JP2008261019A - Surface-treated weatherproof steel material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-treated weatherproof steel material which has a coating film with sufficient durability equivalent to that treated by using hexavalent chromium, even if using no hexavalent chromium and the like having high environmental load, and which is economical and superior in weather resistance. <P>SOLUTION: The surface-treated weatherproof steel material is covered with at least a coating film formed on the steel material surface of the weatherproof steel, wherein the coating film includes a polyvinylbutylal resin forming a complex with vanadic acid and phosphoric acid, a resin compatible with the polyvinylbutylal resin, Fe<SB>2</SB>O<SB>3</SB>and Fe<SB>3</SB>O<SB>4</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to the field of using weathering steel materials used for bridges, various buildings, and the like, and relates to a surface-treated weathering steel material having excellent weather resistance in consideration of environmental load.

  Weatherproof steel is a low alloy steel containing a small amount of elements such as Cu, Ni, Cr, P, Mo, etc., and protects the surface of the weatherproof steel from permeating corrosion factors in the process of corrosive in the atmosphere. A strong rust layer is formed. Since the corrosion rate of the weather-resistant steel on which protective rust is formed has a characteristic that the corrosion rate is remarkably reduced, in recent years, it has attracted attention as a material that suppresses the life cycle cost of the structure.

  Weatherproof steel is used as structures such as bridges and steel towers, but there is a problem that the flow rust generated before protective rust is generated contaminates the surroundings. Then, the technique which performs the surface treatment called a rust stabilization process on the surface of steel-resistant steel, and solves said problem is disclosed.

  For example, in Patent Document 1, weather resistance of a polyvinyl butyral resin containing a simple substance or one or more compounds of iron pigment, phosphoric acid, Pb, Ni, Cu, P, Zn, and Cr, and a resin compatible with the polyvinyl butyral resin. Techniques applied to the surface of steel have been proposed, whereby the initial flow rust has been reduced to about 1/10 of the untreated exposed material.

  Further, for example, Patent Document 2 proposes a surface treatment method for weathering steel in which a rust stabilization treatment mainly including a polyvinyl butyral resin is performed and a resin having a good weather resistance is applied thereon. According to this, initial flow rust is suppressed, and protective rust can be formed even in a place where the corrosive environment is severe.

  Further, for example, in Patent Document 3, a rust preventive pigment (eg, zinc chromate, etc.), a Cu or Cu-containing compound (eg, cuprous oxide, etc.) and / or a P-containing compound, chlorinated polyolefin, amine or polyamide curable type There has been proposed a method of applying a surface treatment paint having at least one room temperature curable resin such as an epoxy resin and an isocyanate curable acrylic as an essential component.

  The surface treatment technology related to these weathering steels has been applied for more than 20 years, but they all use hexavalent chromium anticorrosive pigments to suppress initial rust and to prevent flow rust. Therefore, it is desired not to use substances with high environmental impact such as hexavalent chromium.

  In such a case, for example, in Patent Document 4, an alkaline earth metal vanadate, a phosphate ester, a polyvinyl butyral resin, a resin having compatibility with the polyvinyl butyral resin, and the like are combined to reduce environmental impact such as hexavalent chromium. A surface treatment agent for weathering steel that does not use high substances, a surface treatment method for weathering steel, and a surface treatment weathering steel excellent in weather resistance are disclosed.

Japanese Patent Publication No.53-22530 Japanese Patent Publication No. 56-33991 Japanese Examined Patent Publication No. 62-58635 JP 2004-204273 A

  However, although the surface treatment described in Patent Document 4 contains many components, it cannot be said that the durability of the coating film is sufficient as compared with the treatment using hexavalent chromium.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and to maintain the durability of the film to the same extent as the treatment using hexavalent chromium without using a material with high environmental impact such as hexavalent chromium. An object of the present invention is to provide a surface-treated weathering steel material that is economical, economical and excellent in weather resistance.

  As a result of intensive studies aimed at achieving the above object, the present inventors have found that the function of a hexavalent chromium-based rust preventive pigment having a high environmental load can be achieved by a coating film structure formed by a specific component composition. The present invention has been completed which exhibits an action equivalent to or better than that of the present invention.

That is, the gist of the present invention is as follows.
(1) A polyvinyl butyral resin complexed with a vanadium compound and a phosphorus compound in contact with a steel material surface of weathering steel, a resin compatible with the polyvinyl butyral resin, and one of Fe ₂ O _{3 and} Fe ₃ O ₄ A surface-treated weathering steel having at least a coating film containing both.

(2) The surface-treated weathering steel material according to (1), wherein the vanadium compound is one or more selected from vanadic acid or vanadate.

(3) The surface-treated weathering steel according to (2), wherein the vanadate is a vanadate excluding ammonium vanadate and an alkali metal salt of vanadate.

(4) The surface-treated weathering steel material according to (1), wherein the phosphorus compound is phosphoric acid.

(5) The surface-treated weathering steel material according to (4), wherein the phosphoric acid is orthophosphoric acid.

(6) The infrared absorption spectrum of the polyvinyl butyral resin and the resin compatible with the polyvinyl butyral resin has two absorption peaks between 1850 cm ^{−1 and} 1550 cm ⁻¹ , and the absorption on the low wave number side The surface-treated weathering steel material according to (1), wherein the peak is larger than the absorption peak on the high wave number side.

(7) The surface-treated weathering steel material according to (1), which has a film containing an acrylic resin as a main component on the upper layer of the coating film.

  When the surface-treated weathering steel of the present invention is applied as a steel used for bridges, buildings, etc., it can reduce the environmental load and stably form a highly protective rust layer. Instead, it has an extremely high industrial value effect that greatly helps to preserve social capital.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  Conventionally, it is considered that when a chromic acid compound and phosphoric acid are added to a polyvinyl butyral resin, they form a complex and thereby provide excellent coating strength and water resistance.

  The surface-treated weathering steel material of the present invention is covered with a resin in which a polyvinyl butyral resin forms a complex with a vanadium compound and a phosphorus compound in the first layer above the surface of the steel material.

As a result of examining various substances and conditions regarding whether or not a polyvinyl butyral resin can be complexed instead of a chromic acid compound, the present inventor has determined that a specific ratio of phosphoric acid and vanadate to the polyvinyl butyral resin. It was clarified that the water resistance durability of the coating film can be improved by forming a complex by adding in the above. That is, resin formed vanadate and phosphate and complex, by the resin measuring infrared absorption spectrum ^(IR), the two transmission peaks at 1850cm ^-1 ~1550cm -1, was complexed It can be distinguished by a peak having a large transmittance on the low wave number side.

  That is, it is considered that the keto type is relatively decreased and the enol type having a high complex-forming ability is increased due to the intensity change of these absorption peaks. Phosphoric acid and vanadate are essential for the formation of the complex, but salts that are relatively soluble in water, such as lithium salt, sodium salt, potassium salt, rubidium salt, cesium salt, and ammonium salt, are polyvinyl butyral and phosphorus. Although it forms a complex with an acid, it is unsuitable because it adversely affects water-resistant adhesion. Therefore, as the vanadate, magnesium vanadate, calcium vanadate, strontium vanadate, barium vanadate, tin vanadate, europium vanadate, gadolinium vanadate, lanthanum vanadate, yttrium vanadate, and the like are preferable.

  It is preferable that the addition amount of vanadate is 5-30 mass% with respect to the resin solid content mass compatible with polyvinyl butyral resin and polyvinyl butyral resin. When the amount is less than 5% by mass, the effect of vanadate is small, and the improvement in water resistance is reduced. On the other hand, if it exceeds 30% by mass, the effect is almost saturated, which is not economical.

  The ratio of the phosphorus element mass to the vanadium element mass is preferably 20 to 150%. If it is less than 20%, the effect of liberating vanadate to form a complex is lowered, and if it exceeds 150%, the coating film increases in viscosity and water resistance is lowered.

  The phosphoric acid compound needs to be dissolved in the processing solution solvent, and orthophosphoric acid, metaphosphoric acid, polyphosphoric acid, and the like can be used. Among these, phosphorus compounds that have the best stability during storage of orthophosphoric acid and are difficult to dissolve in a solvent are not preferred because they have little effect of complex formation.

  Moreover, when adjusting a process liquid, for the storage stability of a process liquid, the solution containing polyvinyl butyral resin and the solution containing phosphoric acid are kept separate, and it mixes and uses when apply | coating to a steel plate. However, it is preferable that a vanadate is mixed on the solution side containing phosphoric acid because a complex is easily formed.

  As a resin that is compatible with the polyvinyl butyral resin, a resin such as melamine or phenol is used. By controlling the amount added, the permeation of moisture can be controlled. The amount to be added is preferably about 1 to 10% by mass relative to the mass% of the polyvinyl butyral resin. If it is less than 1% by mass, there is no effect of modification. Conversely, if it exceeds 10% by mass, the complex formation ratio between the polyvinyl butyral resin, vanadic acid and phosphoric acid is lowered, so that the strength of the coating film may be lowered. is there.

Further, Fe ₂ O ₃ and Fe ₃ O ₄ are added to the polyvinyl butyral resin. These aid the formation of protective rust by oxidizing iron ions from the steel by the effect of matching the rust appearance of the weather resistant steel and the self-reducing action of the iron oxide. It is preferable to add 5 to 20% by mass of Fe ₂ O _{3 and} 50 to 150% by mass of Fe ₃ O _{4 with} respect to the resin solid mass. Moreover, since the swelling of the coating film due to rust expansion is reduced by setting the pigment volume concentration (PVC) in the coating film to 40% or more together with the pigment described later, the amount of moisture permeation to the steel surface is also appropriate. It is necessary to make a proper amount.

  In addition, when it is desired to improve the salt resistance, adding one or more rust preventive pigments such as metasilicate, phosphite, aluminum phosphomolybdate, zinc phosphate, etc., while maintaining water-resistant adhesion It works to improve anticorrosion. That is, phosphite acts as a reducing agent for rust prevention, and examples thereof include calcium phosphite, magnesium phosphite, zinc calcium phosphite, and strontium phosphite. Phosphoric acid or aluminum phosphomolybdate generates condensed phosphate ions, orthophosphate ions, molybdate ions, and forms a complex with iron ions on the surface of the steel material to act as rust prevention and adsorbs to the polyvinyl butyral resin film. Suppresses the transmission of multivalent ions. The total addition amount of these additives excluding vanadate and iron-based pigments is preferably in the range of 1 to 20% by mass relative to the mass of the solid resin having compatibility with the polyvinyl butyral resin and the polyvinyl butyral resin. If it is less than 1% by mass, the effects of water-resistant adhesion and corrosion resistance are not observed. If it exceeds 20% by mass, it is difficult to form a resin film, and the physical strength may be lowered to the extent that it is impractical. is there.

  In addition, coloring pigments such as titanium dioxide, carbon black, titanium yellow, and phthalocyanine green can be added by replacing talc, mica, barium sulfate, calcium carbonate as extender pigments with antirust pigments, It can be used to control oxygen permeability.

  The film thickness of the first layer of the surface-treated weathering steel material of the present invention is preferably in the range of 10 to 100 μm. If the thickness is less than 10 μm, the unevenness of the steel material cannot be covered uniformly, and it becomes difficult to obtain a uniform film exhibiting the function. Even if the thickness is increased, the effect is saturated and the cost is increased, which is not preferable.

  Furthermore, in the surface-treated weathering steel material on which the second layer resin film is formed, the thickness of the weathering resin film is preferably in the range of 30 to 150 μm. If the thickness is less than 30 μm, it is insufficient to hide the base, and if the thickness is too thick, the effect is saturated.

  In order to form a second layer resin film having weather resistance, paints having excellent weather resistance and corrosion resistance such as silicon alkyd resin, chlorinated rubber resin, acrylic resin, epoxy resin, tar epoxy resin, polyurethane resin paint, etc. Can be used. Of these resins, acrylic resins that are resistant to photodegradation and the like and have a good long-term landscape are particularly preferred. A resin film formed from these resin-based paints has good adhesion to a resin film mainly composed of polyvinyl butyral resin and has a high environmental barrier effect. For these resin-based paints, raw materials used in general paints such as color pigments, extender pigments, various additives, etc. can be used. Therefore, the pigment volume ratio in the resin is preferably 50% or more.

  The surface-treated weathering steel material of the present invention is prepared by removing the scale of the surface of the weathering steel material with a power tool, sand blasting, shot blasting, etc., adjusting the surface, and then applying the processing material containing the above components and drying. Form a film. The level of surface adjustment is preferably St2 or higher for power tools and SIS Sa2 or higher for blasting. The treatment agent can be applied by brushing, air spraying, airless spraying, etc., as in the case of normal paints, and dried by heating to room temperature or up to 200 ° C. to form a film.

  The weather-resistant steel material is not particularly limited as long as it is a low alloy steel containing Cu, Ni, Cr, P, Mo and the like. Based on the treatment method for obtaining the surface-treated weathering steel material of the present invention, when the surface treatment agent is applied to the weathering steel, the surface treatment may be performed at the steel plate stage, and the steel plate is cut, processed, and assembled into product shapes and dimensions. The surface treatment may be performed at the finished stage, or the surface treatment may be performed after the product is installed at the final installation place, and the construction stage can be selected in consideration of cost, workability and the like.

  Hereinafter, the present invention will be specifically described based on examples.

  A weathering steel (JIS SMA 400AW) test piece (150 mm × 75 mm × 5 mm) was blasted, and a treatment liquid having the composition shown in Table 1 was applied to a predetermined film thickness. As a pigment, an iron oxide pigment was added in an amount of 50% by mass relative to the resin solid mass. As resin, what added phenol resin by mass ratio 10: 1 to polyvinyl butyral resin as resin compatible with it was used.

The treatment liquid used in Examples and Comparative Examples was centrifuged, and a coating film was prepared from the resin liquid from which the pigment was separated, and each was subjected to FT-IR analysis, and an infrared absorption spectrum of 1850 cm ^{−1 to} 1550 cm ⁻¹ was obtained. investigated. Examples of infrared absorption spectra are shown in FIGS. The coating film having a large infrared absorption spectrum on the low wave number side was described as “◯” in Table 1.

  The evaluation method is 200 cycles of combined cycle test (CCT) (test condition (1 cycle): 30 ° C., 5% NaCl aqueous solution spray, 0.5 hour → 30 ° C., 95% RH, 1.5 hour → 50 ° C., 20 % RH, 2 hours → 30 ° C., 20% RH, 2 hours) and the discoloration of the coating film due to rust after each of the one-year exposure tests in the countryside of Kimitsu City was evaluated.

  As the evaluation criteria, in the case of CCT, ◎: no bulge, ○: partial bulge, △: small bulge, ×: bulge in the order of exposure test, ◎: no discoloration, ○ Evaluation was made in the order of: slight discoloration, Δ: some discoloration, x: clear discoloration.

  As shown in Table 1, the results show that the formation of a complex of polyvinyl butyral resin, vanadic acid, and phosphoric acid is good for the swelling of the coating film, except for alkali metals and ammonium salts that are highly soluble in water. It can be seen that the corrosion resistance and protective rust formation when using this vanadate is equivalent to that using a conventional hexavalent chromium-based rust preventive pigment and is particularly good.

  Next, a test piece was prepared by forming a weather-resistant coating film on the steel materials of Example 1 and Comparative Example 1 using the top coating composition shown in Table 2. A weathering acceleration test using a sunshine weather meter was performed for 5000 hours and a corrosion resistance test using a CCT cycle test (200 cycles). CCT was evaluated by the presence or absence of blistering, and the weather resistance promotion test was evaluated in the order of ◎: no discoloration, ◯: slight discoloration, Δ: some discoloration, ×: clear discoloration. The results are shown in Table 2. It can be seen that by providing a weather-resistant resin on the top, it is possible to maintain a beautiful appearance for a long time and to contribute to improvement of durability. In particular, it can be seen that discoloration can be significantly suppressed by providing an acrylic resin in the upper layer.

  As mentioned above, although preferred embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is a figure which shows the infrared absorption spectrum of the epoxy resin layer of Example 1. It is a figure which shows the infrared absorption spectrum of the epoxy resin layer of the comparative example 1.

Claims (7)

A polyvinyl butyral resin complexed with a vanadium compound and a phosphorus compound in contact with the steel material surface of the weathering steel, a resin compatible with the polyvinyl butyral resin, and one or both of Fe ₂ O _{3 and} Fe ₃ O ₄ ; A surface-treated weathering steel material having at least a coating film containing   The surface-treated weathering steel according to claim 1, wherein the vanadium compound is at least one selected from vanadic acid and vanadate.   The surface-treated weathering steel according to claim 2, wherein the vanadate is a vanadate excluding an ammonium salt of vanadic acid and an alkali metal salt of vanadic acid.   2. The surface-treated weathering steel according to claim 1, wherein the phosphorus compound is phosphoric acid.   The surface-treated weathering steel according to claim 4, wherein the phosphoric acid is orthophosphoric acid. The infrared absorption spectrum of the polyvinyl butyral resin and the resin compatible with the polyvinyl butyral resin has two absorption peaks between 1850 cm ^{−1 and} 1550 cm ⁻¹ , and the absorption peak on the low wave number side is a high wave. 2. The surface-treated weathering steel according to claim 1, wherein the surface-treated weathering steel is larger than the absorption peak on the several side.   2. The surface-treated weathering steel according to claim 1, wherein the surface-treated weathering steel has an acrylic resin as a main component on the upper layer of the coating film.

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