JPS6141273B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing corrosion of iron-based metal surfaces.

The surface of ferrous metals is prone to rust and corrosion. Therefore, various measures have been taken since ancient times to prevent corrosion. Plating, metalliconing, and painting are all ways to prevent corrosion. Among these, plating is superior in terms of making the surface beautiful, but it requires a high cost to implement, and the corrosion prevention effect is not good at that rate. Metallicon is made by thermally spraying other rust-resistant metals into particles and attaching them to the surface as a layer of sintered material, similar to millet roe. that's why,
The surface layer produced by metallicon contains pinholes therein and is therefore not sufficient in terms of corrosion protection. Painting has a more pronounced anti-corrosion effect than the ones mentioned above, but in order to paint without pinholes, it is necessary to apply a liquid paint and let it harden at around room temperature. The drawbacks were that it took time and was difficult to incorporate into a continuous production process. As described above, all of the conventional means have drawbacks.

As mentioned above, when metallicon is used, many pinholes are generated on the surface. In terms of volume ratio, this pinhole is about 1 to 1% of the total volume.
It is said that the percentage is as high as 10%. In the past, no particular effort was made to close this pinhole. The reason for this is that since the surface of Metallicon is made up of metal particles hardened into millet-like shapes, there are small irregularities all over the surface, so even if this surface is painted, it is not easy to make it smooth. This is because it was thought that it was not. In particular, powder coating this surface was completely unthinkable.

Powder coating can be completed in a short period of time by simply heating and melting the granular paint to adhere it and then cooling it. Therefore, powder coating can be easily incorporated into a series of manufacturing processes because there is no need to wait for a long time until it hardens, unlike when using liquid paint. The inventor focused on the above-mentioned advantages of powder coating and attempted to use powder coating for corrosion prevention of ferrous metal surfaces.
However, when the powder paint was actually applied directly to the surface of a ferrous metal, it was found that the corrosion protection effect was not sufficient, and within a short period of time, the ferrous metal surface became corrosion resistant and the paint layer peeled off. The same thing happened when metallicon was applied to the surface of iron-based metal and powder coating was applied thereon.

The inventor attempted to apply a special primer to the metallic surface of the iron-based metal, cure the primer, and then apply powder coating thereon.
Here, the special primer is a solution that contains a high temperature curing resin and is dissolved in an organic solvent, and the organic solvent has a boiling point lower than the curing temperature of the resin. This is what I did. Therefore,
This primer is applied in liquid form, and when heated, the solvent first evaporates, and then it hardens. The inventor discovered that when a coating film is formed using such a primer, the coating film remains on the surface of the ferrous metal for a long time even if the coated product thus obtained is exposed outdoors for a long time. It was discovered that the surface of ferrous metals does not corrode for a long time. It has also been found that zinc, aluminum, or an alloy thereof is suitable as a material for the metallicon. This invention was made based on such knowledge.

In addition, the inventor discovered that by grinding the ferrous metal surface to form a new rough surface before applying metallicon to the ferrous metal surface, the adhesion between the ferrous metal surface and the surface metal layer of metallicon becomes stronger. I acknowledged that it would happen. Furthermore, for grinding the surface of ferrous metals, it is suitable to grind by spraying solid particles with compressed air, and among these methods, so-called "grid blasting" is a method in which a cast iron abrasive material called "grid" is sprayed as solid particles. I have found that it is most suitable to do this. This invention was thus completed.

This invention involves thermally spraying zinc, aluminum, or their alloys in the form of particles onto the surface of a ferrous metal to form another metal layer, then applying a solution of a high-temperature hardening resin in an organic solvent, and heating it to remove the solvent. This relates to a corrosion prevention method for ferrous metal surfaces, which is characterized by volatilizing the resin, curing the resin, and then applying powder of another thermosetting or thermoplastic resin, and heating and melting it to form a film. be.

Next, each requirement of this invention will be explained in detail. First, as the iron-based metal, not only cast iron and pig iron but also various iron alloys and other metals mainly composed of iron can be used. Moreover, the shape of iron-based metals does not matter. That is, the shape may be a plate, a cylinder, or any other shape.

First, an abrasive is sprayed onto the surface of the above-mentioned iron-based metal to form new irregularities on the surface. As the abrasive material, both natural products and artificial products can be used. Diamonds are natural products,
Emery, spinel, garnet, etc. can be used, and as artificial products, alumina, silicon carbide,
Boron carbide, cast iron particles, etc. can be used.
Among these, it is preferred to use cast iron particles or grids. It is desirable to use compressed air to spray the abrasive material. The unevenness created by these abrasive materials has a height difference of about 50 microns at most between the peak and valley of the protrusion in the cross section.
In other words, it is better to set Rmax50 microns as the standard.

In the method of this invention, particles of zinc, aluminum, or an alloy thereof are thermally sprayed onto the surface of the above-mentioned iron-based metal to form a layer of another metal. The alloy in this case is a zinc alloy or an aluminum alloy, such as a zinc alloy used for die casting, an aluminum-copper alloy, an aluminum-copper-silicon alloy, an aluminum-silicon alloy, or the like. Zinc, aluminum and their alloys are used in the form of wires. The filaments are heated and melted using gas or electricity, and then blown with compressed air or nitrogen gas to adhere to the surface of the ferrous metal. As already mentioned, this operation is a well-known operation generally called metallicon. In this invention,
This known operation is used as is.

In the method of this invention, an organic solvent solution of a resin having the property of curing at high temperatures is applied onto a layer of other metals made of metallicon. Curing at high temperatures means that curing does not proceed at temperatures below 90°C.
The curing reaction does not proceed until the temperature reaches around 100°C, more specifically, 90°C or higher, particularly 120°C, and more preferably 150°C or higher. Further, the resin is used by dissolving it in an organic solvent. The organic solvent has a boiling point lower than the curing temperature of the resin, preferably the difference is 10°C to 50°C, more preferably 20°C to 20°C.
Use one at 40℃. This solution contains a curing agent in order to accelerate curing of the resin. The layer formed by curing this resin is called a primer layer or undercoat layer because it is on the metal layer formed by metallicon and below the powder coating layer, which will be described later. be able to.

A more specific description of the characteristics of the high temperature curable resin is as follows. In general, thermosetting resins have the property of curing when the initial condensate thereof is heated. The progress of curing in this case is observed as an increase in viscosity. Therefore, as shown in FIG. 1, when the horizontal axis represents the temperature and the vertical axis represents the viscosity of the resin, the thermosetting resin draws a straight line A or a curved line B upward to the right. Among these, the high temperature curable resin used in this invention has a viscosity that increases only gradually at temperatures below 90℃, but rapidly increases at temperatures above 90℃, resulting in the relationship shown in curve C. It shows change. Rapidly increasing the viscosity here means, for example, that the viscosity increase rate between 90℃ and 120℃ is at least twice the viscosity increase rate between 60℃ and 90℃, particularly 3 times or more, preferably 4 times or more. They say things that become. In other words, the viscosity increases rapidly above 90°C, and at 220°C (and more preferably at 200°C),
This is a resin that completely cures.

As the high temperature curable resin forming the undercoat layer, aromatic epoxy resins, phenoxy resins, and acrylic resins can be used. As a hardening agent,
Isocyanate compounds, epoxy compounds, and other acids such as 1.10 decanedicarboxylic acid (dodecanedioic acid) (DDA) can be used. The material forming the undercoat layer contains an organic solvent in addition to the above resin and curing agent, and may further contain various fillers. As the organic solvent, xylene, methyl isobutyl ketone, cellosolve acetate, etc. can be used. As the filler, titanium oxide, talc, etc. can be used.

Examples of commercially available resins suitable as materials for forming the undercoat layer include YP from Toto Kasei Co., Ltd.
The product sold under the product name -40-ASM40 falls under this category. This resin is based on phenoxy resin as a high temperature curing resin. Further, it is preferable to use isocyanate-based Desmodule AP as a curing agent. These are dissolved in xylene and methyl isobutyl ketone and used as a paint. When this paint is heated, the solvent first evaporates, and the resin hardens in a solvent-free state, so the formed film has no bubbles, and is therefore convenient for carrying out the method of this invention. It is. In addition, Etone is available from Kawakami Paint Co., Ltd. as a high-temperature curing resin that forms the undercoat layer.
A one-component epoxy miscoating agent sold under the name No. 2900 is suitable, and an overnight primer sold under the name Epico No. 1000 from Nippon Oil & Fats Co., Ltd. is suitable. Both Eton No. 2900 and Epico No. 1000 already contain a hardening agent, so thinner is added as an organic solvent and applied. When the former is heated to 180°C to 200°C, and the latter is heated to 170°C to 190°C for 10 to 20 minutes, it cures and forms a uniform undercoat layer without bubbles.

The basecoat layer is applied in solution over the metallized surface as described above. Therefore, the undercoat layer penetrates well into the pinholes on the surface of the metallicon. At the same time, the undercoat layer forms a film over the entire surface of the metallicon.
Therefore, when the undercoat layer is formed, all pinholes on the metallicon surface will disappear. Furthermore, since an organic solvent is used as a solvent in the resin solution, the solvent easily evaporates. In particular, if a material whose boiling point is somewhat lower than the temperature at which curing of the resin rapidly progresses is used, the organic solvent will first volatilize as it is heated, and the resin will be cured after the organic solvent has finished volatilizing. Additionally, if you use a resin that rapidly hardens at a temperature of 100°C or higher, there will be no moisture present when the resin hardens, so the resin will harden without foaming at all. , resulting in the formation of an undercoat layer with few or no pinholes.

In the method of this invention, after forming an undercoat layer, a powder coating is deposited thereon and heated and melted to form a film. This film forming step is a well-known operation called powder coating. In this process, a powder of thermosetting resin or thermoplastic resin is used as a powder coating, and this is attached to the ferrous metal, and the ferrous metal is heated to melt the powder and fuse together to form a coating. That is to say.
At this time, since the resin is melted and fused, unlike the metal particles of metallicon, it is fused sufficiently so that it does not retain its powder form at all, thus forming a film without pinholes. do. Since the above-mentioned undercoat layer is present under the film thus formed, the film adheres well to the undercoat layer, thus providing a strong covering over the entire surface.

After powder coating is performed in this manner, if a more beautiful gloss is desired on the surface, it may be further coated with another paint. For topcoating,
A clear polyurethane paint is suitable.

The method of this invention has the feature that it can be carried out continuously in a short period of time, so it can be incorporated into a continuous process as a surface corrosion protection method for ferrous metals, and the product obtained in this way has excellent corrosion resistance. It has the characteristic of being. Among these, the first characteristic is explained as follows. First, the first metallicon process can be performed continuously in a short period of time. Further, in the next step of forming the undercoat layer, an organic solvent is used to volatilize the organic solvent and heated to promote hardening of the stem fat, so this step can also be carried out continuously in a short period of time. The final powder coating step can also be carried out continuously in a short period of time. Therefore, the method of the present invention in which these steps are combined can be completed as a whole continuously in a short period of time. The superiority of the product is explained as follows. First, since a metal layer such as zinc or aluminum produced by metallicon exists on the surface of the iron-based metal, the surface of the iron-based metal is less likely to rust. There is an undercoat layer on top of it, and since it is applied in a solution state, it penetrates into the pinholes on the surface of the metallicon, and after the solvent evaporates, it hardens to form a film, and therefore the undercoat layer has no pinholes. Furthermore, it is covered with a powder coated film, which firmly adheres to the undercoat layer to form a uniform film.
As a result, the ferrous metal is coated without pinholes by the powder coating film, the undercoat layer, and the metallicon surface layer.
Provides sufficient corrosion protection.

In addition, in the above method, when new irregularities are formed on the surface by spraying an abrasive, the metal layer formed by metallicon digs into the irregularities formed on the ferrous metal surface, thereby causing Since an anchoring effect is added, the metal layer formed of metallicon and the ferrous metal are firmly connected. Therefore, the product will exhibit better corrosion protection.

Since the product obtained by the method of this invention has such a large corrosion-proofing effect, the method of this invention is suitable for making structures used outdoors, such as balustrades.

Next, the superiority of the method of this invention will be specifically explained with reference to Examples and Comparative Examples.

Example 1 A 3 mm thick iron plate was grid blasted to form new irregularities on its surface. In Grid Blast,
A #50 cast iron grid was used to form irregularities of Rmax50 microns on the iron plate, and the surface was finished to resemble white metal. Next, a zinc wire was thermally sprayed onto this using a gas-sprayed metallicon to form a zinc layer approximately 100 microns thick.

An undercoat layer was formed on this zinc layer. To form the undercoat layer, phenoxy resin (YP) manufactured by Toto Kasei Co., Ltd.
−40−ASM40) was used. This resin is curable at high temperatures and has a curing initiation temperature of 170°C to 180°C. As an undercoat, 40 parts by weight of the above phenoxy resin (hereinafter simply referred to as "parts"), 20 parts of titanium oxide, and 20 parts of talc were mixed with 10 parts of cellosolve acetate and xylene.
After dissolving or dispersing it in 10 parts, 10 parts of Desmodyur AP dissolved in 90 parts of xylene was mixed in a 1:1 ratio and used.

After applying the primer, the temperature of the iron plate was raised to 220°C, and all the solvents such as cellosolve acetate were volatilized at the cutting stage. The resin was cured by holding at 220°C for 10 minutes.

Next, a polyester powder paint was applied on top of it using electrostatic force, and then heated to 200°C.
It was held for 20 minutes to melt the powder into a film. In this way, the corrosion protection treatment could be completed continuously in less than one hour.

The iron plate obtained in this way is mixed with 5% salt water.
After 1500 hours of spray contact, there was no peeling of the paint film, and it was confirmed that the steel plate was not corroded.

Comparative Example 1 In this comparative example, the treatment was carried out in exactly the same manner as in Example 1, except that a room temperature curable resin was used instead of a high temperature curable resin as the undercoat and a long time was spent on curing.

As a resin, Toto Kasei Co.'s Epototo YD-
011 was used. 30 parts of this resin, 20 parts of titanium oxide,
20 parts of talc was blended and dissolved in 10 parts of methyl isobutyl ketone and 20 parts of xylene. Further, 70 parts of amine curing agent G715 and 30 parts of xylene were added to this, and this was used as an undercoat. Since this primer was curable at room temperature, it was left to cure at 20° C. for 4 days. Therefore, this method cannot be incorporated as part of a continuous process.

After forming the undercoat layer in this manner, it was treated in exactly the same manner as in Example 1 to obtain a product. This product produced numerous air bubbles in the outer layer of the powder coating. It was assumed that these bubbles were caused by the solvent contained in the primer or moisture in the air.

When this product was tested by spraying salt water on it in the same manner as in Example 1, the coating film lifted and peeled off after 300 hours. Therefore, this product was recognized to have insufficient anticorrosion effect.

Comparative Example 2 This Comparative Example was treated in the same manner as Comparative Example 1, except that although the undercoating agent was curable at room temperature, in this Comparative Example it was heated to accelerate curing.

The curing of the primer was accelerated as follows.
First, after applying the primer of Comparative Example 1, it was left at room temperature for 20 minutes, and then held at 80° C. for 30 minutes in an attempt to accelerate curing by heating. As a result, a large number of bubbles were observed in the undercoat layer. This is because the heating accelerated the hardening of the resin and increased its viscosity, but it still contained solvent.
It was presumed that this was due to vaporization in the resin.

Thereafter, powder coating was performed in the same manner as in Comparative Example 1, and thus a product was obtained. When this product was subjected to a salt water test in the same manner as Comparative Example 1,
After 500 hours, the surface of the iron plate rusted, and the paint film lifted and peeled off.

[Brief explanation of the drawing]

FIG. 1 schematically shows the viscosity characteristics of the high temperature curable resin used in the present invention.

Claims (1)

[Claims] 1. Another metal layer is formed by thermally spraying zinc, aluminum, or an alloy thereof in the form of particles on the surface of an iron-based metal, and then an organic solvent solution of a high temperature curing resin is applied and heated. A method for preventing corrosion of iron-based metal surfaces, which comprises volatilizing a solvent, curing the resin, and then applying powder of another thermosetting or thermoplastic resin, and heating and melting the resin to form a film. 2. The iron-based metal according to claim 1, wherein an abrasive is sprayed onto the surface of the iron-based metal to form new irregularities on the surface, and the zinc, aluminum, or an alloy thereof is thermally sprayed thereon. Corrosion prevention method for metal surfaces.