JPS5840045B2 - Method for manufacturing bolts, nuts or washers with excellent corrosion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing screw products with excellent corrosion resistance, that is, bolts, nuts, and washers, and more specifically, bolts whose corrosion resistance is significantly improved by resin processing.
This invention relates to a method for manufacturing nuts or washers.

Screw products such as bolts, nuts, and washers are indispensable as basic element parts in industrial fields such as the machinery industry and the steel construction industry, and are widely used in various fields, such as the assembly of various industrial machines, It is widely used in the construction of industrial plants, land and offshore structures, etc., especially for applications where there are many opportunities for contact with corrosive gases and liquids, such as chemical industrial plants and offshore and underwater structures. There is a demand for screw products with excellent corrosion resistance.

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 sometimes damaged during handling and tightening of screws, and there are still problems in terms of corrosion resistance. .

The inventors of the present invention have conducted various studies with the aim of developing resin-treated screw products that can maintain excellent corrosion resistance over a long period of time without damaging the coating during handling or tightening. As a result, by using a type of polyamide-imide as the undercoat resin and a thermosetting resin containing finely powdered polytetrafluoroethylene dispersed therein as the topcoat resin, the above-mentioned method was achieved by double coating them. The inventors have discovered that the object can be achieved and have completed the present invention.

Therefore, according to the present invention, on the surface of a metal bolt, nut or washer, A) the following component 1) the following formula (1) where R represents a divalent aromatic hydrocarbon group and Ar is 3
11) A solvent for the polyamideimide, and 1ii) If necessary, a polyfunctionality capable of reacting with the polyamideimide. After applying the undercoat coating composition containing the compound, drying, and heat-curing the coating film if necessary, B) finely powdered polytetrafluoroethylene is added to a solvent solution of a heat-curable resin binder. Provided is a method for producing a bolt, nut or washer with excellent corrosion resistance, which comprises applying a top coating composition containing a dispersed top coating composition, drying it, and then curing it by heating.

The method of the present invention will be explained in more detail below.

In addition, in the following description, when a bolt, a nut, and a washer are collectively expressed, they are collectively referred to as a "screw member."

Screw member The screw member targeted by the present invention is not particularly limited, and the method of the present invention can be applied to any type of metal screw member. The method is particularly applicable to threaded members made of steel (e.g., ordinary steel, carbon steel, alloy steel, stainless steel, etc.) that are susceptible to corrosion, such as hexagonal bolts, nuts, bolts with irregular heads, nuts,
It can exhibit excellent effects when used on fully threaded bolts, differential 11 double threaded bolts, nuts, stud bolts, nuts, etc.

Although such a screw member may be subjected to the method of the present invention as it is, it is generally advantageous to previously perform a surface treatment such as plasting, degreasing, acid cleaning, chemical conversion treatment, etc.

These surface treatments can be performed by methods known per se; for example, plasting includes sandblasting, shotblasting, etc., degreasing includes cleaning with caustic soda, petroleum solvents, etc., and acid cleaning includes cleaning with sulfuric acid. , washing with hydrochloric acid, etc., and chemical conversion treatments include phosphate treatment, sholate treatment, electroless plating, and the like.

These base treatments can be performed individually or in combination of two or more types depending on the condition of the screw member to be treated.

When carrying out the method of the present invention, the screw members used are:
It is desirable to carry out a chemical conversion treatment in advance. For example, phosphate treatment may be used to form a film of a metal salt of phosphoric acid such as zinc phosphate or manganese phosphate, or electroless plating may be used to form a film of a metal such as nickel copper. It is advantageous to form a film.

The thickness of the coating deposited by such conversion treatment is not critical, but generally a range of from about 2 to about 15 microns, preferably from about 3 to about 8 microns, is sufficient.

Undercoating According to the method of the present invention, an undercoat is applied to the screw member which has been appropriately prepared as described above.

As mentioned above, the undercoat coating composition used in the method of the present invention has the following components: 1) the following formula (1) where R represents a divalent aromatic hydrocarbon group and Ar is 3
11) A solvent for the polyamide-imide, and 11 [) If necessary, a polyamide-imide that can react with the polyamide-imide. Contains a functional compound as an essential component.

In the above formula (1), the "divalent aromatic hydrocarbon group" represented by R has at least one monocyclic or polycyclic aromatic ring such as a benzene ring and a naphthalene ring, preferably 1 to 2. and contains two aromatic rings, these two aromatic rings include a divalent hydrocarbon group that is interconnected directly or through at least one atom, and the The aromatic ring may be further substituted with a lower alkyl group, a lower alkoxy group, a halogen atom, or the like.

The aromatic hydrocarbon group can thus generally have 6 to 20, preferably 12 to 15 carbon atoms.

Representative examples of such divalent aromatic hydrocarbon groups are as follows.

In the formula, Y represents a direct bond or a linear or branched lower alkylene group, -〇--8- or -8O2
A divalent aromatic hydrocarbon group represented by 1 representing - is preferred.

In this specification, the term "lower" means that the group or compound to which this term is attached contains 5 or less carbon atoms, preferably 3 or less carbon atoms.

On the other hand, examples of the "trivalent aromatic hydrocarbon group J(Ar)" in formula (1) include the following, and further substituents such as a lower alkyl group, a lower alkoxy group, and a halogen atom on the aromatic ring. Also included are substituted aromatic hydrocarbon groups corresponding to the above groups having.

As Ar, the type shown by C is most suitable.

Therefore, specific examples of preferable structural units represented by the above formula (1) include the following: etc.

Generally, the polyamideimide used in the present invention preferably consists essentially only of the structural unit of formula (1) explained above, but in some cases, it may contain up to 10 morphs of other structural units as minor components. It's okay to stay.

The polyamideimide described above is known per se, or can be produced by a method known per se.

For example, it is easily produced by the reaction of anhydrous aromatic tribasic acid halide (e.g., trimellitic anhydride halide) with an aromatic diamine, or the reaction of anhydrous aromatic tribasic acid (e.g., trimellitic anhydride) with an aromatic diisocyanate. be able to.

It is desirable that the polyamide-imide used in the present invention has film-forming properties, and is usually dissolved in N-methyl-2-pyrrolidone or sulfuric acid solution with a concentration of 0.5 g/IOM polymer.
The value of intrinsic viscosity measured at 0'C is 0.1 to 0.6,
Preferably, it is within the range of 0.2 to 0.5.

According to the present invention, the polyamideimide described above is dissolved or dispersed in a solvent when used as a coating composition for an undercoat.

The solvent that can dissolve or disperse the polyamideimide varies depending on the type of the polyamideimide, but for example, N-
Methyl-2-pyrrolidone, N,N-dimenalacetamide, dimenalformamide, dimenal sulfoxide,
Examples include a single organic polar solvent such as tetramenalene sulfone, or a polar mixed solvent of these polar solvents and an organic non-polar solvent such as menal isobunal ketone, benzene, toluene, and xylene.

Particularly preferred solvent systems include N-methyl-2-pyrrolidone alone; a combination of N-methyl-2-pyrrolidone and methyl isobunal ketone; and a combination of N-methyl-2-pyrrolidone and N,N-dimenalacetamide. Combination; N-methyl-2-pyrrolidone and xylene combination; N-methyl-
Examples include a combination of 2-pyrrolidone, N,N-dimenalacetamide and methylisobunal ketone.

The concentration of polyamideimide in these solvents is not critical and can be varied widely depending on the type of polyamideimide used and the desired coating viscosity, but is generally 5 to 40% by weight, preferably 10 to 30% by weight. It is appropriate to set it to about %.

The polyamide-imide used in the present invention is a so-called heat-resistant polymer material, and forms a film with sufficiently excellent heat resistance and mechanical strength without using a cross-linking agent. A polyfunctional compound that reacts with the polyamideimide may be used together with the polyamideimide.

Such polyfunctional compounds include, for example, glycerin,
Polyhydric alcohols such as trimenalolpropane, tris-β-hydroxyl enal isocyanurate, and pentaerythritol; polyhydric alcohols having an amino group such as aminopropane-1,2-diol, and the like.

The coating composition for undercoating of the present invention, which contains the above polyamideimide dissolved or dispersed in the above solvent, may contain appropriate amounts of other additives such as a leveling agent, if necessary. I don't mind.

When applying the above-mentioned undercoat coating composition to a screw member that has been subjected to undercoat treatment as described above,
It is advantageous if the screw member is preheated.

Although the preheating temperature is not strictly limited, it is generally between about 50 and about 220'C, more preferably between about 120 and about 200'C, since preheating to too high a temperature may have an adverse effect on the base treatment coating. It is suitable to heat at a temperature between .degree.

Further, the preheating time is usually about 5 to about 30 minutes, so that the center of the screw member is sufficiently heated.

The above-mentioned primer coating composition can be applied to the preheated screw member according to a conventional method, such as spray coating, air spray coating, airless coating, airless electrostatic coating, dipping, or powder coating. It can be applied according to the method, brush coating, roller coating, etc., and the coating thickness is generally 4 to 20% as the film thickness after drying.
The thickness is preferably within the range of 6 to 15 microns.

The screw member coated with the primer coating composition is then dried.

Drying is usually done in a hot air oven, electric oven, infrared drying oven, etc.
A temperature that is at least 20°C or more lower than the temperature at which the baking effect of the primer coating composition appears, preferably about 100°C to about 2°C.
Advantageously, the coating is carried out at a temperature in the range of 0.000°C, at least until the surface of the coating is tacky to the touch.

It is preferable that the dried coating film is then directly subjected to the top coating process described below, but in some cases, the primer coating film may be prebaked to some extent.

However, complete baking of the basecoat at this stage may significantly reduce the adhesion of the topcoat, so complete baking should be avoided, and the degree of baking that is possible at this stage should be avoided. can be easily determined by one skilled in the art by small scale test experiments.

Top Coating The screw member to which the base coat coating composition has been applied and dried is then further coated with a top coat coating composition.

As described above, the top coat coating composition used in the method of the present invention is comprised of finely powdered polytetrafluoroethylene dispersed in a solvent solution of a thermosetting resin binder.

As mentioned above, the top coating composition used in the present invention is characterized in that it contains finely powdered polytetrafluoroethylene, and this powdered polytetrafluoroethylene is
Usually, it is made by grinding solid polytetrafluoroethylene, about 0.1 to 5 microns, more preferably about 0.5 microns.
It is desirable to have an average particle size within the range of about 1.5 microns.

The content of the polytetrafluoroethylene is not strictly limited and can be changed depending on the type of solvent solution of the resin binder serving as the dispersion medium, but the content of the polytetrafluoroethylene and the resin binder is Generally from 20 to 75% by weight, preferably from 40 to 75% by weight, based on the amount
Advantageously, it is within the range of 60% by weight.

Further, the thermosetting resin binder that becomes the matrix for dispersing the above-mentioned polytetrafluoroethylene fine powder is a film-forming resin that permanently solidifies or hardens as a film when heated and/or oxidized. , polyamideimide resin, polyesterimide resin, phenolic resin, epoxy resin, alkyd resin, polyurethane resin, petroleum (hydrocarbon) resin, amino resin (urea resin, melamine resin, triazine resin, etc.), thermosetting silicone resin, etc. be done.

Among these resins, polyamideimide resins of the type described above for the base coating composition are particularly preferred.

As the solvent for forming the solution of the resin binder, water and various known solvents that dissolve the thermosetting resin are used. When a suitable polyamide-imide resin is used, the coating composition for the undercoat is used. The solvent systems mentioned above are advantageously used.

The combined concentration (solids content) of polytetrafluoroethylene and resin binder in these solvents is generally from about 5 to about 50% by weight, preferably from about 10 to about 30% by weight, based on the weight of the solution. Within range.

The top coating composition used in the present invention may optionally include:
In addition, other additives such as lubricants (e.g. graphite, molybdenum sulfide, etc.), pigments (e.g. titanium white, benzene, carbon black, etc.), dryers (e.g. cobalt naphthenate, etc.), stabilizers (e.g. : vinyl resin, cellulose resin, etc.).

An example of a coating composition containing fine polytetrafluoroethylene powder as described above for use in the present invention is disclosed in U.S. Pat.
Coating compositions containing polyamideimide resins as binders, which are described in U.S. Pat.
From 1oids Company” Emralon
333'', available as ``Emralon RJ-31OA''.

According to the present invention, the above-mentioned top coat coating composition is applied to the surface of the screw member that has been coated with the base coat.

Prior to this application, the screw member should be heated to at least 50°C or above.
Preheating is preferably carried out to a temperature of 120° C. or higher and at least 20° C. lower than the temperature at which the baking effect of the primer coating composition appears.

However, when performing the above-mentioned undercoating process consecutively, the temperature of the undercoated screw member is already 50°C.
Needless to say, in the above case, there is no need to preheat again.

The top coating composition may be applied by a method known per se, such as spray coating, air spray coating, airless coating, airless electrostatic coating, dipping, powder coating, brush coating, roller coating, etc. The coating thickness is generally from about 4 to about 20 microns, preferably from about 6 to about 15 microns as a dry film thickness.
Advantageously, it is in the micron range.

The threaded member thus coated with the top coating composition is then dried and baked.

This drying and baking can be carried out continuously in a heating oven.

Drying can generally be carried out at a temperature in the range of 50 to 200°C for about 5 to about 60 minutes, and baking can generally be carried out at a temperature of about 80 to about 350°C, depending on the resin used for the basecoat and topcoat coating compositions. It can be carried out for about 2 to about 60 minutes at a temperature of .

In the present invention, it is preferable to apply and bake the undercoat and topcoat at the same time, that is, by a two-coat, one-bake method.

The screw parts coated with the top coat as described above can be used as they are for various purposes as a product, but if necessary, the screw parts coated with the top coat may be coated with wax as a post-treatment. You may also make a bet.

It has been found that this further improves the corrosion resistance of the screw member.

This waxing can be easily carried out, for example, by dipping the screw member coated with the above-mentioned top coat in a solvent solution of mineral oil-based semi-hard wax.

According to the method of the present invention described above, it has a very thin double protective film, and has an intermediate grade (grade 2, 2A-2B) according to the JIS standard.
, 6G-6H) or higher can be provided.

Furthermore, despite having such a thin protective coating, the screw member provided by the method of the present invention has extremely excellent performance as shown below.

That is, the threaded member provided by the present invention, particularly the threaded member obtained using a polyamide-imide resin as the resin binder in the top coating composition, has various excellent effects as described below.

■ It has excellent heat resistance, being able to withstand continuous use temperatures of up to 230°C and intermittent use temperatures of up to 260°C.

- It has corrosion resistance of more than 1100 hours in a salt spray test, and can be removed even if the screw has been corroded considerably beyond the above test time.

■ Has excellent chemical properties against chemicals such as acetone, benzene, xylene, toluene, methyl alcohol, N-nonal-2-pyrrolidone, hydrochloric acid, sulfuric acid, nitric acid, and sodium hydroxide.

■ Has excellent dielectric breakdown strength that can withstand voltages up to 1200V.

■ The coating film will not be damaged even under a load such that the screw tightening stress is 60 kgf/sit.

■ Excellent lubrication function, easy to tighten and manage screws,
Troubles associated with tightening or removal are prevented.

Therefore, the screw member provided by the present invention can be used for land and sea structures, chemical plant equipment and pipelines, land and sea transport, transportation facilities, underground, underwater and underwater structures, etc. It can exhibit excellent corrosion resistance, weather resistance, strength, and electrical properties.

It is also effective when used in areas where crevice corrosion, electrolytic corrosion, pitting, etc. may occur.

Incidentally, screw parts made of ordinary steel or structural alloy steel coated with a coating also have the advantage that they can be provided on the market at a much lower cost than screw parts made of stainless steel.

Next, the present invention will be further explained with reference to Examples.

In addition, in the following examples, bolts, nuts, and washers that were phosphate-treated by the method described below were used.

The screw designations are 16 counters (5/8-11UNC) and 19 counters (3/4-10UNC), and the screw accuracy is 2A.
-2B class chrome-molybdenum steel stud bolts, carbon steel hexagonal nuts, and carbon steel flat washers are immersed in trichlorethylene to remove oil valves, then taken out and dried.

Next, these are immersed in a phosphate film chemical conversion treatment solution having the following composition heated to a temperature of about 50 to 60°C, and held for about 2 to 5 minutes.

Next, the bolts, nuts, and washers are taken out from the treatment solution, thoroughly washed with water, and then dried with hot air at a temperature of about 80 to 120°C.

This resulted in bolts, nuts and washers having a phosphate coating with a film thickness of 0.002-0.005 mm.

Example 1 The bolts, nuts, and washers that had been subjected to the phosphate film conversion treatment as a coating base as described above were preheated under various combinations of preheating temperature and preheating time shown in Table 1 below.

After that, it has a repeating structural unit represented by the following formula,
Intrinsic viscosity in N-methyl-2-pyrrolidone solvent, concentration 0
．． 5g/100rIl11 0.41 at 30°C
A known polyamide-imide resin having a value of 100% was added to a mixed solvent having the following composition of 2 parts by weight of N-menal-2-pyrrolidone, 2 parts by weight of dimenalacetamide, and 3 parts by weight of menalisobunalketone, so that the resin concentration was approximately 15%. A coating composition for undercoat is prepared by dissolving the coating composition for undercoat, and this coating composition for undercoat is sprayed using an airless coating machine, and dried under the drying temperature and time conditions listed in Table 1 below to form a film. Primer coatings approximately 8 microns thick were formed under five different conditions.

Next, Ache 5on Colloid having the following composition was applied to the undercoat film of the bolt, nut, and washer on which the undercoat film was formed under the conditions of each experiment number shown in Table 1 above.
A resin mixture made by s Company, namely (1) a mixture of 14/10 (parts by weight) of polyamideimide and polytetrafluoroethylene fine particles (average particle size of about 1μ) [Emurarono "RJ-31OA], or (il) polyamide A mixture of 14/13/3 (parts by weight) of imide, polytetrafluoroethylene fine particles (average particle size approximately 1μ), and graphite fine particles (average particle size approximately 1μ) [
Emralon 333] was prepared with the following composition: 2 parts by weight of N-methyl-2-pyrrolidone, 2 parts by weight of dimenalacetamide, and 3 parts by weight of menalisobunalketone.The concentration of the resin mixture (solid content) was about 15 A top coat coating composition was prepared by dissolving the top coat composition in such a manner that the top coat composition was sprayed using an airless atomizer, and then treated under the drying and sintering heat conditions shown in Table 2 below. Approximately 8μ
A top coat film having a film thickness of .

In both cases, the total film thickness is approximately 16μ.

Performance tests were conducted on the bolts, nuts, and washers treated with resin as described above using the following method.

For comparison, the following coating film was formed under coating film formation conditions as similar as possible to those described above: (a) Two-layer coating film of Emralon RJ-31OA (total film thickness of about 16μ) (0) Emralon 333-2 Layer coating film (total film thickness approximately 16μ
) (c) Phenol-based paint film (film thickness: approx. 16 μm) Epoxy-based paint film (film thickness: approx. 16 μm) (e) As a base coat (f) Two-layer paint film (film thickness) of coating composition for undercoat Total thickness approximately 16μ
) and the following plating film: (g) Electric cadmium plating (MFCdln-c)
(7) Electrogalvanizing (MFZn [[-C) (IJ)
Nine types of bolts, nuts, and washers having hot-dip galvanization (HDZ-35) were prepared, and similar performance tests were conducted on these bolts, nuts, and washers.

Salt water spray test The bolts and nuts painted as above were
Based on 5-Z-2371 (salt water spray test method), tests were conducted continuously under the conditions of salt water concentration of 5% and spray temperature of 35°C, and the following damage judgment criteria A: rust covering the entire surface of bolts and nuts was tested. occurrence.

B: Peeling or blistering of the coating film.

C: The fitted bolt and nut cannot be removed.

D: As the product strength of bolts and nuts decreases, the time required to reach any one of these four types of states is measured, and this is shown as the corrosion resistance time.

The test results are shown in Table 3 below. ■ Torque test The bolts, nuts, and washers with a nominal screw diameter of 19m111, which were painted as described above, were subjected to a torque test (see JIS-B1186 for details on the torque test method) using a bolt testing machine (torque testing machine), and the results were as follows. The torque coefficient is calculated using Equation-1, and the load at the point where the torque coefficient changes rapidly due to damage to the coating due to an increase in load is determined.

The results are shown in Table 3 below.

Note that 1 in the “Experimental Conditions” section of the table below
a , 1 b t 1 c +1-d and 1-e
indicates the undercoat and topcoat film forming conditions shown in Coating-1 and Table-2, and (1) and (11) correspond to the types of the resin mixtures used in the topcoat coating composition.

0 Chemical resistance test The bolts, nuts, and washers painted as described above were subjected to acetone, benzene, xylene, toluene, menal enal ketone, menal alcohol, N-methyl under the conditions shown in Table 4 below. 2-pyrrolidone, hydrochloric acid, sulfuric acid, nitric acid,
Soaked in picric acid, sodium hydroxide and saline,
The following damage criteria A: Peeling or blistering of the paint film.

B: Erosion of the metal base of bolts and nuts.

C: Dissolution of coating composition.

D: The fitted bolt and nut cannot be removed.

E: Decrease in product strength of bolts and nuts.

Accordingly, the time required to reach any one of these five states is measured, and this is shown as the corrosion resistance time (Hr).

The test results are shown in Table 4 below.

■ Electrical characteristic test Bolts painted as described above (thread designation: 16WL)
TIL1 total length 85mm), nut (nominal screw size 16 flats, height 16mm) and washer (outer diameter 80rnw1 inner diameter 18s!m)
, thickness 3 am), install it so that one nut and washer are located at each end of an uncoated carbon steel ring (outer diameter 32 mm, inner diameter 1811L1L1 height 35 mm), and tighten the bolt. Tightening stress is 30 kgf/
JI for the specimen tightened to sit.
Based on S-C-3005 (Plastic insulated wire test method)
Regarding the insulation resistance Ω when ■, the following two conditions (1) Electrical characteristics of the bolt and ring (II)
The electrical characteristics of the nut and ring were measured.

The test results are shown in Table 5 below.

(E) Prepare a specimen tightened in exactly the same manner as described in the electrical property test section in the pre-heat resistance test, place it in a Matsufuru electric furnace, and perform the test under the following conditions (2). 1) 210℃, 220℃,
Heating is performed under five temperature conditions of 230°C, 240'C and 250°C for 1200 hours each.

(River) 240℃, 250℃, 2608C, 27
The operation of heating for 8 hours each at 0℃ and 280℃ and then air cooling was performed once a day, resulting in a total of 60℃.
Heating tests were conducted at 6° with 60 operations per day.

The following three methods are used for this product. Changes in the properties of the coating and its effects are investigated by observing the state of peeling of the coating on the threaded surface of the fitting thread between the bolt and nut, and the stable properties are determined just before the temperature at which rapid changes in the properties of the coating and its effects appear. The indicated temperature is indicated as the maximum operating temperature.

The test results are shown in Table 5' below. The experimental conditions in the table are the same as those shown in Cloth-5-1 above.

Example 2 The bolts, nuts, and washers that had been subjected to the phosphate film chemical conversion treatment as a paint base as described above were subjected to preheat treatment under the preheat temperature and time conditions shown in Table 6 below. The used undercoat coating composition was sprayed using an airless coating machine, and dried under the drying temperature and time conditions shown in Table 6.
Undercoat films having two types of film thickness shown in Table 6 were formed.

Next, Table 6 below shows the two types of top coating compositions used in Example 1 above on the undercoat films of bolts, nuts, and washers on which the undercoat film was formed under the conditions of each experiment number: (:) Preparation composition of Emralon RJ-310A (11)
The prepared composition of Emlaron 333 was sprayed using an airless coating machine and then treated under the drying and baking heat conditions shown in Table 7 below to form top coat films having two types of film thickness shown in Table 7.

In both cases, the total film thickness was kept constant at 16 μm.

Performance tests were conducted on the bolts, nuts, and washers treated with resin as described above using the following method.

For comparison, the following coating films were prepared in the same manner as above: (a) Electrolytic cadmium plating (MFCdll) (b) Electrolytic galvanizing (MFZn river) *shi→
A known soft wax for metals (JIS K1801NP-2
) coated with a film thickness of 6μ.

Three types of bolts, nuts, and washers were prepared, and performance tests were also conducted on these bolts, nuts, and washers.

Salt Water Spray Test The bolts and nuts coated as described above were subjected to a salt spray test under the same test method and conditions as in the salt water spray test of Example 1, using the same damage criteria.

The test results are shown in Table 8 below.

(2) Torque Test The bolts, nuts, and washers painted as described above were subjected to a torque test using the same test method and conditions as in the torque test of Example 1.

The results are shown in Table 8 below.

In addition, 2 in the “Experimental conditions” section of the table below
-a and 2-b indicate the undercoat and topcoat film forming conditions shown in Coat-6 and Table 7, and (i) and (il) correspond to the type of the resin mixture used in the topcoat coating composition. do.

0 Chemical Resistance Test The bolts, nuts, and washers painted as described above were subjected to chemical resistance tests using the same chemicals, test method, and conditions as in the chemical resistance test of Example 1, and according to the same damage criteria. A sex test was conducted.

The test results are shown in Table 9 below. 0 Electrical property test Using the bolts, nuts, and washers painted as described above, electrical tests were carried out using the same shape and size of the specimen as in the electrical property test of Example 1, and under the same test method and conditions. A characteristic test was conducted.

The test results are shown in Table 10 below. Example 3 After preheating the bolts, nuts, and washers that were treated with phosphate coating as a base for painting as described above under various combinations of preheating temperature and time shown in Table 11 below,
The same resin as the polyamideimide resin used in Example 1 was mixed with the following composition 2N-methyl-2-pyrrolidone.
2 parts by weight dimenalacetamide 2
A coating composition for an undercoat is prepared by dissolving the resin in a mixed solvent containing 3 parts by weight of methyl isobunal ketone and 2 parts by weight of xylene to a resin concentration of about 15%. was sprayed with an airless paint machine, and Table 1
Dry under the conditions of drying temperature and time shown in Table 11.
Undercoat films having the three film thicknesses shown below were formed under four different conditions.

Next, the Acheson Colloids used in Example 1 was applied to the undercoat film of the bolt, nut, and washer on which the undercoat film was formed under the conditions of each experiment number shown in Table 11 above.
Company's resin mixture, namely 1-emralon [F] RJ-310AJ, was mixed with the following composition: 2 N-Menal-2-pyrrolid 7 2 parts by weight Dimenal acetamide
2 parts by weight Menal Isobnal Ketone
3 parts by weight xylene
A top coat coating composition is prepared by dissolving the above mixture (solid content) in a mixed solvent having 2 parts by weight to a concentration of about 15%, and this top coat coating composition is sprayed using an airless coating machine. After that, they were treated under the drying and sintering heat conditions shown in Table 12 below to form top coat films having three types of film thickness shown in Table 12 under four different conditions.

In addition, the coating films of experiment numbers 4-a and 4-b have a constant value of 14μ, and the coating films of experiment numbers 4-C and 4-d have a constant value of 16μ.

Performance tests were conducted on the bolts, nuts, and washers treated with resin as described above using the following method.

For comparison, the following painting base was applied in the same manner as above: (A) Manganese phosphate film (film thickness: approximately 8μ) (D)
Two types of bolts, nuts, and washers that had been subjected to shot blasting were prepared with an undercoat film and a topcoat film formed on them under the same conditions as in Experiment No. 3-a, and these bolts, nuts, and washers were prepared. , nuts and washers were also tested.

Salt Water Spray Test The bolts and nuts coated as described above were subjected to a salt water spray test using the same test method and conditions as in the salt water spray test of Example 1, using the same damage criteria.

The test results are shown in Table 13 below.

■ Torque test results The bolts, nuts and washers painted as above were tested.
The torque test was conducted under the same test method and conditions as in the torque test of Example 1 above.

The results are shown in Table-13.

In addition, 3- in the "Experimental conditions" section of Table-13
a, 3-b, 3-c and 3-d indicate the undercoat and topcoat film forming conditions shown in Coating-11 and Table-12 above.

Example 4 Bolts, nuts, and washers that had been treated with phosphate coating as a base for painting as described above were subjected to preheat treatment under various combinations of preheat temperature and preheat time shown in Table 14 below. A polyamide-imide resin having the same chemical structure as used in Example 1 and exhibiting an intrinsic viscosity of 0.29 at a concentration of 0.5.9/1001n11 and a temperature of 30°C in N-methyl-2-pyrrolidone solvent. , the following composition: N-menal-2-pyrrolidone 8 parts by weight xylene
A base coat coating composition was prepared by dissolving the resin in a mixed solvent having 2 parts by weight at a resin concentration of approximately 15%, and this base coat coating composition was sprayed using an air spray coating machine to obtain the following results: The undercoat coatings were dried under the conditions of the drying temperature and time shown in Table 14, and undercoat films having two types of film thicknesses shown in Table 14 were formed under the two types of conditions.

Next, the Ache 5on Colloid used in Example 1 was applied to the undercoat film of the bolt, nut, and washer on which the undercoat film was formed under the conditions of each experiment number shown in Table 14 above.
s Company's resin mixture, namely (I) "Emralon RJ-310Al" or (ii) "Emralon 333", with the following composition: N-methyl-2-pyrrolidone, 4 parts by weight, dimenalacetamide, 2 parts by weight, xylene.
A top coat coating composition is prepared by dissolving the above mixture (solid content) in a mixed solvent having 2 parts by weight to a concentration of about 15%, and this top coat coating composition is applied using an air spray coating machine. After spraying, the following table-1
Table 15
Topcoat films having the two types of film thicknesses shown below were formed under four different conditions.

In all cases, the total coating film was kept constant at 15μ.

Performance tests were conducted on the bolts, nuts, and washers treated with resin as described above using the following method.

For comparison, the following coating film was prepared in the same manner as above:
*(a) Hot-dip aluminum plating (film thickness: approx. 20μ) (0) Hot-dip galvanization (film thickness: approx. 20μ) (c) Epoxy coating film containing approximately 60% zinc fine particles (film thickness: approx. 15μ) ) We prepared four types of bolts, nuts, and washers with epoxy coatings (film thickness: approx. 15μ) containing about 5% fine grains of molybdenum disulfide, and conducted performance tests on these bolts, nuts, and washers. Ta.

Salt Water Spray Test The bolts and nuts coated as described above were subjected to a salt water spray test using the same test method and conditions as in the salt water spray test of Example 1, using the same damage criteria.

The test results are shown in Table 16 below.

(2) Torque Test The bolts, nuts, and washers painted as described above were subjected to a torque test using the same test method and conditions as in the torque test of Example 1.

The results are shown in Table 16 below.

Please note that 4-4 in the “Experimental Conditions” section of the table below
a, 4-b, 4-c and 4-d indicate the undercoat and topcoat film forming conditions shown in Coating-14 and Table-15, and ([) and (11) are the conditions used for the topcoat coating composition. This corresponds to the type of resin mixture mentioned above.

EXAMPLE Bolts, nuts, and washers treated with phosphate film and acid as a base for painting as described above were subjected to various combinations of preheating temperature and preheating time as in Example 1 (see Table 1). After preheating, it has a repeating structural unit represented by the following formula, and has an intrinsic viscosity of 0.59/100W in N-methyl-2-pyrrolidone solvent.
L1. A known polyamide-imide resin exhibiting a value of 0.35 at a temperature of 30'C was prepared with the following composition N-methyl-2
-Pyrrolidone 2 parts by weight dimenalacetamide
2 parts by weight Menal Isobnal Ketone 3
An undercoat coating composition was prepared by dissolving the resin in a mixed solvent having a resin concentration of about 15% by weight, and this undercoat coating composition was sprayed using an airless sprayer to obtain the coating composition of Example 1. Bolts were dried under the drying temperature and time conditions listed in Table 1 to form an undercoat film with a film thickness of approximately 8 μm under five different conditions, and then the bolts on which the undercoat film was formed in this way; Acheson Co11oid, the same as used in Example 1, on the base coat of the nut and washer.
The above mixture was dissolved in a resin mixture manufactured by S Company, i.e., "Mixed Emlaron RJ-310AI having the following composition: 2 parts by weight of N-methyl-2-pyrrolidone, 2 parts by weight of dimenalacetamide, 3 parts by weight of methyl isobunal ketone". After spraying the top coating composition prepared by dissolving the solid content to a concentration of about 15% using an airless coating machine, the coating composition was dried and baked under the heat conditions shown in Table 2 of Example 1. A topcoat film having a film thickness of about 8 μm was formed.

Note that the total film thickness is approximately 16μ.

Regarding the bolts, nuts, and washers resin-treated as described above, the experiment numbers are indicated in accordance with experiment numbers 1-a, 1-b, 1-cll-d, and ie of Example 1. , 5-a, 5-b, 5-c15-d and 5-
A performance test was conducted in the same manner as in Example 1, and the results are summarized in Table 17.

Claims (1)

[Scope of Claims] 1. On a metal surface, A) the following component i) the following formula (I) In the formula (I), nut, or washer, R represents a divalent aromatic hydrocarbon group, and Ar represents a divalent aromatic hydrocarbon group. 3
11) A solvent for the polyamide-imide, and 111) If necessary, a polyfunctional polyamide-imide that can react with the polyamide-imide. :
B) finely powdered polytetrafluoroethylene in a solvent solution of a heat-curable resin binder; 1. A method for producing a bolt, nut or washer with excellent corrosion resistance, which comprises: applying a top coating composition containing a top coat dispersed in the material, drying, and then curing by heating. 2 As the polyamide, a structural unit represented by the above formula (1) where R is the following formula, and Y represents a direct bond or represents a lower alkylene group, -〇-, -S-, or -8O2. 2. A method according to claim 1, characterized in that the polyamideimide has the following properties: 3. The method according to claim 1, wherein the polyamide-imide is a polyamide-imide having a structural unit represented by the following formula. 4. Claims 1 to 4, wherein the top coating composition is a composition containing finely powdered polytetrafluoroethylene dispersed in an organic solvent solution of polyamideimide resin.
The method described in any of Section 3.