JP2016008320A - Corrosion resistant layer for ferrous metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosion resistant layer capable of suppressing a blister of a coating film after coating, and an anticorrosion method capable of suppressing a blister of a coating film after coating.SOLUTION: (A corrosion resistant layer for a ferrous metal includes (a) a zinc/silicon-containing aluminum pseudoalloy spray coating film layer, (b) a primary coating film layer thereon, and (c) an acrylic resin coating film layer having a glass transition temperature (Tg) of 50-80°C and a number average molecular weight of 25,000-60,000. An anticorrosion method of a ferrous metal includes (1) a step for spraying a zinc wire material and a silicon-containing aluminum alloy wire material containing 3-14 mass% of silicon to form a spray coating film layer and practicing ordinary pore-sealing treatment, (2) a step for coating the outside of the spray coating film layer with acrylic resin paint to form the a primary coating film layer of the acrylic resin coating film layer, and (3) a step for coating the outside of the primary coating film layer with top coating paint containing (c) the acrylic resin to form an outermost layer of the acrylic resin coating film.

Description

  The present invention relates to a corrosion-resistant layer for ferrous metals having a zinc-silicon-containing aluminum pseudoalloy spray coating. More specifically, the present invention relates to an outer surface corrosion-resistant layer that prevents swelling during long-term use of an iron-based metal having a zinc-silicon-containing aluminum pseudoalloy spray coating.

  Ferrous metal pipes that have an anticorrosion layer formed on the outer surface by metal spraying have been used in various fields. Ferrous metal pipes that are buried in the ground such as water and sewage pipes that require corrosion resistance. It is used for etc. In many cases, such external metal spraying uses zinc, and zinc-aluminum alloys and zinc-aluminum pseudo-alloys are also known. These sprayed layers have a mechanism in which they themselves become sacrificial anodes in corrosive environments and produce corrosion products, which serve as a protective layer against the corrosion of the base iron-based metal.

  In recent years, pseudoalloy sprays of zinc and silicon-containing aluminum have been developed to further improve the corrosion resistance of these zinc-based sprayed layers, and the corrosion products are denser than conventional zinc sprays or zinc-aluminum pseudoalloy sprays. It has been reported that a strong protective layer can be formed, and further excellent corrosion resistance can be obtained, thereby extending the corrosion resistance life (Patent Document 1).

JP 2012-149336 A

  However, when an iron-based metal having a zinc-silicon-containing aluminum pseudoalloy spray coating is coated on the outer surface thereof, there may be cases where the coating is blistered in the durability test. There are many regulations on water pipes that need to pass various tests, one of which is the combined cycle corrosion test (CCT) to examine long-term durability. However, in a coating having a zinc-silicon-containing aluminum pseudoalloy spray coating, swelling may occur in the anticorrosion layer, and improvement thereof has been desired. The bulge appears due to the corrosion reaction of the zinc-silicon-containing aluminum pseudo-alloy spray coating, and the inside is usually hollow.

  Then, this invention makes it a subject to provide the corrosion-resistant layer which can suppress generation | occurrence | production of the swelling of the coating film after coating in the ferrous metal which has a zinc-silicon containing aluminum pseudo-alloy sprayed layer. Another object of the present invention is to provide a corrosion-resistant method capable of suppressing the occurrence of swelling of a coated film after coating in an iron-based metal having a zinc-silicon-containing aluminum pseudoalloy sprayed layer.

  In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, in an iron-based metal having a zinc-silicon-containing aluminum pseudoalloy spray coating, the outermost layer has a specific glass transition temperature and a number average molecular weight. By using an acrylic resin, the present inventors have found that the above problem can be solved by preventing the swelling of the coating film and completed the present invention.

  That is, the present invention is an anticorrosion layer for iron-based metals, comprising (a) a zinc-silicon-containing aluminum pseudoalloy spray coating layer and (b) a primary paint coating layer thereon, and ( c) It has an acrylic resin coating layer having a glass transition temperature (Tg) of 50 to 80 ° C. and a number average molecular weight of 25,000 to 60,000.

  In the anticorrosion layer for iron-based metal of the present invention, it is preferable that (a) a zinc-silicon-containing aluminum pseudoalloy spray coating layer is further sealed.

  In the corrosion-resistant layer for iron-based metal of the present invention, it is preferable that the (b) primary coating film layer is a resin coating layer of an acrylic resin coating.

  The present invention relates to an iron-based metal or cast iron pipe provided with the above-mentioned corrosion-resistant layer for iron-based metal.

  The present invention relates to a corrosion resistance method for an iron-based metal, wherein (1) a step of spraying a zinc-silicon-containing aluminum pseudoalloy on the outer surface of the iron-based metal to form a sprayed coating layer, (2) an outer side of the sprayed coating layer. And (3) a glass transition temperature (Tg) of 50 to 80 ° C. and a number average molecular weight on the outside of the primary paint film layer. It includes a step of applying a paint containing 25,000 to 60,000 acrylic resin to form an outermost layer of the acrylic resin film.

  The iron-based metal corrosion resistance method of the present invention preferably further includes a step of subjecting the sprayed coating layer to a sealing treatment.

  In the iron-based metal corrosion resistance method of the present invention, the iron-based metal is preferably a cast iron pipe.

  ADVANTAGE OF THE INVENTION According to this invention, the corrosion resistance of the iron-type metal which has a zinc-silicon containing aluminum pseudo alloy sprayed coating, especially the swelling of the coating film after coating can be prevented.

It is the photograph of the composite cycle test 120th day of the cast iron pipe in which the corrosion-resistant layer of Example 1 (a) and Comparative Example 1 (b) was applied.

  The corrosion-resistant layer for iron-based metals of the present invention has (a) a zinc-silicon-containing aluminum pseudoalloy spray coating layer and (b) a primary coating film layer thereon, and (c) a glass transition temperature ( Tg) It is characterized by having an acrylic resin film layer having a number average molecular weight of 25,000-60,000 at 50-80 ° C. The glass transition temperature is measured by a differential scanning calorimeter (DSC). The number average molecular weight is a value in terms of polystyrene calculated by gel permeation chromatography (GPC).

((A) Zinc-silicon-containing aluminum pseudoalloy spray)
The metal sprayed coating in the present invention is a zinc-silicon-containing aluminum pseudoalloy sprayed coating. The zinc-silicon-containing aluminum pseudoalloy spray coating can be formed by spraying a zinc wire and an aluminum alloy wire containing 3 to 14% by mass of silicon. A pseudo-alloy spray coating using a zinc alloy containing aluminum instead of zinc is also within the scope of the present invention. These thermal sprays are described in detail in JP 2012-149336 A. The silicon-containing aluminum alloy wire used for the zinc-silicon-containing aluminum pseudoalloy spray coating more preferably contains 3 to 13% by mass of silicon, and most preferably 5 to 13% by mass. When the amount is more than 13% by mass, the sprayed wire becomes hard and tends to affect the spraying operation. Further, the film thickness of the zinc-silicon-containing aluminum pseudoalloy spray coating can be appropriately set depending on the type of iron-based metal, the type of thermal spray material, and the use of the obtained metal member. For example, cast iron for water pipes If, approximately 200g / m ² ~400g / m ² are ^{preferred, 260g / m 2 ~300g / m} 2 is more preferable.

(Iron-based metal)
In the present invention, an iron-based metal means an iron-based metal in which zinc-silicon-containing aluminum pseudoalloy spraying is effective, for example, cast iron, steel, and the like, and a cast iron pipe, particularly a cast iron pipe used for a water and sewage pipe Are preferably used.

((B) Primary paint film layer)
The corrosion resistant layer for iron-based metal of the present invention is primary-coated on a zinc-silicon-containing aluminum pseudoalloy spray to form a primary coating film layer. The primary coating is performed with a paint containing various additives such as a pigment, a dispersant, and a surface conditioner as necessary in the resin component. The resin component is not particularly limited as long as it is generally used for metal coating such as acrylic resin and epoxy resin, particularly for iron-based metal coating. For use in water pipes, for example, paints specified in Japan Water Works Association Standard JWWA K139 “Ductile Cast Iron Pipe Synthetic Resin Paint for Waterworks” can be suitably used.

  Among them, when the primary paint is a paint having a relatively high moisture permeability such as an acrylic resin paint, the conventional top coat tends to cause swelling in the paint film, so that the effect of the present invention is exhibited. Can do. Further, from the viewpoint of compatibility with the outermost layer (c) acrylic resin coating layer, the primary coating is most preferably an acrylic resin coating.

(Outermost layer (c) acrylic resin coating layer (top coating layer))
For the acrylic resin coating layer of the corrosion resistant layer for iron-based metal of the present invention, a top coating containing an acrylic resin having a glass transition temperature (Tg) of 50 to 80 ° C. and a number average molecular weight of 25,000 to 60,000 is preferably used. Can be used. The acrylic resin that is a resin component is a copolymer mainly composed of acrylic acid, methacrylic acid, alkyl acrylate ester, and alkyl methacrylate ester. As described above, it is suitable for metal coating, particularly iron-based metal coating. It is not particularly limited as long as it is generally used. For use in water pipes, for example, paints specified in Japan Water Works Association Standard JWWA K139 “Ductile Cast Iron Pipe Synthetic Resin Paint for Waterworks” can be suitably used. Also, a methyl methacrylate / butyl methacrylate acrylic resin is most preferably used since the effect has been sufficiently confirmed.

  If the glass transition temperature of the acrylic resin in the top coating is in the range of 50 to 80 ° C., it can be used without any particular problem. However, if corrosion resistance at higher temperatures is required, it is further 55 It is preferable that the temperature is higher than or equal to ℃, and it is further preferable that the temperature is lower than or equal to 75 ℃ in view of adhesion. Further, the number average molecular weight of the acrylic resin in the top coat can be used without any problem as long as it is in the range of 25,000 to 60,000. However, in consideration of the coating workability, it is 50,000. The following is preferable.

  In addition, the zinc-silicon-containing aluminum pseudoalloy spray coating of the corrosion resistant layer for iron-based metal of the present invention is preferably subjected to a normal sealing treatment.

  Examples of the sealing treatment include treatment with an aqueous treatment liquid containing an additive such as colloidal silica, an inorganic compound such as colloidal silica, and a resin component such as an acrylic resin and an epoxy resin similar to the primary paint.

(solvent)
For the preparation of each coating film layer constituting the corrosion resistant layer for iron-based metal of the present invention, that is, (b) primary coating film layer and (c) acrylic resin coating layer (top coating film layer), it is usually used for metal coatings. Common solvents that can be used can be used. Specifically, for example, hydrocarbon solvents such as toluene, xylene, cyclohexane, n-hexane, and octane; methanol, ethanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, ethylene glycol monomethyl ether, etc. Alcohol solvents; ester solvents such as methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. These solvents can be used alone or in combination of two or more.

(Pigment)
In the anticorrosion layer for iron-based metal of the present invention, a pigment can be blended in order to impart sufficient colorability to the primary paint and the top coat. Specifically, coloring pigments such as titanium dioxide, iron oxide, carbon black (for example, trade name MA100, manufactured by Mitsubishi Chemical Corporation), cyanine blue, cyanine green, etc .; calcium carbonate, talc, barium sulfate, clay, etc. Extender pigments; rust preventive pigments such as zinc phosphate, calcium phosphate, and aluminum phosphomolybdate. These may be used alone or in combination of two or more if necessary.

(Additive)
Each coating film layer constituting the corrosion-resistant layer for iron-based metal of the present invention, that is, (b) primary coating film layer and (c) acrylic resin coating layer (top coating film layer) is generally used for metal coatings. The various additives used can be used. Specifically, it is composed of a defoaming agent composed of silicone or organic polymer; a surface conditioner composed of silicone or organic polymer; a viscosity modifier composed of amide wax or organic bentonite (sagging agent); silica, alumina or the like. Matting agents; dispersants composed of polycarboxylates; ultraviolet absorbers composed of benzophenone, hindered amine light stabilizers, phenolic antioxidants, waxes, and other known additives. These can be used alone or in admixture of two or more if necessary.

  For the production of each paint used for each paint film layer of the corrosion-resistant layer for iron-based metal of the present invention, equipment conventionally used for paint production is used. The production method is not particularly limited. For example, after a pigment, an additive (pigment dispersant, viscosity modifier, etc.), a solvent, etc. are added to a commercially available resin component, it is desired to be dispersed by a roll mill, SG mill, disper, etc. Paint is obtained.

  The method of applying each paint used for the iron metal corrosion resistant layer of the present invention is not particularly limited, but it is applied by a method such as brush coating, roller coating, air spray coating, airless spray coating, dip coating or shower coat coating. The

  The thickness of the outermost layer of the primary paint film layer and the acrylic resin film is appropriately set depending on the application of the iron-based metal to be painted, and is not particularly limited. For example, in the case of a cast iron pipe used for water and sewage, it can be appropriately set within a range of approximately 10 μm to 100 μm.

  Further, as one aspect of the present invention, (1) a step of spraying a zinc-silicon-containing aluminum pseudoalloy on the outer surface of an iron-based metal to form a sprayed coating layer, (2) on the outside of the sprayed coating layer A step of applying an acrylic resin paint to form a primary paint film layer of the acrylic resin film; and (3) a glass transition temperature (Tg) of 50 to 80 ° C. and a number average molecular weight of 25 on the outside of the primary paint film layer. There is a method for corrosion resistance of iron-based metal, which includes a step of applying a paint containing acrylic resin of 1,000,000 to 60,000 and forming the outermost layer of the acrylic resin film. The above description of the corrosion resistant layer for iron-based metals is applied to the outermost layer of the thermal spray coating layer, the primary paint coating layer, and the acrylic resin coating used in the method.

The detail of the component used in the Example and the comparative example is shown below.
<Zinc-silicon-containing aluminum pseudoalloy spray>
Pseudoalloy spraying of zinc and aluminum containing 12% silicon

<Sealing treatment>
Kurimoto Coat TS Block (Amorphous silica-based sealing agent containing 13.5% by weight of acrylic resin, 13.0% by weight of amorphous silica, 0.5% by weight of additive, and 73% by weight of water: manufactured by Dainippon Paint Co., Ltd. )

<Primary painting>
Kurimoto Coat WR Gray (Latex paint containing 44.0% by weight of acrylic resin, 43.0% by weight of coloring and extender pigment, 3.0% by weight of additive, and 10% by weight of water: manufactured by Dainippon Paint Co., Ltd.)

<Top coat painting>
Acrylic resin top coating composition A
ACRYDIC WYL-567 (manufactured by DIC Corporation): methyl methacrylate / butyl methacrylate copolymer, Tg: 69 ° C., number average molecular weight (Mn): 32,000
Top coating composition B
ACRYDIC WYL-588 (manufactured by DIC Corporation): Methyl methacrylate / butyl methacrylate copolymer, Tg: 47 ° C., number average molecular weight (Mn): 20,000

The number average molecular weight (Mn) was measured under the following conditions.
[GPC measurement conditions]
Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 detector: RI (differential refractometer)
Column temperature: 40 ° C
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection amount: 100 μL (tetrahydrofuran solution with a sample concentration of 4 mg / mL)
Standard sample: A calibration curve was prepared using the following monodisperse polystyrene.
(Monodispersed polystyrene)
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

Production Example 1: Production of Topcoat Paint The topcoat paint was produced by stirring with the composition shown in Table 1.

Example 1 and Comparative Example 1
A zinc-silicon-containing aluminum was sprayed at 260 g / m ² on a ductile cast iron pipe having a nominal diameter of 100 to form a zinc-silicon-containing aluminum pseudoalloy spray coating on the cast iron pipe. On the obtained zinc-silicon-containing aluminum pseudoalloy spray coating, sealing treatment was applied at 100 g / m ² , and Kurimoto Coat WR gray was applied as a primary coating by spraying at a film thickness of 60 μm and dried. Either the top coating composition A or B prepared in the production example was applied by spraying or brushing with a film thickness of 20 μm and dried. Here, Example 1 was applied with the top coating composition A and Comparative Example 1 was applied with the top coating composition B. After drying, the cast iron pipe was cut into a 150 × 90 mm tile-shaped test piece, and the portion other than the test surface was coated with a liquid epoxy resin paint and dried. Thereafter, an X-shaped scratch of 0.3 × 50 mm was made on the surface of the test piece.

Test Example The test pieces obtained in Example 1 and Comparative Example 1 were subjected to a combined cycle test (CCT) to evaluate the appearance of the coating film such as white rust, red rust, and presence or absence of swelling.

Combined Cycle Test The test pieces obtained in Example 1 and Comparative Example 1 were subjected to a combined cycle test for 120 days in accordance with JIS K 5600-7-9 (2006) cycle corrosion test method cycle A. The appearance of the coating film was visually judged according to the following criteria. The results are shown in FIG.

  In Example 1, no particularly large change was observed except for the cross cut portion, and only white rust was observed in the cross cut portion. On the other hand, in Comparative Example 1, blisters were widely observed around the crosscut portion, and further red rust was observed (indicated by arrows in FIG. 1).

  From these results, it can be seen that in Example 1 in which the specific acrylic resin coating layer is combined with the zinc-silicon-containing aluminum pseudo-alloy spray coating of the present invention in the outermost layer, swelling can be suppressed almost completely.

Claims (8)

(A) A zinc-silicon-containing aluminum pseudoalloy spray coating layer and (b) a primary coating film layer thereon, (c) a glass transition temperature (Tg) of 50 to 80 ° C., and a number average molecular weight of 25 An anticorrosion layer for iron-based metal, comprising an acrylic resin coating layer of 1,000,000 to 60,000. The corrosion-resistant layer for ferrous metals according to claim 1, wherein (a) the zinc-silicon-containing aluminum pseudoalloy spray coating layer is sealed. (B) The corrosion resistant layer for an iron-based metal according to claim 1 or 2, wherein the primary paint film layer is a resin film layer of an acrylic resin paint. The iron-type metal in which the corrosion-resistant layer of any one of Claims 1-3 was given. The cast iron pipe in which the corrosion-resistant layer of any one of Claims 1-3 was given. On the outer surface of the ferrous metal,
(1) a step of thermally spraying a zinc-silicon-containing aluminum pseudoalloy to form a sprayed coating layer;
(2) A step of applying an acrylic resin paint on the outside of the sprayed coating layer to form a primary paint film layer of the acrylic resin coating, and (3) a glass transition temperature (Tg) on the outside of the primary paint film layer. ) Corrosion resistance of an iron-based metal characterized by including a step of coating an overcoat containing an acrylic resin having a number average molecular weight of 25,000 to 60,000 at 50 to 80 ° C. to form an outermost layer of the acrylic resin film Method. Furthermore, the corrosion-resistant method of Claim 6 including the process of performing a sealing process to a sprayed coating layer. The corrosion resistance method according to claim 6 or 7, wherein the ferrous metal is a cast iron pipe.