JP6441655B2 - Ground treatment liquid, method for producing organic coated galvanized steel pipe using ground treatment liquid, and organic coated galvanized steel pipe - Google Patents

Description

  The present invention relates to a base treatment liquid, a method for producing an organic-coated galvanized steel pipe using the base treatment liquid, and an organic-coated galvanized steel pipe.

  Of the pipes for transporting combustion or industrial gas, galvanized steel pipes are used for pipes used in a low corrosive environment. On the other hand, polyethylene-coated steel pipes are used for pipes that are buried and used in the ground. The underground is an acidic to weak alkaline corrosive environment. When a galvanized steel pipe is used in an acidic ground, the zinc elution reaction is accelerated. Therefore, the use of galvanized steel pipes can be avoided for pipes buried in the ground.

  However, recently, the gas passing through the piping may contain a trace amount of corrosive components. In this case, corrosion occurs on the inner surface of the pipe. Therefore, it is preferable that a galvanized layer is formed on the inner surface of the steel pipe even if the pipe is buried in the ground. Therefore, a steel pipe having a galvanized layer on the inner surface of the steel pipe and an organic resin layer such as polyethylene for corrosion prevention is required on the outer surface of the steel pipe.

  When the galvanizing treatment is performed on the inner surface of the steel pipe, the steel pipe is generally immersed in molten galvanized water. In this case, a galvanized layer is formed not only on the inner surface of the steel pipe but also on the outer surface of the steel pipe. Therefore, when manufacturing the above-mentioned steel pipe, it is preferable to form an organic resin layer on the outer surface galvanized layer.

  In order to improve the adhesion between the steel pipe and the organic resin layer as the anticorrosion coating, a base treatment is usually performed. Chromate treatment is known as a base treatment for the organic resin layer. It is known that the underlayer formed by the chromate treatment has excellent corrosion resistance and enhances adhesion with the organic resin layer. The underlying layer formed by the chromate treatment may be used as it is as a corrosion-resistant coating.

  However, the chromate treatment solution contains hexavalent chromium. Hexavalent chromium has a high environmental impact. Therefore, there is a demand for a base treatment solution that does not contain hexavalent chromium, replacing the chromate treatment solution.

  Regarding the ground treatment liquid not containing hexavalent chromium, in the field of automobiles and home appliances, Japanese Patent Application Laid-Open No. 2002-332574 (Patent Document 1), Japanese Patent Application Laid-Open No. 2011-032576 (Patent Document 2), and Japanese Patent Application Laid-Open No. 2010-53424. (Patent Document 3) and Japanese Patent Laid-Open No. 2001-316845 (Patent Document 4). Furthermore, in the field of steel pipes for line pipes, it has been proposed in Japanese Patent Application Laid-Open No. 2003-34881 (Patent Document 5) and Japanese Patent Application Laid-Open No. 2014-31552 (Patent Document 6).

The surface treatment liquid disclosed in Patent Document 1 contains a zirconium carbonate complex ion, a vanadyl ion (VO ²⁺ ), and an oxycarboxylic acid. The above-mentioned base treatment liquid further has a solid content concentration of zirconium: 10-30%, vanadium: 5-20%, oxycarboxylic acid: 20-50%, dimercaptosuccinic acid: 0.01-1%, phosphoric acid Ammonium: 0.01 to 1% is contained. The plated steel material disclosed in Patent Document 1 has a corrosion-resistant coating layer obtained from the above-described base treatment liquid as an adhesion amount of 200 to 1200 mg / m ² . Preferably, the corrosion-resistant coating layer contains 10 to 30% of zirconium compound as zirconium, 5 to 20% of vanadyl compound as vanadium, and dimethylcaptosuccinic acid: 0.01 to 1%.

The surface layer of the corrosion-resistant coating of the plated steel material disclosed in Patent Document 2 includes a zirconyl cation component A, an anion component B selected from phosphate ions and hydroxyethylidene diphosphonate ions, and a cation component selected from Mg and Ca It is made of C and may contain 90% by mass or less of resin. The above corrosion-resistant coating satisfies (Equation 1) and (Equation 2) with the total charge (mmol · m ⁻² ) of each component A, B, and C in the coating satisfying (Equation 1) and (Equation 2). The components consist essentially of components A, B and C. The coating amount in terms of the total charge amount of the anion component B is in the range of 1 to 10 mmol · m ⁻² . (Formula 1) 0.49 ≦ A / B ≦ 1.3, (Formula 2) 0.3 ≦ (A + C−B) /B≦0.3.

The coating of the surface-treated metal plate disclosed in Patent Document 3 is a metal oxide coating containing at least one selected from the group consisting of Si, Ti, Zr, V, Nb, Ta, P, and W, and / or Or it is a metal hydroxide-type film. These coatings are formed by cathodic electrolysis in a treatment bath mainly composed of a fluorometal compound. The metal oxide film and / or hydroxide film is an independent granular deposit formed by cathodic electrolysis or a granular deposit in contact with each other, and the major axis per piece is 5 to 300 nm. There are 10 or more in 1 × 10 ⁻¹² m ² .

  The surface treatment liquid disclosed in Patent Document 4 is (a) 0.01 to 100 g / L of (a) a silane coupling agent and / or a hydrolysis condensate thereof in 1 liter of a metal surface treatment agent, and (b) water dispersion. Silica (solid content) 0.05 to 100 g / L, and (c) 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. (A) (b) (c) is included as an essential component, and (d) a thiocarbonyl group-containing compound is 0.01 to 100 g / L and / or (e) a water-soluble acrylic resin is 0.1 to 100 g. / L included.

  The manufacturing method of the anticorrosion coating steel material disclosed in Patent Document 5 includes a 0.001-1.0 mol / l ammonium molybdate, a 0.001-0.05 mol / l silane coupling agent on the steel surface, or 0 After applying a base treatment in which a mixed aqueous solution containing 0.001 to 1.0 mol / l of magnesium phosphate is brought into contact, an anticorrosion coating treatment is applied.

  The steel material ground treatment solution disclosed in Patent Document 6 dissolves a zirconium compound, a vanadium compound, ammonium phosphate, a silane coupling agent and / or a hydrolysis condensate thereof in an aqueous solvent, and has a pH value. Consists of 8 or more and 12 or less solutions.

JP 2002-332574 A JP 2011-032576 A JP 2010-53424 A JP 2001-316845 A JP 2003-34881 A JP 2014-31552 A

  Each of the ground treatment liquids of Patent Documents 1 to 4 contains inorganic metal ions such as zirconium ions. In order to improve the solution stability of the base treatment liquid containing inorganic metal ions and to improve the corrosion resistance of the base layer, it is preferable to contain a counter anion with respect to the inorganic metal ions.

  Patent Document 1 contains a chelating agent, Patent Document 2 contains oxycarboxylic acid or dimercaptosuccinic acid, and Patent Document 3 contains a thiocarbonyl group-containing compound as a counter anion, respectively. As described above, when an organic compound is contained as a counter anion, complex formation with metal ions in the treatment liquid and stability of the coating are enhanced. However, when forming a coating or organic resin layer after the surface treatment, an organic compound used as a counter anion is generated as a gas from the coating. This organic compound gas reduces the adhesion of the organic resin layer formed on the underlying layer.

  The ground treatment liquid of Patent Document 4 is mainly composed of a fluorometal compound. When this surface treatment solution is used, fluoride ions may remain in the coating. Fluoride ions enhance adhesion by etching the surface when forming a liquid layer film. However, fluoride ions are highly corrosive. For this reason, fluoride ions remaining in the coating may corrode the steel material or promote peeling of the organic resin layer.

  Furthermore, the techniques disclosed in Patent Documents 1 to 4 are intended for automobiles, home appliances, residential building materials, and the like. The thickness of the organic resin layer of the steel material used in these fields is about 300 μm. On the other hand, the thickness of the organic resin layer formed on the outer surface of the steel pipe buried in the ground exceeds 1 mm. As the organic resin layer becomes thicker, it becomes easier to peel off. Therefore, high adhesion is required for the galvanized steel pipe buried in the ground.

  In the base layer formed with the base treatment liquid disclosed in Patent Document 5, peeling of the organic resin layer due to immersion in hot salt water may not be suppressed. Furthermore, rust may occur from the end of the steel material.

  The ground treatment liquid disclosed in Patent Document 6 is for directly forming a ground layer on a steel base material. When forming a base layer on a galvanized layer using the base treatment liquid described in Patent Document 6, the base layer may not be formed uniformly, and the adhesion of the organic resin layer to the steel may be reduced.

  An object of the present invention is to provide a base treatment liquid capable of forming a base layer capable of enhancing the adhesion of an organic resin layer even on a galvanized layer, and an organic-coated galvanized steel pipe using the base treatment liquid It is to provide a manufacturing method.

  The base treatment liquid according to the present invention forms a base layer between the galvanized layer on the outer surface of the galvanized steel pipe and the organic resin layer. The base treatment liquid is composed of an aqueous solvent, a zirconium compound having a metal Zr equivalent concentration of 0.05 to 10.50 mass%, a vanadium compound having a metal V equivalent concentration of 0.004 to 0.400 mass%, and phosphate ions. 0.07 to 7.50 mass% ammonium phosphate in terms of converted concentration, 0.1 to 10 mass% of silane coupling agent and / or its hydrolysis condensate in terms of solid content, and solid content converted concentration And 0.2 to 10% by mass of a silica compound, and has a pH of 8 to 12.

  The surface treatment liquid according to the present invention contains a silica compound. Therefore, even on the galvanized layer, the base treatment liquid is uniformly dispersed, and a uniform base layer can be formed.

In the method for producing an organic-coated galvanized steel pipe according to the present invention, the surface roughness of the galvanized layer formed on the outer surface is 10 to 50 μm in terms of a ten-point average roughness Rzjis in accordance with JIS B0601 (2001). A step of preparing a galvanized steel pipe having a coverage of a pure zinc layer of 30 to 90% on the surface of the layer, and applying the above-mentioned base treatment liquid on the galvanized layer, and 50 to 1500 mg / in terms of metal Zr a step of forming a base layer having an adhesion amount of less than m ² and a step of forming an organic resin layer on the base layer.

  In the method for producing an organic-coated galvanized steel pipe according to the present invention, a galvanized steel pipe having a galvanized layer remaining on the outer surface and having irregularities formed on the surface of the galvanized surface is prepared. And an organic resin layer is formed. In this case, the adhesion of the organic resin layer to the galvanized steel pipe is further enhanced. As described above, since the galvanized layer remains on the outer surface of the galvanized steel pipe, generation of rust at the end of the steel pipe is particularly suppressed.

An organic coated galvanized steel pipe according to the present invention includes a steel pipe, a galvanized layer, an underlayer, and an organic resin layer. The galvanized layer is formed on the outer surface of the steel pipe, and the surface roughness is 20 to 50 μm in terms of 10-point average roughness Rzjis according to JIS B0601 (2001), and the coverage of the pure zinc layer on the surface is 30 to 30 μm. 90%. The underlayer is formed on the galvanized layer and has an adhesion amount of 50 to less than 1500 mg / m ^{2 in} terms of metal Zr. The organic resin layer is formed on the base layer.

  The organic coated galvanized steel pipe according to the present invention includes a galvanized layer having irregularities. This unevenness further increases the adhesion of the organic resin layer to the steel pipe. Further, the galvanized layer suppresses the generation of rust particularly at the end of the steel pipe.

  Hereinafter, embodiments of the present invention will be described in detail. As a result of investigation and examination, the present inventors have obtained the following knowledge.

  (1) When forming a base layer on a galvanized layer, compared with the case where a base layer is directly formed on the steel material surface, a base treatment liquid is hard to disperse | distribute uniformly. If the surface treatment liquid contains an appropriate concentration of silica compound, the surface treatment liquid can be easily dispersed uniformly on the galvanized layer, and the ground layer can be easily formed uniformly. As a result, when an organic resin galvanized steel pipe is manufactured by forming an organic resin layer on the base layer, the adhesion of the organic resin layer to the galvanized steel pipe is enhanced. Furthermore, since the organic coated galvanized steel pipe has a galvanized layer on the outer surface, it is excellent in corrosion resistance.

  (2) In order to improve the adhesion between the base layer and the organic resin layer, the surface roughness of the galvanized layer on the outer surface of the galvanized steel pipe is 20 to 50 μm in terms of 10-point average roughness Rzjis according to JIS B0601 (2001). And the coverage of the pure zinc layer on the surface of the galvanized layer is 30 to 90%. In this case, the adhesion between the base layer and the organic resin layer is further enhanced. In order to set the surface roughness of the galvanized layer and the coverage of the pure zinc layer within the above ranges, for example, blasting is performed on the galvanized layer on the outer surface of the steel pipe. The blasting process is, for example, shot blasting, grid blasting, sand blasting, or the like.

  Based on the above findings, the present invention has been completed. Hereinafter, the surface treatment solution according to the present invention and a method for producing an organic-coated galvanized steel pipe using the surface treatment solution will be described in detail.

[About ground treatment solution]
The surface treatment liquid according to the present invention contains an aqueous solvent, a zirconium compound, a vanadium compound, ammonium phosphate, a silane coupling agent and / or a hydrolysis condensate thereof, and a silica compound.

  Each of the above components (zirconium compound, vanadium compound, ammonium phosphate, silane coupling agent, hydrolysis condensate of silane coupling agent, silica compound, aqueous medium) may contain one kind or two or more kinds. . Hereinafter, “%” related to the component of the base treatment liquid means mass%.

[Zirconium compound]
The zirconium compound is a water-soluble zirconium compound. The zirconium compound may be an inorganic compound or an organic compound. Zirconium compounds include, for example, ammonium zirconium carbonate, ammonium zirconyl carbonate, basic zirconium carbonate, zirconium acetate, zirconium nitrate, potassium zirconium carbonate, zircon hydrofluoric acid, zircon ammonium fluoride, zircon potassium fluoride, zircon sodium fluoride, zirconium acetylacetonate, Zirconium butoxide 1-butanol solution, zirconium n-propoxide and the like. The ground treatment liquid may contain one kind or two or more kinds of zirconium compounds.

  Preferably, the zirconium compound is one or more selected from the group consisting of zirconium ammonium carbonate, zirconyl ammonium carbonate, and potassium zirconium carbonate, and more preferably selected from the group consisting of zirconium ammonium carbonate and zirconyl ammonium carbonate. 1 or more types. These zirconium compounds can reduce the anion and cation remaining in the underlayer after heating as much as possible, and can further adjust the pH to the alkali side.

  The content of the zirconium compound in the base treatment solution is 0.05 to 10.50 mass% in terms of metal Zr. When two or more zirconium compounds are contained, the content of the zirconium compound means the total content of the zirconium compound.

  If the zirconium compound content is too low, the underlayer is not sufficiently formed. In this case, the corrosion resistance of the steel pipe and the adhesion of the organic resin layer are lowered. If the zirconium compound content is too high, the corrosion resistance increases, but the adhesion of the organic resin layer to the steel pipe decreases. Therefore, the content of the zirconium compound is 0.05 to 10.50% by mass in terms of metal Zr. A more preferred lower limit of the zirconium compound content is 0.50% by mass in terms of metal Zr. A more preferable upper limit of the zirconium compound content is 7.00% by mass in terms of metal Zr.

[Vanadium compounds]
The vanadium compound is a water-soluble vanadium compound and may be an inorganic compound or an organic compound. Two or more vanadium compounds may be contained. When two or more kinds of vanadium compounds are contained, the vanadium compound content (%) means the total content (%) of a plurality of vanadium compounds.

  Examples of vanadium compounds 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. Vanadium sulfate, vanadium nitrate, vanadium phosphate, vanadium biphosphate, vanadium acetate, vanadium acetylacetonate, vanadyl acetylacetonate, and the like.

  Those that form metavanadic acid and vanadic acid salts are, for example, sodium, potassium and ammonium.

  Preferably, the vanadium compound is a vanadate compound. More preferably, the vanadium compound is ammonium vanadate, and more preferably ammonium metavanadate.

  The content of the vanadium compound in the treatment liquid is 0.004 to 0.400% by mass in terms of metal V. If the vanadium compound content is too low, the corrosion resistance of the steel pipe decreases. On the other hand, if the vanadium compound content is too high, the corrosion resistance increases, but the adhesion of the organic resin layer to the steel pipe decreases. Therefore, the content of the vanadium compound is 0.004 to 0.400% by mass in terms of metal V. The minimum with preferable vanadium compound content is 0.044 mass% in metal V conversion density | concentration. The upper limit with preferable vanadium compound content is 0.220 mass% in metal V conversion density | concentration.

[Ammonium phosphate]
Ammonium phosphate is, for example, primary ammonium phosphate or secondary ammonium phosphate. Further, the ammonium phosphate may be an ammonium salt of condensed phosphoric acid such as tripolyphosphoric acid, metaphosphoric acid, pyrophosphoric acid or the like. The base treatment liquid may contain two or more kinds of ammonium phosphate.

  The content of ammonium phosphate in the ground treatment solution is 0.07 to 7.50% by mass in terms of phosphate ions. If the ammonium phosphate content is too low, the corrosion resistance of the steel pipe decreases. On the other hand, if the ammonium phosphate content is too high, the corrosion resistance increases, but the adhesion of the organic resin layer to the steel pipe decreases. Therefore, the content of ammonium phosphate is 0.07 to 7.50% by mass in terms of phosphate ions. A preferable upper limit of the ammonium phosphate content is 3.75% in terms of phosphate ion.

[Silane coupling agent]
The silane coupling agent contains one or more functional groups selected from the group consisting of an amino group containing active hydrogen, an epoxy group, a vinyl group, a mercapto group, and a methacryloxy group.

  Silane coupling agents include, for example, N- (aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycol. Sidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, vinyltriethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3 -Methacryloxypropyltrimethoxysilane and the like. The base treatment liquid may contain one kind or two or more kinds of silane coupling agents.

  The silane coupling agent may be selected based on the type of the organic resin layer formed on the base layer. For example, when using an epoxy primer or an epoxy resin as the organic resin layer, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane A silane coupling agent containing an epoxy group such as 3-glycidoxypropyltrimethoxysilane is particularly preferable.

  The silane coupling agent may be a partially hydrolyzed condensate that has been partially hydrolyzed in advance in order to promote the formation of the underlayer. The silane coupling agent may contain a partially hydrolyzed condensate and an unhydrolyzed silane coupling agent.

  The content of the silane coupling agent in the treatment liquid is 0.1 to 10% in terms of solid content of the silane coupling agent. When the ground treatment liquid contains a plurality of silane coupling agents, the content of the silane coupling agents means the total content of the plurality of silane coupling agents.

  If the silane coupling agent content is too low, the adhesion between the organic resin layer and the underlayer will be reduced. In this case, the corrosion resistance of the steel pipe decreases. On the other hand, if the content of the silane coupling agent is too high, the liquid stability of the base treatment liquid is lowered. Therefore, content of a silane coupling agent is 0.1-10 mass% in solid content conversion density | concentration of a silane coupling agent. The minimum with preferable content of silane coupling agent is 0.5 mass% in solid content conversion density | concentration of a silane coupling agent. A more preferable upper limit of the silane coupling agent content is 5% by mass in terms of solid content of the silane coupling agent.

[Silica compound]
The silica compound is colloidal silica having hydrophilicity. Since colloidal silica has a large specific area, it has high adsorptivity. Therefore, if the silica compound is contained in the base treatment liquid, the silica compound is dispersed in the base layer mainly composed of Zr oxide, and the cohesiveness of the base layer is enhanced. As a result, the adhesion of the coating material to the steel pipe is increased.

  The colloidal silica having hydrophilicity is, for example, trade names manufactured by Nissan Chemical Industries, Ltd .: Snowtex-20, Snowtex-30, Snowtex-40, Snowtex-C, Snowtex-O, Snowtex-S, Snow Tex-50, Snowtex-20L, Snowtex-XS, Snowtex-SS, Snowtex-XL, Snowtex-YL, Snowtex-ZL, Snowtex-OUP, Snowtex-N, Snowtex-OL, etc. It is a colloidal solution of fine particle silica having a particle size of 4 to 100 nm.

  Other colloidal silica that can be used is, for example, silica-based fine particles synthesized by a dry method. Silica-based fine particles synthesized by the dry method are, for example, trade names manufactured by Nippon Aerosil Co., Ltd .: AEROSIL 130, AEROSIL 200, AEROSIL 200V, AEROSIL 200CF, AEROSIL 200FAD, AEROSIL 300, AEROSIL 300CF, AEROSIL 380, AEROSIL OX50, AEROSIL , AEROSIL MOX, etc. The base treatment liquid may contain one kind or two or more kinds of silica compounds.

  Content of the silica compound in a base-treatment liquid is 0.2-10 mass% in solid content conversion density | concentration of a silica compound (colloidal silica). If the silica compound content is too low, the above effect is difficult to obtain. If the silica compound content is too high, the liquid stability of the base treatment liquid is lowered. Specifically, if the silica compound content is too high, zirconium ions and the like are precipitated in the ground treatment solution.

[Aqueous solvent]
The solvent of the ground treatment liquid is an aqueous solvent. The aqueous solvent may be a solvent composed only of water, or may be a mixed solvent containing water and a water-miscible organic solvent. More specifically, the solvent of the base treatment solution may be water alone, but may contain a water-miscible organic solvent and water as long as the amount is less than water and metal ions do not precipitate.

  The aqueous solvent may further contain one or more organic solvents. Examples of the organic solvent include formaldehyde aqueous solution (formalin), ethanol, 2-propanol and the like. If the aqueous solvent contains an organic solvent, the underlayer is strengthened.

[Other components of surface treatment solution]
The ground treatment liquid may further contain other components other than the above components. The base treatment liquid may contain, for example, one or more of pH adjusting acid, alkali, antifoaming agent, chelating agent, surfactant, solution stabilizer and the like.

  Chelating agents are, for example, carboxylic acid chelating agents and phosphonic acid chelating agents. A preferred surfactant is a nonionic surfactant. The solution stabilizer is, for example, a glycol solvent.

  The ground treatment liquid of the present invention may further contain an organic resin. In this case, the underlayer is strengthened. Since the base treatment liquid is an aqueous solution, a preferable organic resin is an aqueous resin, that is, a water-soluble or water-dispersible organic resin. The organic resin is, for example, acrylic resin, phenol resin, epoxy resin, urethane resin, polyester resin, urea resin, melamine resin, butyral resin, and derivatives thereof.

  The preferable content of the organic resin in the treatment liquid is 10% by mass or less in terms of resin solid content. If the content of the organic resin is too high, the corrosion resistance of the steel pipe is lowered.

  The surface treatment liquid may further contain one or more selected from the group consisting of pigments, dyes and fluorescent materials. In this case, the application | coating condition to the steel pipe surface of a surface treatment liquid can be confirmed visually. The dye is, for example, a copper complex dye. Examples of the fluorescent substance include luminol, quinine, umbelliferone, and the like.

[PH of ground treatment solution]
The pH of the ground treatment solution is 8-12. That is, the pH of the ground treatment solution is on the alkali side. If the pH of the ground treatment solution is less than 8 (neutral to acidic side), the components of the ground treatment solution are precipitated or gelled. Furthermore, the corrosion resistance of the steel pipe is reduced. On the other hand, even if the pH of the ground treatment solution is too high, the ground treatment solution gels. Therefore, the pH of the ground treatment solution is 8-12. A preferred upper limit of the pH of the ground treatment solution is 10.

  The ground treatment liquid according to the present invention does not contain hexavalent chromium. Preferably, the base treatment liquid further contains no chromium compound including trivalent chromium.

[Method of manufacturing coated galvanized steel pipe]
The method for producing a coated galvanized steel pipe using the above base treatment liquid includes a step of preparing a galvanized steel pipe (referred to as a preparatory step), a step of performing a base treatment (base treatment step), and a step of forming an organic resin layer (Coating process). Hereinafter, each process is explained in full detail.

[Preparation process]
First, a galvanized steel pipe is prepared. The galvanized steel pipe of this embodiment includes a galvanized layer on the outer surface and the inner surface. The galvanized layer is formed by a known galvanizing process. The adhesion amount of the formed galvanized layer is, for example, 350 to 600 g / m ² in terms of metal Zn, and more preferably 400 to 550 g / m ² .

  The surface roughness of the galvanized layer on the outer surface of the galvanized steel pipe is 20 to 50 μm in terms of a ten-point average roughness Rzjis. The ten-point average roughness Rzjis is determined by the following measurement method. A roughness curve is measured using a stylus roughness meter in accordance with JIS B0601 (2001). The measurement direction of the roughness curve is the circumferential direction (C direction) of the galvanized steel pipe. Further, the low-frequency cutoff value is 0.8 mm, and the evaluation length is 4 mm. Based on the roughness curve, the ten-point average roughness Rzjis (μm) is obtained.

  Furthermore, the coverage of the pure zinc layer on the surface of the galvanized layer is 30 to 90%.

  In the galvanized steel pipe having the above-mentioned roughness and the coverage of the pure zinc layer, the outer surface galvanized layer has appropriate irregularities to enhance the adhesion, and the galvanized layer itself remains. Therefore, the adhesion between the base layer and the organic resin layer formed on the galvanized layer is enhanced, and the corrosion resistance is also enhanced.

The coverage (%) of the pure zinc layer on the surface of the galvanized layer means the area ratio of the pure zinc layer on the surface of the galvanized layer. The coverage of the pure zinc layer is measured by the following method. Among the galvanized layers on the outer surface of the galvanized steel pipe, test pieces including the plated layer are collected from four points every 90 ° around the central axis of the steel pipe. For each test piece, the element distribution of Fe and Zn in a 10 mm × 10 mm field of view is measured at 200 × magnification using an electron beam microanalyzer (EPMA). Zn is basically detected over the entire field of view. On the other hand, Fe is detected in the alloy layer. Therefore, in the field of view of 10 mm × 10 mm, the area of the region where Fe is detected is measured with image processing software to determine the area of the alloy layer. And the coverage (%) of the pure zinc layer in each visual field is calculated | required by following Formula.
Coverage of pure zinc layer = (total area of visual field−area of alloy layer) / total area of visual field × 100
The average coverage of the pure zinc layer in each field of view is defined as the coverage (%) of the pure zinc layer on the surface of the galvanized layer.

  The galvanized steel pipe having the above-described galvanized layer on the outer surface is manufactured, for example, by the following method. Blasting (shot blasting, sand blasting, etc.) is performed on the outer surface of the galvanized steel pipe to remove the surface oxide layer of the galvanized layer. In this case, the outermost surface of the plating layer on the outer surface of the steel pipe contains a pure zinc layer and an FeZn alloy layer. Further, blasting is continued, and the surface roughness of the galvanized layer is set to 20 to 50 μm with a 10-point average roughness Rzjis based on JIS B0601 (2001), and the coverage of the pure zinc layer on the surface of the galvanized layer is set to 30 to 90%.

  If the surface roughness of the galvanized layer is 20 to 50 μm in terms of 10-point average roughness Rzjis based on JIS B0601 (2001), and the coverage of the pure zinc layer on the surface of the galvanized layer is 30 to 90%, Adhesion between the base layer and the organic resin layer is increased. Furthermore, the corrosion resistance of the steel pipe can be maintained because the outer surface galvanized layer remains even after the processing (such as blasting). A preferable lower limit of the roughness Rzjis is 25 μm. A preferable upper limit of the roughness Rzjis is 45 μm. A preferable lower limit of the coverage of the pure zinc layer is 35%. A preferable upper limit of the coverage of the pure zinc layer is 80%.

  When blasting is performed, it is preferable to wash the blasting powder remaining on the outer surface of the steel pipe after blasting. Washing is performed by air or water washing, for example.

[surface treatment]
The prepared galvanized steel pipe is subjected to a surface treatment using the above-described surface treatment solution.

  First, the ground treatment solution is prepared. The production method (preparation method) of the ground treatment liquid is not particularly limited. For example, water (or a mixed solvent of water and an organic solvent) is prepared as an aqueous solvent. While stirring the aqueous solvent, a zirconium compound, a vanadium compound, ammonium phosphate, a silane coupling agent, and a silica compound are added to the aqueous medium to produce a base treatment solution.

  An aqueous solution of each component (zirconium compound, vanadium compound, ammonium phosphate, silane coupling agent, and silica compound) may be produced in advance, and the aqueous solution of each component may be mixed to produce a ground treatment solution.

  In the case where the production place and the use place of the ground treatment liquid are different, the treatment liquid is first prepared in a high concentration state within a range not impairing the stability in consideration of transportation costs and the like. And you may dilute with an aqueous solvent immediately before application | coating to steel materials, and you may adjust the density | concentration of a surface treatment liquid. The preferable total content of the zirconium compound, vanadium compound, ammonium phosphate, silane coupling agent, and silica compound in the surface treatment solution during the surface treatment is 5 to 20%.

  A base treatment liquid is applied on the galvanized layer on the outer surface of the galvanized steel pipe to form a base layer (base treatment). The ground treatment method is not particularly limited.

  For example, the ground treatment liquid is sprayed and applied to the outer surface of a steel pipe that has been heated to 40 ° C. or higher in advance. After spraying, handle the excess surface treatment solution with a rubber squeegee. Thereafter, the steel pipe is heated to 60 ° C. or higher by heating using induction heating or the like. By heating, the base treatment liquid is dried to form a base layer.

  Instead of spraying the ground treatment liquid, a sponge soaked with the ground treatment liquid may be pressed against the outer surface of the steel pipe to apply the ground treatment liquid to the outer surface of the steel pipe. Moreover, you may apply | coat a surface treatment liquid on the outer surface of a steel pipe using a spray. The surface treatment liquid may be applied to the outer surface of the steel pipe by immersing the steel pipe in a bath in which the surface treatment liquid is stored. You may dry a base-treatment liquid by methods other than a heating.

The adhesion amount of the underlayer is 50 to less than 1500 mg / m ^{2 in} terms of metal Zr. If there is too little adhesion amount, the corrosion resistance of a steel pipe will fall. On the other hand, if the amount of adhesion is too large, cohesive failure tends to occur in the underlayer, and the underlayer tends to peel off. Therefore, the adhesion amount of the underlayer is 50 to less than 1500 mg / m ^{2 in} terms of metal Zr. A preferable lower limit of the adhesion amount of the underlayer is 100 mg / m ² in terms of metal Zr. A preferable upper limit of the adhesion amount of the underlayer is 1350 mg / m ² in terms of metal Zr.

The adhesion amount of the underlayer is measured by the following method. A specimen having a length of 50 mm is cut out from the organic-coated galvanized steel pipe. After cutting the test piece in half, the organic resin layer is burned out in an electric furnace at 600 ° C. Thereafter, surfaces (inner surface and end surface) other than the outer surface on which the base layer is formed are sealed. This test piece is immersed in heated hydrochloric acid or hydrofluoric acid to dissolve the steel material surface. Zirconium ions adhering to the surface of the test piece after dissolution are quantitatively analyzed by induction plasma spectroscopy (ICP) to determine the amount of adhesion (mg / m ² ) in terms of metal Zr.

[Coating process]
In the covering process, an organic resin layer is formed on the base layer. Two or more organic resin layers may be formed.

  The organic resin layer is not particularly limited as long as it contains an organic resin. The organic resin layer is, for example, an epoxy resin, a polyethylene resin, a polypropylene resin, a urethane resin, or the like.

  When two or more organic resin layers are formed, the uppermost organic resin layer may contain carbon black or an antioxidant. An organic resin layer containing carbon black or an antioxidant is referred to as an anticorrosion resin layer. The anticorrosion resin layer has excellent anticorrosion and corrosion resistance.

  The lowermost organic resin layer may have adhesiveness. Hereinafter, the organic resin layer having adhesiveness is referred to as an adhesive resin layer. The adhesive resin layer is, for example, a modified organic resin layer having adhesiveness.

  A preferable total film thickness of the organic resin layer is 2.2 mm or more. The total film thickness means the film thickness of the organic resin layer when only one kind of organic resin layer is formed. When two or more kinds of organic resin layers are formed, all the organic resin layers Means the total film thickness. A preferable upper limit of the total film thickness of the organic resin layer is 11 mm.

  When two or more organic resin layers are formed, the anticorrosion resin layer is formed as the uppermost layer, and the adhesive resin layer is formed as the lowermost layer, the preferred film thickness of the anticorrosion resin layer is 2.0. -10 mm. A preferable film thickness of the adhesive resin layer is 0.1 to 1.0 mm.

  An adhesive layer (referred to as an adhesive layer) may be formed between the base layer and the organic resin layer. The main component of the adhesive layer is, for example, epoxy resin, modified polyethylene, or asphalt. When forming the adhesive layer, a step of forming the adhesive layer is performed after the base treatment step and before the coating treatment step.

  In the step of forming the adhesive layer, a solution as a raw material for the adhesive layer is applied on the base layer. Heat or light is applied to the applied solution to cure the solution to form an adhesive layer.

  When the main component of the adhesive layer is an epoxy resin, the preferable average film thickness of the adhesive layer is 20 to 200 μm. Epoxy resins include liquid epoxy resins and powder epoxy resins. When the main component of the adhesive layer is a liquid epoxy resin, the preferable average film thickness of the adhesive layer is 20 to 50 μm. When the main component of the adhesive layer is a powder epoxy resin, the preferable average film thickness of the adhesive layer is 50 to 200 μm.

  When the main component of the adhesive layer is modified polyethylene, the preferable average film thickness of the adhesive layer is 50 to 300 μm. When the main component of the adhesive layer is asphalt, the preferable average film thickness of the adhesive layer is 100 to 500 μm.

  The organic coating galvanized steel pipe is manufactured by the above manufacturing process.

  The manufactured organic coated galvanized steel pipe includes a steel pipe as a base material, a galvanized layer, a base layer, and an organic resin layer on the outer surface.

  The galvanized layer is formed on the outer surface of the steel pipe (base material). The galvanized layer contains a pure zinc layer and an FeZn alloy layer. The galvanized layer may also be formed on the inner surface of the steel pipe.

The underlayer is formed on the galvanized layer. The foundation layer is manufactured from the above-described foundation treatment liquid. The adhesion amount of the underlayer is 50 to less than 1500 mg / m ^{2 in} terms of metal Zr.

  The organic resin layer is formed on the galvanized layer. Two or more organic resin layers may be formed.

  In the organic coating galvanized steel pipe manufactured by the above manufacturing method, the adhesion of the organic coating material to the galvanized steel pipe (the galvanized layer) is high due to the base layer manufactured with the above-described base treatment liquid. Therefore, the organic coating material is difficult to peel from the galvanized steel pipe. Furthermore, the galvanized layer remains and the underlayer also exhibits corrosion resistance. Therefore, the organic coated galvanized steel pipe exhibits excellent corrosion resistance.

  Hereinafter, the present invention will be specifically illustrated by examples. However, the present invention is not limited by these examples.

[Preparation of treatment solution for underlayer formation]
The ground-treatment liquid of the test numbers 1-33 containing the component shown in Table 1 was prepared.

The meanings of the symbols of each component of the ground treatment liquid in Table 1 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 A: hydrophilic fumed silica: manufactured by Nippon Aerosil Co., Ltd. Trade name AEROSIL 200
B: Hydrophilic fumed silica: manufactured by Nissan Chemical Industries, Ltd. Product name Snowtex-20L

“Zr concentration” in Table 1 means the Zr equivalent concentration (mass%) of the corresponding zirconium compound. “V concentration” means the V equivalent concentration (mass%) of the corresponding vanadium compound. “PO ₄ concentration” means the phosphate ion equivalent concentration (mass%) of the corresponding ammonium phosphate. “Concentration” in the column of “silane coupling agent” means the solid content equivalent concentration (mass%) of the silane coupling agent. The “concentration” in the column of “silica compound” means the solid content converted concentration (mass%) of the silica compound.

  The ground treatment liquids of test numbers 1 to 32 were produced by the following method. Ion exchange water was prepared as an aqueous solvent. While stirring the ion-exchanged water, the components shown in Table 1 were added, and further, a nonionic surfactant was added and mixed. The pH of each surface treatment solution was as shown in Table 1. The pH of each ground treatment solution was measured using a glass electrode pH meter (trade name D-52S, manufactured by Horiba, Ltd.).

  In Test Nos. 1-21 and 25-30, a ground treatment solution excellent in solution stability was obtained.

  For reference, in test number 31, a commercially available chromate treatment solution containing hexavalent chromium (manufactured by Nihon Parkerizing Co., Ltd., trade name: PALM) was used as the base treatment solution.

[Manufacture of organic coated galvanized steel pipe]
A plurality of galvanized steel pipes having a diameter of 15 mm were prepared. The adhesion amount of the galvanized layer on the outer surface of each galvanized steel pipe was in the range of 350 to 600 g / m ^{2 in} terms of metal Zn.
A blast treatment was performed on the galvanized steel pipe to adjust the surface roughness of the outer surface. Specifically, grid blasting was performed on the galvanized steel pipe. In the grid blast process, the blast process was implemented with respect to the galvanized steel pipe which moves on a conveyance roll with the moving speed of 10-15 m / min.

  The galvanized steel pipe after the blast treatment was heated using induction heating, and the outer surface temperature was maintained at 60 ° C. Thereafter, a base treatment solution was applied to the outer surface of the galvanized steel pipe to form a base layer. The sponge impregnated with the ground treatment liquid was pressed against the outer surface of the steel pipe, and the ground treatment liquid was applied to the outer surface of the galvanized steel pipe. The amount of adhesion of the undercoat layer was varied depending on the strength of pressing the sponge, the amount of the undercoat solution applied to the sponge, and the composition of the undercoat solution.

  After forming the base layer, an organic resin layer was formed by the following method. First, an adhesive resin layer made of polyethylene resin (trade name Modic HA-590K, manufactured by Mitsubishi Chemical Corporation) was formed on the base layer. The average film thickness of the adhesive resin layer was 0.3 mm in any test number.

  After forming the adhesive resin layer, an anticorrosion coating layer was formed on the adhesive resin layer. The anticorrosion coating layer was made of polyethylene resin (trade name HE122R manufactured by Nippon Polyethylene Co., Ltd.), and the average film thickness of the anticorrosion coating layer was 2.2 mm in any test number. The organic coating material provided with two layers (adhesive resin layer, anticorrosion coating layer) was formed by the above process, and the organic coating galvanized steel pipe was manufactured.

[Measurement of outer surface roughness of galvanized steel pipe after blasting]
Roughness Rzjis was calculated | required with the above-mentioned method based on JISB0601 (2001) with respect to the outer surface of the galvanized steel pipe after a blast process.

[Base adhesion measurement test]
The adhesion amount of the base layer of the galvanized steel pipe was measured by the following method. A test piece having a length of 50 mm was cut out from the organic-coated galvanized steel pipe. After cutting the test piece in half, the organic resin layer was burned off in an electric furnace at 600 ° C. Then, surfaces (inner surface and end surface) other than the outer surface on which the underlayer was formed were sealed with a trade name Neo Gosei made by Shinto Paint Co., Ltd. This test piece was immersed in heated hydrochloric acid or hydrofluoric acid to dissolve the surface of the steel material. Thereafter, zirconium ions or chromium ions adhering to the surface of the test piece were quantitatively analyzed by induction plasma spectroscopy (ICP). Thus, with regard to the test numbers 1 to 32, the amount of deposition of the metal Zr in terms sought (mg / m ^2), with respect to the test No. 33, was determined amount of deposition of metallic Cr converted (mg / m ^2).

[Initial adhesion measurement test]
Cutter scratches having a width of 10 mm and a length of 150 mm were placed in the organic resin layer of the organic-coated galvanized steel pipe. Furthermore, the organic resin layer and the steel pipe interface were peeled about 10 mm in the axial direction of the steel pipe by using a dedicated jig processed into a flea shape from the end of the steel pipe.

The peeled portion was pulled in the longitudinal direction of the steel pipe at a pulling speed of 10 mm / min, and the adhesion (kgf) was measured. Based on the measurement results of adhesion, the following evaluation was made. If it was “◯” or more, it was judged that the adhesion was excellent.
A: Adhesive strength is 10 kgf or more,
○: Adhesion strength is 3.5 kgf or more and less than 10 kgf,
X: Adhesion force is less than 3.5 kgf.

[Hot salt water immersion peel test]
A test piece (150 mm × 100 mm) was collected from the organic-coated galvanized steel pipe. The collected test piece was immersed in 3% brine (NaCl) at a temperature of 50 ° C. for 28 days. The maximum peel distance of the organic resin layer was measured from the end face of the test piece after 28 days. Furthermore, the presence or absence of rusting of the test piece after 28 days was visually confirmed.

The evaluation criteria were as follows. If it was “◯” or more, it was judged that the adhesiveness was excellent.
A: Maximum peel distance is less than 3 mm,
○: The maximum peel distance is 3 mm or more and less than 10 mm,
X: The maximum peeling distance is 10 mm or more.

The criteria for rusting were as follows.
○: No rusting
X: There is rusting.

[Cool cycle test]
A test piece (150 mm × 100 mm) was collected from the organic-coated galvanized steel pipe. A total of 7 cycles of the thermal cycle test was carried out with a temperature of −30 ° C., 8 hours, a temperature of 50 ° C., a relative humidity of 95% RH, and 14 hours as one cycle. After the test, the maximum peel distance of the organic resin layer from the end face of the test piece was measured. The relative humidity was controlled only when the temperature was 50 ° C.

The evaluation criteria were as follows. If it was “◯” or more, it was judged that the adhesion was high.
A: Maximum peel distance is less than 3 mm,
○: The maximum peel distance is 3 mm or more and less than 10 mm,
X: The maximum peeling distance is 10 mm or more.

[Test results]
Table 1 shows the test results.

  All of the ground treatment solutions of Test Nos. 1 to 14 had an appropriate composition. Furthermore, the production conditions for these test numbers were appropriate. Therefore, the organic coated galvanized steel pipe showed excellent adhesion in any of the initial adhesion strength measurement test, the hot salt water immersion peeling test, and the cooling cycle test. Furthermore, the generation of rust was not confirmed in the hot salt water immersion peel test, and the organic-coated galvanized steel pipe also showed excellent corrosion resistance.

  In these test numbers, even when compared with test number 31 using the chromate treatment solution, the adhesiveness and corrosion resistance were equivalent or better.

  On the other hand, in test number 15, although the surface treatment solution was appropriate, the coverage of the pure zinc layer on the surface of the galvanized layer was too high, and as a result, the surface roughness of the galvanized layer was too small. Therefore, the adhesion in the initial adhesion measurement test, the hot salt water peeling test, and the cooling / heating cycle test was low.

  In test number 16, although the surface treatment solution was appropriate, the coverage of the pure zinc layer on the surface of the galvanized layer was too low, and as a result, the surface roughness of the galvanized layer was too large. Therefore, generation | occurrence | production of rust was confirmed in the hot salt water peeling test.

  In test number 17, the base treatment liquid did not contain a silica compound. For this reason, the adhesion in the initial adhesion measurement test, the hot salt water peeling test and the cooling / heating cycle test was low, and the occurrence of rust was confirmed in the hot salt water peeling test.

  In test number 18, the base treatment liquid did not contain a silane coupling agent. For this reason, the adhesion in the initial adhesion measurement test, the hot salt water peeling test and the cooling / heating cycle test was low, and the occurrence of rust was confirmed in the hot salt water peeling test.

In test number 19, the content of the zirconium compound in the ground treatment solution was too high. As a result, the adhesion amount of the underlayer exceeded 1500 mg / m ² or more. For this reason, the adhesion in the initial adhesion measurement test, the hot salt water peeling test and the cooling / heating cycle test was low, and the occurrence of rust was confirmed in the hot salt water peeling test.

In test number 20, the content of the zirconium compound in the ground treatment solution was too low. Furthermore, the adhesion amount of the underlayer was 50 mg / m ² or less. For this reason, the adhesion in the initial adhesion measurement test, the hot salt water peeling test and the cooling / heating cycle test was low, and the occurrence of rust was confirmed in the hot salt water peeling test.

  In test number 21, the base treatment liquid did not contain a vanadium compound, ammonium phosphate, a silane coupling agent, and a silica compound. For this reason, the adhesion in the initial adhesion measurement test, the hot salt water peeling test and the cooling / heating cycle test was low, and the occurrence of rust was confirmed in the hot salt water peeling test.

  In test number 22, the pH of the ground treatment solution was too low. Therefore, the ground treatment liquid was gelled. On the other hand, in test number 23, the pH of the ground treatment solution was too high. Therefore, the ground treatment liquid was gelled. In test number 24, the content of the silica compound in the ground treatment solution was too high. Therefore, zirconium ions in the ground treatment liquid were precipitated. The ground treatment liquids of test numbers 22 to 24 could not be used.

  In test number 25, the content of the vanadium compound in the ground treatment solution was too low. As a result, the adhesion in the hot salt water peeling test and the cooling / heating cycle test was low, and furthermore, the occurrence of rust was confirmed in the hot salt water peeling test.

  In test number 26, the content of the vanadium compound in the ground treatment solution was too high. As a result, the adhesion in the initial adhesion measurement test and the thermal cycle test was low.

  In test number 27, the content of ammonium phosphate in the ground treatment solution was too low. As a result, the adhesion in the initial adhesion measurement test, the hot salt water peeling test and the cooling cycle test was low, and the occurrence of rust was confirmed in the hot salt water peeling test.

  In test number 28, the content of ammonium phosphate in the ground treatment solution was too high. As a result, the adhesion in the hot salt water peeling test and the cold cycle test was low.

  In test number 29, the content of the silane coupling agent in the ground treatment solution was too low. As a result, the adhesion in the initial adhesion measurement test, the hot salt water peeling test and the cooling cycle test was low, and the occurrence of rust was confirmed in the hot salt water peeling test.

  In test number 30, since the content of the silane coupling agent in the ground treatment liquid was too high, the ground treatment liquid gelled.

The embodiment of the present invention has been described above. However, the above-described embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately changing the above-described embodiment without departing from the spirit thereof.

Claims (2)

The surface roughness of the galvanized layer formed on the outer surface is 20 to 50 μm in terms of 10-point average roughness Rzjis based on JIS B0601 (2001), and the coverage of the pure zinc layer on the surface of the galvanized layer is 30. Preparing a galvanized steel pipe that is ~ 90%;
On the galvanized layer,
An aqueous solvent,
A zirconium compound of 0.05 to 10.50% by mass in terms of metal Zr,
0.004-0.400 mass% vanadium compound in metal V equivalent concentration,
0.07-7.50 mass% ammonium phosphate in terms of phosphate ion equivalent,
A solid content equivalent concentration of 0.1 to 10% by mass of a silane coupling agent and / or a hydrolysis condensate thereof,
Containing 0.2 to 10% by mass of silica compound in terms of solid content,
Applying a base treatment solution having a pH of 8 to 12 to form a base layer having an adhesion amount of less than 50 to 1500 mg / m ^{2 in} terms of metal Zr;
And a step of forming an organic resin layer on the foundation layer. It is used for the manufacturing method of the organic coating galvanized steel pipe of Claim 1, and the said surface roughness of the said galvanized layer formed on the said outer surface is ten-point average roughness Rzjis based on JISB0601 (2001). a 20 to 50 m, and the galvanized layer on the outer surface of the galvanized steel pipe coating ratio of the pure zinc layer is 30% to 90% at the surface of the galvanized layer, wherein between the organic resin layer A base treatment liquid for forming a base layer,
An aqueous solvent,
A zirconium compound of 0.05 to 10.50% by mass in terms of metal Zr,
0.004-0.400 mass% vanadium compound in metal V equivalent concentration,
0.07-7.50 mass% ammonium phosphate in terms of phosphate ion equivalent,
A solid content equivalent concentration of 0.1 to 10% by mass of a silane coupling agent and / or a hydrolysis condensate thereof,
Containing 0.2 to 10% by mass of silica compound in terms of solid content,
A ground treatment solution having a pH of 8-12.