JP5689039B2 - Surface treatment liquid for fastening parts - Google Patents

Description

  The present invention relates to a surface treatment liquid used for the surface treatment of fastening parts, and more particularly to a surface treatment liquid for forming a surface treatment film that does not contain chromium and has excellent corrosion resistance with reduced environmental load.

  Conventionally, galvanized fastening parts such as screws, bolts and nuts with good corrosion resistance have been used. However, when exposed to humid atmosphere, exhaust gas atmosphere, atmosphere near the coast, etc. for a long time, the surface becomes white. Rust is generated and the appearance is deteriorated. Further, when the corrosion further progresses, the base material corrodes and red rust is generated, and the strength of the base material is deteriorated. In order to prevent such rust, a method of chromating a galvanized fastening part has been adopted. However, the chromate treatment places a great burden on the treatment of the waste liquid containing chromium ions. In addition, the abolition of hexavalent chromium and the demand for chromium-free materials are increasing as a means of reducing environmentally hazardous substances.

  As a chromium-free treatment liquid used for a galvanized steel sheet, for example, Patent Document 1 discloses a coating using an acidic liquid composition containing a fluorine compound such as titanium or zirconium and a cation such as cobalt, manganese, magnesium, or aluminum. Has been shown to form.

  Patent Document 2 discloses a water-soluble polyvalent metal phosphate compound, hexafluorotitanic acid (or a salt thereof), a vanadium compound, and a chelating agent as a surface treatment liquid used for the surface treatment of a galvanized steel sheet. A surface treatment liquid containing is shown.

JP-A-5-195244 JP 2008-274388 A

  However, when the above-mentioned processing liquid is applied to a fastening part, the corrosion resistance is not good. This is because the fastening parts have severe irregularities in the shape, especially the zinc coated on the protrusions is highly reactive, so it reacts with the above acidic treatment liquid and the zinc coating disappears due to the reaction. is there.

  On the other hand, when the treatment liquid is changed from neutral to alkaline in order to suppress the reaction with the zinc coating, the adhesion is remarkably deteriorated and the corrosion resistance is not good.

  Further, as the acidity of the treatment liquid decreases from strong acidity to weak acidity, the liquid becomes unstable and non-uniform precipitation tends to occur. When such a treatment liquid is applied to a fastening part, a non-uniform film is likely to be formed, and the adhesion of the film is lowered, thereby easily deteriorating the corrosion resistance.

  It is an object of the present invention to provide a fastening component that has a low reactivity with respect to a coating material containing zinc or a zinc alloy of an uneven fastening component and that forms a film having good adhesion and good corrosion resistance with the coating portion. The object is to provide a stable surface treatment solution.

  Furthermore, an object of the present invention is to provide a base material having good adhesion to the top coating layer in the case where a top coating is further coated on the surface of the fastening part formed with the surface treatment liquid. An object of the present invention is to provide a surface treatment liquid capable of forming a film having a function.

The present invention relates to a surface treatment liquid for forming a film on the surface of a fastening part coated with a coating material containing zinc or a zinc alloy, and one or more of primary aluminum phosphate and primary magnesium phosphate 2 types, hexafluoro titanic acid or its salt, a chelating agent, and 1 or more types of magnesium compounds selected from magnesium hydroxide, magnesium oxide, and magnesium carbonate, and pH shall be adjusted to 2-5. It is the surface treatment liquid for fastening parts characterized by these.

  Moreover, this invention is a surface treatment liquid for fastening parts for the said surface treatment liquid to form a membrane | film | coat on the fastening part which performed the coating process with the coating material containing zinc or a zinc alloy.

  Moreover, this invention is a surface treatment liquid for fastening components by which surface treatment liquid is adjusted to pH 3-4.

  Moreover, this invention is a surface treatment liquid for fastening parts whose said chelating agent is 1-hydroxy ethylidene-1, 1- diphosphonic acid.

  Further, the present invention is a surface treatment liquid for fastening parts, the pH of which is adjusted with an aqueous ammonia solution.

  According to the present invention, a surface treatment that forms a film with low film corrosion resistance and good reactivity with a coating layer containing zinc or a zinc alloy of an uneven fastening part and having good adhesion to the coating layer. A liquid can be provided, and thereby a coated fastening part having good corrosion resistance can be provided.

  Further, according to the present invention, when the surface of the coated fastening part with the surface treatment liquid is further coated with a top coating, the coating has good adhesion with the top coating and has a better corrosion resistance. Parts can be provided.

  In the present invention, as a fastening part coated with a coating material containing zinc or a zinc alloy, screws, bolts, nuts, washers, rivets, pins, wrench, retaining rings, screws, screws, Examples include fastening parts used for fixing members such as washers, spacers, and shims.

  Examples of the coating treatment with a coating material containing zinc or zinc alloy include zinc plating, zinc alloy plating, coating treatment with zinc rich paint, etc., and particularly suitable for fastening parts coated with zinc plating. A protective film can be formed.

  The zinc plating or zinc alloy plating is not particularly limited, but includes hot dip galvanizing, hot dip Zn-5 mass% Al alloy plating, hot dip Zn-55 mass% Al alloy plating, electrogalvanizing, electric Zn-Ni alloy plating, etc. Can be mentioned.

  The primary aluminum phosphate and primary magnesium phosphate contained in the surface treatment liquid of the present invention are components that are the main (base) for forming a film. Any of primary aluminum phosphate and primary magnesium phosphate can be suitably used as long as they are industrially manufactured and commercially available. The primary aluminum phosphate preferably has an Al / P molar ratio of 0.7 / 3 to 1.2 / 2, and the primary magnesium phosphate has an Mg / P molar ratio of 0.00. 7/2 to 1.2 / 2 are preferred.

  These primary aluminum phosphates and primary magnesium phosphates can be used alone or in combination of two.

  The concentration of primary aluminum phosphate and primary magnesium phosphate (hereinafter, in the present invention, one or two of them may be collectively referred to as a phosphate compound) in the surface treatment liquid is determined by the surface treatment. It is preferable to use an amount of 1% by weight or more and 50% by weight or less with respect to the whole liquid. If the amount is less than 1% by weight, hydrolysis may occur and precipitation may occur. If the amount exceeds 50% by weight, the phosphate compound precipitates exceeding the solubility of the phosphate compound, and the stability of the surface treatment solution is problematic. May occur.

  Further, the hexafluorotitanic acid (titanium hydrofluoric acid) contained in the surface treatment liquid of the present invention is industrially produced and commercially available, whether it is free or a salt thereof. Any material can be suitably used.

  Examples of the salt of hexafluorotitanic acid include salts with alkali metals such as lithium, potassium and sodium, and ammonium salts.

  Specific compounds include sodium hexafluorotitanate (sodium titanium fluoride), potassium hexafluorotitanate (potassium titanium fluoride), lithium hexafluorotitanate (lithium titanium fluoride), and ammonium hexafluorotitanate (ammonium titanium fluoride). Can be mentioned. Of these, the hexafluorotitanate is preferably ammonium hexafluorotitanate.

  In the surface treatment liquid of the present invention, the hexafluorotitanic acid can be used alone or in combination with a free salt thereof, or the free product and salt thereof can be used in combination.

  Hexafluorotitanic acid (hereinafter sometimes referred to as hexafluorotitanate in the meaning including hexafluorotitanate) is 10 parts by weight or more and 1000 parts by weight or less with respect to 100 parts by weight of the phosphate compound. It is preferable to contain. If the amount is less than 10 parts by weight, a uniform and dense film having excellent corrosion resistance cannot be formed, and the formed film has low mechanical strength. On the other hand, when the amount exceeds 1000 parts by weight, the amount of titanium that does not participate in the bonding increases so much that a uniform and dense film having excellent corrosion resistance cannot be formed, and the mechanical strength of the formed film is lowered.

  In the surface treatment liquid of the present invention, by containing hexafluorotitanic acid, the phosphate groups of this phosphate compound form a bond (phosphate group-titanium-phosphate group) with titanium interposed therebetween. Can do. This bond formation can form a film at a low baking temperature. This film has a high alkali resistance and a high mechanical strength by forming a bond with titanium interposed.

  As the chelating agent contained in the surface treatment liquid of the present invention, any chelating agent can be used as long as it can form a film having a network structure by reaction with a phosphate compound. be able to.

  Examples of such chelating agents include phosphonic acid chelating agents and oxycarboxylic acid chelating agents. In the present invention, phosphonic acid chelating agents are particularly preferred.

  Specific examples of the phosphonic acid-based chelating agent include aminotrimethylenephosphonic acid, 1-hydroxyalkylidene-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, Mention may be made of their salts.

  In particular, 1-hydroxyalkylidene-1,1-diphosphonic acid or a salt thereof is preferable from the viewpoint of solubility when producing the surface treatment liquid. More preferred is 1-hydroxyethylidene-1,1-diphosphonic acid or a salt thereof.

  Examples of the salt of the chelating agent include salts with alkali metals such as lithium, potassium and sodium, and ammonium salts.

  The chelating agent in the surface treatment liquid is preferably contained in an amount of 10 parts by weight to 1000 parts by weight with respect to 100 parts by weight of the phosphate compound. If it is less than 10 parts by weight, sufficient corrosion resistance cannot be obtained, and if it exceeds 1000 parts by weight, the formed film may be sticky.

  The surface treatment liquid of the present invention contains a chelating agent, and in addition to the dehydration condensation reaction between the phosphate groups of the phosphate compound, a reaction between the phosphate compound and the chelating agent results in a network (network) structure. A film is formed. This film formation can form a uniform and dense film at a low baking temperature. Therefore, this surface treatment liquid can form a film having excellent corrosion resistance on a fastening part coated with a coating material containing zinc or a zinc alloy at a low baking temperature.

  The surface treatment liquid of the present invention is adjusted so that the pH of the surface treatment liquid is in the range of 2 to 5 after dissolving predetermined amounts of the phosphate compound, hexafluorotitanic acid and chelating agent in an aqueous medium. Can be manufactured.

  The aqueous medium may be water alone or a mixed solvent of water and a water-soluble organic solvent, but is preferably water alone.

  In order to adjust the pH of the surface treatment solution, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or an alkaline agent such as an aqueous ammonia solution can be used. Of these, ammonia water which is mostly diffused during application and baking and does not affect the film is preferred.

  When pH adjustment of the surface treatment liquid is not performed, since the pH is low, if it is applied as it is, the coating layer containing zinc or the zinc alloy is damaged by the reaction or dissolved and disappears. For this reason, corrosion resistance falls remarkably.

If the pH of the surface treatment liquid is lower than 2, the effect of suppressing the reactivity with respect to the coating layer is small, and if it is larger than 5, the stability of the surface treatment liquid is poor and the adhesion is deteriorated.
The more preferable pH range of the surface treatment liquid of the present invention is 3-4.

  The surface treatment solution of the present invention tends to weaken the dehydration condensation reaction of the phosphate compound as the pH increases from strong acidity around pH 1, and as a result, film formation by the dehydration condensation reaction becomes insufficient, resulting in As a result, the corrosion resistance of the covering material tends to deteriorate.

  In order to prevent this, by adding a magnesium compound to the surface treatment liquid, the dehydration condensation reaction is promoted, and a film having good adhesion can be obtained stably even at pH 3-4.

  Examples of the magnesium compound include magnesium carbonate, magnesium hydroxide, and magnesium oxide, and these can be used alone or in combination of two or more.

  The magnesium compound may be added when the phosphate compound or hexafluorotitanic acid is dissolved in an aqueous medium, or may be added after the phosphate compound or hexafluorotitanic acid is dissolved in an aqueous medium.

  With this magnesium compound, there is little variation in film physical properties, and better corrosion resistance can be obtained.

  It is preferable to contain a magnesium compound so that it may become 0.2-20 weight part with respect to a phosphate compound. When the amount is less than 0.2 parts by weight, when the pH is maintained at 3 to 4 with an aqueous ammonia solution, the effect of improving the film formation is not so much observed. When the amount exceeds 20 parts by weight, the stability tends to be inferior.

  Since the surface treatment liquid of the present invention thus obtained does not contain harmful chromium compounds, problems such as environmental pollution due to the use of conventional chromium compounds do not occur.

  This surface treatment liquid is applied to the surface of a fastening part coated with a coating material containing zinc or a zinc alloy and baked at a low temperature, whereby a uniform and dense film is formed.

  The surface treatment liquid can be applied to the fastening part by a method commonly used in this technical field. For example, methods such as spraying, application, and immersion can be adopted.

  For example, when the dipping method is used, a fastening part coated with a coating material containing zinc or a zinc alloy is dipped in the surface treatment solution, pulled up, and applied by centrifugal shaking. Thereby, it is possible to apply a film of about 0.2 to 5 μm.

  Although baking is not specifically limited, For example, it can carry out by baking methods, such as a hot air type, an infrared type, and an induction heating type. The baking temperature can be 50 ° C. or higher and 200 ° C. or lower. If the baking temperature is less than 50 ° C., baking will be insufficient and film formation will not be possible, and if it exceeds 200 ° C., the corrosion resistance of the film will not be improved, resulting in poor production efficiency.

  A top coating can be further applied to the surface of the fastening part coated with the surface treatment liquid thus obtained for the purpose of high corrosion resistance, design (coloring), and the like. An organic resin paint or an inorganic paint can be used as the top coat.

  As such a top coat, an industrial baking curable organic resin paint is preferable, and an epoxy-based, polyester-based, acrylic-based, or fluorine-based organic resin paint, or selected from these is particularly preferable. An organic resin paint obtained by mixing two or more of them can be used.

  When coating with a top coating based on an organic resin coating, adhesion to an inorganic coated fastening component is a problem. For example, when these organic resin paints are directly coated on a galvanized fastening part, it is difficult to form a coating layer with poor conformability and wettability and good adhesion. On the other hand, it was found that the fastening parts coated with the surface treatment liquid of the present invention have good conformability and wettability with the top coating, resulting in extremely good adhesion and good corrosion resistance.

  The method of applying the top coating is preferably performed by immersing the galvanized fastening part coated with the surface treatment liquid of the present invention in the top coating and applying it by pulling it up or applying it by centrifugation after lifting. It is. Thereby, it is possible to apply a film of about 3 to 20 μm.

  Although baking is not specifically limited, For example, it can carry out by baking methods, such as a hot air type, an infrared type, and an induction heating type. The baking temperature can be 80 ° C. or higher and 350 ° C. or lower.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by this. In the examples and comparative examples,% of the surface treatment liquid represents weight%, and the balance is water.

Example 1
As surface treatment liquid, primary aluminum phosphate (Al / P atomic ratio = 0.9 / 3) 8.5%, titanium hydrofluoric acid 4.0%, titanium ammonium fluoride 0.8%, water An aqueous solution containing magnesium oxide 0.6%, 1-hydroxyethylidene-1,1-diphosphonic acid 7.1%, magnesium hydroxide 0.6% and the balance water was prepared as a chelating agent. The pH at this time was 1.1. Furthermore, an aqueous ammonia solution was added to the aqueous solution in an amount of 6.8% in terms of ammonia to adjust the pH to 3.3, thereby producing a surface treatment liquid. The stability of this surface treatment solution was evaluated by the method shown below. The results are shown in Table 1.

In addition, as a fastening part, a screw (PH type, diameter 5 mm, length 20 mm, no degreasing and washing) subjected to electrogalvanizing (second grade, plating thickness of about 5 μm) was used, and then the surface treatment liquid produced above was used. The surface treatment solution was applied by dipping, pulling up and centrifuging. This was baked at 100 ° C. to form a film having a coating amount of 3.5 g / m ² (adhesion thickness of about 1.5 μm). Evaluation of corrosion resistance (white rust) of this screw was performed by the following method. The results are shown in Table 1.

(Method for evaluating the stability of the surface treatment solution)
After adjusting the surface treatment liquid, in order to grasp the difference more clearly, it was held at 40 ° C. for one month, and the state of the precipitate was visually confirmed and evaluated.

(Method for evaluating the corrosion resistance of screw members)
After applying the surface treatment liquid to the screw member and baking at 100 ° C., using a salt spray device conforming to JIS Z-2371 standard, the salt water concentration is 5%, the temperature in the tank is 35 ° C., the spray pressure is 200 psi (14.1 kg / It was exposed to a salt spray environment under the condition of cm ² ), and the number of screws having white rust on the surface was visually confirmed after 96 hours of the test.

Examples 2 to 7 and Reference Example 1
The surface treatment liquids of Examples 2 to 7 and Reference Example 1 were produced in the same manner as in Example 1 except that the composition of the surface treatment liquid was as shown in Table 1. The stability of each surface treatment solution was evaluated in the same manner as in Example 1. The results are shown in Table 1. Further, the surface treatment liquids of Examples 2 to 7 and Reference Example 1 were applied to galvanized screws in the same manner as in Example 1, and the corrosion resistance was evaluated in the same manner as in Example 1.

Example 8
In the same manner as in Example 1, a commercially available polyester paint (made by Taiho Paint Co., Ltd., trade name “My Coat Black”) is used as the top coat on the surface of the screw coated with galvanizing, and immersed in the paint. Then, the surface of the coated screw was covered with a top coating by centrifugally shaking off. This was baked at 140 ° C. to form a film having a coating amount of 6.5 g / m 2 (adhesion thickness of about 4 μm). Evaluation of corrosion resistance (red rust) of this top coat screw was performed by the following method. The results are shown in Table 2.

(Method for evaluating corrosion resistance of coated screws)
The occurrence of red rust is considered to indicate that corrosion has occurred from the part where zinc plating is missing due to sacrificial corrosion protection, so visually confirm the number of screws with red rust after 500 hours of testing. did.

  In addition, the screw of each Example was good by visual evaluation without a defective part such as coating unevenness in the top coat layer.

  In addition, the screws of the respective examples were not peeled off in a peel test using an adhesive tape.

Examples 9 to 14 and Reference Example 2
In the same manner as in Example 8 , a film with a top coat was formed on the surface of the screw coated with zinc plating in the same manner as in Examples 2 to 7 and Reference Example 1, and Examples 9 to 14 and Reference Example were formed. Two screws were produced. Evaluation of corrosion resistance (red rust) of this top coat screw was performed by the following method. The results are shown in Table 2.

Comparative Examples 1-4
The screws of Comparative Examples 1 to 4 were produced and evaluated in the same manner as in Example 1 except that the composition of the surface treatment liquid was as shown in Table 1 and the amount applied to the screw member was as shown in Table 1. The results are shown in Table 1.

Comparative Examples 5-8
The surface of the screw subjected to coating on galvanized in the same manner as in Comparative Example 1-4, in the same manner as in Example 8, to form a film by top coating, to produce a screw of Comparative Example 5-8, the Evaluation of corrosion resistance (red rust) of the top coat screw was performed by the following method. The results are shown in Table 2.

  In Table 1, PA represents primary aluminum phosphate, PM represents primary magnesium phosphate, MOH represents magnesium hydroxide, and MCO represents magnesium carbonate.

In the stability of Table 1, 〜 to × indicate the following results.
◎: No precipitate, ○: Slightly precipitate, △: Slight precipitate is observed, ×: Whole cloudiness or gelation

In the corrosion resistance of Table 1, ◎ to × indicate the following results.
A: Occurrence number 0/5, O: Occurrence number 1/5, Δ: Occurrence number 2-3 / 5, X: Occurrence number 4-5 / 5

In the corrosion resistance of Table 2, ◎ to × indicate the following results.
A: Occurrence number 0/5, O: Occurrence number 1/5, Δ: Occurrence number 2-3 / 5, X: Occurrence number 4-5 / 5

Claims (5)

  A surface treatment liquid for forming a film on a surface of a fastening part coated with a coating material containing zinc or a zinc alloy, comprising at least one of primary aluminum phosphate and primary magnesium phosphate, hexafluoro It contains titanic acid or a salt thereof, a chelating agent, one or more magnesium compounds selected from magnesium hydroxide, magnesium oxide and magnesium carbonate, and the surface treatment solution is adjusted to pH 2-5. Surface treatment liquid for fastening parts. The surface treatment liquid for fastening parts according to claim 1, wherein the surface treatment liquid is a surface treatment liquid for forming a film on a fastening part that has been coated with a coating material containing zinc or a zinc alloy. The surface treatment liquid for fastening parts according to claim 1 or 2 , wherein the surface treatment liquid is adjusted to pH 3-4. The surface treatment liquid for fastening parts according to any one of claims 1 to 3 , wherein the chelating agent is 1-hydroxyethylidene-1,1-diphosphonic acid. The surface treatment liquid for fastening parts according to any one of claims 1 to 4 , wherein the surface treatment liquid is a surface treatment liquid whose pH is adjusted with an aqueous ammonia solution.