JPH10113613A - Anticorrosive paint coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of easily forming a double-anticorrosive coat of a zinc coat and a baking coat on a steel structure by a series of processes. SOLUTION: After a body to be treated made of steel is heated to prescribed temperature, powder paint or the like 3 in which zinc fine particles are mixed is contacted with it using a fluidized immersion tank or the like. After a baking coat in which zinc fine particles are dispersed is formed as an inner layer, powder paint or the like 5 not containing zinc fine particles is rapidly contacted with it before the body to be treated and the inner layer coating film itself are not cooled to form a resin powder coat or the like is formed on the inner layer and form a double-anticorrosive coating film. By this method, a double- anticorrosive coat excelling in anticorrosion is formed on a steel structure with tight adhesion and at low cost. This coat is used in a corrosive region. It has a wide application to various kinds of steel structures such as houses, bridges, and steel towers as a long life anticorrosive coat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion coating for a steel structure used in a corroded area such as a coastal area.

[0002]

2. Description of the Related Art Double corrosion protection coating of zinc plating and organic coating is often used for corrosion protection of steel structures in a strongly corrosive environment such as a coastal zone. This is because, in the case of a steel substrate, corrosion of the steel under the coating film progresses due to mechanical damage of the organic coating film or permeation of moisture through the coating film, and the volume expansion of rust at that time is severe, so that coating is performed. The peeling of the film will increase,
This is because if zinc plating is applied to the base, such a problem does not occur because the volume expansion of rust is small in addition to the good corrosion resistance of zinc itself. In particular, as an organic coating on zinc plating, powder coating that can easily form a thick coating film,
Alternatively, double-corrosion protection coating using reaction-curing baking coating has extremely high durability, so it is an important structure and requires long-term maintenance-free protection, such as for bridge facilities and telephone poles in coastal areas. Used in

[0003] However, this double anticorrosion coating has problems such as that the cost of galvanizing the steel material is large and that the adhesion of the coating film on the galvanization is not easy. For this reason, as described above, the application has been limited particularly to a structure requiring high reliability.

[0004] On the other hand, "zinc rich paint" in which zinc fine particles are mixed with a solvent type paint is used instead of plating.
May be used for undercoating of cold-setting paints.
However, zinc-rich paint cannot be applied as a base treatment for baking coating involving high-temperature heating, which is excellent in adhesion of the coating film and coating film performance, because zinc-rich paint is destroyed by heat.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and a simple anticorrosion coating of a zinc coating and a baking coating on a steel structure is performed in a series of steps. It is intended to provide a method for forming the same.

[0006]

Means for Solving the Problems To achieve the above object, a coating method according to the present invention comprises heating a steel object to be treated to a predetermined temperature and then mixing the zinc fine particles with a fluid immersion tank or the like. After the paint etc. are brought into contact and the baking coating in which the zinc fine particles are dispersed is formed as the inner layer, the powder coating etc. that do not contain the zinc fine particles are brought into contact with the object to be processed and the inner layer coating film themselves while not cooling. Then, a powder coating of a resin is formed on the inner layer to form a double anticorrosion coating film.

As a baking method, in the case of powder coating, a method according to the electrostatic coating method can be used in addition to the fluid immersion method. After spraying a powder coating material mixed with zinc fine particles on an object to be processed by an air gun or the like, heating to a predetermined temperature, and forming a powder coating in which the zinc fine particles are dispersed as an inner layer, immediately containing the zinc fine particles. No powder coating is sprayed, and then heated if necessary to form a resin powder coating on the inner layer, similarly forming a double anticorrosion coating.

The above zinc fine particles may be in the form of fine particles or flakes. When the zinc fine particles are flake-like particles, the average thickness is preferably about 10 μm or less and the average major axis is about 500 μm or less. If the size is larger than the above-mentioned size, it becomes difficult to form a uniform coating film. When the zinc fine particles are in the form of fine particles, the average particle diameter is preferably 5 to 20 μm. 5
If it is less than μm, handling may be inconvenient and the working efficiency may be degraded. Conversely, if it exceeds 20 μm, it becomes difficult to form a uniform coating film.

[0009] Such zinc fine particles are added to the powder coating material, and the addition amount is preferably 5 to 30% by mass. If the amount is less than 5%, the effect of the inner layer in which the zinc fine particles are dispersed as described later is reduced, while if it exceeds 30%, the adhesion of the coating film may be insufficient.

The above-mentioned powder coating can be, for example, a saturated polyester resin powder coating, a polyethylene resin powder coating, or an epoxy resin powder coating.

[0011]

According to the present invention, formation of an inner layer in which zinc fine particles serving as a function of galvanizing are dispersed and formation of an outer layer as an anticorrosion coating can be processed in a series of steps of powder and baking coating.
Double anticorrosion coating is possible at almost the same cost as baking coating of ordinary steel structures.

Further, the inner layer in which the zinc fine particles are dispersed can effectively prevent the peeling of the coating film due to the volume expansion of rust generated in the case of the steel base material as well as the galvanized layer, and the sacrificial anticorrosive action of zinc allows the inner layer to disperse. The effect of preventing corrosion of steel when moisture permeates the surface of the steel substrate can also be expected. Furthermore, since the steel base and the resin are in direct contact and adhere to each other, a higher adhesive force can be obtained as compared with the case of painting on a galvanized surface.

[0013]

Next, a typical embodiment of the present invention will be described. FIG. 1 is a schematic diagram of a process in a first embodiment according to the present invention in the case of performing double anticorrosion coating of a saturated polyester resin or the like having a layer containing zinc fine particles as an inner layer on a steel workpiece.

First, a steel workpiece 1 to be coated is heated to 250 to 300 ° C. in a heating furnace 2 and then a saturated polyester resin powder coating containing 5 to 30% by mass of zinc fine particles 3
Is immersed for 2 seconds in the fluid immersion tank 4 filled with, and immediately after being taken out, is immersed for 4 seconds in the fluid immersion tank 4 filled with the saturated polyester resin powder coating material 5. Thereafter, the article is held in the atmosphere for about 1 minute and air-cooled, and then placed in a water tank 7 containing water 6 for several minutes to be water-cooled. Thereafter, by taking out and drying, a copper object to be treated 8 having a double anticorrosive coating by baking coating of a saturated polyester resin or the like in which zinc fine particles are dispersed in the inner layer is obtained. Under this condition, the thickness of the coating film is the inner layer 2
00 μm and the outer layer is 400 μm.

FIG. 2 shows a second embodiment according to the present invention, in which a double-corrosion-proof coating of a saturated polyester resin or the like having a layer containing zinc fine particles as an inner layer on a steel object to be processed is performed according to an electrostatic coating method. FIG.

First, a saturated polyester resin powder coating material 3 containing zinc fine particles in a mass ratio of 5 to 30% is sprayed onto a steel workpiece 1 to be coated so as to have a predetermined thickness. Next, the article is transferred to a heating furnace 2 having a furnace temperature of about 300 to 350 ° C. and heated for about 5 minutes to form a first-layer coating film. Subsequently, the article is taken out into the atmosphere,
Saturated polyester resin powder paint 5 or the like 5 is immediately sprayed by an air gun 9 in an amount to achieve a predetermined film thickness. Subsequently, the film is transferred again to the heating furnace 2 having a furnace temperature of about 300 to 350 ° C., and is heated for about 5 minutes to form a second-layer coating film. Thereafter, the article is held in the atmosphere for about 1 minute and air-cooled, and then placed in a water tank 7 containing water 6 for several minutes to be water-cooled. Thereafter, by taking out and drying, the steel workpiece 8 to which double anticorrosion coating is applied by baking coating of a saturated polyester resin or the like in which zinc fine particles are dispersed in the inner layer is obtained.

The adhesion strength of the coating film formed by the method of the above two examples was a strong value of about 5 N / mm ² in an adhesion test in which an adhesive having a cross-sectional area of 2 cm ² was adhered. This value is extremely higher than the adhesion force of 1 to ² N / mm ² when powder coating of a saturated polyester resin or the like is performed on the zinc plating by a usual method. Thus, it was confirmed that the method according to the present invention can provide a double anticorrosion coating film having high adhesion.

Next, a salt water spray test specified in JIS Z 2371 was performed on the test piece with the cross cut, and as a result, a saturated polyester powder coating or the like having the same thickness without an inner layer in which zinc fine particles were dispersed was used. , Peeling of the coating film began to be observed in 14 days, but no peeling of the coating film was observed in the test piece of this example even in the test for 60 days. Thus, it can be confirmed that the inner layer containing zinc fine particles greatly contributes to the improvement of the anticorrosion performance as in the case of zinc plating in the case of ordinary double anticorrosion coating.

Examples according to the above-described method are summarized in Table 1.

[0020]

[0021]

[0022]

As described above, according to the present invention, it is possible to form a double anticorrosive coating having excellent corrosion resistance on a steel structure with good adhesion at a low price. This coating is expected to be widely applied as a long-life anti-corrosion coating for various steel structures such as houses, bridges and steel towers used in corroded areas.

[Brief description of the drawings]

FIG. 1 is a process schematic diagram of a first embodiment of the present invention.

FIG. 2 is a process schematic diagram of the first embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steel to-be-processed object 2 Heating furnace 3 Saturated polyester resin powder coating containing zinc fine particles, the same polyethylene resin powder coating or epoxy resin powder coating 4 Fluid immersion layer 5 Saturated polyester resin powder coating, polyethylene resin powder coating Or epoxy resin powder coating 6 water 7 water tank 8 steel object to be treated with double anticorrosion coating 9 air gun

Claims (8)

[Claims] A first powder coating material containing zinc fine particles and a second powder coating material containing no zinc are sequentially baked on a steel object to be processed, whereby zinc fine particles are contained in the resin. A method for coating an anticorrosion coating film, comprising forming a two-layer anticorrosion coating film comprising a first inner layer (undercoat layer) in which is dispersed and a second outer layer (overcoat layer) consisting only of a resin. 2. A step of sequentially baking and coating the first powder coating containing zinc fine particles and the second powder coating not containing zinc, wherein the steel object is heated to a predetermined temperature. 2. The method for coating an anticorrosion coating according to claim 1, wherein the first powder coating containing zinc fine particles is brought into contact with the first powder coating, and then the second powder coating containing no zinc is brought into contact with the first powder coating. 3. In the step of sequentially baking and coating the first powder coating containing zinc fine particles and the second powder coating not containing zinc, the zinc fine particles are applied to a steel workpiece by an air gun or the like. After spraying the first powder coating including the first powder coating to a predetermined thickness, the temperature is maintained at a predetermined temperature equal to or higher than the melting point of the first powder coating, and after forming a baked coating film, the zinc fine particles are quickly dispersed. 2. The method for coating an anticorrosion coating according to claim 1, wherein a second powder coating not containing is sprayed to a predetermined thickness, and further heated and melted if necessary. 4. The method according to claim 1, wherein the zinc fine particles have an average thickness of about 10 μm or less.
The method for coating an anticorrosion coating film according to any one of claims 1 to 3, which is a fine flake-like particle having an average major axis of about 500 µm or less. 5. The method according to claim 1, wherein the zinc fine particles are fine particles having an average particle diameter of 5 to 20 μm. 6. The method according to claim 1, wherein the powder coating is a saturated polyester resin powder coating. 7. The method according to claim 1, wherein the powder coating is a polyethylene resin powder coating. 8. The method according to claim 1, wherein the powder coating is an epoxy resin powder coating.