture.

In the present invention, a chelating agent and a coupling agent may be further contained. As the chelating agent, tannic acid, phytic acid or the like can be used, and as the coupling agent, a titanate coupling agent or a silane coupling agent can be used.
These can be used alone or as a mixture of both. These are generally used in the range of 0.1 to 2% by weight. If it is less than 0.1% by weight, the adhesion of the coating film to the surface of the weather-resistant steel cannot be improved, and the significance of its use is lost, and it is possible to use it in excess of 2% by weight. It is uneconomical because no further improvement in the adhesion of the treated film can be obtained.

The coating liquid used in the present invention may contain a coating auxiliary agent in addition to the above-mentioned components. As such paint auxiliary agents, auxiliary agents usually used for paints such as color pigments, rust preventive pigments and sedimentation preventing agents can be added. These may be appropriately selected and used as necessary. As the color pigment, for example,
In order to make the coating film have a color similar to that of natural stable rust of weather resistant steel, for example, carbon black or graphite can be used, and chromate, phosphate or molybdate pigments can be used as the rust preventive pigment. The use of such a rust preventive pigment is preferable because it can gradually cause dense and stable rust of the weather resistant steel over a long period of time. When using the color pigment and the rust preventive pigment, it is preferable to use them in the range of 0.1 to 10% by weight. 0.
If it is less than 1% by weight, these effects cannot be sufficiently achieved.
If it exceeds 0% by weight, the properties of the coating film become brittle and deteriorate, which is not preferable.

[Action]

When the coating solution according to the present invention is applied to the surface of the weather-resistant steel according to the method of the present invention, it causes etching on the steel surface and chemical bonding with the steel to form a treated film firmly adhered thereto. At this time phosphoric acid and when added, the rust preventive pigment changes the Fe ²⁺ ion eluted from the steel into a sparingly soluble Fe compound and Fe ³⁺ to prevent rust contamination, and at the same time phosphoric acid and the metal compound used in the present invention. As a result, Fe ³⁺ ions formed on the steel surface are converted into amorphous rust to promote the formation of stable rust. Further, when the weather-resistant steel is treated and processed according to the present invention, when the black scale and rust that may be formed during the previous hot rolling are not completely removed on the surface thereof, the chelating agent and / or the chelating agent according to the present invention and / or When a coupling agent is added, these can chemically bond the coating-treated film-rust-steel surface to compensate for the deterioration of the adhesive strength, and to produce strong adhesion.

In addition, the bisphenol-based epoxy resin used in the present invention is a resin which itself has excellent adhesiveness to hydrogen bond with the steel surface, and also has excellent corrosion resistance, chemical resistance, and dryness, and is a relatively thick film. Can be formed.

The above-mentioned metal compound desired in the present invention is dissolved in a trace amount by phosphoric acid in the coating film and is retained in the form of ions. Unfavorably, for example, in an environment where acid rain shakes, it gradually dissolves under a coating film for a long period of time and becomes a metal ion, and Fe ions are amorphous together with alloy elements eluted from the weathering steel itself. Change to stable rust of quality. Therefore, it is advisable to separate phosphoric acid from other components and mix it with the coating solution before use.

In addition, Fe ₂ O ₃ + Fe ₃ O ₄ prevents or reduces the diffusion of moisture in the air, especially rain, and oxygen in the coating film, and the color and properties of the film are stable, similar to natural stable rust. Has the effect of rusting.

Phosphoric acid also improves the adhesion of the treated film and prevents red rust contamination, accelerates the amorphizing action of the rust formed, and promotes the formation of stable rust.

As described above, the bisphenol-based epoxy resin forms a relatively thick film, but also has a function as a color-developing agent that holds other additive components thinly and uniformly on the surface of the weather resistant steel.

〔Example〕

 The present invention will be specifically described below with reference to examples.

Examples 1 to 15 Liquid A was prepared by mixing the components shown in Table 1 below. In the production of solution A, first, a bisphenol epoxy resin is mixed with a solvent and well stirred and dissolved, and this is put into a ball mill and mixed with other components, and mixed until the particle size of the dispersion becomes 20 μ or less. , Dispersed. The numerical values shown in Table 1 are parts by weight.

Separately from the solution A, 20 parts by weight of orthophosphoric acid and 80 parts of acetone are used.
By mixing parts by weight with stirring, solution B was prepared.

Immediately before use, liquids A and B were mixed at the ratios shown below, and each mixed liquid was applied to the weather-resistant steel by air spraying to a dry film thickness of 25μ, and dried indoors for 7 days. And it was used for the test.

In Example 9, the ratio of A liquid / B liquid was 80/20, and in all the other examples, the ratio of A liquid / B liquid was 90/10.

For comparison, in Comparative Example 1, a commercially available long exposure type wash primer was used and similarly coated, and in Comparative Example 2, a commercially available weather resistant steel rust stabilizing agent was used. The primer of Comparative Example 1 is manufactured by Shinto Paint Co., Ltd. in which a base consisting of butyral resin, phenol resin, zinc chromate ZTO, color pigment, solvent and additive is mixed with an acid solution consisting of phosphoric acid, solvent and water. The trade name of Comparative Example 2 is butyral resin, phenol resin, Fe ₂ O.
₃ + Fe ₃ O ₄ , zinc chromate ZTO, color pigment, solvent, additive base, and phosphoric acid, solvent, acid solution consisting of water, mixed and used by Shinto Paint Co., Ltd. (Lascol N primer) And is a treating agent having the composition of JP-B-53-22530.

A salt spray test (JIS K 5400) was carried out on weatherproof rust samples formed with coating films according to the above-mentioned respective examples and comparative examples.
7.8), water resistance test (JIS K 5400 7.
2) 4-month atmospheric exposure test (JIS K 5400 9.
4 (3)). Scratch was included in the exposure test sample. The test results are shown in Table 2 below. In the table, ◎ indicates no abnormality, ○ indicates slight rusting, Indicates a little point rust, and △ indicates a large point rust. For the primary adhesion, a dry film thickness of 25 μ was applied to weather-resistant steel, dried for 7 days, and then a crevice test was conducted at 2 mm intervals. Regarding the secondary adhesion, after a salt spray test and a water resistance test, the sample was left indoors for 1 day, and after 4 months of an exposure test, a crepe test at 2 mm intervals was performed.

As is clear from the data in Table 2 above, the weathering steel treated by the method of the present invention is superior in appearance and adhesion in each test as compared with the conventional Comparative Examples 1 and 2.

Further, the weather-resistant steel treated with the treatment liquid of Example 1 and Comparative Examples 1 and 2 was subjected to an exposure test for 3 years on a raft floated on the sea surface of Fukae Bay in Kobe City. As a result, as shown in Table 3, Example 1 Good stable rust was formed on the weather resistant steel of Comparative Examples 1 and 2.
No good stable rust was formed on the weathering steel of No.

[Effects of the Invention] According to the method of the present invention, when various kinds of structures, such as bridges, towers, sluices, vehicles, buildings, and marine structures are made of weather-resistant steel, the conventional rust stabilization treatment method can be applied. Compared to,
It has excellent rust resistance even in the presence of water and salt, and can form stable rust after a long period of time.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-59-56459 (JP, A) JP-A-58-15570 (JP, A) JP-B-58-39915 (JP, B2) JP-B-53- 22530 (JP, B2) JP 58-17833 (JP, B2) JP 56-33991 (JP, B2)

Claims (4)

[Claims] 1. 0.1 to 10% by weight of P, Cu, Cr, Ni, Si
And one or more compounds of Mo, 1 to 20% by weight of Fe ₂ O ₃
+ Fe ₃ O ₄ , 0.1 to 10% by weight of phosphoric acid, 10 to 40% by weight of a bisphenol-based epoxy resin, and the balance being a coating solution comprising a solvent and a coating auxiliary agent. Method for rust stabilizing surface treatment of weather resistant steel. 2. The coating auxiliary agent is a rust preventive pigment, and is 0.1 to 1.
A method according to claim 1 in an amount of 0% by weight. 3. 0.1 to 10% by weight of P, Cu, Cr, Ni, Si
And one or more compounds of Mo, 1 to 20% by weight of Fe ₂ O ₃
+ Fe ₃ O ₄ , 0.1 to 10% by weight of phosphoric acid, 10 to 40% by weight of bisphenol epoxy resin, 0.1 to 2% by weight of at least one chelating agent and coupling agent, and the balance. A rust-stabilized surface treatment method for weather-resistant steel, characterized in that a coating solution consisting of a solvent and a coating auxiliary agent is applied. 4. The coating auxiliary agent is a rust preventive pigment, and is 0.1 to 1.
A method according to claim 3 in an amount of 0% by weight.