JPH06146005A - Corrosion resistive structure for metal - Google Patents

Abstract

PURPOSE:To provide a hose clip which has superior corrosion resistance and is suitably attached, specially, in a corrosive environment. CONSTITUTION:The surface of a hose clip base material made of steel is plated with aluminum as a 1st membrane. Then, a 2nd membrane is formed thereupon by metal powder-chromium oxidation. On the 2nd membrane, a 3rd membrane is formed by using water-based treating liquid containing water-based resin and a silica material. The hose clip 1 which never loses its corrosion resistance even when expanded in diameter at the time of attachment to a rubber hose 3 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal rustproof structure.

[0002]

2. Description of the Related Art Generally, metal (mainly steel) members are widely coated with zinc such as electrogalvanized for rust prevention, and are also used for hose clips for tightening the outer circumference of rubber hoses. In order to prevent rust, a lot of electrogalvanizing treatment has been conventionally performed. However, in recent years, the corrosive environment has deteriorated due to salt damage, etc., and higher rust prevention power is required for metal parts, and pollution problems in the treatment process,
In addition, the problem of breakage due to hydrogen embrittlement of hose clips treated by electroplating has been highlighted. For this reason, surface treatments other than electroplating have been adopted.

As a powerful surface treatment, chromic acid called metal powder-chromium oxidization treatment (dacrotizing, dacrotized treatment (“Dacrotize” is a registered trademark for the treated product)), metal powder ( Mainly zinc,
A method of coating a metal base with a coating composition comprising aluminum) and a chromic acid reducing agent and baking the coating (US Pat. No. 3,382,081, JP-B-52-904, and JP-B-52).
-1901 and other practical surface technology (published by Japan Metal Surface Technology Association) '85 VOL. 32 / NO. 6 2nd 272-27
9).

In order to further improve the rust preventive performance of the metal powder-chromium oxidization treatment film, the metal powder-chromium oxidization treatment film is used as the first film, and 1 to 2 is formed on the first film.
The invention of forming a film containing silicic acid as a main component which does not contain a resin having a size of μm or more as the second film is Japanese Patent Publication No. 60-44145.
It is disclosed in the publication. In this invention, the pores existing in the first coating are filled and the adhesion to the metal base and the bonding force between the first coatings are improved.

[0005]

However, even if the above-mentioned conventional invention is applied to a hose clip, there is a problem that its rustproofing performance is still insufficient. The reason for this is that in the above invention, since the second coating does not contain a resin, the second coating containing silicic acid as the main component lacks in stretchability, and when the metal base material is elastically deformed, the second coating is It is considered that this is because the material cannot be stretched due to the elastic elongation of the material and the second coating film may be cracked. Therefore, it is considered that when rainwater or the like splashes on the member, water penetrates from the cracked portion to promote corrosion and cause red rust in a short time.

[0006]

In order to solve such a technical problem, the inventor of the present invention has an excellent rust preventive performance even if a film formed by a water-based treating agent is elastically deformed. As a result of conducting research for making an anticorrosion structure, the present invention has been completed.

According to the present invention, a rust preventive structure which does not cause red rust for a long period of time and is excellent in rust preventiveness can be obtained. In addition, the one to which wax is added can have a rust preventive structure with good lubricity due to its lubricity.

For example, the hose clip 1 for a radiator of a passenger car shown in FIG. 1 will be described as an example. A hose clip base material (metal base material) is a steel material having a plate thickness of 1.6 mm and a plate width of 18 mm, and a ring having a diameter of 37 mm. It is molded into. Then, an elastic rubber hose 3 is inserted and connected to the outer circumference of the tip of the tube 2, and the outer circumference of the rubber hose 3 at this portion is surrounded and fixed by an annular hose clip 1,
It prevents the hose from coming off. At this time, the hose clip 1 comes into contact with a rubber hose containing sulfur or carbon, and is placed in an environment where corrosion due to electrolytic corrosion is promoted.

Here, as shown by the solid line in FIG. 1, the hose clip 1 is elastically expanded in diameter when it is assembled to a rubber hose, and the inner surface thereof is elastically expanded. For this reason, the stretchability is also required for the coating when it is assembled to the hose, otherwise the coating will crack.

The molded metal base material is subjected to pretreatment such as degreasing and surface adjustment as necessary, and is plated with aluminum to form the aluminum layer of the first coating. Aluminum plating is economical aluminum electroplating electrodeposited from a molten salt in a liquid state at room temperature, and is desirable from the viewpoint of the environment of the workplace, but may be electroplated aluminum electrodeposited from a high temperature molten salt,
Further, other plating methods such as a hot dipping method and a vacuum deposition method may be adopted. In the case of electroaluminum plating, 2 μm is required to obtain a uniform film, and the effect cannot be expected below this. On the other hand, it is economically undesirable to set the thickness to 12 μm or more.

Next, a treatment is carried out by a predetermined method to form a metal powder-chromium oxidization treatment coating of the second coating.

The coating method is usually a tank basket method (dip) in which a metal base material is placed in a basket and immersed in a processing solution prepared by a predetermined procedure in a tank, and then pulled up to remove excess processing solution by centrifuging. It is more efficient to adopt the spin method), but it is also possible to adopt the hanger method (dip drain method) of hanging on the overhead conveyor, dipping it in the bath and painting.
The coating method such as spray coating can be carried out without any limitation. After this coating process, a baking process is performed under predetermined conditions. If the amount of the second coating film obtained by repeating the above treatment once or more is 50 mg / dm @ 2 or less, the performance cannot be sufficiently exhibited, and if it is too large, it is not economically preferable. Usually, about 60 to 900 mg / dm2 is preferable, and more preferably 100 to 500 mg / dm2.
It is dm2. Further, at this time, it is preferable that the second coating is formed as uniformly as possible on the metal substrate.

The treatment liquid for forming the third coating is a water-based resin-silica material or a water-based mixed solution containing a water-based resin-silica material-wax.

As the water-based resin, an acrylic resin, an alkyd resin, an epoxy resin, a polyester resin, a silicone resin or the like can be used as long as it is a water-soluble type, a dispersion type, an emulsion type or the like, which is stable even when diluted with water. Is.

As the silica material, silicates, colloidal silica, silica powder and the like can be used, but it is necessary that they are compatible with the resin. When the amount of silica material is 100 or less relative to the resin solid content of SiO2, the effect of improving the corrosion resistance is not sufficient, while when it is 200 or more, the adhesion performance is deteriorated, which is not preferable. Is preferred, and more preferably 3 to 1
00.

As the wax, those which can be dispersed in water such as powder type and water dispersion type and water-soluble type can be used, and polyethylene wax is preferably used. The amount of wax added is as follows: resin solids and SiO2
When the total amount is 100 or less, the effect of lubricity does not appear at 0.05 or less. Further, even if added in an amount of 200 or more, improvement in lubricity cannot be expected, and therefore, addition of 0.1 to 100 is usually preferable.

In addition, it is possible to add additives such as a dispersant, a wetting agent and a thickener, if necessary, and it is also possible to use pigments such as an extender pigment, a coloring pigment and a rust preventive pigment. . As a coating method, a tank basket method (dip spin method) is adopted, but a hanger method (dip drain method) may be adopted, and other coating methods such as curtain coating method and spray coating method may be used. Although a baking treatment is carried out to form the third coating, a drying time of 60 ° C. or lower requires a long time, which is not preferable in terms of productivity. On the other hand, it is not preferable to be higher than the temperature at which carbonization of organic substances such as resin and wax proceeds. Usually, the temperature is preferably 60 to 250 ° C, more preferably 120 to 200 ° C. And 5-60
Bake for about 1 minute.

If the amount of the third coating film obtained by repeating the above treatment once or more is 50 mg / dm2 or less, the performance cannot be sufficiently exhibited, and if it is too large, it is not economically preferable. Usually, it is preferably about 60 to 1000 mg / dm 2, and more preferably 60 to 300 mg / dm 2. Further, at this time, it is preferable that the third coating is formed as uniformly as possible on the metal substrate.

In particular, when zinc powder is used as the metal powder of the second coating, the first coating enhances the anticorrosion property because the aluminum of the first coating is electrochemically rapidly dissolved in salt water. It is considered that a highly protective product containing aluminum ions is formed in the corrosion product covering the surface of the zinc powder. Further, it is considered that the third coating does not lose the adhesiveness to the second coating for a long period of time due to the sacrificial anticorrosion of the first coating with aluminum.

[0020]

EXAMPLES Examples in which the present invention is applied to a hose clip for an automobile will be described below together with comparative examples. 1. Effect of third coating (preparation of test sample) Steel material with a plate thickness of 1.6 mm and a plate width of 18 mm is used as the hose clip base material, and the diameter is 37 m.
After being formed into a ring shape of m and subjected to heat treatment (austempering treatment), shot blasting treatment was performed. A publicly known electro-aluminum plating was applied in the following manner to form a first coating.

The formation of the aluminum layer of the first coating was carried out as follows. The conditions of this aluminum electroplating are 50 to 1 by applying an electric current of 1 to 2 A / dm2 to a plating bath of triethylene aluminum-NaF-toluene at 80 ° C.
It was electrodeposited for 00 minutes. The thickness of the first coating was 2.0 μm. This was used as the first film-treated sample.

Next, a second film was formed. This is prepared by dissolving chromic anhydride and calcium oxide in deionized water in amounts such that chromic anhydride is 6.9% and calcium oxide is 1.2%. Yes.). Metallic zinc flakes (thickness 0.1-0.3 μm,
60% of the average length of the longest part is about 1.5 μm) is dispersed in propylene glycol mixed with 0.2% of a surfactant (alkylphenol polyethoxy addition compound type surfactant) to make the total amount 100%. As the second composition).

The first and second compositions were mixed at a weight ratio of 58:42 by pouring the former into the latter with slow stirring and stirred overnight at room temperature. The obtained mixed liquid was dip-coated on the sample subjected to the first film treatment by a tank basket method, and after the dipping, centrifugal separation was performed to attach a predetermined treatment liquid. After that, the hose clip was heated so that the surface temperature of the hose clip reached 300 ° C. in the electrically heated hot air circulation furnace for 10 minutes, and then allowed to cool indoors. This process was repeated twice. The adhesion amount was 100 mg / dm 2 on average (about 7 μm in thickness).

The sample subjected to the above treatment was used as a second film-treated sample, and the prepared treatment liquids for forming the third film were applied by dipping in a tank basket system, and after the dipping, centrifugal shaking was performed. A predetermined treatment liquid was attached. After that, a predetermined heat treatment was performed in an electrically heated hot air circulation furnace, and this treatment was repeated twice to obtain a film.

When preparing the treatment liquid for forming the third film, in addition to the above, a dispersant, a wetting agent or a thickening agent may be added, or a coating disperser may be used to obtain various thicknesses. To obtain a third film. This was used as the test sample of the example or comparative example.

Comparative Example 1 A test sample was prepared by forming only the second film without forming the third film.

(Comparative Example 2) Sodium silicate (JIS1
No.) 50%, deionized water 50%, the third coating film was formed with the treatment liquid and used as a test sample. The baking condition was 170 ° C. for 20 minutes, and the adhesion amount was about 40 mg / dm 2.

(Comparative Example 3) Water-soluble alkyd resin-A
(Solid content 70%, pH 8 to 9) A third coating was formed with a treatment liquid mixed in a ratio of 30% and deionized water 70% to obtain a test sample. The baking conditions are 140 ° C-20 minutes,
The adhered amount was about 60 mg / dm 2.

Comparative Example 4 Aqueous acrylic resin-B (solid content 41.5%, pH 8.3 to 9.0) 50%,
A third coating was formed with a treatment liquid mixed with deionized water at a ratio of 50%, and used as a test sample. Baking conditions are 160 ° C-2
At 0 minutes, the adhered amount was about 60 mg / dm 2.

(Comparative Example 5) A third coating film was formed with a treatment liquid in which the ratio of water-based epoxy resin-C (solid content 50%) 35% and deionized water 60% was used to prepare a test sample. The baking conditions are 140 ° C for 20 minutes, and the adhesion amount is about 60 mg.
It was / dm2.

Comparative Example 6 Water-soluble epoxy resin-C (solid content 50%, pH 9.4 to 10.2) 20%, water-dispersed polyethylene wax-E (solid content 40%, p)
H 9, particle size 3 μm, density 0.97, softening point 12
(8 ° C.) 25% and deionized water 55% were added to the treatment liquid to form a third film, which was used as a test sample. The baking condition was 140 ° C. for 20 minutes, and the adhesion amount was about 50 mg / dm 2.

Comparative Example 7 Water-soluble epoxy resin C (solid content 50%, pH 9.4 to 10.2) 20%, color pigment (carbon black dispersion, solid content 29%) 2
%, 78% of deionized water was added to form a third coating film, which was used as a test sample. Baking conditions are 140 ° C-
After 20 minutes, the amount deposited was about 60 mg / dm 2.

(Example 1) Water-soluble epoxy resin-C (solid content 50%, pH 9.4 to 10.2) 20%, colloidal silica-F (SiO2 20 to 21%, NaO)
2 0.35%>, pH 9.5-10, particle size 10-2
0 mμ) 30% and deionized water 50% were mixed to form a third coating film, which was used as a test sample. The baking condition is 140 ° C for 20 minutes, and the adhesion amount is about 60 mg / dm2.
Met.

Example 2 Water-soluble epoxy resin C (solid content 50%, pH 9.4 to 10.2) 20%, colloidal silica-G (SiO2 20 to 21%, NaO)
2 0.04%>, pH 9.5-10, particle size 10-2
0 mμ) 30% and deionized water 50% were mixed to form a third coating film, which was used as a test sample. The baking condition is 160 ° C for 20 minutes, and the adhesion amount is about 60 mg / dm2.
Met.

(Example 3) Water-soluble epoxy resin-C (solid content 50%, pH 9.4 to 10.2) 20%, amine silicate-H (SiO2 25.0%, pH 1)
1.0) A third coating was formed with a treatment liquid mixed at a ratio of 30% and deionized water 50%, and used as a test sample. The baking condition is 140 ° C for 20 minutes, and the adhesion amount is about 60 mg / dm2.
Met.

(Example 4) Water-soluble epoxy resin-C (solid content 50%, pH 9.4 to 10.2) 20%, amine silicate-H (SiO2 25.0%, pH 1)
1.0) 20%, water dispersion type polyethylene wax E (solid content 40%, pH 9, particle size 3 mμ, density 0.97, softening point 128 ° C.) 15%, deionized water 5
A third coating was formed with the treatment liquid mixed at a ratio of 0% to obtain a test sample. The baking conditions were 140 ° C. and 20 minutes, and the adhesion amount was about 60 mg / dm 2.

(Example 5) Water-soluble epoxy resin-C (solid content 50%, pH 9.4 to 10.2) 20%, amine silicate-H (SiO2 25.0%, pH 1)
1.0) 30%, color pigment (carbon black dispersion, solid content 29%) 2%, rust preventive pigment 1%, deionized water 47% to form a third coating film, It was used as a test sample. The baking conditions were 140 ° C. and 20 minutes, and the adhesion amount was about 60 mg / dm 2.

(Example 6) Water-soluble alkyd resin-A
(Solid content 70%, pH 8-9) 20%, amine silicate-H (SiO2 25.0%, pH 11.0)
A third coating was formed with a treatment liquid mixed in a ratio of 30% and deionized water 50%, and used as a test sample. The baking condition is 1
At 40 ° C. for 20 minutes, the adhered amount was about 60 mg / dm 2.

(Example 7) Aqueous acrylic resin-B (solid content 41.5%, pH 8.3 to 9.0) 20%, amine silicate-H (SiO2 25.0%, pH 1)
1.0) A third coating was formed with a treatment liquid mixed in a ratio of 30% and deionized water 50% to obtain a test sample. The baking condition is 160 ° C. for 20 minutes, and the adhesion amount is about 60 mg / dm.
Was 2.

Comparative Examples 1 to 5 on which this third coating is formed,
About each of the hose clips of Examples 1 to 5, three pieces were attached to a rubber hose into which a resin rod was inserted, and a corrosion resistance test was performed. The rubber hose used here is one that has been known to have a high degree of corrosion.

The corrosion resistance test was a combined cycle test. This combined cycle test method has a temperature of 50 ° C. and a humidity of 95.
Step 1 is a process of spraying salt water at% RH or more for 17 hours, step 2 is a process of blowing hot air at a temperature of 70 ° C and humidity of 40% RH for 3 hours, and step 3 is a process of soaking in salt water at a temperature of 50 ° C for 2 hours. And the step of blowing outside air for 2 hours is step 4, and a total of 24 hours is one cycle. This combined cycle test method is under severer conditions than the JIS-Z-2371 neutral salt spray test method salt spray test, and rust is further accelerated and generated. The test results are evaluated 30 cycles and 60 after the start of the test.
It was performed after the lapse of cycles. As for the evaluation method, the degree of corrosion of the test sample was visually observed and evaluated by the following criteria.

◯: No occurrence of red rust Δ: Spot rust spreads and a small amount of rust juice begins to flow ×: Rust juice flows significantly. The results are shown in Table 1.

[0043]

[Table 1]

2. Influence of Thickness of Each Coating Next, in order to know the influence of the corrosion resistance of the thickness of each coating, test samples of various thicknesses were prepared for the first, second and third coatings and tested.

The test sample had the composition of Example 3 described above, and the test sample was prepared by changing the treatment time and the like. Then, the corrosion resistance was judged by the same combined cycle test method as described above. The results are shown in Table 2.

[0046]

[Table 2]

[0047]

[Brief description of drawings]

FIG. 1 is a front view showing a state where a hose clip is assembled.

[Explanation of symbols]

 1 ... Hose clip, 2 ... Tube, 3 ... Rubber hose

Claims (2)

[Claims] 1. A first coating formed by aluminum plating on the surface of a metallic base material, a second coating formed by metal powder-chromium oxidation treatment, and a third coating formed by an aqueous treatment liquid further containing an aqueous resin and a silica material. Metal rustproof structure covered by and. 2. A first coating formed by aluminum plating on the surface of a metal base material, a second coating formed by metal powder-chromium oxidation treatment, and an aqueous treatment liquid containing an aqueous resin, a silica material and a wax. Metal rustproof structure covered with three coatings.