JPS6020464B2 - Surface treatment method for metal parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of metal materials, and more particularly, the present invention relates to a method for surface treatment of metal materials, particularly bolts, nuts, or washers, which have excellent performance such as heat resistance, load resistance, and film adhesion. The present invention relates to a method for forming a base for painting.

Screw products such as bolts, nuts, and washers are manufactured by the mechanical industry,
It is indispensable as a basic component in industrial fields such as the steel construction industry, and is widely used in various fields.

For example, it is widely used in the assembly of various industrial machines, the construction of industrial plants, and the construction of land and offshore structures.
In particular, screw products with excellent corrosion resistance are required for applications where screws often come into contact with corrosive gases and liquids, such as in chemical industrial plants, offshore and underwater structures, and the like. Incidentally, screw products for machinery and steel construction industries are generally made of steel, and are subjected to corrosion-resistant treatment when used for the above-mentioned purposes. One method for such corrosion-resistant treatment is to plate steel screw products with a highly corrosion-resistant metal such as cadmium or zinc. However, this plating method has the problem of disposing of plating waste liquid, and although the corrosion resistance of metal-plated screw products is somewhat improved compared to untreated ones, it is not fully satisfactory.
As an alternative to this plating method, a method of processing screw products with resin has recently been proposed, and phenol resin, epoxy resin, fluororesin, etc. are used as the coating resin.

However, conventionally proposed resin processed products have problems with the adhesion and mechanical properties of the resin coating, and the coating is damaged during handling or when tightening screws, and there are still problems in terms of corrosion resistance. Therefore, the corrosion resistance of a resin coating system for metal members is expressed not only by the durability of the resin film itself, but also by the adhesion between the film and the surface of the metal member and the corrosion resistance of the surface of the metal member. Adhesion between the metal member and the surface of the metal member is important.

This adhesion is determined by the adhesion between the base layer formed by pretreatment of the resin coating and the resin film, and the durability of the base layer itself (
(heat resistance, load resistance, corrosion resistance, etc.) have a major influence. Surface treatment methods for improving the corrosion resistance of resin coating systems for metal parts include mechanical treatment methods such as the plasto method, and chemical conversion treatment methods such as the phosphate method and chromate method. The synthetic treatment method is the most superior and widely used.

However, the phosphate chemical conversion treatment method that has been used in the past has not been applied to bolts, nuts, and washers (hereinafter collectively referred to as "screw members"), which is the main objective of the present invention.
It is unsuitable for use as a base treatment for painting (collectively referred to as ) for the following reasons. That is, since a high stress is applied to the threaded portion when it is installed vertically, a high degree of load resistance and strong adhesion to the surface of the metal base material are first required for the coating base. In addition, in order to withstand harsh usage conditions, such as high-temperature corrosive environments, screw members are usually
Competitive painting is performed using heat-resistant resins such as phenolic resin, epoxy resin, fluororesin, polyamide-imide resin, and modified silicone resin, but in this adjoining painting process, the object to be coated is exposed to high temperatures, so the resin Heat resistance is required not only for the film but also for the base layer. In this way, the three properties of load-bearing properties, corrosion resistance, and heat resistance are strictly required for the coating base layer of screw members. However, the zinc phosphate-based chemical conversion coating that has been most commonly used in the phosphate chemical treatment method for metal parts has poor heat resistance (approximately 110°C or less), and the preheating temperature at around 230:00 is Cannot withstand scaling temperatures. On the other hand, zinc phosphate-calcium phosphate mixed systems and iron phosphate-based chemical conversion films, which have improved the heat resistance of zinc phosphate-based chemical conversion films, are superior to zinc phosphate-based chemical conversion films in terms of heat resistance, but have the disadvantage of inferior corrosion resistance. . On the other hand, manganese phosphate-based chemical conversion coatings are also known, but these coatings tend to thicken with conventional treatment methods and have problems with adhesion to resin coatings and load-bearing properties. Therefore, the present inventors have conducted various studies with the aim of providing a method for forming a coating base that firmly adheres to the resin film and metal substrate surface and exhibits excellent durability even under high temperature and high load conditions. As a result, they found that the above object can be achieved by sequentially treating with two specific types of acidic phosphate chemical treatment solutions having different treatment solution compositions, and have completed the present invention.

Thus, according to the present invention, the surface of the metal part, particularly the threaded member, is coated with an acidic material containing monobasic sodium phosphate and/or both monobasic zinc phosphate and monobasic calcium phosphate as essential components. After treatment with a phosphate chemical treatment solution (first solution), 'b--is treated with an acidic phosphate chemical treatment solution (second solution) containing manganese monophosphate as an essential component and having a higher free acidity than the first solution. A method for surface treatment of a metal member is provided, the method comprising treating the surface with a liquid.

The method of the present invention is applicable not only to screw members but also to other mechanical parts that require heat resistance and load resistance, such as valves, flanges,
It can be advantageously used for forming a base for painting metal parts such as bearings, or for base treatment when lining the surface of metal (for example, a pipe) with resin.
The method of the present invention will be explained in more detail by taking as an example a case where a particularly suitable threaded portion is used as the metal member.

Screw member The screw member to which the method of the present invention can be applied is not particularly limited, and the method of the present invention can be applied to any type of metal screw member. The method of the invention is particularly applicable to threaded parts made of steel (e.g., universal steel, carbon steel, alloy steel, stainless steel, etc.) that are susceptible to corrosion, such as hexagonal bolts, nuts, bolts with irregular heads, nuts, fully threaded bolts, and nuts. It can exhibit excellent effects when used on double-threaded bolts, nuts, shielded bolts, nuts, etc.

Such a screw member may be subjected to the method of the present invention as it is, but may be subjected to preliminary treatments such as degreasing, acid cleaning, surface conditioning, etc., if necessary.

These pretreatments can be carried out by methods known per se; for example, degreasing and cleaning can be carried out using caustic soda or various organic solvents (for example, acetone, trichloroethylene, perchlorethylene, trichlorestane, etc.). Acid cleaning can be performed using sulfuric acid, hydrochloric acid, etc. In addition, prior to carrying out the method of the present invention, the screw member can be surface-conditioned using an aqueous titanium phosphate colloid solution, thereby further improving the load bearing capacity and adhesion of the phosphate chemical conversion coating. You can force it.

Titanium phosphate colloid aqueous solution is titanium phosphate (Ti02
・P207) can be formed by dissolving or dispersing it in water, and usually has a solid content concentration of 0.1 to 50.
A range of 2 to 10 minutes is advantageously used, preferably from 2 to 10 hours. The treatment with the titanium phosphate colloid aqueous solution can be carried out in accordance with a method known per se, for example, by subjecting the threaded portion to treatments such as dipping, brushing, and spraying at a temperature of room temperature to about 100°C. The thus pretreated screw member is then subjected to a base forming treatment according to the present invention. Treatment with first liquid According to the present invention, the screw member pretreated as described above is first treated with monosodium phosphate [NaH2
PQ], and/or zinc monophosphate [Zn (Sun 2P04
)2] and monocalcium phosphate [Ca(5P04)2]
It is treated with an acidic phosphate chemical treatment solution (first solution) containing both of these as essential components.

The concentration of the above-mentioned essential components in the first liquid can be varied widely depending on the type of metal material to be treated, processing conditions, etc., but in general, sodium monophosphate is
Preferably in the range of 5 to 30 evenings/day; monochrome zinc phosphate in the range of 1 to 200 evenings/day, preferably 3 to 30 evenings/day; and monobasic calcium phosphate preferably in the range of 1 to 200 evenings/day. It is advantageous to use it within the range of 5 to 30 evenings. In the present invention, monobasic sodium phosphate can be used alone, but monobasic zinc phosphate is used in combination with monobasic calcium phosphate. The ratio of zinc monophosphate and calcium monophosphate when used in combination is not strictly limited and can be varied widely taking into account various conditions, but in general, zinc monophosphate and calcium monophosphate are used in combination. It is suitable to use the weight ratio of monocalcium phosphate to 1/loo to 30/1, preferably 1/10 to 3/1. Of course, monobasic sodium phosphate may be used in combination with monobasic zinc phosphate and/or monobasic calcium phosphate. In addition to the metal phosphate component described above, the first liquid contains an acid for keeping the liquid on the acidic side.

As such acid, phosphoric acid (Japanese 3P04) is most suitable, but other acids such as nitric acid, hydrochloric acid, etc. can also be used alone or together with phosphoric acid. These acids generally have a free acidity of the first liquid of 0 to 5.0, preferably 0.5 to 3.0.
used in amounts within the range of Here, "free acidity" refers to the o. INNaO
represents the private number of H (bromophenol full indicator).
Furthermore, the first liquid may contain additives conventionally used in the phosphate chemical treatment of metals, if necessary.

Examples of such additives include those described below. '1' Reaction accelerator, such as nitrates, sulfates, halides of metals such as nickel, cobalt, iron, chromium, aluminum, magnesium, etc.

Specifically, copper nitrate, nickel nitrate, cobalt chloride, etc. '2} Oxidizing agents, such as nitrous acid, hydrogen peroxide, hypochlorous acid, sodium nitrite, etc.

'31 Other additives such as fluoroboric acid, tartaric acid, citric acid, nitrobenzene, nitrourea, etc.

These additives can be used at conventionally used concentrations, e.g.
Preferably in the range of 0.01 to 5 minutes; the oxidizing agent is 0 to
It can be used in a range of 30 days, preferably 0.01 to 3 days.

Further, the other additives mentioned above can be used in a range of 0.01 to 3 ta. Thus, the first liquid used in the invention can generally have a total acidity within the range of 5 to 3 u, preferably 14 to 17.

Here, the "total acidity" refers to the number of 0.1N NaOH (phenolphthalein indicator) required for titration of the treated solution 10. The treatment of the threaded member with the first liquid having the composition described above can be carried out according to a method known per se, for example,
This can be done by means such as impregnating, brushing, and spraying.

The temperature and time during the treatment can be changed depending on the composition of the treatment liquid and the treatment means, but it is generally preferable that the treatment temperature is within the range of about 400C to about 600C, and the treatment time is about 300C. 2 minutes is sufficient. By treatment with the first liquid,
A thin microcrystalline phosphate film is formed that tightly adheres to the surface of the metal part of the screw member.

The thickness of this phosphate film is generally 0.5 to 6 microns,
Preferably it can be within the range of 1 to 3 microns. The threaded member thus treated preferably has a thickness of approximately 5 pins.
After washing with water at ~70°C, it is subjected to treatment with a second liquid according to the invention.

Processing with the second liquid The screw member treated with the first liquid as described above is then treated with an acidic material containing manganese monophosphate [Mn (Japanese 2P04) 2] as an essential component and whose free acidity is higher than that of the first liquid. Treated with phosphate chemical treatment solution (second solution).

The concentration of monomanganese phosphate in the second liquid can be varied widely depending on the conditions of the treatment with the first liquid, but is generally 1 to 200%, preferably 10 to 200%.
Advantageously, it is within that range.

Further, it is important that the second liquid has a higher free acidity than the first liquid, and the free acidity of the second liquid is generally 1 to li, preferably 4 to 4, depending on the free acidity of the first liquid. It can be within the range of 8.

The free acidity of the second liquid is at least 1.0% lower than the free acidity of the first liquid within such a range. More preferably, it is higher than 3.0. Examples of acids that can be included in the second liquid to maintain the free acidity of the second liquid within the above range include the same acids as mentioned for the first liquid, particularly phosphoric acid and/or nitric acid. Furthermore, the second liquid can contain additives similar to those mentioned for the first liquid, such as reaction accelerators and oxidizing agents, but in particular, the concentration of the oxidizing agent should be equal to or lower than that of the first liquid. It is desirable to do so.

A second liquid of such composition can generally have a total acidity within the range of 10-70, preferably 25-50.
The treatment with the second liquid can also be carried out according to methods known per se, such as dipping, brushing, spraying, and the like.

The temperature and time at that time can be changed depending on the composition of the treatment liquid, treatment means, etc., but the treatment temperature is generally about 50°C to about 75qo
A treatment time of about 2 minutes to about 1.5 minutes is sufficient. By the treatment with the second liquid described above, a tertiary phosphate chemical conversion film with a microporous structure grows on the surface of the microcrystalline tertiary phosphate chemical conversion film formed by the treatment with the first liquid. do.

The thickness of the film formed by this second liquid is generally 0.
Desirably it is in the range of 5 to 7 microns, preferably 1 to 3 microns, so the total thickness of the phosphate conversion coating according to the method of the invention is generally 1 to 10 microns, preferably 2 to 4 microns. Advantageously, it is within the range of . Although the exact reason why a film having a microporous structure is formed in the treatment with the second liquid is not clear, it is generally presumed as follows.

In other words, the effects of free acidity, oxidizing agent concentration, and processing temperature have been observed and demonstrated as factors affecting film morphology, and the former two factors are involved in the formation and suppression of porous structures, respectively. , the latter temperature factor is responsible for the size and morphology of the coating crystals. The processing temperature was adjusted to the conventional conditions (90 to 100
It was confirmed that by lowering the temperature from 50°C to 75°C used in the present invention, a thick film with large grain flames changes to a thin film with fine grains. Also,
It has also been found that when the free acidity of the second liquid is made larger than the above range, a porous structure is formed, and that the formation of a porous structure is suppressed by adding a large amount of an oxidizing agent. These two factors are known to influence the acid eclipse reaction, that is, hydrogen gas generation, and the oxidation of hydrogen gas (extinction of gas), respectively. Therefore, it is presumed that the hydrogen gas generated during the reaction process with the second liquid under specific treatment conditions makes a major contribution to the formation of the microporous structure. The threaded member treated as described above can be post-treated with a chromate (Cr203) aqueous solution or an anticorrosive compound such as dicyclohexylamine nitrite, 1,2,3-benzotriazole, etc., if necessary.

According to the method of the present invention, a phosphate chemical conversion treatment film is formed in which a microcrystalline phosphoric acid film is firmly bonded to the surface of a metal member, and a film with a microporous structure grows toward the upper layer. As demonstrated in the examples below, this film exhibits remarkable effects in that it has excellent heat resistance, load resistance, and adhesion.

Therefore, the phosphate chemical conversion coating formed by the method of the present invention is extremely suitable as a coating base for heat-resistant paints.

Heat-resistant paints that can be applied to metal parts, particularly screw parts, treated by the method of the present invention include aromatic polyamide resins, polyamideimide resins, silicone resins, etc., and these can be applied using conventional methods. Can be applied. Among them, the screw member treated according to the present invention is
The method described in Hakama Kaisho 56-1 Madara No. 72, that is, the following component i) the following formula (1), where R represents a divalent aromatic hydrocarbon group, and Ar is 3
ii) a solvent for the polyamideimide,
and iii) If necessary, after applying an undercoat coating composition containing a polyfunctional compound capable of reacting with the polyamideimide, drying, and curing the coating film by heating if necessary, {B) Heat resistant, Particularly suitable for resin coating with excellent corrosion resistance.

For details of this method, see the above publication. Next, the method of the present invention will be explained in more detail with reference to Examples.

Example 1 Composition of the first liquid Composition of the second liquid Steel bolts (hexagonal), nuts, and washers were immersed in trichlorethylene to remove fats and oils, tin washed, and immersed in acetone. It was dried with hot air at 12,000 ℃.

Next, these were surface-conditioned with a (Ti02/P207) colloid aqueous solution (liquid temperature 65q0, soaked for 5 seconds/5 minutes), then immersed in the first solution kept at 50-600C for 1 minute, and then soaked for 60-70 minutes. Washed with hot water. Next, it was immersed in a second solution kept at the same temperature for 49 seconds, washed, washed with acetone, and dried with hot air at 80 to 120 oo. Through these treatments, bolts, nuts, and washers having a phosphate coating with a microporous structure having a thickness of 2 to 4 mm were obtained. A heat-resistant coating was applied to the obtained object to be treated in the following manner. After preheating the object to be coated by IQ at 200 qo, a known polyamideimide resin having a repeating unit represented by the following formula and exhibiting an intrinsic viscosity of 0.41 at 30 q0 in N-methyl-2-pyrrolidone solvent was prepared as follows. Composition: N-methyl-2-pyrrolidone 2 parts by weight Dimethylacetamide 2 Methyl isobutyl ketone
The resin concentration in the mixed solvent having 3.
% to prepare a coating composition for undercoating.

This coating composition for undercoat was sprayed using an airless sprayer and dried at 200°C for 5 minutes to form an undercoat film having a thickness of about 8 to 10 inches.Then, under the above conditions, an undercoat film was formed. Acheson Coiloi ship Compa having the following composition on the base coat coating of bolts, nuts and washers:
NY resin mixture, that is, a mixture of 14/10 (parts by weight) of polyamideimide and polytetrafluoroethylene fine particles (average particle size of about 1 mountain) [Emuralon RJ-3
10A] with the following composition N-methyl-2-pyrrolidone
2 parts by weight dimethylacetamide
A top coating composition was prepared by dissolving and suspending the above resin mixture (solid content) in a mixed solvent containing 2 methyl isobutyl ketone 3 at a concentration of about 15%. After spraying this top coat coating with an airless coating machine,
After drying for a few minutes, an ant coating treatment was performed under the conditions shown in Table 1 below to form a top coat film having a thickness of about 8 to 1 coat. Performance tests were conducted on the bolts, nuts, washers, and test panels that had been surface-treated and painted (undercoat and topcoat) as described above in the following manner. For comparison, the same paint treatment as above was applied to bolts, nuts, washers, and test panels that had been treated with zinc phosphate-based chemical conversion treatment (conventional treatment), which is the most commonly used surface treatment method. A similar performance test was also conducted on the

The chemical conversion treatment conditions according to the conventional method are shown below. Composition of treatment liquid Zn (QP〇4) 24-9 evening/
SoNi(N03)2 0.
1 Melon P04 1.5
〃HN03
4.3〃NaOH (amount necessary to give free acidity 2.0) Total acidity, 18.0 points Treatment conditions: 65°C, 1.5 to 3 minutes Test method After heating the test panel as it was or the coated product for a predetermined period of time in an overflow chamber set at a predetermined temperature, various performances of the coating film system were evaluated using the following methods.

1. Determination of the presence or absence of wrinkles and blisters Abnormalities in the film formation (wrinkles, blisters, etc.) due to the coating film formation process and heating operation were visually observed and determined.

This test was conducted on bolts, nuts, and test panels. 2 Goban Peeling Test The paint-treated test panel was subjected to the test method described in the Japan Paint Manufacturers Association's "Paint Test Method" to determine the ratio of the number of goblets that did not peel out of 100 goblets on one surface.

3 Gardner Bending Test Painted test panels were subjected to a bending test according to the method described in JIS K5400, and the presence or absence of peeling, blistering, etc. of the paint film was observed with the naked eye.

4. Salt water mist test A set of painted bolts and nuts and a test panel were subjected to a salt water mist test according to the method described in JIS K5400, and the following criteria were met: A: Rust occurred over the entire surface of the bolts and nuts.

B: Peeling or blistering of the paint film.

C: The fitted bolt and nut cannot be removed.

Accordingly, the time required to reach either of these states was determined.

5 10% sodium hydroxide immersion test Painted bolts and nuts were immersed in a 10% sodium hydroxide aqueous solution at room temperature for 7 days, and the presence or absence of abnormalities such as blistering and peeling was examined and evaluated in the following 3 grades. .

Kamitei Jisho is also full of Futomumagisago 6 Vertical attachment test A set of painted bolts, nuts, and washers was attached to a high-strength bolt tester (torque tester), and the Mariker vertical attachment torque curve was first determined. .

From this curve, find the load at the point where the attached torque ratio to the axial force suddenly changes, and define this as the point at which the lubricating effect is lost (i.e.,
loss point of the coating system including the base layer). This test method complies with JIS-B-1136. The above test results are shown in Tables 2 and 3, and as is clear from the tables, the base formed by the method of the present invention has better heat resistance,
It can be seen that the load resistance, adhesion and corrosion resistance are significantly improved.

Table 1 Top coat film formation conditions, dawning conditions Table 2 Dawning conditions and performance table 3 Performance after heating operation* Sooting conditions A: 220°C, 60 minutes Example 3 Composition of first liquid Total acidity 16.0 Point After cleaning and pre-treating steel bolts, nuts or washers using the same machine as in Example 1,
The samples were immersed in the first solution having the above composition for 1.5 minutes and washed with hot water.

The treatment operation and performance test method for the second liquid treated skin were the same as in Example 1. The results obtained are shown in Table 4, and it is clear that the coating formed by the method of the present invention is excellent as a coating base for screw members. Husband adjacency condition A: 2200,
60 Example 3 Composition of the first liquid After cleaning and pretreating steel bolts, nuts, or washers in the same manner as in Example 1, the composition of the first liquid was 40 to 50.
It was immersed in the first liquid maintained at qo for 1.5 minutes and washed with hot water.

Processing operations and performance test methods after the second liquid treatment are shown in Example 1.
It is similar to The results obtained are shown in Table 5, and it is clear that the chemical conversion coating formed by the method of the present invention is excellent as a coating base for screw members. Table 5 Performance after heating operation x dawning conditions A: 220°C, 60 minutes

Claims (1)

[Scope of Claims] 1. The surface of a metal member is treated with (a) an acidic phosphate chemical conversion treatment solution containing both monobasic sodium phosphate and/or monobasic zinc phosphate and monobasic calcium phosphate ( After treatment with (b) an acidic phosphate chemical treatment solution (second solution) containing manganese monophosphate as an essential component and having a higher free acidity than the first solution. A method for surface treatment of metal members, characterized in that: 2. The method according to claim 1, wherein the metal member is a bolt, nut, or washer. 3. The method of claim 1, wherein the treatment with the first liquid is carried out at a temperature within the range of about 40<0>C to about 60<0>C. 4. The method of claim 1, wherein the treatment with the second liquid is carried out at a temperature within the range of about 50<0>C to about 75<0>C. 5. The method of claim 1, wherein the second liquid has a free acidity within the range of 1-15.