JP2006225761A - Chromium-free rust inhibitive treatment method for metal product having zinc surface and metal product treated thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chromium-free surface treatment method which imparts practical rust inhibitive performance to a metal product having a zinc surface to which it was difficult to impart rust inhibitive performance of practical level when a chromium-free surface treatment agent for forming a silica-based film is applied. <P>SOLUTION: A conversion-coated film of zinc phosphate etc. is formed on the zinc surface of the metal product as pretreatment, and the silica-based film is formed by applying a chromium-free surface treatment agent which uses alcohol or mixture of water and alcohol as a solvent to the conversion-coated film. As a result, when an aqueous surface treatment agent containing alcohol is applied, it is possible to suppress the formation of white rusting for 72 hours or longer in the salt spray test. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-chromium antirust treatment method for a metal member having a zinc surface such as a galvanized product, and a metal member having a zinc surface subjected to a nonchromium antirust treatment. The zinc surface in the present invention can be a surface made of a zinc alloy.

  Chemical conversion treatment is a means for producing a stable compound on a metal surface by chemical or electrochemical treatment, and it is described in JIS standard books that there are phosphate treatment, black dyeing treatment, chromate treatment and the like. The main purpose of applying a chemical conversion treatment to metal products is to improve rust prevention performance, improve the adhesion of the coating applied to the surface, and color the surface.

  The surface of a metal member having a zinc surface, for example, a galvanized metal product is conventionally subjected to a chemical conversion treatment using an aqueous solution containing chromic acid such as chromate treatment, or a chemical conversion treatment not containing a chromic acid component. . In most cases, a method of imparting rust prevention performance by coating a coating film mainly composed of an organic resin on the surface thereof has become widespread.

  Since chromic acid is toxic and carcinogenic, a policy not to use products containing hexavalent chromium from Europe is proposed, and active development of surface treatment agents that do not contain chromic acid (chromate) components It has been broken. Several non-chromium surface treatment methods have been proposed in already published patent documents, but at present, galvanized chemical conversion products using trivalent chromium for the purpose of rust prevention are finally at the stage of practical application. Just entered. However, the trivalent chromium chemical conversion treatment is not easy to manage the liquid, and has a problem that a part of the trivalent chromium component is changed to hexavalent chromium and is discharged into the waste water.

  A metal member having a zinc surface, for example, a surface of a galvanized metal product is subjected to a non-chromium chemical conversion treatment, and a film is formed thereon with a surface treatment agent containing water-based silica or the like to improve rust prevention performance. A method has also been proposed.

  For example, Patent Document 1 discloses that a galvanized surface is blackened by chemical conversion, and this chemical conversion surface is coated with an aqueous solution such as silicate aqueous solution or colloidal silica, surface-treated, and coated with a siliceous film to prevent rust. A method of imparting performance is disclosed. However, the galvanized steel sheet treated with rust prevention by this method generates white rust in less than 48 hours in the salt spray test specified in JIS, and the rust prevention performance is insufficient in practice.

  In Patent Document 2, a surface of a zinc-based plated steel sheet is subjected to a phosphate conversion treatment, and in addition to an organic resin as a main component, an aqueous solution containing a thiocarbonyl group-containing compound, a phosphoric acid compound, fine silica, a silane coupling agent, etc. A thin film on the treated surface, or an aqueous solution containing a vanadic acid compound, thiocarbonyl group-containing compound, phosphoric acid compound, fine silica, silane coupling agent, etc. in addition to the organic resin as the main component. What formed the film is disclosed. It states that there is no change even if this surface-treated galvanized steel sheet sample is placed in a salt spray tester for 168 hours.

  Patent Document 3 discloses a coated metal sheet obtained by applying a non-chromium chemical conversion treatment to a zinc-based plated steel sheet and applying a polyester-based undercoating paint (4 to 25 μm) containing a non-chromium anticorrosive pigment and an overcoating paint to the surface. In addition, modified silica (Shieldex; silica fine powder manufactured by Fuji Silysia Chemical Co., Ltd.) is illustrated as a non-chromium-based rust preventive pigment.

  Patent Document 4 discloses a steel sheet obtained by subjecting a steel sheet subjected to hot dip zinc alloy plating (including Al and Mg) to chemical conversion treatment, undercoating the surface with a water-based paint, and further overcoating it. The chemical conversion treatment liquid contains an aqueous resin such as an acrylic emulsion, a titanium compound such as hexafluorotitanic acid and titanium hydrofluoric acid, and a zirconium compound such as hexafluorozirconic acid, and an aqueous resin such as an acrylic emulsion as an undercoat paint. A water-based paint in which a silica-based anticorrosive pigment (sealdex) is dispersed is exemplified. A water-based paint containing a water-based resin such as an acrylic emulsion as a main component and having a titanium oxide pigment dispersed therein is applied as a top coat. In this example, the sample steel plate with the top coating applied is put in a salt spray tester and evaluated by the degree of swelling of the coating film, so the rust prevention characteristics are not clear.

  Patent Document 5 discloses that a commercially available galvanized steel sheet (electrogalvanized steel sheet and hot-dip galvanized steel sheet, and commercially available products are usually chromated) is subjected to a zinc phosphate conversion treatment, and a non-chromium coating is applied to this surface. A formed steel sheet is disclosed. This film was coated with a weakly acidic aqueous solution containing a phenolic water-soluble organic resin, a titanium compound such as ammonium titanium fluoride or a zirconium compound such as zirconium hydrofluoric acid, and a silane coupling agent such as mercaptopropyltrimethoxysilane. A film is formed. It states that when a sample of a surface-treated galvanized steel sheet is placed in a salt spray tester for 72 hours, there is a sample that does not generate white rust.

  Patent Document 6 discloses that a surface treatment agent containing alcohol and silica is applied to a galvanized surface subjected to chemical conversion treatment to improve rust prevention performance (white rust resistance). However, the film formed by applying the surface treatment agent has a resin as a main component, and the film of the surface treatment agent cannot be said to be siliceous. According to the examples described in Examples, 51 wt% or more of a resin component containing a curing agent resin such as a melamine resin is included. Furthermore, only an example in which a surface treatment agent is applied to a galvanized surface subjected to chromate treatment using hexavalent chromium is described.

  Patent Document 7 discloses a hot-dip galvanized steel sheet that uses, as a surface treatment agent, a silica sol of an ethanol solvent obtained by adding water and hydrochloric acid to an ethanol solution of tetraethoxysilane and hydrolyzing it. It is disclosed that it is dipped in the surface treatment agent, applied and baked on the surface. In the antirust performance of the surface-treated steel sheet in the salt spray test disclosed in the patent document, white rust appears in 12 hours in the sample coated with silica sol. The reason for this poor rust prevention performance is considered to be that a film having a film thickness thinner than 0.3 μm was applied because the silica sol solution having a silica component concentration of 5% by weight was applied.

  In the previous application (Japanese Patent Application No. 2004-052991), the present inventors have prepared a non-chromium surface treatment agent that forms a siliceous film that can suppress the occurrence of red rust for a long time when applied to the surface of a galvanized metal member. Has proposed. In this non-chromium surface treatment agent, an effective amount of an ultrafine titanium oxide powder in which the average particle diameter of the dispersed primary particles is 70 nm or less (preferably 40 nm or less) is blended.

  In Japanese Patent Application No. 2004-73736, a surface treatment agent that is effective in inhibiting white rust generation, which is an alcohol solution mainly composed of an alkoxysilane oligomer having a specific weight average molecular weight, was proposed.

  That is, a surface treatment agent of an alcohol solution containing an alkoxysilane oligomer having a weight average molecular weight of 1000 to 10000 as a main component is applied to the surface of a galvanized product and the surface of zinc is coated with a thin siliceous film to generate red rust. Of course, the occurrence of white rust can be suppressed for a long time. In this case, if compatibility with the underlying galvanizing is good, generation of white rust can be suppressed for 300 hours or more in the salt spray test.

  It is preferable to use NON-VOC water as the solvent for the surface treatment agent. However, when a non-chromium surface treatment agent containing only water as a solvent is applied to the surface of a galvanized product, the occurrence of red rust can be suppressed for a long time (as described in Patent Document 1). Rust occurs quickly.

  The present inventors ordered metal members such as bolts (no chromate treatment) that were whitened and galvanized under various conditions from a plurality of suppliers, and applied a surface treatment agent of an alcohol solution containing an alkoxysilane oligomer as a main component. As a result, it was found that the rust prevention performance fluctuates greatly depending on the galvanizing conditions.

  Therefore, a small apparatus for barrel galvanization was introduced, and an attempt was made to investigate the cause of the difference in rust prevention performance when a zincate bath was constructed and a surface treatment agent was applied to galvanized bolts and screws. However, because the phenomenon in the galvanizing bath to which the brightener is added is very complicated, the cause of the difference in rust prevention performance has not been elucidated, but some causal relationships have been grasped. For example, it has been found that rust prevention performance when a surface treatment agent is applied is impaired when pickling is performed by washing with dilute nitric acid, which is usually performed before chromate treatment.

  In addition, it was found that when the current density of galvanization is increased so that the galvanization is completed in a short time, the rust prevention performance is deteriorated when the surface treatment agent is applied.

Furthermore, when a zinc bolt is galvanized on a small bolt or screw having an outer diameter of 3 mm or less using a barrel plating apparatus, a surface treatment agent is applied even if galvanization is performed at an appropriate current density calculated in advance. It was found that sometimes the expected level of rust prevention performance could not be imparted.
JP 61-253381 A JP 2000-248367 A JP 2001-81578 A JP 2002-317279 A JP 2003-253464 A JP 05-001391 A Japanese Patent Laid-Open No. 2001-64782

  The object of the present invention is to apply a non-chromium surface treatment agent that forms a siliceous film to a metal member having a zinc surface that is difficult to provide a practical level of rust prevention performance, for example, a galvanized material that has poor compatibility with a surface treatment agent. Another object of the present invention is to provide a surface treatment method for improving the rust prevention performance of a metallic member against white rust.

  Specifically, when a surface treatment agent that forms a siliceous film is applied, a non-chromium surface treatment is applied to the surface of a metal member having a zinc surface that is difficult to impart a practical level of rust prevention performance. Accordingly, an object of the present invention is to provide a non-chromium rust preventive treatment method capable of suppressing the occurrence of white rust for 72 hours or more, which is considered to be practical in the salt spray test specified in JIS-Z-2371.

  It is another object of the present invention to provide a non-chromium rust preventive treatment method capable of imparting a practical level of white rust suppression performance even to a galvanized metal member coated with an aqueous surface treatment agent.

  As a result of various studies on the electrogalvanization conditions and the treatment conditions before and after the galvanization, the present inventors have found that the anticorrosion performance of the metal member having the zinc surface by adding a single effort before applying the non-chromium surface treatment agent. As a result, the present inventors have found a surface treatment method for improving the temperature.

  In the non-chromium antirust treatment method for a metal member having a zinc surface according to the present invention, a chemical conversion treatment is performed on the surface of the metal member having a zinc surface to form a chemical conversion treatment film on the zinc surface. Applying a non-chromium surface treating agent solution containing a silica component or a component that changes to silica in an alcohol solvent or a mixed solvent of water and alcohol to form a siliceous film having an average thickness of 0.5 to 3 μm. Features. The non-chromium surface treatment agent solution used in the present invention preferably contains 10 to 25% by weight of a silica component or a component that changes to silica in terms of silica.

  When the surface treatment of a metal member having a zinc surface is performed by applying the non-chromium rust prevention treatment method according to the present invention, the rust prevention performance in a salt spray test according to JIS-Z-2371 is improved, and there is practicality. The generation of white rust can be suppressed for 72 hours or more.

  The non-chromium rust preventive treatment method for a metal member having a zinc surface according to the present invention may be a metal member having a zinc surface plated with zinc or a zinc alloy, or a cast product of a zinc-based alloy as a main component. preferable.

  In the non-chromium antirust treatment method for a metal member having a zinc surface according to the present invention, the silica component is colloidal silica, and the solvent can be a mixed solvent of water and alcohol.

  In the non-chromium antirust treatment method for a metal member having a zinc surface according to the present invention, the component that changes to silica is an alkoxysilane oligomer obtained by polycondensation by hydrolysis of an alkoxysilane monomer, and the solvent can be alcohol. . It is preferable that the weight average molecular weight of this alkoxysilane oligomer is 1000-10000.

  In the non-chromium antirust treatment method for a metal member having a zinc surface according to the present invention, the non-chromium surface treating agent solution contains an effective amount of ultrafine titanium oxide powder having an average particle size of the dispersed primary particles of 40 nm or less. Is preferred. The non-chromium surface treatment agent solution contains 0.3 to 2% by weight, preferably 0.5 to 1.5% by weight of titanium oxide ultrafine powder.

  In the non-chromium antirust treatment method for a metal member having a zinc surface according to the present invention, it is preferable that the non-chromium surface treatment agent solution contains an effective amount of a silane coupling agent. The non-chromium surface treating agent solution preferably contains 4 to 16% by weight, more preferably 6 to 14% by weight of a silane coupling agent.

  In the non-chromium antirust treatment method for a metal member having a zinc surface according to the present invention, an aqueous solution mainly composed of zinc phosphate can be used as the non-chromium chemical conversion treatment solution. The non-chromium chemical conversion treatment solution preferably contains 0.5 g / liter to 5 g / liter of zinc ions and 2.0 g / liter to 20 g / liter of phosphate ions.

  In the metal member having a zinc surface subjected to the non-chromium rust prevention treatment of the present invention, a chemical conversion treatment film is formed on the zinc surface of the metal member having a zinc surface, and the average particle size of primary particles is formed on the surface of the chemical conversion treatment film. A siliceous film having a thickness of 0.5 to 3 μm containing an effective amount of ultrafine titanium oxide powder having a diameter of 40 nm or less is coated. This siliceous film preferably contains 2 to 10% by weight of titanium oxide ultrafine powder, and preferably contains 65% by weight or more of silica.

  The metal member having a zinc surface subjected to the non-chromium rust prevention treatment according to the present invention preferably has a chemical conversion treatment film mainly composed of zinc phosphate formed on the zinc surface.

  The metal member having a zinc surface subjected to another non-chromium rust prevention treatment according to the present invention has a chemical conversion treatment film formed on the zinc surface, and a surface treatment mainly comprising an alcohol solution of an alkoxysilane oligomer on the surface. An agent solution is applied and coated with a siliceous film having a thickness of 0.5 to 3 μm.

  The metal member having a zinc surface subjected to the non-chromium rust prevention treatment according to the present invention is preferably an aqueous solution containing 0.5 to 5 g / liter of citric acid in the chemical conversion treatment solution. Further, the chemical conversion treatment solution containing citric acid according to the present invention preferably contains 2 to 20 g / liter of an aqueous silica sol in terms of silica in addition to citric acid and 0.6 to 6 g / liter of zinc ions.

  The metal member having a zinc surface that has been subjected to non-chromium rust prevention treatment according to the present invention may have a chemical conversion treatment film having a dark color. That is, the lightness is preferably 4 or less in the Munsell color system.

  The metal member having a zinc surface subjected to non-chromium rust prevention treatment according to the present invention is preferably a machine screw having a screw portion outer diameter of 3 mm or less obtained by electrogalvanizing the metal member by a barrel method.

  By applying the non-chromium anticorrosion treatment method for a metal member having a zinc surface according to the present invention, the occurrence of white rust caused by the oxidation of zinc on the zinc surface is compared to when only the non-chromium surface treatment agent is applied. Can be deterred for a long time. This effect is remarkable when applied to a metal member having a zinc surface that exhibits only inferior rust prevention performance when a surface treatment agent is applied.

  In addition, the prevention of white rust generation, which has been difficult with the conventional treatment with a non-chromium surface treatment agent, is performed using the non-chromium antirust treatment method of the present invention, that is, a mixed solvent of non-chromium chemical conversion treatment, water and alcohol. By applying a surface treatment method in combination with an aqueous surface treatment agent solution, the occurrence of white rust can be suppressed for 72 hours or more, which is considered to be practical.

  In addition, for small screws that have been galvanized, a non-chromium surface treatment agent solution of an alcohol solvent that is effective in suppressing white rust formation is applied due to the plating current density being biased to a part of the surface. However, the occurrence of white rust cannot be prevented for a long time, but by applying the non-chromium rust preventive treatment method of the present invention in which chemical conversion treatment is performed as a pretreatment, the occurrence of white rust can be suppressed for a long time. An effect is obtained.

  In addition, the generation of white rust can be suppressed for a long time by applying the non-chromium rust preventive treatment method of the present invention to an alloy die-cast member mainly composed of zinc.

  In addition, when a citrate-based chemical conversion treatment agent is used, it is possible to perform a chemical conversion treatment without leaving the surface of the zinc textured. By applying the solvent surface treating agent solution, the time until white rust is generated can be extended.

  In addition, the effect of reducing deterioration in rust prevention performance when evaluated in a salt spray test after being subjected to a light resistance test on an iron plate that has been subjected to a zinc phosphate chemical conversion treatment on the galvanized surface. There is. The light resistance test is a method generally applied in Japan for the evaluation of internal parts of automobiles. When the zinc phosphate chemical conversion treatment is performed as a pretreatment, the surface-treated galvanized steel sheet exhibits excellent rust prevention performance even after a light resistance test.

  Furthermore, yellow coloration by baking performed to avoid hydrogen embrittlement can be decolorized with a citric acid-based chemical conversion treatment agent, and it is said that there is practicality by applying a surface treatment agent solution of an alcohol solvent thereon. Generation of white rust can be suppressed over 72 hours.

  The present inventors perform a non-chromium chemical conversion treatment, preferably a zinc phosphate chemical conversion treatment on the surface of a metal member, and apply a surface treatment agent solution using an alcohol solvent or a mixed solvent of water and alcohol to form a siliceous film. And when the siliceous membrane | film | coat was formed in the surface of a metal member, it discovered that the rust prevention performance with respect to generation | occurrence | production of the white rust of the metal member which has a zinc surface could be improved notably. The mixed solution preferably contains 15 to 40% by weight of an alcohol component.

In the present invention, the meaning of the siliceous film is a film mainly composed of silica (SiO ₂ ), preferably a film containing 65% by weight or more of silica.

  If the surface treatment agent using an alcohol solvent or a mixed solvent of water and alcohol is not compatible with the surface of the zinc to be treated, a salt spray test based on JIS is performed when these surface treatment agents are applied. , White rust occurs within 24 hours. However, if a chemical conversion treatment is performed on the zinc surface in advance, the time until white rust is generated in the salt spray test can be extended to 72 hours or more.

  On the other hand, the time until red rust occurs in the salt spray test varies depending on the treatment conditions, but becomes longer if the zinc layer is thicker.

  The non-chromium chemical conversion treatment can be applied to the surface of a metal member having a zinc surface in a prescribed formulation using a commercially available chemical conversion treatment agent. However, since there is a difference in the rust prevention performance of the final product obtained depending on the type of the chemical conversion treatment agent, it is preferable to select a non-chromium chemical conversion treatment agent that can be tested in advance to reliably improve the rust prevention performance.

  Among various non-chromium chemical conversion treatments, the zinc phosphate chemical conversion treatment has a relatively stable and improved rust prevention performance. When a chemical conversion treatment is performed on the plated zinc surface, the thickness of the zinc plating layer is consumed and red rust is quickly generated. Therefore, it is preferable not to form a thick chemical conversion treatment film. In many cases, the surface of the chemically treated zinc surface becomes satin and improves the adhesion to the coating film of the surface treatment agent, and this also improves the rust prevention performance when the surface treatment agent is applied by applying the chemical conversion treatment. This is considered to be one reason.

  Among the non-chromium chemical conversion treatment agents used for the treatment of the zinc surface, there are those that can color the surface of the zinc from dark to black. Since the film formed of the surface treatment agent used in the present invention is colorless and transparent, the color colored by the chemical conversion treatment can be used as it is as the product color. If the type of chemical conversion treatment to be colored is performed, the non-chromium antirust treatment method of the present invention can be used as a coloring method for a metal member having a zinc surface.

  Many metal members having a zinc surface are galvanized metal members, and there are electrogalvanization and hot dip galvanization. Furthermore, there is zinc alloy plating in any case. In addition to zinc plating and zinc alloy plating, the non-chromium rust preventive treatment method of the present invention can also be applied to cast products (including die cast products) of alloys containing zinc as a main component.

  It is preferable that the non-chromium surface treating agent solution in an alcohol solvent that forms a siliceous film contains an alkoxysilane oligomer having a weight average molecular weight of 1000 to 10,000 as a component that changes to silica. When the weight average molecular weight of the alkoxysilane is less than 1000, the rust preventive performance of the surface treatment agent is lowered, and when it is more than 10,000, the surface treatment agent solution becomes unstable and the surface treatment agent is easily gelled. As the gelation proceeds, the rust prevention performance of the surface treatment agent is impaired and the pot life is exhausted.

  Although the rust prevention performance is slightly inferior, in addition to the alcohol solution of the alkoxysilane oligomer having a weight average molecular weight of less than 1000, a commercially available alcohol solvent colloidal silica may be used as the main component of the surface treatment agent solution for forming the siliceous film. it can.

  An alkoxysilane oligomer having a weight average molecular weight of 1000 to 10000 is, for example, an alcohol solution such as tetraalkoxysilane such as tetraethoxysilane or alkyltrialkoxysilane (with isopropyl alcohol or the like so that the concentration converted to a silica component becomes a target concentration in advance). It is preferable to dilute) water in which a small amount of an acid catalyst such as hydrochloric acid, nitric acid, sulfuric acid or acetic acid is dissolved and mixed so that the oligomer has the target weight average molecular weight. . In this synthesis reaction, for example, when the temperature is kept at 30 to 40 ° C. while stirring all day and night, condensation polymerization proceeds and an alkoxysilane oligomer having a saturated weight average molecular weight is synthesized.

  Instead of using a monomer such as tetraethoxysilane as a raw material for polycondensation, a commercially available oligomer that has been prepolymerized to a tetramer of tetraethoxysilane or the like in advance is used as the raw material so that the target weight average molecular weight can be achieved. Can also be polycondensed.

  It is preferable to mix | blend the component which forms the siliceous membrane | film | coat mix | blended in a surface treating agent solution so that it may become 10 to 25 weight% in the quantity converted into the silica component. In addition to an effective amount of the silane coupling agent, an effective amount of titanium oxide ultrafine powder having an average particle size of the dispersed primary particles of 40 nm or less is preferably added to the surface treatment agent solution. It is preferable to select a silane coupling agent that does not become unstable when mixed with an alcohol solution of an alkoxysilane oligomer, and it is particularly preferable to use a silane coupling agent having an epoxy functional group that hardly changes pH. A preferable blending amount of the silane coupling agent in the surface treating agent solution is 4 to 16% by weight. Moreover, the preferable compounding quantity of the titanium oxide ultrafine powder by which the dispersion process was carried out is 0.3 to 2 weight%. When the amount of the silane coupling agent is small, the rust prevention performance is small, and when it is large, the cost of the surface treatment agent increases because the silane coupling agent is relatively expensive. The same applies to the titanium oxide ultrafine powder. In addition, it is preferable to add 0.2 to 2% by weight of a resin that is soluble in alcohol such as polyvinyl butyral in the surface treating agent solution. The addition of a small amount of a resin component is effective in reducing the hardness of the formed film and improving the adhesion to the ground. When the amount of the resin is large, the resin becomes unstable and gelation tends to occur. Furthermore, it is preferable to add a small amount of a dispersant in order to prevent agglomeration and sedimentation of the titanium oxide ultrafine powder dispersed in the surface treating agent solution.

  As the surface treating agent solution using a mixed solvent of water and alcohol as a solvent, a surface treating agent solution mainly comprising a commercially available colloidal silica aqueous solution can be used. As alcohol, isopropyl alcohol, ethyl alcohol, methyl alcohol, butyl alcohol, etc. can be mixed and used. However, since the pH of the colloidal silica aqueous solution is adjusted to the alkali side or the acid side, it tends to gel when the pH fluctuates during mixing. Therefore, it is necessary to mix so as to avoid gelation.

  Zinc that has been subjected to non-chromium chemical conversion treatment by using a non-chromium surface treatment agent solution that forms a siliceous film using a mixed solvent of water and alcohol as a solvent, compared with a surface treatment agent solution that uses only water as a solvent. Rust prevention performance that suppresses the occurrence of white rust when applied to the plating surface is clearly improved. In the non-chromium aqueous surface treating agent solution used in the present invention, it is necessary that at least 10% by weight of the solvent is alcohol, and the mixing ratio (weight ratio) of water and alcohol in the solvent is preferably 6%. : 4-9: 1, more preferably 7: 3-8: 2. Also in the surface treating agent solution using water and alcohol as a solvent, an effective amount of an ultrafine titanium oxide powder in which the average particle diameter of primary particles subjected to dispersion treatment is preferably 40 nm or less is blended. More preferably, an effective amount of a silane coupling agent is blended.

  The blending amount of the ultrafine titanium oxide powder in the surface treating agent solution is 0.3 to 2% by weight, more preferably 0.5 to 1.5% by weight. By blending the dispersion-treated titanium oxide ultrafine powder, the effect of suppressing the occurrence of red rust in the salt spray test for a long time can be obtained. When the amount of the titanium oxide ultrafine powder is large and the dispersion is not complete, the siliceous film tends to be colored white, and the surface treatment agent becomes expensive. In this case, the content of the ultrafine titanium oxide powder in the siliceous film is preferably 2 to 10% by weight.

  As the titanium oxide ultrafine powder, those commercially available for photocatalysts can be used. However, since the commercially available titanium oxide ultrafine powder for photocatalyst is usually a powder composed of secondary particles in which a large number of primary particles of 10 to 40 nm are collected, in order to obtain the effect of improving the rust prevention performance with a small addition amount. Distributed processing is required. In the dispersion treatment, a commercially available titanium oxide ultrafine powder is preferably mixed with a high boiling alcohol such as ethyl cellosolve, propylene glycol monomethyl ether, n-butyl alcohol to form a slurry, and this slurry is subjected to a dispersion treatment by a bead mill or the like. The titanium oxide ultrafine powder is preferably blended in the surface treatment agent solution in the state of a dispersion-treated slurry. It is not easy to crush the titanium oxide ultrafine powder composed of micron-sized secondary particles into nanosized primary particles, and the average particle size is 100 nm even if the titanium oxide ultrafine powder slurry is dispersed with a bead mill. Often stays at the level of secondary particles. However, by carrying out the dispersion treatment, the effect of improving the rust prevention performance by the surface treatment agent can be obtained by adding a small amount of ultrafine titanium oxide powder.

  The compounding quantity of the preferable silane coupling agent in a surface treating agent solution is 4 to 16 weight%. By blending the silane coupling agent, gelation when alcohol or titanium oxide ultrafine powder slurry is mixed in the colloidal silica aqueous solution can be suppressed, and the pot life of the surface treatment agent can be extended. If the blending amount of the silane coupling agent is small, the blended effect cannot be obtained, and if the blending amount is large, the surface treatment agent becomes expensive. A more preferable blending amount of the silane coupling agent in the surface treating agent solution is 6 to 14% by weight.

  Application of the surface treating agent solution to the metal member having a zinc surface is preferably performed by a dip-and-spin method for a zinc-plated bolt or nut. When the dip and spin method cannot be applied, various methods such as a dip drain method, a spray method, and a roll coater method can be used. The coating performed by the dip-and-spin method can sufficiently improve the rust prevention performance by one coat and one bake. However, by repeating twice (2 coats, 2 bake), the entire surface of zinc can be covered with the coating film of the surface treatment agent, thereby reducing variations in the rust prevention performance of each metal member.

  Since low molecular weight alcohol easily evaporates, a dry siliceous film can be formed by applying a surface treatment agent and leaving it in the room. However, since condensation may occur with the vaporization of the alcohol, it is preferable to suppress evaporation by mixing a high-boiling point alcohol to avoid this. Preferably, the surface treatment agent is baked at 90 to 150 ° C. for about 15 minutes. When the baking temperature is low, the rust prevention performance is lowered, and when it is too high, the coating film of the surface treatment agent is easily peeled off.

  The average thickness of the non-chromium surface treatment film formed on the zinc surface is 0.5 to 3 μm. When the thickness is less than 0.5 μm, the rust prevention performance is lowered, and even when the thickness is more than 3 μm, the improvement of the rust prevention performance cannot be expected. When the coating is thick, the coating tends to be peeled off. The average thickness of the film is more preferably 1 to 2 μm. The thickness of the coating of the non-chromium surface treatment agent to be applied can be changed depending on the level of rust prevention performance required for a metal member having a zinc surface.

  A phenomenon in which the expected level of rust prevention performance cannot be obtained when electrogalvanizing is applied to a small bolt or screw with an outer diameter of 3 mm or less with a barrel and a surface treatment agent is applied to the plated surface is charged in the barrel. However, it is considered that the plating current with a large density flows unevenly on the surface of some bolts and screws.

  The present inventors applied a zinc phosphate conversion treatment to this small galvanized bolt that could not provide the expected level of rust prevention performance even when a surface treatment agent was applied, and a siliceous film was formed on this chemical conversion treated surface. When a non-chromium surface treatment agent for forming sapphire was applied, it was found that the rust prevention performance against white rust was significantly improved.

  In the present invention, the antirust performance is evaluated according to the salt spray test method defined in JIS-Z-2371. That is, a method of spraying 5% by weight salt solution in a test machine, keeping the temperature at 35 ° C., and examining the occurrence of white rust and red rust every 24 hours was adopted. Therefore, white rust does not appear for 72 hours or more refers to a case where white rust is observed after 96 hours or more. If the condition that white rust does not occur for 72 hours or more is satisfied, there are many uses where the metal member can be used. Therefore, the condition that generation of white rust can be suppressed for 72 hours or more was attached. If a combination of various surface treatment conditions including plating conditions is appropriate, it is possible to provide a metal member capable of suppressing the occurrence of white rust for 144 hours or more, and further for 288 hours or more.

  In addition to the suitability of the combination of surface treatment conditions, the rust prevention performance varies depending on the thickness of the galvanizing. For example, when the galvanized layer is consumed and thinned by the chemical conversion treatment, red rust is generated as soon as the plated layer is thinned. For this reason, it is preferable to adjust the chemical conversion film so as not to exceed the required thickness. The occurrence of red rust when a galvanized metal member surface-treated by the non-chromium rust preventive treatment method of the present invention is placed in a salt spray tester usually occurs in 300 to 2000 hours.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

  The non-chromium surface treating agent solution used for the test was prepared by the following procedure. First, 5 parts by weight of ethyl cellosolve was mixed with 1 part by weight of titanium oxide ultrafine powder (Super Titania F-6, Showa Denko Co., Ltd., average particle size of about 15 nm) to form a slurry. A ball mill (a 2 liter wide-mouth polypropylene bottle is used in the container, and 5 kg of pulverized balls in which the same weights of zirconia balls having a diameter of 3 mm and 5 mm are mixed in this container, and an amount of slurry that is approximately the same level as the upper surface of the zirconia ball layer. In a container placed on a gantry rotating at about 60 RPM so that the wide-mouthed polypropylene bottle can be rotated in the vertical direction) and dispersed for 48 hours to obtain a titanium oxide ultrafine powder dispersed slurry 1 Got.

  Similarly, 5 parts by weight of propylene glycol monomethyl ether (PGME) is mixed with 1 part by weight of titanium oxide ultrafine powder (Tynoch A-100 manufactured by Taki Chemical Co., Ltd., average particle size of primary particles is about 10 nm). Then, the slurry was similarly dispersed by a ball mill for 48 hours to obtain a titanium oxide ultrafine powder dispersion slurry 2.

  In addition, 5 parts by weight of ion-exchanged water is mixed with 1 part by weight of ultrafine titanium oxide powder (Super Titania F-6) to form a slurry, which is similarly dispersed for 48 hours with a ball mill to obtain an aqueous titanium oxide super A fine powder dispersion slurry 3 was obtained. Table 1 summarizes the compositions of the titanium oxide ultrafine powder dispersion slurries 1, 2 and 3 prepared here.

  Next, a small amount of hydrochloric acid and water are added to a dilute solution of tetraethoxysilane in isopropyl alcohol, and the mixture is kept at 35 ° C. while stirring and subjected to hydrolysis and polycondensation reaction for 24 hours. The weight average molecular weight is about 2200 (polystyrene standard). And an alkoxysilane oligomer (measured by silica component equivalent concentration of about 20% by weight, pH of about 3.5) of gel permeation chromatograph (measured by model HLC-8120GPC manufactured by Tosoh Corporation) using tetrahydrofuran as a solvent. Was synthesized.

  With respect to 65 parts by weight of this alkoxysilane oligomer, 5 parts by weight of a silane coupling agent having an epoxy group (TSL8350 of Toshiba GE Silicone Co., Ltd., silica component equivalent concentration is about 25% by weight), polyvinyl butyral (Sekisui Chemical Co., Ltd.) 5 parts by weight of a 10% by weight solution of ESREC BM-1) made in) and 5 parts by weight of ethyl cellosolve, 5 parts by weight of isopropyl alcohol, and 6 parts by weight of titanium oxide ultrafine powder dispersion slurry 1 were mixed. Thus, a non-chromium surface treating agent solution 1 in an alcohol solvent was obtained.

  In addition, silane coupling to 60 parts by weight of colloidal silica aqueous solution (Snowtex XS manufactured by Nissan Chemical Industries, Ltd., average particle diameter of colloidal silica particles of about 5 nm, pH of about 11, and silica component of about 20% by weight). DYNOL as a wetting agent that also functions as an antifoaming agent in a mixture of 10 parts by weight of an agent (TSL8350 from Toshiba GE Silicone Co., Ltd.), 10 parts by weight of isopropyl alcohol, and 6 parts by weight of titanium oxide ultrafine powder dispersion slurry 2. 0.05 part by weight of 604 (manufactured by Nissin Chemical Industry Co., Ltd.) was added to obtain a non-chromium surface treating agent solution 2 using water and alcohol as solvents.

  Furthermore, 8 parts by weight of an epoxy group-containing silane coupling agent (TSL8350 from Toshiba GE Silicone Co., Ltd.) and 72 parts by weight of colloidal silica aqueous solution (Snowtex XS manufactured by Nissan Chemical Industries, Ltd.), water-based titanium oxide A non-chromium surface treating agent solution 3 containing 0.06 part by weight of dynol 604 (manufactured by Nissin Chemical Industry Co., Ltd.) and 6 parts by weight of the ultrafine powder dispersion slurry 3 and water as a solvent is added. Obtained.

  Furthermore, 123 parts by weight of an alkoxysilane oligomer having the same weight average molecular weight of 2200 as used in the non-chromium surface treating agent solution 1 and polyvinyl butyral (BL-1 manufactured by Sekisui Chemical Co., Ltd.) were dissolved in isopropyl alcohol. 9 parts by weight of a 10% by weight solution, 14.7 parts by weight of a silica sol solution of an isopropyl alcohol solvent (IPA-ST (including about 30% by weight of a silica component) manufactured by Nissan Chemical Industries, Ltd.), and ethyl cellosolve 17.1 A non-chromium surface treating agent solution 4 in an alcohol solvent was prepared by mixing 1 part by weight and 14.6 parts by weight of isopropyl alcohol. Table 2 summarizes the composition of the non-chromium surface treating agent solutions 1, 2, 3, and 4 prepared here.

  Next, a chemical conversion treatment solution for test was prepared. Zinc 1.0 g / liter, nickel 0.05 g / liter, magnesium 1.0 g / liter, phosphate ion 4.0 g / liter, nitrate ion 2.5 g / liter, nitrite ion 0.05 g / liter, the balance being water Zinc phosphate tetrahydrate, basic nickel carbonate (II) hydrate, dibasic magnesium phosphate, 85 wt% phosphoric acid, 60 wt% nitric acid, sodium nitrite and ion-exchanged water were mixed to form a non-chromium chemical conversion. Treatment liquid 1 was obtained.

  Moreover, zinc 0.8g / liter, magnesium 2.0g / liter, phosphate ion 8.0g / liter, nitrate ion 4.0g / liter, nitrite ion 0.05g / liter, fluorine ion 0.01g / liter, remainder Is mixed with zinc phosphate tetrahydrate, dibasic magnesium phosphate, 85 wt% phosphoric acid, 60 wt% nitric acid, sodium nitrite, hydrofluoric acid and ion-exchanged water so that it becomes water. Got.

  In addition, a zinc phosphate chemical conversion treatment solution manufactured by Chemicoat Co., Ltd. (referred to as Chemocoat No. 422, non-chromium chemical conversion treatment solution 3) and a surface preparation agent Chemmicron S-2 (a pretreatment agent manufactured by Chemicoat Co., Ltd., titania sol) Prepared). Table 3 summarizes the compositions of the non-chromium chemical conversion treatment liquids 1, 2 and 3.

  The non-chromium surface treating agent solution was applied to the surface of a metal member having a zinc surface by a dip and spin method, which is a kind of coating method. That is, a whitening galvanized bolt or the like (without chromate treatment) is dipped in a surface treating agent solution, wetted, removed, transferred to a stainless steel bowl attached to a centrifuge, and about 4 cm at a rotation radius of about 15 cm and a rotation speed of about 500 RPM. Rotating for 2 seconds, it was applied by an application method in which excess surface treatment agent solution adhering to the surface of a bolt or the like was shaken off by centrifugal force.

  Rust prevention performance was evaluated using a salt spray tester based on JIS-Z-2371, and the surface of the sample (washed with a water shower) was observed with the naked eye every 24 hours to check the occurrence of white rust and red rust. . The antirust performance of each sample was recorded and evaluated at the time when white rust and red rust occurred on two of the three samples.

Example 1 and Comparative Example 1
Whitening (no chromate treatment) galvanized bolts (M8, half screw, thread length approx. 20 mm) in Company A's zinc chloride bath are immersed in the pretreatment agent Chemmicron S-2 for 30 seconds and then kept at 60 ° C. The zinc surface was soaked in the non-chromium chemical conversion solution 3 for 30 seconds, subjected to zinc phosphate chemical conversion treatment, washed with water and dried. The surface of this galvanized bolt became a satin finish by chemical conversion treatment, and the galvanized luster disappeared. The non-chromium surface treating agent solution 1 was applied to the chemically treated galvanized bolt by the dip-and-spin method described above, held at 80 ° C. for 10 minutes, then heated to 150 ° C. and held at this temperature for 20 minutes. The surface treatment agent was baked (Example 1).

  Separately, a non-chromium surface treating agent solution 1 of an alcohol solvent was applied to three white galvanized bolts galvanized in a zinc chloride bath of Company A by a dip-and-spin method, kept at 80 ° C. for 10 minutes, and then kept at 150 ° C. The temperature was raised and held for 20 minutes, and the non-chromium surface treatment agent was baked (Comparative Example 1).

  The galvanized bolts subjected to the non-chromium surface treatment of Example 1 and Comparative Example 1 were put in a salt spray tester based on JIS-Z-2371 to evaluate the rust prevention performance. As a result, the galvanized bolt subjected to the non-chromium surface treatment of Example 1 generated white rust in 192 hours and red rust in 672 hours. On the other hand, the galvanized bolt of Comparative Example 1 generated white rust in 48 hours and red rust in 600 hours. That is, comparing Example 1 with Comparative Example 1, the compatibility with the non-chromium surface treatment agent is poor (the rust prevention performance is poor when the non-chromium surface treatment agent solution is applied). It can be seen that by applying the surface treatment agent after the zinc chemical conversion treatment, the rust prevention performance against the occurrence of white rust is remarkably improved when the surface treatment agent is applied.

Example 2 and Comparative Example 2
Cyan bath whitening (no chromate treatment) by the same company A 3 galvanized bolts (M8 half screw, thread length approx. 20 mm) were immersed in the pretreatment agent Chemmicron S-2 for 30 seconds in the same manner as in Example 1. Then, it was immersed in a non-chromium chemical conversion treatment liquid 3 kept at 60 ° C. for 30 seconds to subject the zinc surface to a zinc phosphate chemical conversion treatment, washed with water and dried. The surface of this galvanized bolt became textured by chemical conversion treatment. The non-chromium surface treating agent solution 1 was applied to the galvanized bolt subjected to the chemical conversion treatment, held at 80 ° C. for 10 minutes, then heated to 150 ° C. and held for 20 minutes, and the non-chromium surface treating agent was baked ( Example 2).

  Next, in the same manner as in Comparative Example 1, non-chromium surface treatment of an alcohol solvent was applied to three galvanized bolts (not compatible with non-chromium surface treatment agent) of a cyan bath by the same company A. The agent solution 1 was applied by the dip and spin method, held at 80 ° C. for 10 minutes and dried, then heated to 150 ° C. and held for 20 minutes, and the non-chromium surface treatment agent was baked (Comparative Example 2). The galvanized bolts subjected to the non-chromium surface treatment of Example 2 and Comparative Example 2 were put into a salt spray tester based on JIS-Z-2371 to evaluate the rust prevention performance. As a result, in the galvanized bolt subjected to the non-chromium surface treatment of Example 2, white rust was generated in 192 hours and red rust was generated in 624 hours. In contrast, the galvanized bolt of Comparative Example 2 generated white rust in 48 hours and red rust in 648 hours.

Example 3 and Example 4
The three whitening zinc plating bolts of the zinc chloride bath (the same whitening zinc plating bolt as in Example 1) and the whitening zinc plating bolt of the cyan bath (the same whitening zinc plating bolt as in Example 2) by Company A It was soaked in the treatment agent Chemmicron S-2 for 30 seconds and then subjected to chemical conversion treatment with the non-chromium chemical conversion treatment liquid 1 kept at 60 ° C. (both colors changed to blackish). Next, the non-chromium surface treating agent solution 1 is applied to these chemically treated galvanized bolts, held at 80 ° C. for 10 minutes and dried, heated to 150 ° C. and held for 20 minutes, and the non-chromium surface treating agent is applied. Baking and galvanized bolts with non-chromium surface treatment of Example 3 and Example 4 respectively were obtained. As a result of putting the galvanized bolt with the non-chromium surface treatment of Example 3 and Example 4 into a salt spray tester and investigating rust prevention performance, the bolt of Example 3 generated white rust in 148 hours and 576 hours. Then, red rust was generated, and the bolt of Example 4 had white rust in 148 hours and red rust in 648 hours.

Example 5 and Comparative Example 3
Zinc chloride whitening galvanized bolts manufactured by company B (this galvanized bolt has a relatively good compatibility with the surface treatment agent) are immersed in Chemron S-2 (pretreatment agent) for 30 seconds, and then kept at 60 ° C. The zinc phosphate chemical conversion treatment was performed by immersing in the non-chromium chemical conversion treatment liquid 2 for 30 seconds (at this time, the surface of the galvanized sheet became satin). Next, the non-chromium surface treating agent solution 1 was applied in the same manner as in Example 1 to obtain a galvanized bolt subjected to the non-chromium surface treatment of Example 5. Separately, non-chromium surface treatment solution 1 was applied to three zinc chloride bath whitening zinc plating bolts of Company B in the same manner as in Comparative Example 1 to obtain a non-chromium surface-treated zinc plating bolt of Comparative Example 3. . As a result of putting these three bolts in a salt spray tester and examining the antirust performance, the bolt of Example 5 generated white rust in 260 hours and red rust in 1680 hours. On the other hand, the galvanized bolt with the non-chromium surface treatment of Comparative Example 3 generated white rust in 192 hours and red rust in 1704 hours.

Example 6 and Comparative Example 4
Zincate bath whitening galvanized bolt by Company C (this galvanized bolt has relatively good compatibility with the surface treatment agent) 3 pieces were immersed in Chemmicron S-2 for 30 seconds and then kept at 60 ° C. No. 3 was subjected to a zinc phosphate chemical conversion treatment for 30 seconds (at this time, the surface of the galvanized surface became zincy with the metallic luster of zinc disappeared). Next, the non-chromium surface treating agent solution 1 was applied in the same manner as in Example 1 to obtain a galvanized bolt subjected to the non-chromium surface treatment of Example 6. Separately, non-chromium surface treating agent solution 1 was applied to three zincate bath whitening galvanized bolts of Company C in the same manner as in Comparative Example 1 to obtain a non-chromium surface-treated galvanized bolt in Comparative Example 4. As a result of putting these three bolts into a salt spray tester and examining the antirust performance, the bolt of Example 6 generated white rust in 240 hours and red rust in 1200 hours. On the other hand, the galvanized bolt with the non-chromium surface treatment of Comparative Example 4 generated white rust in 168 hours and red rust in 1704 hours.

Example 7 and Comparative Example 5
A zincate galvanizing bath manufactured by Dipsol Co., Ltd. was erected in a bath of a small barrel plating apparatus having a barrel volume of about 2.9 liters. Next, 80 pieces (about 1.7 kg) of M8 half screw bolts (thread length: about 20 mm) subjected to pickling and alkali degreasing treatment are put in the barrel so that the average current density becomes 0.8 to 1.0 A / dm ^2. Then, while rotating a barrel immersed in a plating bath at 9 RPM, a plating current was passed through for about 30 minutes to apply a zinc plating with an average thickness of about 10 μm to the bolt surface. Three zinc plating bolts that have been washed with water while omitting dilute nitric acid washing (picking) are immersed in Chemmicron S-2 for 30 seconds, and then immersed in non-chromium chemical conversion liquid 3 kept at 60 ° C. for 30 seconds to perform zinc phosphate chemical conversion treatment. (At this time, the galvanized surface disappeared from the metallic luster of zinc and became satin). After washing with water and drying, the non-chromium surface treating agent solution 1 was applied in the same manner as in Example 1 to obtain a non-chromium surface-treated galvanized bolt in Example 7. Further, non-chromium surface treating agent solution 1 was applied to three galvanized bolts of the same type in the same manner as in Comparative Example 1 to obtain a non-chromium surface-treated galvanized bolt in Comparative Example 5.

  As a result of putting these three bolts in a salt spray tester and examining the rust prevention performance, the bolt of Example 7 generated white rust in 216 hours and red rust in 1104 hours. On the other hand, the galvanized bolt with the non-chromium surface treatment of Comparative Example 5 generated white rust in 192 hours and red rust in 1128 hours.

Example 8 and Comparative Example 6
Build a zincate zinc plating bath manufactured by Dipsol Co., Ltd. in a small barrel plating machine equipped with a 1.6 liter barrel. Place about 300 g of M2.5 small screws in the barrel and galvanize the small screws. gave. The plating conditions were set so that the average current density was 1.0 A / dm ^2, and the barrel was immersed in the plating bath was rotated at 10 RPM, and the plating current was passed for about 22 minutes, and the average thickness was about 7 μm on the surface of the small screw. The galvanization was applied.

  These three galvanized small screws were immersed in Chemmicron S-2 for 30 seconds and then immersed in a non-chromium chemical conversion solution 3 maintained at 60 ° C. for 30 seconds to perform zinc phosphate conversion treatment (the galvanized surface was made of zinc). The metallic luster disappeared and it became satin). After washing with water and drying, the non-chromium surface treating agent solution 1 was applied in the same manner as in Example 1 to obtain a non-chromium surface-treated galvanized bolt in Example 8. Moreover, the non-chromium surface treating agent solution 1 was applied to three galvanized small screws of the same type in the same manner as in Comparative Example 1 to obtain a non-chromium surface-treated galvanized bolt in Comparative Example 6.

  As a result of putting these three small screws into a salt spray tester and examining the rust prevention performance, the small screws of Example 8 generated white rust in 168 hours and red rust in 504 hours. On the other hand, the galvanized small screw subjected to the non-chromium surface treatment of Comparative Example 6 generated white rust in 124 hours and red rust in 552 hours.

Example 9 and Comparative Example 7
Three M2 small screws (thread length 3 mm) galvanized in a chloride bath of company D are immersed in Chemmicron S-2 for 30 seconds, and then immersed in non-chromium chemical treatment solution 3 kept at 60 ° C. for 30 seconds. A chemical conversion treatment was applied (the surface became satin). The non-chromium surface treating agent solution 1 was applied to the surface subjected to the chemical conversion treatment in the same manner as in Example 1 and baked to obtain a galvanized machine screw of Example 9. Separately, the non-chromium surface treatment solution 1 was applied to three M2 machine screws galvanized in a chloride bath of Company D in the same manner as in Comparative Example 1, and the galvanized machine screws subjected to the non-chromium surface treatment of Comparative Example 7 Got. As a result of putting three of these small screws into a salt spray tester and examining the antirust performance, the small screw of Example 9 generated white rust in 168 hours and red rust in 216 hours. On the other hand, the galvanized small screw subjected to the non-chromium surface treatment of Comparative Example 7 generated white rust in 24 hours and red rust in 144 hours.

Example 10 and Comparative Example 8
Three zincate whitening galvanized bolts (same bolts as in Example 6) by Company C were immersed in Chemmicron S-2 for 30 seconds, and then immersed in non-chromium chemical conversion liquid 3 maintained at 60 ° C. for 30 seconds to form zinc phosphate. The galvanized surface disappeared and became a satin finish. After washing with water and drying, non-chromium surface treating agent solution 2 of a mixed solvent of water and alcohol was applied in the same manner as in Example 1 to obtain a non-chromium surface-treated galvanized bolt of Example 10. Separately, non-chromium surface treatment solution 2 was applied to three zincate bath whitening galvanized bolts of Company C in the same manner as in Comparative Example 1 to obtain a galvanized bolt subjected to non-chromium surface treatment in Comparative Example 8. As a result of putting these three bolts into a salt spray tester and investigating rust prevention performance, the bolt of Example 10 generated white rust in 120 hours and red rust in 1176 hours. On the other hand, the galvanized bolt subjected to the non-chromium surface treatment of Comparative Example 8 generated white rust in 24 hours and red rust in 1200 hours.

Comparative Example 9 and Comparative Example 10
3 zincate bath galvanized bolts (whitening) by Company C were immersed in Chemmicron S-2 for 30 seconds and then immersed in non-chromium chemical conversion solution 3 kept at 60 ° C. for 30 seconds to perform zinc phosphate conversion treatment (Zinc The plating surface has lost its luster and has become satin). Next, the non-chromium surface treating agent solution 3 using water as a solvent was applied in the same manner as in Example 1 to obtain a galvanized bolt subjected to the non-chromium surface treatment of Comparative Example 9. Separately, the non-chromium surface treating agent solution 3 was applied to three zincate bath whitening galvanized bolts of Company C in the same manner as in Comparative Example 1 to obtain a non-chromium surface-treated galvanized bolt in Comparative Example 10. As a result of putting these three bolts into a salt spray tester and examining the rust prevention performance, the bolt of Comparative Example 9 generated white rust in 24 hours and red rust in 1128 hours. On the other hand, the galvanized bolt with the non-chromium surface treatment of Comparative Example 10 generated white rust in 24 hours and red rust in 1152 hours.

Example 11 and Comparative Example 11
Three zinc die-cast members (diameter: about 10 mm, inner diameter: 6 mm, length: about 15 mm) were degreased and then immersed in Chemmicron S-2 for 30 seconds, and then immersed in non-chromium chemical conversion treatment liquid 3 kept at 60 ° C. for 30 seconds. Was subjected to a zinc phosphate chemical conversion treatment (the surface became satin). Next, the non-chromium surface treating agent solution 1 was applied in the same manner as in Example 1 to obtain a zinc die-cast member subjected to non-chromium surface treatment in Example 11. Separately, non-chromium surface treating agent solution 1 was applied to three zinc die cast members of the same type in the same manner as in Comparative Example 1 to obtain a non-chromium surface-treated zinc die cast member of Comparative Example 11.

  As a result of putting three each of these zinc die-cast members into a salt spray tester and investigating rust prevention performance, the zinc die-cast member of Example 11 generated white rust in 432 hours (since it is zinc, no red rust is produced). On the other hand, in the zinc die-cast member subjected to the non-chromium surface treatment of Comparative Example 11, white rust occurred in 192 hours.

  Table 1 summarizes Examples 1 to 11 and Comparative Examples 1 to 11 described above.

Examples 12 to 15 and Comparative Examples 12 to 15
An iron plate (dimension 50 × 50 × 2 mm, plating thickness 8 μm) galvanized in a zincate bath and an iron plate (dimension 50 × 50 × 2 mm, plating thickness 7 μm) galvanized in a chloride bath were obtained. About the iron plate galvanized with this zincate bath, the sample (Example 12) which chemically converted with the non-chromium chemical conversion liquid 3 and the sample (Comparative Example 12) which are not subjected to chemical conversion treatment were prepared. In addition, a sample (Example 13) obtained by subjecting an iron plate galvanized in a chloride bath to a chemical conversion treatment with a non-chromium chemical conversion solution 3 and a sample not subjected to a chemical conversion treatment (Comparative Example 13) were prepared.

  The samples of Examples 12 and 13 and Comparative Examples 12 and 13 were coated with alcohol solvent-based non-chromium surface treating agent solution 1 by the dip and spin method and baked at 130 ° C. Several samples from Examples 12 and 13 and Comparative Examples 12 and 13 were put in a light resistance test apparatus based on JASO M346. Of the samples of Examples 12 and 13 subjected to chemical conversion treatment with the non-chromium chemical conversion treatment solution 3, samples subjected to light exposure in the light resistance test are referred to as samples of Examples 14 and 15, respectively. Further, among the samples of Comparative Examples 12 and 13 subjected to chemical conversion treatment with the non-chromium chemical conversion treatment solution 3, samples subjected to light exposure in the light resistance test are referred to as Comparative Examples 14 and 15, respectively.

  The sample put in the light resistance test apparatus and the sample not put in the light resistance test apparatus were simultaneously put in a spray tester based on JIS-Z-2371 salt water to evaluate the rust prevention performance. The results are shown in Table 5. From the results shown in Table 5, it can be seen that the sample subjected to the chemical conversion treatment and coated with the surface treatment agent has little deterioration in the rust prevention performance against the occurrence of white rust by the light resistance test.

JASO M346 is an accelerated light resistance test method using a xenon arc lamp (an artificial light source close to sunlight) for automobile interior parts. In this test method, the temperature was maintained at 89 ± 3 ° C. and the humidity at 50 ± 5%. Radiation exposure is performed so that the cumulative radiation exposure amount of light having a wavelength in the range of 300 to 400 nm is 100 MJ / m ^{2 in an} atmosphere.

Example 16 and Comparative Example 16
1 g of citric acid in 1 liter of ion-exchanged water, 30 g of aqueous silica sol (Snowtex-O manufactured by Nissan Chemical Industries, Ltd.) (6 g in terms of silica) and 3 g of zinc chloride (1.44 g in terms of zinc) By dissolving, a citric acid-based non-chromium chemical conversion treatment solution 4 shown in Table 6 was prepared.

Dipsol Co., Ltd. zinc plating solution zinc plating solution was built in a small barrel plating machine with a barrel volume of 1.6 liters, and 1.14 kg of M3 screw (thread length: 8 mm) was placed in the barrel of the plating machine. The plating is set so that the average current density is 0.8 to 1.0 A / dm ² , the barrel is rotated at 10 RPM, the plating current is passed for about 40 minutes, the substrate is washed with water and dried to obtain a plating thickness of 9.5 μm. M3 screws were obtained.

  When this galvanized M3 screw was baked (heated at 200 ° C. for 4 hours) to prevent hydrogen embrittlement, it was colored yellow. When this colored screw was immersed in the non-chromium chemical conversion treatment solution 4 kept at 25 ° C. for 10 seconds, washed with water and dried, the yellow coloring could be removed. A non-chromium surface treatment agent solution 1 based on an alcohol solvent was applied to the screw subjected to chemical conversion treatment (Example 16) and the screw not subjected to chemical conversion treatment (colored yellow) (Comparative Example 16) by the dip-and-spin method. It was applied and baked at 120 ° C. for 10 minutes.

  Table 7 shows the results of evaluation of rust prevention performance by putting 10 screws of Example 16 and Comparative Example 16 in a salt spray tester based on JIS-Z-2371. From the results of Table 7, the effect of improving the rust prevention performance by performing the chemical conversion treatment is small, but this chemical conversion treatment has the effect that the yellow color generated by baking can be removed without making the surface a satin finish. .

Example 17 and Comparative Example 17
In the same manner as in Example 16, baking was performed by heating M2.6 screws (screw portion length: 14 mm, plating thickness: 9.5 μm) galvanized in a zincate bath manufactured by Dipsol Co., Ltd. to 200 ° C. for 4 hours. Next, a pickling treatment (yellowing decolorization) soaked in a 0.2% dilute nitric acid aqueous solution and dried as it is (Comparative Example 17), and after pickling treatment, immersed in a non-chromium chemical conversion treatment solution 4 at 25 ° C. for 10 seconds A dried screw (Example 17) was prepared. The previously prepared non-chromium surface treating agent solution 4 was baked after galvanization and baked and pickled in Comparative Example 17, and after pickling, it was further dipped in the non-chromium chemical conversion treatment solution 4 and dried. The dip and spin method was applied to both of the screws. Each of these 5 screws subjected to surface treatment was put into a salt spray tester based on JIS-Z-2371 to evaluate rust prevention performance. As a result, white rust was observed in 2 out of 5 screws after 144 hours, whereas white rust was observed in 3 out of 5 screws after 24 hours. The salt spray test results are also shown in Table 7.

  Metal products that have been pickled after washing with dilute nitric acid after galvanization have little improvement in rust prevention performance even when alcohol-based non-chromium surface treatment solution 1 or 4 is applied, but the above-mentioned citric acid-based non-chromium chemical conversion treatment It has been found that when the alcohol-based non-chromium surface treatment solution 1 or 4 is applied after the chemical conversion treatment with the liquid 4, a practical level of rust prevention performance can be imparted without making the surface textured.

Claims (23)

A metal component having a zinc surface is subjected to a chemical conversion treatment with a non-chromium chemical conversion treatment solution to form a chemical conversion treatment film, and a silica component or silica is added to the surface of the chemical conversion treatment film in an alcohol solvent or a mixed solvent of water and alcohol. A non-chromium anticorrosive treatment method for a metal member having a zinc surface on which a non-chromium surface treating agent solution containing a component that changes to a surface is formed to form a siliceous film having an average thickness of 0.5 to 3 μm. 2. The non-chromium rust preventive treatment method for a metal member having a zinc surface according to claim 1, wherein the non-chromium surface treating agent solution contains 10 to 25% by weight in terms of silica component or a component that changes to silica. The non-chromium surface treating agent solution contains 0.3 to 2% by weight of a titanium oxide ultrafine powder having an average particle size of 40 nm or less of dispersed primary particles. Chrome anti-rust treatment method. The non-chromium antirust treatment method for a metal member having a zinc surface according to claim 2, wherein the non-chromium surface treatment agent solution contains 4 to 16% by weight of a silane coupling agent. The non-chromium surface treatment agent solution contains 10 to 25% by weight of colloidal silica as a silica component in a mixed solvent of water and alcohol in terms of silica, and prevents non-chromium of a metal member having a zinc surface according to claim 2. Rust treatment method. The non-chromium surface treating agent solution contains 10 to 25 wt% of an alkoxysilane oligomer obtained by hydrolyzing an alkoxysilane monomer and subjected to polycondensation as a component that changes to silica in terms of silica in an alcohol solvent. A non-chromium antirust treatment method for a metal member having a zinc surface as described in 1. The non-chromium antirust treatment method for a metal member having a zinc surface according to claim 6, wherein the alkoxysilane oligomer has a weight average molecular weight of 1,000 to 10,000. The non-chromium antirust treatment method for a metal member having a zinc surface according to claim 1, wherein the non-chromium chemical conversion treatment solution is an aqueous solution containing zinc phosphate. The non-chromium antirust treatment method for a metal member having a zinc surface according to claim 2, wherein the non-chromium chemical conversion treatment solution is an aqueous solution containing zinc phosphate. The non-chromium antirust treatment method for a metal member having a zinc surface according to claim 5, wherein the non-chromium chemical conversion treatment solution is an aqueous solution containing zinc phosphate. The non-chromium antirust treatment method for a metal member having a zinc surface according to claim 6, wherein the non-chromium chemical conversion treatment solution is an aqueous solution containing zinc phosphate. The non-chromium antirust treatment method for a metal member having a zinc surface according to claim 6, wherein the non-chromium chemical conversion treatment solution is an aqueous solution containing 0.5 to 5 g / liter of citric acid. The non-chromium of the metallic member having a zinc surface according to claim 12, wherein the non-chromium chemical conversion treatment solution further contains 2 to 20 g / liter of aqueous silica sol converted to silica and 0.6 to 6 g / liter of zinc ions. Rust prevention treatment method. 2. The non-chromium antirust treatment method for a metal member having a zinc surface according to claim 1, wherein the metal member having a zinc surface is a metal member plated with zinc or zinc alloy, or a cast product of an alloy mainly composed of zinc. The metal member having a zinc surface is 2 to 10% by weight of the chemical conversion treatment film formed on the surface, and the average particle size of the primary particles subjected to the dispersion treatment formed on the chemical conversion treatment film is 40 nm or less. A metal member having a non-chromium rust-proof zinc surface coated with a siliceous film having a thickness of 0.5 to 3 μm containing titanium oxide ultrafine powder and 65% by weight or more of silica. The metal member having a zinc surface subjected to non-chromium rust prevention treatment according to claim 15, wherein the silica is generated from an alkoxysilane oligomer. The metal member having a zinc surface subjected to non-chromium rust prevention treatment according to claim 15, wherein the chemical conversion treatment film is made of zinc phosphate. The metal member having a zinc surface subjected to non-chromium rust prevention treatment according to claim 15, wherein the chemical conversion treatment film has a dark color. The metal member having a zinc surface subjected to non-chromium rust prevention treatment according to claim 15, wherein the metal member is a small screw having an outer diameter of 3 mm or less that is electrogalvanized by a barrel method. A metal member having a zinc surface has a thickness of 0.1 mm and includes a chemical conversion film formed on the surface and 65 wt% or more silica formed from an alkoxysilane oligomer formed on the chemical conversion film. A metal member having a zinc surface which is coated with a 5 to 3 μm siliceous film and which has been subjected to a non-chromium antirust treatment. The metal member having a zinc surface subjected to non-chromium rust prevention treatment according to claim 20, wherein the chemical conversion treatment film is made of zinc phosphate. The metal member having a zinc surface subjected to non-chromium rust prevention treatment according to claim 20, wherein the chemical conversion treatment film has a dark color. 21. The metal member having a zinc surface subjected to non-chromium rust prevention treatment according to claim 20, wherein the metal member is a small screw having a screw portion outer diameter of 3 mm or less electrogalvanized by a barrel method.