JP2001277425A - Heavy corrosion-proof coated steel material coated with corrosion-proof resin layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide not only substrate treatment excellent in cathodic peel resistance at a high temperature reaching 100 deg.C but also a heavy corrosion-proof coated steel material high in reliability. SOLUTION: As the substrate treatment of a heavy corrosion-proof coating, treatment using a metal powder containing zinc as main component and a chromic acid aqueous solution is applied to a steel material and the treated steel material is baked and dried to form a film layer 2, and a resin primer layer 4 and a corrosion-proof coating layer 5 with a thickness of 0.3 mm or more are successively laminated on the film layer 2. Since an iron exposed part is eliminated by the substrate treatment, corrosive electrolytic reaction is suppressed and cathodic peel resistance at a high temperature can be enhanced and a corrosion-proof coating high in reliability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty anticorrosion coated steel material which is subjected to cathodic protection such as a countermeasure for flaws at the time of construction of a line pipe. About.

[0002]

2. Description of the Related Art When a long-term anticorrosion property is required for a line pipe or the like, a heavy anticorrosion coated steel pipe coated with a polyolefin resin is used. Since pipes are often used buried, cathodic protection is also used in order to suppress corrosion of steel materials at flaws, assuming that penetration flaws will occur during transportation and construction work on resin-coated steel pipes. However, since cathodic protection causes cathodic peeling to reduce the coating adhesive strength around the flaw, cathodic peeling resistance is important for heavy corrosion-resistant coated steel pipes used for line pipes. On the other hand, as a conventional technology,
By applying chromate treatment and resin primer treatment to the base treatment of the heavy corrosion protection coating, the cathode peeling resistance is greatly improved. The chromate treatment agent used for the undercoat treatment has a large effect of suppressing the cathode peeling, and a phosphoric acid chromate having improved high-temperature cathode peelability as shown in Japanese Patent No. 1696992, and a silane coupling agent added as shown in Japanese Patent No. 1985806. Some have improved performance.

[0003]

Since cathodic peeling resistance is important, various improvements have been made in heavy corrosion resistant coated steel materials. In particular, in recent years, demands for use in a high-temperature environment represented by polypropylene have been increasing, and a heavy-duty corrosion-resistant coated steel material excellent in peeling resistance at a high temperature of 100 ° C. has been demanded. On the other hand, the chromate treatment agent represented by Japanese Patent No. 1991880 has a limit in the achievable high-temperature performance. Further, in the method of adding a silane coupling agent, which is the third component as typified by Japanese Patent No. 1696992, a problem is likely to occur in the stability of the processing solution. Therefore, there is a demand for a base treatment that is excellent in cathode peeling resistance in each temperature range up to a high temperature. Chromate treatment used for heavy duty anticorrosion coatings is a thick film of several μm, and has a defect that the film itself drastically shrinks during drying, cracks and a decrease in adhesion to steel materials easily. Lower. On the other hand, a method of lowering the drying temperature of the chromate film on the steel material can be considered. However, in this case, since the elution property of the film increases, the secondary adhesion after immersion decreases. Accordingly, there is a demand for an undercoating film having excellent cathode peeling resistance by a stable treatment alone or in combination with a chromate treatment.

[0004] The present invention is intended to reduce the defects in the treatment of the steel material surface by replacing or combining the chromate-treated film in heavy corrosion protection coated steel material typified by polyolefin coating, and to provide electrical stability such as electric potential and insulation. By providing a base treatment with excellent cathode peel resistance,
It is intended to provide a highly corrosion-resistant coated steel material having high reliability.

[0005]

The gist of the present invention is as follows. (1) On the surface of the steel material subjected to the base treatment, a treatment coating composed of a metal powder containing zinc as a main component and a dry component of a chromic acid aqueous solution is applied, and a resin primer layer and an anticorrosion resin layer having a thickness of 0.3 mm or more are formed. Coated heavy corrosion resistant coated steel. (2) On the surface of the steel material subjected to the base treatment, a coating composed of a metal powder containing zinc as a main component and a dry component of a chromic acid aqueous solution is applied, and the surface is further treated with a chromating agent containing fine-particle silica and partially reduced chromic acid. Heavy corrosion protection coated steel material coated with a resin primer layer and a corrosion protection resin layer having a thickness of 0.3 mm or more after the treatment. (3) The anticorrosion resin layer according to (1), wherein the anticorrosion resin layer is a modified polyolefin alone, or a two-layer coating of a modified polyolefin adhesive layer and a polyolefin, or a polyurethane resin coating. Anticorrosion coated steel. (4) The anticorrosion resin layer according to (2), wherein the anticorrosion resin layer is a modified polyolefin alone, or a two-layer coating of a modified polyolefin adhesive layer and a polyolefin, or a polyurethane resin coating. Anticorrosion coated steel.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a means for solving the above-mentioned problems, the present inventors have proposed a method of drying a metal powder containing zinc as a main component and a chromic acid aqueous solution as shown in the sectional view of FIG. After forming the treated coating layer 2 composed of the components on the steel material 1 surface,
A resin primer layer 4 and an anticorrosion resin coating layer 5 having a thickness of 0.3 mm or more are sequentially laminated and used. Alternatively, FIG.
As shown in FIG. 2, a treated coating layer 2 composed of a metal powder containing zinc as a main component and a dry component of a chromic acid aqueous solution, a coating chromate treatment 3 containing dry silica is performed thereon, and thereafter, a primer treatment is performed. The resin primer layers 4, 0.
An anti-corrosion resin coating layer 5 having a thickness of 3 mm or more is sequentially laminated and used. In this case, as the anticorrosion resin layer, a modified polyolefin alone, a two-layer coating of a modified polyolefin adhesive layer and a polyolefin, or a polyurethane resin coating is desirable. The present invention provides a heavy-duty corrosion-resistant coated steel material excellent in cathodic peeling resistance by the above-mentioned laminated coating.

Hereinafter, the present invention will be described in detail.
The steel material used in the present invention is ordinary steel, or C, Si,
Steel with controlled Mn, nitrogen and oxygen, and Cu, N
It is a high alloy steel to which elements such as i, Cr, Mo, Nb, Ti, Al, Mg, V, and Ca are added. Typical varieties are steel pipes to which heavy corrosion protection coating is applied, and steel pipe piles, steel pipe sheet piles, steel sheet piles, H-section steel, wire rods and the like used in marine structures and the like. In order to remove scale, contaminants, and the like on the surface of these steel materials, any one of base treatments such as alkali degreasing, pickling, sand blasting, grid blasting, and shot blasting is always performed.

Next, the treatment comprising a zinc-based metal powder used in the present invention and a dry component of a chromic acid aqueous solution will be described. As the metal powder containing zinc as a main component, a metal powder containing at least 50% or more of zinc is used. As the other components in the metal powder, a metal lower than iron, such as Mg and Al, is used except for trace components. The shape may be arbitrary, but a scaly shape is desirable. In addition, one having an average thickness of 1 μm or less is used. The metal powder containing zinc as a main component may be used as a mixture with another metal powder, for example, an aluminum powder. The proportion of the metal powder containing zinc as a main component in the treatment liquid is 5 to 50 parts by weight. The aqueous solution of chromic acid is an aqueous solution containing hexavalent chromium at a ratio of 0.1 to 10% by weight in the aqueous solution, for example, a solution obtained by dissolving chromic anhydride in water. The present invention is only required to bake and dry an aqueous solution of zinc-based metal powder and hexavalent chromium to form a film having a thickness of 0.1 to 3 μm. For the purpose of adjusting the adhesion of phosphoric acid, boric acid, cobalt salt, nickel salt, and water-soluble dispersing resins such as acrylic, polyester, urethane, polyethylene, epoxy, butadiene,
A polyvinyl-based, melamine-based, phenol-based, or alkyd-based resin, glycol, a suspending / dispersing agent, or a surfactant is appropriately added and used. By coating the above component solution on the surface of the steel material subjected to the base treatment and drying by heating to 100 ° C. or more, a film layer in which the gap between the zinc powders is filled with a solution drying component such as chromium is formed. As a commercially available treatment, for example, there is a dacromet treatment (Dacro Shamrock Japan).

There is a problem that the number of processing steps increases, but
If cathode peelability or adhesion to the coating is required,
After forming the above treated film, apply chromate treatment and dry.
Perform dry baking. Coating type chromate treatment
50-800mg / m^TwoSo that the adhesion amount of place
Chromic anhydride (Cr
O _Three) Is partially reduced with an organic reducing agent
Mixed with hexavalent chromium ions and trivalent chromium ions
And any mixture of silica-based fine particles.
5-50 silica particles synthesized by a dry method
The primary particles having a diameter of nm are subjected to secondary aggregation. Example day
AEROSIL 130, AERO made by this Aerosil
SIL 200, AEROSIL 200V, AERO
SIL 200CF, AEROSIL 200FAD,
AEROSIL 300, AEROSIL 300C
F, AEROSIL 380, AEROSIL OX5
0, AEROSIL TT600, AEROSIL M
These are silica fine particles such as OX. The amount of silica fine particles added
In the range of 0.5 to 4.0 with respect to the total amount of chromium added
Added. The rate of reduction from hexavalent to trivalent chromium
The range is preferably 10 to 70% with respect to the system. More needed
Phosphoric acid etc. in the range of 0.1 to 2 with respect to total chromium, depending on
May be added. If the stability of the liquid is not a problem,
Silane coupling agent, emulsion resin, etc.
It may be added.

Next, the resin primer used will be described. A thermosetting resin is used as a primer used in the heavy-corrosion-coated steel material of the present invention, and a resin obtained by adding a curing agent and an inorganic pigment to an epoxy resin, a polyurethane resin, or a polyester resin is used as a main component. As a polyurethane resin, a moisture-curable one-pack type using a prepolymer,
Alternatively, a two-liquid curing type using a reaction between an isocyanate and a polyol is typical. In particular, an epoxy resin is preferably used for the primer to meet the requirement of high heat resistance. Generally, bisphenol A type and bisphenol F type resins are used singly or as a mixture as the main component. If high-temperature properties are required, a polyfunctional phenol novolak or a halogenated resin is used in combination with the above-mentioned bisphenol A type or bisphenol F type resin. When a two-part curing type amine-based curing agent or an imidazole compound which is a latent curing agent and a dicyandiamide or phenol-based curing agent is used in combination as the curing agent, adhesion and corrosion resistance are excellent. The inorganic pigment to be added is 3 to 30 vol% based on the total volume.
When added in the range, the shrinkage strain is reduced, and the adhesion characteristics are greatly improved. For inorganic pigments, pigments such as silica, titanium oxide, wollastonite, mica, talc, kaolin, chromium oxide, zinc borate, zinc borate, zinc phosphate,
Alternatively, a metal powder such as zinc or Al, a ceramic powder, or the like, or an anticorrosive pigment such as strontium chromate is used as appropriate. These pigments may be subjected to a silane coupling treatment on the surface in order to improve the wettability with the resin.

Using the above thermosetting resin primer,
By combining with the above-described chromate treatment, it is possible to provide a base treatment for a heavy corrosion-resistant coated steel material having excellent performance in peel resistance. When the resin primer is supplied as a liquid, a method such as roll or brush coating, ironing, air spray coating, or the like is used. When supplied in the form of powder, a method such as electrostatic powder coating is used, and
Paint in the range of m. When the film thickness is smaller than 10 μm, many pinholes are generated. On the other hand, although the upper limit of the film thickness varies depending on the type of the resin, in the case of a thick film coating exceeding 500 μm, characteristics such as impact resistance at a low temperature tend to be deteriorated.

After the above base treatment, a heavy duty anticorrosion coating is applied.
As the resin to be coated, any resin such as vinyl chloride, polyester, acrylic, epoxy, and fluorine-based resin may be used as long as it has excellent durability and barrier properties against water and oxygen, but polyolefin resin and polyurethane resin are preferable. In particular, polyolefin resins are excellent in corrosion resistance such as resistance to cathodic peeling and in price. Polyolefin resin, as its main component, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene,
It is a resin containing a conventionally known polyolefin such as polypropylene, and a known polyolefin copolymer such as an ethylene-propylene block or a random copolymer, a polyamide-propylene block or a random copolymer. As other components, carbon black or other coloring pigments, a filler, an antioxidant, an ultraviolet absorber, a hindered amine-based weathering agent and the like are added in any combination as heat resistance and weathering resistance measures.

When a polyolefin resin is used for coating,
A polyolefin-modified adhesive is used for the lower layer portion that comes into contact with the primer of the base. This adhesive is a known polyolefin such as polyethylene, polypropylene, and nylon, and a known polyolefin copolymer resin, modified with an unsaturated carboxylic acid such as maleic acid, acrylic acid, or methacrylic acid, or an acid anhydride thereof. And known modified polyolefins such as those obtained by appropriately diluting a modified product thereof with a polyolefin resin. 50-7
0.3 to 100 μm thin modified polyolefin adhesive layer
Although a method using a combination of 5 mm polyolefin resin layers is preferable from the viewpoint of the balance between price and performance, the polyolefin coating layer is omitted and the modified polyolefin resin layer is used in 0.1%.
It may be coated as 3 mm or more and used as an anticorrosion layer. As the polyolefin coating method, for example, an extrusion coating method in which a resin melted by heating with a die is directly coated on a steel material is used. Alternatively, there is a method in which a preformed polyolefin sheet is attached to a heated steel material, or a method in which pulverized polyolefin is powder-coated and melted to form a film. According to these methods, a polyolefin anticorrosion coating layer having a thickness of 0.3 mm or more is formed.

[0014]

EXAMPLES AND COMPARATIVE EXAMPLES As a metal powder containing zinc as a main component, zinc powder in the form of flakes (particle size: 1.33 to 1.54 μm / measured by the Blaine method) and granular aluminum powder (1 μm or less) were used. A water-soluble epoxy resin and a polymer alcohol were added to a chromic acid aqueous solution to prepare a suspended and dispersed aqueous solution. On the other hand, as a chromating agent for coating, chromic acid solution is added to dry silica (Aerosil 20).
0: manufactured by Nippon Aerosil Co., Ltd.) in a weight ratio to total chromium of 1.0, and the phosphoric acid component in a weight ratio to total chromium of 0.1.
5 and partially reduced to 40% using dextrin as a reducing agent to produce a chromate treating agent corresponding to Japanese Patent No. 1696992.

[0015] Heavy corrosion protection coated steel material 200A, length 5.
Using a 5 m steel pipe, a polypropylene-coated steel pipe shown in Table 1 was produced. The surface of the steel pipe was first blasted with a grid, and then a treatment solution of a chromium aqueous solution containing a metal powder containing zinc as a main component and an Al powder was applied, and then the steel material was heated to 200 ° C. in a heating furnace. Thereafter, a powdered primer obtained by half-reacting an epoxy resin (including a bisphenol A type main ingredient, 20% of a phenol novolak resin, an imidazole curing accelerator, a phenolic curing agent, and a silica-based inorganic pigment) is used. Average film thickness 50 μm
The electrostatic powder coating was performed so that Then, using a two-layer T-die, a 0.1 mm modified polyolefin adhesive layer as a lower layer and a 2 mm polypropylene resin layer as an upper layer were extrusion-coated in a spiral manner by rotating and conveying, and the steel pipe was water-cooled. 1 to 7 polypropylene-coated heavy duty corrosion-resistant steel pipes were produced.

Further, in the case where the chromate treatment was combined, similarly, a polypropylene-coated steel pipe shown in Table 1 was produced using a steel pipe having a length of 200 A and a length of 5.5 m. First, the surface of the steel pipe is blasted with a grid, and then a treatment solution of a chromium aqueous solution containing a metal powder containing zinc as a main component and an Al powder is applied.
Heated to ° C. Then, after cooling to 30 ° C. by allowing to cool, the above-mentioned chromate treatment agent is applied and dried, and then the steel pipe is heated again, using an epoxy resin powder primer so as to have an average thickness of 50 μm. Painting was carried out. Then, using a two-layer T-die, a 0.1 mm modified polyolefin adhesive layer as a lower layer and a 2 mm polypropylene resin layer as an upper layer were extrusion-coated in a spiral manner by rotating and conveying, and the steel pipe was water-cooled. 8 to 10 polypropylene-coated heavy duty corrosion-resistant steel pipes were produced. Further, as a comparative example, a coated steel pipe of level 11 was prepared as a case where the polyolefin coating was omitted.

On the other hand, as a comparative example, a heavy corrosion protection coated steel material subjected to a chromate treatment, and a case where the chromate treatment was not carried out, a grid blast treatment was applied to a 200A, 5.5 m long steel pipe surface, and a coating chromate treatment was performed. In the case of carrying out, after applying the roll so that the chromium adhesion amount becomes 500 mg / m ² and drying it, electrostatic powder coating was performed using a powder primer so that the average film thickness became 50 μm. Thereafter, the steel pipe was heated to 200 ° C., and a 0.1 mm modified polyolefin adhesive layer was formed as a lower layer and a 2 mm polypropylene resin layer was formed as an upper layer by extrusion using a two-layer T-die. After cooling with water, a polypropylene-coated heavy-duty corrosion-resistant steel pipe of Comparative Example 12 was produced. Further, a polypropylene-coated steel pipe of Comparative Example 13 which was not subjected to a chromate treatment by the same process was prepared.

The coated steel pipe thus produced was cut into a 150 × 80 mm steel piece, a coating penetrating flaw reaching the steel surface of 8 mmφ was formed at the center of the coating surface, and a cylindrical plastic cell was erected on the coating, and 3% inside the coating. Brine was charged. The voltage was adjusted to -1.5 V with respect to the standard saturated calomel electrode potential on the scratched steel part, and the cathode peel test was performed in ovens at 60 ° C and 100 ° C.
Performed on days 0 and 60.

As is evident from the results of the cathodic peeling test in Table 1, the heavy duty anticorrosion coating material of the present invention shows remarkably superior performance as compared with the conventional coating chromate treatment or untreated. Further, when the undercoat treatment and the chromate treatment of the present invention are combined, further excellent cathode peeling resistance can be obtained.

[0020]

[Table 1]

[0021]

According to the heavy corrosion protection coated steel material of the present invention, the use of the undercoat treatment of the present invention for the heavy corrosion protection coating against the occurrence of peeling from the flaws when the electrolytic protection is carried out enables the conventional coating type. A high peeling suppression effect which cannot be obtained by the chromate treatment can be obtained. Thereby, even in a high-temperature region, excellent cathodic peeling resistance that has not been obtained so far can be obtained, so that a more reliable heavy-duty anticorrosion coating can be provided.

[Brief description of the drawings]

FIG. 1 shows an example of a cross-sectional view of a coating configuration of a heavy-corrosion-coated steel material of the present invention.

FIG. 2 shows another example of a sectional view of the coating structure of the heavy corrosion-resistant coated steel material of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steel material 2 Dry coating with metal powder containing zinc as a main component and chromic acid aqueous solution 3 Coating type chromate treatment layer containing fine silica particles 4 Primer resin layer 5 Corrosion prevention coating layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B32B 27/40 B32B 27/40 (72) Inventor Hiroyuki Mimura 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation AE03 BB74X CA33 DA15 DB02 DC05 EB13 EB38 EC01 EC03 EC10 4F100 AA20D AB01B AB03A AB10 AB13B AB18B AK01C AK01E AK03E AK07 AK51E AK53 AL06E BAD BA01 BA01 BA01 BA01 BA01 BA10 BA01 BA10 BA01 BA01 BA10 BA01 BA01 BA01 BA01 BA01 JK06 JM02B YY00E

Claims (4)

[Claims] 1. A surface of a steel material which has been subjected to a base treatment, is provided with a treated coating comprising a metal powder containing zinc as a main component and a dry component of a chromic acid aqueous solution, and a resin primer layer, an anticorrosive resin having a thickness of 0.3 mm or more. Heavy corrosion protection coated steel with a layer coating. 2. A coating comprising a metal powder containing zinc as a main component and a dry component of a chromic acid aqueous solution is applied to the surface of the steel material subjected to the undercoating treatment, and is further treated with a chromate treating agent containing fine particle silica and partially reduced chromic acid. A heavy corrosion resistant coated steel material coated with a resin primer layer and a corrosion resistant resin layer having a thickness of 0.3 mm or more after surface treatment. 3. The anticorrosion resin layer according to claim 1, wherein the anticorrosion resin layer is a modified polyolefin alone, a two-layer coating of a modified polyolefin adhesive layer and a polyolefin, or a polyurethane resin coating. Heavy corrosion resistant coated steel. 4. The anticorrosion resin layer according to claim 2, wherein the anticorrosion resin layer is a modified polyolefin alone, a two-layer coating of a modified polyolefin adhesive layer and a polyolefin, or a polyurethane resin coating. Heavy corrosion resistant coated steel.