JP4846213B2 - Corrosion resistant coating composition for screws - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a corrosion-resistant coating composition for screws, and more particularly to a water-dilutable, chromium-free corrosion-resistant coating composition for screws that can form a coating for corrosion protection of metal substrates such as iron. .

  A zinc-chromium-containing composite coating composition is known as an effective means for protecting metal substrates such as steel mainly from rust. Among them, effective compositions include boric acid or boron oxide, a water-soluble chromic acid compound and zinc or aluminum alone or a mixture thereof, an alloy powder thereof, a glycol compound, water and / or as disclosed in Patent Document 1. It is a metal anticorrosion coating composition made of an organic solvent, and is widely used in the industry including the automobile industry.

Patent No. 1320297 The composition described in Patent Document 1 is applied on a metal substrate and baked at a temperature of about 300 ° C. for a predetermined time, so that most of the chromic acid component contained in the composition becomes insoluble. Provide a coating coating with a corrosion resistance of several microns. This coating can exhibit excellent corrosion resistance in various environments including severe salt damage environment in a thin state of a few microns, so it is used by processing various metal substrates (mainly steel), especially thin coating Since it is a film, it has been used as an effective treatment for members having threads such as bolts that need to be fastened for nearly 30 years.

  This composition is a quite effective means in terms of suppressing loss due to metal corrosion, and the contained chromic acid compound is almost insoluble in the film state, and the composition is recovered and used in the processing step. Although it is an environmentally friendly treatment that does not cause loss to the outside, it has become desirable to maintain the environment at a high social level in recent years. It is no longer desired.

  For this reason, compositions that do not contain chromic acid compounds have been desired and developed in recent years. One of them was a chromium-free coating composition as described in Patent Document 2.

U.S. Pat. No. 5,868,8819 The chromium-free coating composition contained a particulate metal of zinc or aluminum and contained a silane compound as a binder. This non-chromium-containing coating composition has desirable coating properties and, like a zinc-chromium-containing composite coating composition, can exhibit its performance with a particularly thin coating film, so it has bolts and threads that need to be fastened. It is expected to be used in place of a zinc-chromium-containing composite coating composition as an effective treatment for other members.

  However, at present, bolts and other members whose surfaces are treated with a composite coating composition containing zinc-chromium are attached to predetermined portions of predetermined members by automation in an industrial line, and bolts are tightened. There are many cases. For this reason, when the composition applied to a member such as a bolt is changed, the setting of the tightening condition is inevitably changed according to the change, and the optimum tightening condition (for the screw tightening represented by the torque coefficient) is changed. A great deal of effort is required to select a material having an excellent characteristic value (hereinafter sometimes referred to as a screw characteristic). Also, when the characteristic value changes, if there is insufficient tightening, the screw will loosen later, and conversely if it is tightened too much, the screw will break. In order to avoid such labor and inconvenience, the user demands an alternative composition having the same performance as the zinc-chromium-containing composite coating composition having such quality that it is not necessary to change the setting of tightening conditions. Has been.

  Some of the chromium-free coating compositions as described above are satisfactory in corrosion resistance performance as an alternative treatment, but may not fully satisfy the user in terms of screw characteristics and the like.

  An object of the present invention is to solve the above problems. That is, an object of the present invention is to provide a corrosion-resistant coating composition for screws, which is a chromium-free coating composition having corrosion resistance equal to or higher than that of a chromium-containing coating composition and having excellent screw characteristics. To do.

  In order to develop a coating composition that has good corrosion resistance without containing a chromic acid compound and has the same screw performance as that of a coating composition that has been proven so far, By examining and evaluating binders, metal materials, or additives, and using zinc alloy powder instead of zinc powder, a coating composition containing no chromic acid compound and having good corrosion resistance and screw characteristics is obtained. I was able to.

As means of this invention for solving the above-mentioned problems,
Claim 1 contains at least one granular metal and at least one binder in a liquid medium composed of water, a glycol compound and / or a low-boiling organic liquid excluding the glycol compound, and the particulate metal and the binder The content of the granular metal with respect to the total of 70% by mass or more, and the granular metal is contained in an amount of less than 4% by mass of aluminum and zinc of at least 50% by mass with respect to the granular metal. preparative, such that the total content of zinc and aluminum is 100 wt% or less with respect to the particulate metal, viewed contains a zinc alloy, wherein the binder is a silane compound, a titanium compound, the group consisting of zirconia compounds and epoxy resins A corrosion-resistant coating composition for screws , comprising at least one selected from
Claim 2 is the corrosion-resistant coating composition for screws according to claim 1, wherein the zinc alloy contains one or more of tin, magnesium, and manganese.
Claim 3, wherein the particulate metal is flaky, Ru screw corrosion coating composition der according to claim 1 or 2.

  According to the present invention, the coating composition according to the present invention has a corrosion resistance comparable to or higher than that of a conventional chromium-containing zinc-based metal powder-containing coating composition, and is applied to the surface of a screw, that is, the surface of a male screw and / or a female screw. When the coating film is formed, it is possible to provide a screw anticorrosive coating composition capable of improving the fastening characteristics between the male screw and the female screw, that is, the screw characteristics.

  The screw corrosion-resistant coating composition according to the present invention (hereinafter sometimes abbreviated as “coating composition”) has a liquid medium composed of water, a glycol compound and / or an organic solvent.

  Examples of the glycol compound include tri- and tetraethylene glycol, di- and tripropylene glycol, monomethyl and ethyl ethers of these glycols, low molecular weight liquid polypropylene glycol, diacetone alcohol, low molecular weight ethers of diethylene glycol, and these Mention may be made of mixtures.

  Examples of the organic solvent include low boiling point organic liquids excluding the glycol compound. The low-boiling organic liquid is preferably a water-soluble solvent having a boiling point of about 100 ° C. or lower under atmospheric pressure, such as low molecular weight alcohols such as methanol, ethanol, n-propyl alcohol and isopropyl alcohol, and methyl ethyl ketone. A water-soluble ketone can be mentioned as a suitable example.

  The liquid medium in this invention may be any one of water, a glycol compound, and the organic solvent, or a mixed solvent of two or more of these. The content ratio of the liquid medium in the coating composition according to the present invention is usually 30% by mass or more, and preferably 50 to 85% by mass.

  The coating composition according to the present invention comprises a particulate metal dispersed in the liquid medium. The granular metal is a zinc alloy. The zinc alloy has an aluminum content of less than 4% by weight, preferably 0.5 to 3.5% by weight, and at least 50% by weight, preferably 55 to 96% by weight, based on the particulate metal. The zinc contained is included so that the total content of zinc and aluminum is 100% by mass or less based on the granular metal. If the zinc content in the zinc alloy is less than 50% by mass, the corrosion resistance becomes insufficient, which is disadvantageous. Moreover, both screw characteristics and corrosion resistance can be satisfied as the content of aluminum in the zinc alloy is less than 4% by mass. However, this zinc alloy may contain tin, magnesium, nickel, cobalt, manganese and the like in addition to zinc and aluminum.

  This zinc alloy is an alloy of zinc and aluminum, preferably in flake form. In the flake-shaped zinc alloy, the content of flake particles having a longest dimension of 13 μm is preferably 50% or more of the total flake particles. If the content of the flake particles having the longest dimension of 13 μm is less than 50%, it may be difficult to form a uniform paste from the binder and the liquid medium, which is not preferable. Further, in the flake-shaped zinc alloy, the content of the flake particles having the longest dimension of the flake particles of 15 μm is desirably 90% or more of the total flake particles. If the content of the flake particles having a longest dimension of 15 μm is less than 90%, it may be difficult to form a uniform paste from the binder and the liquid medium, which is not preferable.

  The content of the zinc alloy with respect to the total of the zinc alloy, the binder, and the liquid medium is usually 50% by mass or less, and preferably 35 to 10% by mass. When the content of the zinc alloy is 50% by mass or more, the treatment liquid composed of the binder and the liquid medium becomes difficult to use, which is not preferable.

  The coating composition of this invention contains a binder. As the binder, at least one selected from the group consisting of a silane compound, a titanium compound, a zirconia compound, and an epoxy resin can be used.

The silane compound suitably used in the present invention is preferably a compound that can be easily diluted with water, and more preferably fully dilutable with water. Useful silane compounds are non-gelling water reducing silanes. In these silanes, the organic functionality is typified by, for example, vinyl trimethoxysilane or methacryloxy, for example vinyl as in methacryloxypropyltrimethoxysilane; and amino as in 3-amino-propyltrimethoxysilane. Preferably, it is epoxy functional for enhanced coating properties and composition stability. These generally contain —Si (OCH ₃ ) ₃ functional groups or —Si (OCH ₂ CH ₃ ) ₃ functional groups or —Si (OCH ₂ CH ₂ CH ₃ ) ₃ functional groups. A suitable content of these silane compounds in the coating composition is generally 3% by mass to 20% by mass of the total composition weight. Particularly useful silane compounds include epoxy functional silanes such as β- (3,4-epoxycyclohexyl) ethyltrimethoxy-silane, 4- (trimethoxysilyl) butane-1,2-epoxide or r-glycid. Examples include oxypropyltrimethoxysilane.

  Examples of the titanium compound include tetraethyl titanate, tetraisopropyl titanate, tetrabutyl titanate, 2-ethylhexyl titanate, and alkyl esters of N-butyl titanate polymer. The content of the titanium compound in the coating composition is preferably 6 to 20% by mass.

  Examples of the zirconia compound include zirconate glycolate, tetra n-propoxy zirconium, tetra n-butoxy zirconium, and zirconyl acetate. The content ratio of the zirconia compound in the coating composition is the same as other binders. As the epoxy resin, fatty acid esters of epoxy resins can be generally used and may be modified as appropriate.

  The coating composition according to the present invention preferably contains a surfactant and a boron-containing compound. Examples of the surfactant include a nonionic drug, for example, a nonionic alkylphenol polyethoxy adduct and the like. An anionic surfactant can also be used. Examples of the anionic surfactant include organic phosphate esters and diester sulfosuccinates, typically sodium bistridecyl sulfosuccinate. The content of such a surfactant in the coating composition is typically 0.01 to 10% by mass of the total coating composition.

  As the boron-containing compound, commercially available orthoboric acid can be used, and various products obtained by heating and dehydrating orthoboric acid, such as metaboric acid, tetraboric acid and boron oxide, and Salts such as zinc borate can also be used. The content of the boron-containing compound in the coating composition is preferably at least 0.1% by mass, and may be contained at a content of 10% by mass or less.

  The coating composition according to the present invention may contain a pH adjuster, a thickener, and other components.

  As the pH adjuster, the pH adjuster is generally selected from alkali metal oxides and hydroxides, and lithium and sodium are preferred alkali metals for enhancing coating binding, and it is a periodic Of the metals belonging to groups IIA and IIB of the table, usually selected from oxides and hydroxides, the compounds are soluble in aqueous solutions, for example strontium, calcium, barium, magnesium, zinc and cadmium It is a compound of this. The pH adjusting agent may also be another compound, such as a carbonate or nitrate of the aforementioned metals.

  The thickener may occupy an amount of 0.01 to 2.0% by weight based on the weight of the coating composition according to the present invention. As this thickener, a commercially available product such as Tang Bellosize 煤 i trademark can be used, and a water-soluble cellulose ether can also be used. Suitable thickeners include ethers such as hydroxyethylcellulose, methylcellulose, methylhydroxypropylcellulose, ethylhydroxyethylcellulose, and methylethylcellulose, and mixtures thereof. Other thickeners that can be used include xanthan gum, associative thickeners such as urethane associative thickeners; and non-ionic associative thickeners that do not contain urethane, Typically, it is an opaque and high boiling liquid that e.g. boils at temperatures above 100 ° C. Other suitable thickening agents include modified clays, such as highly treated hectorite clay, and organic modified and activated smectite clay. It is done.

  The coating composition concerning this invention can be prepared by mix | blending each said component. There is no particular limitation on the preparation method.

  Examples of the object to which the coating composition according to the present invention is applied include a metal base material provided with a male screw or a female screw on the surface, and the male screw or the female screw can be screwed together by another screwing member. it can. Examples of such a metal substrate include bolts and nuts.

  In general, an object to which the coating composition is applied is degreased in advance by an alkali cleaner or solvent vapor cleaning, and the surface is adjusted with an abrasive cloth or shot blasting.

  Coating of the coating composition on the metal substrate may be performed by any method such as spraying, roll coating, dip coating, removing the extra drops by centrifugal shaking after immersion, removing the extra drops by vibration after immersion, or brushing. It can be carried out.

  The coating composition applied to the metal substrate is obtained by a heating method selected from a hot air circulating furnace (IDC combustion furnace or electric furnace), a far infrared ray, an infrared heating furnace, a high frequency induction heating furnace, or a combination thereof. Is heated to 200 ° C. or higher, preferably 250 ° C. or higher for a predetermined time, whereby the curing treatment is performed. Moreover, since the solvent content in a process liquid is volatilized before a hardening process before heat processing as needed, the drying process at temperature lower than a hardening process temperature may be performed. And when forming a film, it is also possible to perform the above-mentioned processing process by one time, and it can also repeat an overcoat process as needed.

  The present invention will be described in detail by way of examples. However, it is not necessary to specify the materials used in these examples, but cold rolled steel plates (SPCC materials) are used as panel materials, and bolts are used. A quenching-treated M10 hexagon bolt (total length 65 mm, screw part length 28 mm, pitch 1.25 mm) was used as the material.

The amount applied to a metal substrate (panel, bolt, etc.) is usually expressed as mass / unit surface area, and generally a treated metal substrate with a known surface area is selected and its weight is weighed first. Then, the coated film is peeled off by immersing in a warmed aqueous sodium hydroxide solution, and then the weight of the substrate is weighed again and subtracted to calculate the coating amount. The coating amount is most expressed as a mass per unit surface area expressed as milligram / square decimeter (mg / dm ² ), and is obtained by a calculated value.

  And the method and evaluation of the corrosion resistance test and the screw characteristic test were performed as follows.

  The corrosion resistance test of the treated metal substrate was performed by a test method specified in JISZ2371 (salt spray test method), and the degree of corrosion of the test article was evaluated in the state of the area where red rust was generated. The evaluation rank is as follows.

○: No red rust △: Red rust within 5% ×: Red rust of 5% or more The screw characteristic test is stipulated in JISB1084. Torque coefficient (K), screw surface friction coefficient (μs), seat surface friction coefficient (μw) ) Was measured by a bolt testing machine (Iwata Tekko Co., Ltd.), and the torque coefficient value and the presence or absence of slip sticks were evaluated. In this case, a quenched M10 hexagon bolt (total length 65 mm, screw part length 28 mm, pitch 1.25 mm) was used as the metal substrate. Other measurement conditions were as follows.

Nut: Zinc plating / yellow chromate treatment M10 (pitch 1.25mm)
Seat plate: SPCC material 3.0 mm thick Method: Nut and seat plate fixed, bolts tightened 4 times per minute Torque coefficient value: Value at axial force of 25 kN (Example 1)
In 18.9 parts by mass of deionized water under stirring, 0.6 part by mass of orthoboric acid and 3 parts by mass of γ-glycidoxypropylmethoxysilane were blended and mixed. After stirring for 3 hours, the mixture was further mixed with 31 parts by weight of deionized water, 0.8 parts by weight of nonionic surfactant (HLB9.5), and 0.8 parts by weight of nonionic surfactant. (HLB13.3) was added and mixed. To this mixture was further added 2 parts by weight of the silane and 2.9 parts by weight of dipropylene glycol. To this mixture, 35.5 parts by weight of zinc aluminum alloy flake paste was added. The paste contains about 89% zinc, about 3% aluminum, and the remaining paste liquid. The alloy flakes have about 50% flake particles having a particle longest dimension of less than about 13 microns. Then, using a dissolver type stirring device, all these components were sufficiently stirred and mixed for about 3 hours.

  Stirring of the mixture obtained by finishing said operation was continued further gently, and further stirring was continued overnight. Subsequently, 2.9 parts by mass of the silane and 0.3 parts by mass of a slurry of hydroxyethyl cellulose slurried in 1.3 parts by mass of deionized water were added. This bath was aged for 6 days to prepare a coating composition.

  The coating composition was processed into a bolt material. The bolt material used was a M10 hexagon bolt (total length 65 mm, thread length 28 mm, pitch 1.25 mm) that had been quenched. As a pretreatment, alkali cleaning was performed, and surface adjustment was performed by shot blasting. Pre-treated bolts are placed in a wire mesh basket, the composition is applied by immersing and pulling the basket into the treatment composition, and after lifting, the excess composition is obtained by performing centrifugal shaking to rotate the basket. Was removed and coating was performed. During the dipping spin, for the first coating, the basket was rotated forward and reverse for 10 seconds each at 250 rpm, and for the second coating, again for 10 seconds each forward and reverse at 270 rpm.

After coating the coating composition, it was baked under the following conditions. The coated bolt was placed on a wire mesh, first preliminarily dried for 10 minutes in a hot air circulating drying oven at a preset temperature of 120 ° C., and then cured for 30 minutes in a hot air drying oven at a preset temperature of 320 ° C. The coating composition of the bolt subjected to this treatment was measured by the above-mentioned predetermined method, and the coating amount was 238 mg / dm ² .

  The bolts treated as described above were then subjected to the corrosion resistance test described above. Even when the salt spray test was conducted for 1000 hours, red rust did not occur on the bolts. Compared with the experimental results of generating red rust when the bolt subjected to the galvanizing / yellow chromate treatment (JIS class 2 grade 2) is subjected to the salt spray test for 500 hours, the coating composition according to the present invention is used. The treated bolt had good corrosion resistance and the same performance as a zinc-chromium-containing composite coating composition (dacrotized treatment) that did not generate red rust until it exceeded 1,000 hours.

  Furthermore, when the screw characteristics were evaluated by the test method described above, the performance was almost the same as that of bolts that have been subjected to the conventional zinc chromium-containing composite coating composition (dacrotized treatment).

(Example 2)
7.4 parts by mass of the silane of Example 1, 1.2 parts by mass of the nonionic surfactant (HLB9.5) of Example 1, and 1.4 parts by mass of the nonionic surfactant (HLB13.3) of Example 1 Part of the mixture and 3.8 parts by weight of dipropylene glycol were mixed together. To this mixture, 24.7 parts by mass of zinc / aluminum alloy flake paste and 8.3 parts by mass of aluminum paste (containing approximately 33% by weight of paste liquid) were added. The paste contained about 90% by weight zinc, about 1% by weight aluminum, and the remaining about 9% by weight paste liquid in the alloy flakes. The alloy flakes had about 98% flake particles having a particle longest dimension of less than about 15 microns. All these ingredients were mixed intensively and homogenized.

  While stirring the homogenized mixture, an aqueous solution containing 0.5 parts by mass of boric acid in 52.3 parts by mass of deionized water was added. Further, 0.4 parts by mass of hydroxyethyl cellulose was added, and stirring was continued overnight to prepare a coating composition.

The bolt was painted by the method described in Example 1. However, the basket was rotated at 300 rpm forward and reverse for 10 seconds each. In the curing process, preliminary drying was performed for 15 minutes in a hot air circulating drying furnace having a set temperature of 70 ° C., and then curing was performed for 40 minutes in a hot air drying furnace having a set temperature of 330 ° C. Bolts that had been subjected to this treatment twice had a coating weight of about 252 mg / dm ² , as measured by the coating composition as described above.

  The treated bolt was then subjected to the corrosion resistance test described above. As a corrosion resistance test, no red rust was generated on the bolt even when a salt spray test was conducted for 1000 hours. The bolts thus treated were evaluated to be extremely good when compared to the case where the galvanized / yellow chromated bolts had red rust in 500 hours as a result of the corrosion resistance test, and the bolts treated with dacrotized were As a result of the corrosion resistance test, the performance was similar to that in which red rust did not occur until 1,000 hours were exceeded.

  Furthermore, when the screw characteristics were evaluated by the above-described test method, the performance was almost the same as that of the bolts subjected to the conventional dacrotized treatment.

(Example 3)
The same conditions as in Example 2 except that 2.9 parts by mass of silane added last is replaced with titanium lactate, and contains about 89% by mass of zinc, about 3% by mass of aluminum, and the remaining paste liquid as the particulate metal component. Zinc-aluminum alloy flake paste 27.3 parts by weight, about 77% by weight zinc, about 14% by weight tin, 3.5 parts by weight zinc-tin alloy flake paste containing the remaining paste liquid and aluminum paste (about 33% paste liquid) The coating composition was prepared using 4.7 parts by mass of (weight content).

In the same manner as in Example 1, the coating composition was applied to the bolt. The coating amount was about 263 mg / dm ² .

  The evaluation results are shown in Table 1.

Example 4
Instead of 2.9 parts by mass of silane added last, 2.9 parts by mass of zirconate glycolate was used, and 33.3 parts by mass of the same zinc aluminum alloy flakes were used instead of 35.3 parts by mass of zinc aluminum alloy flakes. In the same manner as in Example 1, a coating composition was obtained.

In the same manner as in Example 1, the bolt was coated with the coating composition. The coating amount was about 232 mg / dm ² . The evaluation results are shown in Table 1.

(Example 5)
Instead of 2.9 parts by mass of silane added at the end, 2.9 parts by mass of a water-soluble epoxy resin was used. Further, instead of the granular metal component used in Example 1, 89% by mass of zinc, 3% by mass of zinc was used. Zinc-manganese alloy flake paste 3 containing 25.6 parts by weight of aluminum and zinc aluminum alloy flake paste containing 8 parts by weight of paste liquid, 90% by weight of zinc, 2% by weight of manganese, and 8% by weight of paste liquid. This was carried out in the same manner as in Example 1 except that 2 parts by mass and 6.7 parts by mass of aluminum paste (containing approximately 33% by weight of paste liquid) were used.

In the same manner as in Example 1, the bolt was coated with the coating composition. The coating amount was about 255 mg / dm ² . The evaluation results are shown in Table 1.

As a comparative example, 1. Znl / Al = 90/10
2. Zinc chromium-containing composite coating composition (dacrotized treatment)
3. Zinc plating, yellow chromate product
4). Zn5% Al
The results are also shown in Table 1.

Corrosion resistance: Evaluated with red rust generated in 1000 hours of salt spray test ○: No red rust △: Red rust within 5% ×: Red rust screw with 5% or more Characteristic: Torque coefficient ○: Torque coefficient fluctuation 10 compared to standard product △: Torque coefficient value variation within 20% compared to standard product and status evaluation underway ×: Torque coefficient value variation of 20% or more compared to standard product or bad condition evaluation ○: Smooth tightening Done.
Δ: Slight slip is observed during tightening.
X: A slip stick is seen when tightening.

Claims (3)

In a liquid medium composed of water, a glycol compound and / or a low-boiling organic liquid excluding the glycol compound , at least one particulate metal and at least one binder are contained, and the particulate relative to the sum of the particulate metal and the binder The content of the metal is 70% by mass or more, and the granular metal contains aluminum contained in a content of less than 4% by mass with respect to the granular metal and zinc contained in a content of at least 50% by mass, and zinc so that the total content of aluminum is 100 wt% or less with respect to granular metallic least, viewed contains a zinc alloy, wherein the binder is a silane compound, a titanium compound, selected from the group consisting of zirconia compounds and epoxy resins A corrosion-resistant coating composition for screws , comprising one type . The corrosion-resistant coating composition for screws according to claim 1, wherein the zinc alloy contains one or more of tin, magnesium and manganese. The corrosion-resistant coating composition for screws according to claim 1 or 2, wherein the granular metal is in the form of flakes.