JP5946358B2 - Method for producing hexavalent chromium-free organic coated steel - Google Patents

Description

The present invention is suitable for surface treatment of the organic coating of organic coating steel, a method for manufacturing an organic coating steel surface-treated with high processing solution in corrosion resistance and adhesion free of hexavalent chromium.

The present invention is particularly, on the surface of the steel material to be subjected to cathodic protection, the underlayer, underlayer in one layer or two layers or more underlying layer forming treatment liquid for forming a coating structure of the steel material coated in the order of the organic resin layer processing method for producing a coated steel material which has been subjected to.

  The product life of automobiles and home appliances is about 15 years at the longest, whereas large steel structures such as harbor facilities (eg, steel pipe piles, sheet piles) and pipelines are more than 30 years durable and anticorrosive. It is necessary to ensure long-term quality and safety. For this reason, a thick film organic coating (heavy corrosion protection) with an organic polymer such as polyethylene or polypropylene is applied.

  Further, large steel structures such as harbor facilities and pipelines have been subjected to an anticorrosion method in order to prevent steel corrosion (hereinafter, this anticorrosion method is referred to as cathodic protection). Under the cathodic protection environment, the steel material is applied to -1.5 V (vs. SCE), and therefore the end portion of the organic coated steel material and the exposed steel material of the defective portion become a strong cathode, and the corrosion of the steel material is suppressed. On the other hand, since the interface between the organic coating and the steel material becomes a highly alkaline environment due to the cathode reaction, cathode peeling (cathode peeling) in which the organic coating peels off due to a decrease in the durability and adhesion between the organic coating and the steel material. It is known to do.

  In particular, since pipelines are laid under a very low temperature environment in the polar region or a severe day / night temperature difference environment in the desert region just below the equator, they are exposed to a severe cold cycle environment. It is known that organic coatings on the surface of steel and organic coatings peel off due to a decrease in adhesion at the interface between the organic coating and the steel due to the large difference in thermal expansion coefficient between the organic coating coated on the steel surface and the steel in a severe cold cycle environment. Yes.

  Chromate treatment is known as a base treatment for organic resin coating materials such as paints. The chromate treatment is a useful treatment method that exhibits excellent corrosion resistance and at the same time has an effect of improving the adhesion between the organic coating material and the steel material. Until now, the cathode peeling was suppressed by the chromate treatment, the high cooling durability was maintained, and the long-term quality was maintained. However, since the treatment liquid used for chromate treatment contains hexavalent chromium, which is considered to have a relatively high environmental impact, there is a possibility that the use of hexavalent chromium will be restricted in the future due to environmental regulations. There is a need to promote hexavalent chromium-free.

  In response to the request for hexavalent chromium-free, for example, as shown in Patent Documents 1 to 5 below, efforts are being made in industries such as automobiles and home appliances, and also in organic coated steel materials as shown in Patent Document 6. It's getting on.

  In Patent Document 1, at least a water-soluble polyvalent metal phosphate compound, a chelating agent, and a corrosion inhibitor are contained as constituents of a surface treatment solution for a zinc-based plated steel sheet. Disclosed is a treatment liquid for applying a coating on the surface of a galvanized steel sheet, followed by baking at a temperature of 50 ° C. to 200 ° C. to form a film on the surface of the galvanized steel sheet, and a method for producing the surface-treated steel material.

Patent Document 2 discloses a treatment liquid containing a zirconium carbonate complex ion, vanadyl ion (VO ²⁺ ), and oxycarboxylic acid, and has a solid content concentration of zirconium: 10 to 30%, vanadium: 5 to 20 %, Oxycarboxylic acid: 20-50%, dimercaptosuccinic acid: 0.01-1%, ammonium phosphate: 0.01-1% 200 to 1200 mg / m ^{2 as} a plated steel material, preferably 10 to 30% of zirconium compound as zirconium, 5 to 20% of vanadyl compound as vanadium, dimercaptosuccinic acid: 0.01 to 1 in the corrosion-resistant coating layer % Of plated steel is disclosed.

Patent Document 3 includes a resin comprising 90% by mass or less of a zirconyl cation component A, an anion component B selected from phosphate ions and hydroxyethylidene diphosphonate ions, and a cation component C selected from Mg and Ca. A film layer that can be contained, and satisfying (Equation 1) and (Equation 2), where A, B, and C are the total charges (mmol · m ⁻² ) of the components A, B, and C in the film, The ionic component in the film is substantially composed of components A, B, and C, and the film layer in which the film adhesion amount in terms of the total charge amount of the anion component B is in the range of 1 to 10 mmol · m ⁻² is zinc-based. Disclosed are a plated steel material and a surface treatment liquid formed on at least one surface of a plated steel sheet, and methods for producing the same:
(Formula 1) 0.49 ≦ A / B ≦ 1.3,
(Formula 2) 0.3 ≦ (A + C−B) /B≦0.3.

In Patent Document 4, a metal oxide film and / or a metal hydroxide film containing at least one of Si, Ti, Zr, V, Nb, Ta, P, and W is provided on at least one surface of a metal material. A surface-treated metal plate formed by cathodic electrolysis in a treatment bath mainly composed of a fluorometal compound, the metal oxide film and / or hydroxide film formed by the cathodic electrolysis Independent granular precipitates or granular precipitates in contact with each other, each having a major axis of 5 nm to 300 nm and 10 or more in 1 × 10 ⁻¹² m ² A surface-treated metal plate that is excellent in paint adhesion, characterized by being configured, is disclosed.

  In Patent Document 5, 0.01 to 100 g / L of a silane coupling agent and / or a hydrolysis condensate thereof as an essential component and 0 of water-dispersible silica (solid content) in 1 liter of a metal surface treatment solution. 0.05 to 100 g / L, 0.01 to 50 g / L of zirconium compound as zirconium ion and / or 0.01 to 50 g / L of titanium compound as titanium ion, and 0.01 to thiocarbonyl group-containing compound A non-chromate metal surface treatment liquid containing 0.1 to 100 g / L of water-soluble acrylic resin and -100 g / L, a coated steel material and a coated steel material treated with the surface treatment liquid, and a method for producing the same It is disclosed.

  In Patent Document 6, 0.001 to 1.0 mol / l ammonium molybdate, 0.001 to 0.05 mol / l silane coupling agent, or 0.001 to 0.05 mol / l on the steel surface. A method for producing a corrosion-resistant steel material having a corrosion-resistant coating excellent in adhesion durability, which is processed by contacting a mixed solution containing magnesium phosphate, is disclosed.

JP 2002-155375 A JP 2002-332574 A JP 2011-032576 A JP 2010-53424 A JP 2001-316845 A JP 2003-34881 A

  However, non-chromate (6) which can be applied to the surface treatment of organic coated steel materials for large steel structures such as line pipes exposed to harsh environments such as cathodic protection environment and cold cycle environment. (Chromium-free) surface treatment solution has not yet been developed.

  Patent Documents 1 to 6 propose chromate-substitute ground treatments for galvanized steel materials and painted steel materials or coated steel materials, and all use treatment liquids containing inorganic metal ions such as zirconium ions. It has long been known that the addition of a counter anion to an inorganic metal ion is important for improving functions such as solution stability of a treatment solution containing the inorganic metal ion and corrosion resistance of the formed film.

  In this regard, Patent Document 1 adds a chelating agent, Patent Document 2 adds oxycarboxylic acid or dimercaptosuccinic acid, and Patent Document 5 adds a thiocarbonyl group-containing compound. When an organic compound is added as a counter anion in this way, it contributes to the complex formation with metal ions in the aqueous solution and the stability of the film. And the adhesion of the coating at the coating / steel interface is reduced. Patent Document 4 proposes a treatment liquid mainly composed of a fluorometal compound, but fluoride ions may remain in the surface treatment film. Fluoride ions are useful ions for improving film adhesion by etching the surface when forming a liquid layer film. However, fluoride ions are highly corrosive, so if they remain in the film, The peeling of the covering material may be promoted.

  Galvanized steel sheets used for automobiles, home appliances, residential building materials, etc. have a zinc corrosion potential (−1.07 V (vs. SCE)) rather than an iron corrosion potential (−0.65 V (vs. SCE)). Since it is base, zinc on the steel plate is eluted as an anode, and iron becomes a cathode and is anticorrosive, so it has excellent corrosion resistance.

  The surface treatments disclosed in Patent Documents 1 to 3 are applied mainly for the purpose of imparting corrosion resistance to galvanized steel sheets such as automobiles, home appliances, and housing building materials. It is not applicable to large steel structures in cathodic protection environment with a potential of 1.5 V (vs. SCE). These surfaces have the problem of reducing the coating adhesion and adhesion durability at the coating / steel interface in a highly alkaline environment in the heavy anticorrosive substrate of the cathodic protection environment, and progressing the peeling of the coating. Further, even in a cold cycle environment, there is a problem that the adhesion durability at the coating / steel material interface is lowered and the peeling of the coating progresses.

  Although the surface treatments disclosed in Patent Documents 4 to 5 improve the corrosion resistance and adhesion of the coated steel sheet, as in the above, the coating / steel material in the highly alkaline environment in the heavy-duty anticorrosive substrate of the cathode environment of the organic coated steel material It reduces the adhesion and adhesion durability of the interface coating, and advances the peeling of the coating. Further, even in a cold cycle environment, the adhesion durability at the coating / steel material interface is lowered, and the coating is peeled off.

  Patent Document 6 discloses an anticorrosion steel material having an anticorrosion coating excellent in adhesion durability treated by contact with a mixed solution containing ammonium molybdate, a silane coupling agent, or further magnesium phosphate. However, in a cold and hot cycle environment, there is a concern that the adhesion durability of the coating at the coating / steel interface may be lowered and peeling may be advanced.

The present invention aims to provide a manufacturing method of non-chromate undercoat treated organic coating steel by non-chromate undercoating liquid that can be applied to surface treatment of the organic coating steel large steel structures such as harbor facilities and linepipe To do.

  As a result of intensive studies to achieve the above object, we have found a surface treatment solution that can form a ground layer with excellent solution stability, excellent corrosion resistance, adhesion to organic coating, and adhesion durability on the steel surface. It was.

  Specifically, the treatment liquid is an aqueous solution containing a zirconium compound, a vanadium compound, ammonium phosphate, and a silane coupling agent (or a hydrolysis condensate thereof) having a pH of 8 to 12.

Furthermore, when this treatment solution is applied to the surface treatment of an organic coated steel material to form a surface treatment layer mainly composed of insoluble zirconium oxide, it can be applied even in a highly alkaline aqueous solution in a cathodic protection environment or in a cold cycle environment. It was found that the adhesiveness with the organic coating formed on the surface was excellent. Its deposition amount of surface treatment layer is a metal Zr converted at 50 mg / m ² or more is less than 1500 mg / m ^2, organic coating steel, peeling of the organic coating on the cathode stripping and thermal cycle environment organic coating in cathodic protection environments It has also been found that the corrosion resistance is remarkably suppressed and excellent corrosion resistance is imparted to the steel material.

In one aspect, the surface of the steel material, in an aqueous solvent, a zirconium compound, vanadium compound, and ammonium phosphate, a silane coupling agent and / or is its hydrolytic condensate was dissolved, the pH8 to 12 formed from the underlying layer forming the treatment liquid consisting of a solution, a metal Zr converted at 50 mg / m ² or more, the adhesion amount of less than 1500 mg / m ² and the underlying layer, one or more layers of which are formed thereon An organic coated steel material excellent in corrosion resistance, adhesion, cathode peel resistance, and cold cycle durability, characterized by comprising an organic resin layer.

  In a preferred embodiment, the zirconium compound is one or two selected from ammonium zirconium carbonate and zirconyl ammonium carbonate, and / or the vanadium compound is ammonium vanadate.

  This organic coated steel can be subjected to, for example, cathodic protection and / or for line pipes.

The present invention is to form an underlayer comprising a solution having a pH of 8 or more and 12 or less in which a zirconium compound, a vanadium compound, ammonium phosphate, a silane coupling agent and / or a hydrolysis condensate thereof are dissolved in an aqueous solvent. after application of the use process liquid to the steel surface and dried, the metal Zr converted at 50 mg / ^{m 2} or more on the steel material surface, forming the base layer of the adhesion amount of less than 1500 mg / ^{m 2,} then the underlying layer A method for producing an organic coated steel material having excellent corrosion resistance, adhesion, cathode peel resistance, and thermal cycle durability, characterized in that one or more organic resin layers are formed thereon.
In a preferred embodiment, the zirconium compound is one or two selected from ammonium zirconium carbonate and zirconyl ammonium carbonate, and / or the vanadium compound is ammonium vanadate.
In a further preferred embodiment, the underlayer-forming treatment solution is 0.05% or more and less than 10.00% of zirconium zirconium carbonate (NH ₄ ) ₂ [Zr (CO ₃ ) as a zirconium compound in an aqueous solvent. ) ₂ (OH) ₂ ] and / or potassium zirconium carbonate (K ₂ [Zr (CO ₃ ) ₂ (OH) ₂ ]) and a vanadium compound, 0.004% or more and less than 0.400% in terms of V metal Ammonium vanadate (NH ₄ VO ₃ ), 0.07% or more and less than 7.50% ammonium phosphate (NH ₄ ) ₂ HPO ₄ ) in terms of PO ₄ , and 0 in terms of solid content concentration of the silane coupling agent A solution having a pH of 8 or more and 12 or less in which 1 or more and less than 10% of a silane coupling agent and / or a hydrolysis condensate thereof is dissolved ( _{However, (NH 4) 2 [Zr} (CO 3) 2 (OH) 2] or _{K 2 [Zr (CO 3)} 2 (OH) 2]) and _{(NH 4)} 2 HPO ₄₎ the net mass combined with When the value is A and (NH ₄ VO ₃ ) is C, the case where C / A is 0.15 or more is excluded. ), The total concentration of the components is 5 to 20%.

Organic coating steel with a surface treatment layer formed by using the processing solution, even though the underlayer does not contain hexavalent chromium, even in severe corrosive environments, cathodic protection environments and thermal cycling environment, the chromate treatment Excellent corrosion resistance, adhesion, cathode peeling durability, and cold cycle durability equivalent to or better.

  This organically coated steel is used in pipeline steel pipes, water and drinking water, chemical plants and food factories involved in the transportation of natural resources such as oil and natural gas, and methane gas by drilling methane hydrate that sleeps on the seabed and permafrost. It can be applied to applications such as piping, steel pipe piles in harbors, and steel sheet piles.

Matrix steel of the covering steel, steel (e.g., steel plate) is or may be, but the steel pipe is preferably located in such steel sheet piles, shaped steels, particularly steel product for a line pipe is preferred. Before forming the base layer using the treatment liquid of the present invention on the surface of the base steel material, it is preferable to increase the roughness of the steel material surface by shot blasting or sand blasting the steel material surface. The roughness of the steel surface is preferably Rzjis = 20 μm or more and 100 μm or less, and more preferably Rzjis = 30 μm or more and 80 μm or less. It is preferable to clean the blasting powder remaining on the steel surface after blasting by air or water washing.

Before the steel material surface is coated with one or more organic resin layers, the surface treatment is performed according to the present invention using the base layer forming treatment liquid. Underlayer forming treatment liquid in an aqueous solvent, a zirconium compound, vanadium compound, ammonium phosphate, including silane coupling agent and / or a hydrolysis condensate thereof as an essential component, pH is 8 or more 12 The following solution. The components of this treatment liquid will be described in order below. In addition, 1 type, or 2 or more types can be used for each component. In the following description,% related to the composition of the treatment liquid is mass%.

  The zirconium compound used in the treatment liquid is a water-soluble zirconium compound and may be either an inorganic compound or an organic compound. Specific examples include ammonium zirconium carbonate, zirconium zirconium carbonate, basic zirconium carbonate, zirconium acetate, zirconium nitrate, potassium zirconium carbonate, zircon hydrofluoric acid, ammonium zircon fluoride, potassium zircon fluoride, sodium zircon fluoride, zirconium acetylacetonate, Examples thereof include zirconium butoxide 1-butanol solution, zirconium n-propoxide and the like. Among these, from the viewpoint of reducing the anion and cation remaining in the coating after heating as much as possible, and from the viewpoint of adjusting the pH to the alkali side, zirconium ammonium carbonate, zirconyl ammonium carbonate, and potassium zirconium carbonate are preferable. Zirconyl ammonium carbonate is preferred.

  The content of the zirconium compound in the treatment liquid (the total amount when two or more kinds are used, and the same applies below) is preferably 0.05% or more and less than 10.00%, more preferably 0.50 in terms of metal Zr conversion. % Or more and 7.00% or less. If the amount is too small, the corrosion resistance is lowered, and if the amount is too large, the corrosion resistance is improved, but the adhesion of the film is lowered, which is not preferable.

  The vanadium compound used in the treatment liquid is a water-soluble vanadium compound and may be an inorganic compound or an organic compound. Specific examples include vanadic acid compounds such as metavanadic acid (trioxovanadic acid) and salts thereof, vanadium oxides such as vanadium pentoxide, vanadium halides such as vanadium pentachloride and vanadium pentafluoride, and vanadyl sulfate. And vanadium sulfate, vanadium nitrate, vanadium phosphate, vanadium biphosphate, vanadium acetate, vanadium acetylacetonate, and vanadyl acetylacetonate. Examples of those that form metavanadic acid and vanadic acid salts include sodium, potassium, and ammonium. Among these, vanadic acid compounds are preferable, and ammonium vanadate, particularly ammonium metavanadate is preferable.

  The content of the vanadium compound in the treatment liquid is preferably 0.004% or more and less than 0.400%, more preferably 0.044% or more and 0.220% or less in terms of metal V conversion. If the amount is too small, the corrosion resistance is lowered, and if the amount is too large, the corrosion resistance is improved, but the adhesion of the film is lowered, which is not preferable.

  Examples of the ammonium phosphate used in the treatment liquid include primary ammonium phosphate and secondary ammonium phosphate. In addition, ammonium salts of condensed phosphoric acid such as tripolyphosphoric acid, metaphosphoric acid, and pyrophosphoric acid. Is also possible. The content of ammonium phosphate in the treatment liquid is preferably 0.07% or more and less than 7.50%, more preferably 0.07% or more and 3.75% or less, in terms of phosphate ion. If the amount is too small, the corrosion resistance is lowered. If the amount is too large, the corrosion resistance is improved, but the adhesion of the film is lowered, which is not preferable.

  The silane coupling agent used in this treatment liquid has at least one functional group selected from an amino group containing active hydrogen, an epoxy group, a vinyl group, a mercapto group, and a methacryloxy group. Specific examples include N- (aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxy. Propyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, vinyltriethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacryl Roxypropyltrimethoxysilane and the like can be mentioned.

  As the silane coupling agent, a more preferable one can be selected depending on the type of the organic resin layer or primer to be coated as an upper layer on the base layer formed with the present treatment liquid. For example, when an epoxy primer or epoxy resin is used for coating the upper layer, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltrimethoxy A silane coupling agent containing an epoxy group such as silane is preferable, and 3-glycidoxypropyltrimethoxysilane is particularly preferable.

  The silane coupling agent can be used as a partial hydrolyzate that has been partially hydrolyzed in advance in order to promote film formation. A partially hydrolyzed product of a silane coupling agent can be used in combination with an unhydrolyzed silane coupling agent.

  The content of the silane coupling agent in the treatment liquid is preferably 0.1% or more and less than 10%, more preferably 0.5% or more and 5% or less, in terms of solid content of the silane coupling agent. If the amount is small, the adhesion to the upper layer is deteriorated and the corrosion resistance is lowered, but if the amount is large, the liquid stability is lowered, which is not preferable.

Underlayer forming treatment liquid may further contain additional components other than the above. Examples of such additive components include pH-adjusting acids and / or alkalis, antifoaming agents, chelating agents, surfactants, and solution stabilizers. Suitable chelating agents include carboxylic acid chelating agents and phosphonic acid chelating agents. The surfactant is preferably a nonionic type. Examples of the solution stabilizer include glycol solvents.

Processing Rieki may further contain an organic resin for the undercoat layer coating reinforced. Since the treatment liquid is an aqueous solution, it is preferable to use an aqueous resin, that is, a water-soluble or water-dispersible organic resin as the organic resin. Examples of organic resins that can be added include acrylic resins, phenol resins, epoxy resins, urethane resins, polyester resins, urea resins, melamine resins, butyral resins, and derivatives thereof. The content of the organic resin in the treatment solution is preferably 10% or less in terms of resin solid content. When there is too much content of organic resin, corrosion resistance will fall.

  The solvent of the treatment liquid is an aqueous solvent. The aqueous solvent is meant to include a solvent composed only of water and a mixed solvent of water and a water-miscible organic solvent. The solvent may be water alone, but a water-miscible organic solvent may be used in combination as long as the amount is less than water and metal ions do not precipitate. In the case of adding a resin component for strengthening the film, an organic solvent such as an aqueous formaldehyde solution (formalin), ethanol, or 2-propanol can be mixed with water.

PH of underlayer forming treatment solution is 8 to 12 of the alkaline side. When the pH is from neutral to acidic side of less than 8, the components may precipitate or gel, and the long-term corrosion resistance of the treated steel may deteriorate. When the pH exceeds 12, the danger of the treatment liquid is high and handling becomes difficult. The treatment liquid pH is preferably 8 or more and 10 or less.

Process for the preparation of the lower strata forming treatment liquid is not particularly limited. For example, while stirring water (or a mixed solvent of water and an organic solvent), a method in which a zirconium compound, a vanadium compound, ammonium phosphate, a silane coupling agent, and the like are sequentially added to an aqueous solution while stirring, an aqueous solution of each component The method of mixing after forming in advance can be mentioned. If the manufacturing location and usage location of the treatment liquid are different, consider the transportation cost, etc., and prepare the treatment liquid at a high concentration in the range that does not impair the stability. It is also possible to adjust the concentration by diluting with water or a mixed solvent. The total concentration of the components at the use stage is preferably in the range of 5 to 20%.

As can be seen from the above, underlayer forming treatment solution does not contain hexavalent chromium, also preferably does not contain chromium compounds at all, including trivalent chromium.

Using underlayer forming process liquid is not particularly limited. For example, a method in which a treatment liquid is sprayed in a shower on the surface of a steel material heated to 40 ° C. or more in advance, and a surplus solution is handled with a rubber squeegee or the like, a method in which a sponge soaked with a solution is pressed against a preheated steel material surface, Spray coating, dip coating, etc. are possible. Then, it is preferable to form a base layer by heating a steel material to 60 degreeC or more with suitable heating means, such as induction heating, and drying a membrane | film | coat.

Adhesion amount of the formed undercoat layer is a metal Zr converted at 50 mg / m ² or more is preferably less than 1500 mg / m ^2, more preferably 100 mg / m ² or more 1350 mg / m ² or less. When the adhesion amount is less than 50 mg / m ² , the corrosion resistance decreases and the cathode peeling increases. When the adhesion amount is 1500 mg / m ² or more, cohesive failure occurs in the underlayer, so that peeling in a cold cycle environment increases.

The organic resin layer coating on the underlayer formed using a treatment liquid is not particularly limited, it is possible epoxy resins, polyethylene resins, polypropylene resins, and urethane resins. When the organic resin layer to be coated is two or more layers (multiple layers), the uppermost coating layer (hereinafter referred to as an anticorrosion resin layer) may be coated with carbon black or oxidized to improve corrosion resistance and weather resistance. An inhibitor can be added. On the other hand, a modified organic resin layer having adhesiveness (hereinafter referred to as an adhesive resin layer) can be used as the lowermost coating layer.

  The appropriate film thickness (total film thickness in the case of two or more layers) of the organic resin layer that is a coating layer varies depending on the application, but is preferably 2.2 mm or more, more preferably 2.2 mm or more and 10 mm or less. It is. In the case of having the lower adhesive resin layer and the upper anticorrosive coating layer as described above, the thickness of the adhesive resin layer is preferably in the range of 0.1 mm or more and 1.0 mm or less, and the thickness of the anticorrosion coating layer is 2. Within the range of 0 mm or more and 10 mm or less is preferable.

  It is also possible to interpose an adhesive layer such as an adhesive primer or asphalt between the base layer and the organic resin coating layer. For example, a liquid epoxy resin or a powder epoxy resin can be used as the primer. In the case of a liquid primer, the average film thickness is preferably 5 μm or more and 200 μm or less, more preferably 10 μm or more and 150 μm or less, and in the case of a powder epoxy resin, preferably 60 μm or more and 500 μm or less, more preferably 80 μm or more and 200 μm or less. .

  As described above, according to the present invention, an organic coated steel material in which an undercoat layer is formed using an underlayer forming treatment liquid and is coated with at least one organic resin layer is not only resistant to corrosion and adhesion but also resistant to corrosion. Since it has excellent cathode peelability, it can be used in a cathodic protection environment (applied to -1.5 V (vs. SCE)). In addition, since the thermal cycle resistance is also good, it is particularly suitable for a line pipe that may be used in extreme values or desert areas.

  The present invention is specifically illustrated by the following examples, but the present invention is not limited by these examples. Unless otherwise specified, “%” and “parts” in the examples are “% by mass” and “parts by mass” in terms of solid content.

[Preparation of treatment solution for underlayer formation]
The composition of the treatment liquid used is as shown in Table 1. The meanings of the symbols used in the table are as follows.

Z1: ammonium zirconium carbonate / (NH ₄ ) ₂ [Zr (CO ₃ ) ₂ (OH) ₂ ]
Z2: potassium zirconium carbonate / K ₂ [Zr (CO ₃ ) ₂ (OH) ₂ ]
V1: Ammonium metavanadate / NH ₄ VO ₃
P1: dibasic ammonium phosphate / (NH ₄ ) ₂ HPO ₄
S1: 3-glycidoxypropyltrimethoxysilane S2: 3-aminopropyltriethoxysilane PR1: two-component amine curing epoxy primer PR2: one-component curing epoxy primer PR3: powder epoxy primer

  While stirring the ion-exchange water of the solvent, in addition to the indicated components, a nonionic surfactant is added and mixed, and the underlayer-forming treatment liquids of Examples 1 to 11 and Comparative Examples 1 to 9 are mixed. Was prepared. In Examples 1 to 11 and Comparative Examples 1 to 7, treatment solutions having excellent solution stability were obtained. On the other hand, in Comparative Examples 8 and 9, a precipitate was formed in the aqueous solution, and therefore, it was not used in the subsequent tests. For reference, a commercially available chromate treatment liquid (Kansai Paint Co., Ltd. Cosmer 100) containing hexavalent chromium was also used for forming the underlayer.

[Preparation of test piece]
Using an induction heater while moving a carbon steel pipe for piping (JIS G 3452) with a diameter of 114 mm whose outer surface was adjusted to a roughness of Rzjis 30 to 80 μm by grit blasting on a transport roll at a pipe moving speed of 13 m / min. The outer surface temperature of the steel pipe was heated to 60 ° C. The base layer was formed on the outer surface of the steel pipe by ironing (using shower spraying and a rubber squeegee) the base layer forming treatment liquid to be tested. The amount of adhesion varied depending on the strength of ironing and the composition of the treatment solution.

  The chromate treatment liquid was applied to the outer surface of the steel pipe heated to 60 ° C. by an induction heater as instructed by the product, and a base layer was formed.

  Next, using a two-component amine curable liquid primer (Pr1) or a one-component curable liquid primer (Pr2), it was applied to the thickness of 20 μm by the iron coating method, and immediately followed by an induction heater using an induction heater. Was heated to 180 ° C. to form a cured primer film serving as an adhesive layer. In some examples, the steel pipe outer surface temperature was heated to 200 ° C., and a powder epoxy primer (Pr3) was applied using a powder coating machine to form a primer cured film.

  On this cured primer film, a polyethylene resin (Japan) is passed through an adhesive resin layer (thickness: 0.3 mm) made of maleic anhydride-modified polyethylene (trade name Admer NE065, manufactured by Mitsui Chemicals Co., Ltd.) using a melt round die co-pressing device. An anticorrosion resin layer (2.2 mm thick) made of polyethylene (HE122R) was coated to obtain an outer polyethylene-coated steel pipe.

[Evaluation test]
A test piece (150 mm × 100 mm) was cut out from the obtained organic-coated steel tube, and a cold cycle test, a cathode peeling test (CD test), and a hot salt water immersion test were performed. The test method and evaluation method were as follows. The test results are also shown in Table 1.

[Test method and evaluation method]
[Cool cycle test]
In order to remove the heat-affected zone when the test piece was cut out from the steel pipe, the coating of 5 mm width at the end of each test piece was completely excised, and then at −60 ° C. for 8 hours, 80 ° C. and humidity of 95% RH 16 The test was repeated for 20 days in a test tank repeated as one cycle, and after 20 days, the peeling distance of the coating from the end face of the test piece was measured.

The evaluation criteria are as follows. ○ If it is above, it can be said to be acceptable.
◎ Peeling distance is less than 10mm,
○ Peeling distance is 10mm or more and less than 15mm,
X Peeling distance is 15 mm or more.

[Cathode peeling test]
In the cathode (cathode) peel test, an artificial wound having a diameter of 6 mm reaching the steel surface was provided on the organic coating layer of each test piece using a drill with a diameter of 6 mm, and this was contacted with 3% NaCl saline kept at 60 ° C. In the liquid state, it carried out by hold | maintaining for 28 days as a potential of -1.5V with respect to a saturated calomel electrode. The peel distance of the coating from the artificial wound 28 days after the start of the test was measured to evaluate the cathode peelability.

The evaluation criteria are as follows. ○ If it is above, it can be said to be acceptable.
◎ Peeling distance is less than 10mm,
○ Peeling distance is 10mm or more and less than 15mm,
X Peeling distance is 15 mm or more.

[Hot salt water immersion peel test]
In order to remove the heat-affected zone when the test piece was cut out from the steel pipe, the coating at the end 5 mm of each test piece was completely cut out and immersed in 3% salt water (NaCl) at a temperature of 90 ° C. for 28 days. The maximum peel distance of the coating was measured from the end face of the test piece.

The evaluation criteria are as follows. ○ If it is above, it can be said to be acceptable.
◎ Maximum peel distance is less than 3mm,
○ Maximum peel distance is 3mm or more and less than 10mm,
X The maximum peel distance is 10 mm or more.

[Amount of underlying layer (converted to metal Zr or Cr)]
A test piece of 25 mm × 50 mm was cut out from the organic-coated steel pipe, and after the resin layer and the primer layer were burned out in an electric furnace at 600 ° C., the back surface and the end surface were sealed with Shingosei manufactured by Shinto Paint Co., Ltd. This sealed specimen is immersed in heated hydrochloric acid or hydrofluoric acid to dissolve the steel surface, and then the zirconium ions or chromium ions (in the case of chromate coating) dissolved in the liquid are analyzed by induction plasma spectroscopy (ICP). Quantitative analysis was performed. The same measurement was performed on a test piece having no underlayer as a blank, and the amount of adhesion of the underlayer in terms of metal Zr or metal Cr was determined from comparison with the result of the blank.

  As can be seen from Table 1, in Comparative Examples 10 to 12 in which the chromate treatment solution was used for the base treatment before organic coating, the peeling distance of the organic coating was small under any of the tested conditions, and excellent results were obtained. However, the chromate treatment solution has a problem that it contains hexavalent chromium which is harmful to the human body and the environment.

  On the other hand, the treatment liquid for forming an underlayer of the present invention showed excellent performance comparable to a chromate film, although it contained no chromium compound including not only hexavalent chromium but also trivalent chromium. . That is, under any of the test conditions, the peel distance was small, and the cold-heat cycle resistance, the cathode peel resistance, and the heat-resistant salt water immersion were excellent. On the other hand, in the treatment liquids of Comparative Examples 1 to 4 and 7 which do not contain any of the essential components or whose adhesion amount is outside the scope of the present invention, the thermal cycle resistance, the resistance to cathodic stripping, and the heat resistance brine All the immersion properties were reduced. Moreover, in Comparative Examples 5 and 6, the amount of the base layer deposited was too large or too small, so that the performance was still deteriorated.

Claims (3)

An underlayer-forming treatment solution comprising a solution having a pH of 8 or more and 12 or less in which a zirconium compound, a vanadium compound, ammonium phosphate, a silane coupling agent and / or a hydrolysis condensate thereof are dissolved in an aqueous solvent. after application to the steel surface and dried, the metal Zr converted at 50 mg / ^{m 2} or more on the steel material surface, forming the base layer of the adhesion amount of less than 1500 mg / ^{m 2,} then, over the underlayer 1 A method for producing an organic coated steel material excellent in corrosion resistance, adhesion, cathode peel resistance, and cold cycle durability, characterized by forming a layer or two or more organic resin layers. Wherein the zirconium compound is one or two selected from ammonium zirconium carbonate and ammonium zirconyl carbonate, a method of manufacturing an organic coating steel according to claim 1, wherein. The manufacturing method of the organic coating steel materials of Claim 1 or 2 whose said vanadium compound is ammonium vanadate.