JPS5925032B2 - Method of forming a corrosion-resistant film on metal surfaces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a corrosion-resistant metal film on the surface of a metal object, particularly steel, and more specifically, the present invention relates to a method for forming a corrosion-resistant metal film on the surface of a metal object, particularly steel. In order to prevent corrosion of steel, these metals and alloy powders are mixed with steel shot, zinc-iron alloy shot, etc. and blasted onto the surface of the steel. The present invention relates to a method of forming a film of the alloy to prevent corrosion of the steel.

Steel as a metal material is inexpensive and has mechanical strength, and is widely used in various fields.

The problem with steel is that it is susceptible to rust and corrosion. To prevent these defects, depending on the environment in which it will be used, painting or
Corrosion prevention methods such as hot-dip plating, electroplating, metal spraying, and cathodic protection are used. Among these corrosion prevention methods, methods other than cathodic protection coat the steel surface with paint or metal to isolate the steel from a corrosive environment, and rely on the corrosion resistance of the paint or coated metal in the corrosive environment.

In order to apply a corrosion-resistant coating to a steel surface, it is necessary to clean the steel surface by a mechanical or chemical method in order to improve the adhesion between the coating material and the steel.

In the case of hot-dip plating and electroplating, surface cleaning methods using acids or alkalis are mainly used, but pollution control through wastewater treatment poses a large burden on equipment and management.

In painting and metal spraying, the steel surface is blasted with steel grid, steel shot, sand, etc. (hereinafter collectively referred to as shot) as a pretreatment.

It is known that when steel shot is mixed with fine powders of lead, cadmium, zinc, etc. during blasting, a thin film of about 1 μm of these metals is formed on the steel surface.

Especially for soft materials with low melting points such as lead, cadmium, tin, indium, and their alloys, these metals and alloy powders can be directly blasted onto the cleaned steel surface without mixing with steel shot. A thick film with good adhesion of the alloy can be formed.

゛As mentioned above, it is possible to form a thick film with good adhesion on the target metal object with a plastic of only a single metal or alloy without using a steel shot. Metals or alloys with melting points of 400°C or higher, such as zinc, aluminum, magnesium, copper, and their alloys, are used to melt the surface of metals such as steel. No method has yet been found to effectively form a thick corrosion-resistant film on. The present invention has been made to satisfy such demands, and an object of the present invention is to provide a method for forming a thick corrosion-resistant film of a metal or alloy having a melting point of 400° C. or higher on the surface of a metal such as steel.

As a result of intensive research, the inventors of the present invention have found that after mixing powder of a metal or alloy having a melting point of 400 to 1080°C, which is smaller than the average particle diameter of these shot, into steel shot or zinc-iron alloy shot, etc. The inventors have discovered that a film on the metal surface obtained by blasting the surface satisfies the above object, and has thus arrived at the present invention.

That is, in the present invention, 80 to 20% by weight of shot having an average particle size of 80 to 2000μ
The average particle size is smaller than the shot and from 40 to 15
This is a method for forming a corrosion-resistant film on a metal surface, which is characterized by mixing 20 to 80% by weight of powder of a metal or alloy having a melting point of 400 to 1080C in the range of 00μ and then blasting the mixture onto the metal surface.

By using the present invention, it is possible to apply 1 to 2μ of primer, which is the same as that used for primary rust prevention or as a base for coating on metal surfaces.
Whereas previously only a thin film could be obtained, it has now become possible to form a thick film of 4μ or more. The principle behind the formation of this thick film on the metal surface (hereinafter referred to as dry plating) is not clear, but when the formed film is observed under a microscope, the particles are flattened and the boundaries are not clear. This is thought to be due to the combination of the energy of the metal or alloy powder being projected and the impact energy of the shot, resulting in the formation of a thick film. The material of the shot used in the present invention may be any material having a spherical or near-spherical shape that is more rigid, hard, and strong than the mixed metal or alloy, and steel shot is practically suitable.

When zinc or zinc alloy powder is used as the metal or alloy to be shot, a zinc-iron alloy shot can also be used, and has great industrial economic value especially when the purpose is to prevent rust on steel. Other materials such as silica sand, blast furnace slag, and silicon carbide may also be used depending on the type of metal or alloy to be sprayed and the particle size of the powder. The metal or alloy to be projected is
Metals with a melting point of 400 to 1080°C, such as zinc (melting point 420°C), aluminum (melting point 660°C), magnesium (melting point 650°C), copper (melting point 1080°C), silver (melting point 960°C), zinc - Alloys such as aluminum alloy, zinc-copper alloy, zinc-aluminum-copper alloy, and zinc-aluminum-magnesium alloy are mentioned. In the present invention, the relationship between the particle size of the shot (grid) and the particle size of the metal or alloy powder to be projected is important.

In order to apply enough impact energy from the shot to the metal or alloy powder being shot, the average particle size of the metal or alloy powder being shot must be smaller than the average particle size of the shot. Good adhesion. This means that the shot's energy is added to the shot metal or alloy powder, which slams against the metal surface and presses it against the metal surface. That is, the shot must have more energy than the metal or alloy it projects. Therefore, if the speed is the same, the mass of the shot must be large. The average particle size of the shot used in the present invention is 80 to 2000μ, preferably 1
It is 40-1500μ.

In addition, the average particle size of the metal or alloy powder to be projected is 40
-1500μ, preferably 60-900μ. As will be described later, in the present invention, a pneumatic or rotary type blasting machine is used as a means of blasting, but in general, the rotary type produces a thicker deposited film than the pneumatic type, considering only the blasting speed. Even if the mixing ratio of the metal or alloy powder to be projected and the shot is the same, the pneumatic method may be preferable in terms of film thickness depending on the particle size. That is, as the particle size increases, it is necessary to increase the energy applied, and the particle size must be taken into account when using a blasting machine. In this way, when taking into account blasting machines, etc., the particle diameters of the metal or alloy powder and shot are within the above range, but in any case, as mentioned above, the size of the metal or alloy powder to be shot is larger than that of the shot. It is necessary that the average particle size is small. Dry plating is possible even if the average particle size of the shot and the metal or alloy powder to be projected is outside the above range, but it may result in a thin film, it may take time to obtain a desired thick film, or the adhesion may be poor. In addition, the industrial and economic value decreases as the burden on the plaster increases. If the mass of the metal or alloy powder and the shot to be projected becomes larger than necessary, insufficient acceleration energy is likely to occur at a constant speed. Therefore, there is a limit to the particle size of the metal or alloy powder and shot to be projected, and the upper limit of the particle size of the metal or alloy powder to be projected is 1500μ.
, the upper limit of the shot particle size is 2000μ. Furthermore, if the particle size of the metal or alloy powder and shot to be projected is small, the mass per particle will be small, so even if the speed is increased due to the deceleration effect due to air resistance, the amount of adhesion to the metal surface will not increase. From this, the lower limit of the particle size of the metal or alloy powder to be projected is 40 microns, and the lower limit of the particle size of the shot is 80 microns. In the present invention, the metal or alloy to be projected has a melting point range of 400 to 1080°C.

This is because the metal or alloy used in the present invention must have a melting point lower than that of the shot or grit and be soft. If a metal or alloy with a melting point of less than 400° C. is used, a film of the desired thickness can be obtained by simply projecting the metal or alloy without using shots or grit, so the technical problems of the present invention do not occur. If a metal or alloy whose temperature exceeds 1080° C. is used, a film of the desired thickness cannot be obtained on the metal surface.

The mixing ratio of the shot and the powder of the metal or alloy to be projected is such that the powder of the metal or alloy to be projected is mixed in an amount of 20 to 80% by weight based on the total of both.

If it is less than 20% by weight, the film thickness will be thin, and if it exceeds 80% by weight, there will be a problem in adhesion, which are both undesirable.

Steel is mainly used as the metal to be coated, but other metals or alloys can also be applied.

Blasting methods include not only rotary blasting machines, but also
An air blasting machine using compressed air can also be used, but a blasting machine with a high blasting speed can provide a plating film with a predetermined thickness and adhesion in a shorter time.

Practically speaking, blasting at a speed of 50 m/sec or more is desirable. The present invention has been described in detail above, but since the corrosion resistance of plating for the purpose of rust prevention depends on the thickness of the plating, conventional surface cleaning treatments for base materials such as shot blasting and By mixing and blasting the steel shot with metal or alloy powder that is projected during mechanical processing such as tube blasting or sandblasting, a thick corrosion-resistant film is formed for long-term rust prevention rather than primary rust prevention. This made it possible.

In this way, cleaning and anti-rust treatment of the base material surface such as rust removal is possible in one step, and unlike electroplating or chemical plating, water is not used, so there is no need for wastewater treatment facilities or their management. Furthermore, since the process is carried out at room temperature, it is useful for energy saving, and therefore, the present invention is a method of extremely high industrial value. Furthermore, the plating film surface obtained by the present invention is not a smooth mirror surface obtained by melting or electroplating, but is a plating film surface with microscopic irregularities, which improves the adhesion of painting, coating, or lining. It has an anchoring effect, and can be easily subjected to chemical treatments such as chromate or phosphate treatment to add rust prevention effects.

Further, in the present invention, it is also possible to form a partial or local anti-rust plating film on the metal surface using a suitable mask pattern.

EXAMPLES The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

All percentages below are based on weight, except for the area where red rust occurs. Examples 1 to 8 and Comparative Examples 1 to 8 Steel shot and zinc powder were mixed as shown in Table 1, and a pneumatic blasting machine (projection speed 50 m/sec.
c) or rotary blasting machine (projection speed 70~8
0 wL/sec) on the steel surface (hereinafter referred to as
The thickness and corrosion resistance of the resulting plating film were measured.

Corrosion resistance was evaluated by a 5% sodium chloride salt spray test according to JIS Z237l. The results are shown in Table 1. however,
In Examples 3 to 5, zinc-aluminum-magnesium alloy powder was used instead of zinc powder. In addition, for comparison, one example was one in which a commercially available iron-zinc alloy powder was used as a shot and blasted onto the steel surface, and another was one in which the surface was cleaned with a steel shot and then blasted with zinc powder (hereinafter referred to as 2).
The thickness and corrosion resistance of the coatings obtained from each step were measured in the same manner as described above, and the results are shown in Table 1.

Examples 9 to 10 and Comparative Examples 9 to 14 As shown in Table 1, steel shot and zinc powder were mixed in the same manner as in Example 1, and steel was blasted using a pneumatic blasting machine (projection speed 50 m/Sec). The surface was mixed and blasted in one stage, and the thickness of the resulting plating film was measured. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 10 using one-stage mixing blasting, a film of 5 microns or more was obtained and had excellent corrosion resistance. Example 4, especially chromate treatment
and No. 8 have excellent corrosion resistance. In addition, a thicker film can be obtained using a rotary blasting machine because the projection speed is faster than in the embodiment using a pneumatic blasting machine. Comparative Examples 1 and 2 are examples in which a commercially available iron-zinc alloy powder was used as shot, but the resulting films were thin and had significantly poor corrosion resistance.

Although Comparative Examples 3 to 5 are examples in which two-stage blasting was performed, a film having a thickness as high as that of the Examples of the present invention was not obtained, and the corrosion resistance was also inferior.

In Comparative Examples 6 and 7, since the zinc powder mixing ratio was low, a film as thick as that of the examples of the present invention could not be obtained, and the corrosion resistance was poor.

In Comparative Example 8, the zinc powder particle size was larger than the shot particle size, and moreover, the zinc powder particle size exceeded the range of the present invention.
The film is thin and has poor corrosion resistance.

In Comparative Examples 9 and 10, the zinc powder diameter and shot particle diameter are larger than the range of the present invention, but the film thickness is significantly greater than that of Examples 2 and 3, which have a corresponding zinc powder mixing ratio. thin.
★Comparative Examples 11 and 12 have zinc powder particle size larger than shot particle size, but Example 1 or Examples 2 and 3 have a corresponding zinc powder mixing ratio.
The film thickness is significantly thinner than that of Comparative Examples 13-14
Although the zinc powder particle diameter is smaller than the range of the present invention, the film thickness is significantly thinner than in Examples 2 to 3, which have a corresponding zinc powder mixing ratio.

Examples 11 to 19 and Comparative Examples 15 to 17 As the metal or alloy to be projected, a copper alloy (10
% zinc-copper), pure aluminum and aluminum alloy (2.5% magnesium-aluminum), silver, and pure copper powders were mixed with steel shot in the proportions shown in Table 2, and the steel surface was blasted and plated. The thickness of the film was measured.

The results are shown in Table 2. As a comparison, the above-mentioned projecting metal or alloy (10% Zn
Table 2 shows an example of two-stage blasting on a steel surface using 1Cu, pure aluminum, 2.5% magnesium-aluminum and the thickness of the film obtained by this blasting.

Example 11 using mixed single-stage blasting with any projecting metal or alloy as shown in Table 2
In Examples 1 to 16, a thicker film is obtained compared to Comparative Examples 15 to 17 in which two-stage blasting was used.

Claims (1)

Scope of Claims: 1. 80 to 20% by weight of shot or grit with an average particle size of 80 to 2000μ, and a metal having a melting point of 400 to 1080°C and having an average particle size smaller than that of the shot or grit and in the range of 40 to 1500μ, or Alloy powder 20~80
A method for forming a corrosion-resistant film on a metal surface, the method comprising: mixing % by weight and then blasting the metal surface. 2. The method for forming a corrosion-resistant film on a metal surface according to claim 1, wherein the shot is steel shot or iron-zinc alloy shot. 3. The metal or alloy having a melting point of 400 to 1080°C is selected from zinc, aluminum, magnesium, copper, zinc-aluminum alloy, zinc-copper alloy, zinc-aluminum-copper alloy and zinc-aluminum-magnesium alloy. A method for forming a corrosion-resistant film on a metal surface according to scope 1 or 2.