JP2010209456A - Immersion treatment liquid for rust prevention of plated chromium film, and rust-preventing treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rust-preventing treatment liquid which can greatly improve corrosion resistance not only of a plated chromium film obtained from a trivalent chromium bath but also of a plated chromium film obtained from a hexavalent chromium bath, gives little harmful effect on the environment, and does not contain a hexavalent chromium compound, and to provide a rust-preventing treatment method. <P>SOLUTION: The immersion treatment liquid for the rust prevention of the plated chromium film is formed of an aqueous solution containing chromium phosphate. The method for rust-preventing treatment of the plated chromium film includes immersing an article having the plated chromium film thereon into the treatment liquid and further electrolyzing the article in an aqueous solution containing a water-soluble trivalent chromium compound as necessary. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an immersion treatment liquid for rust prevention of a chromium plating film and a rust prevention treatment method for a chromium plating film using the treatment liquid.

  Chromium plating is widely used in various fields such as decoration and industrial use. Plating is mainly performed using a chromium plating bath containing a large amount of hexavalent chromium as a chromium component.

  However, when using a plating bath containing hexavalent chromium, the harmfulness of the mist containing hexavalent chromium generated during plating is a problem, considering the improvement of the working environment and the efficiency of wastewater treatment. Therefore, a trivalent plating bath using a trivalent chromium compound with less toxicity has been widespread (see Non-Patent Document 1 below).

  However, the chromium plating film obtained from a trivalent chromium plating bath (trivalent chromium plating film) has a corrosion resistance when compared with a chromium plating film obtained from a conventional plating bath containing hexavalent chromium (hexavalent chromium plating film). Is generally known to be slightly inferior (see Patent Document 1 below). In addition, since the trivalent chromium plating bath itself does not function to form a chromate film, there is a problem in that the corrosion resistance of a portion where the chromium plating does not precipitate such as the inside of the pipe is inferior to that of the hexavalent chromium plating (see below). Non-patent document 1).

For this reason, at present, for the purpose of improving the corrosion resistance of the trivalent chromium plating film, it is immersed in a chromic acid (CrO ₃ ) aqueous solution, which is a hexavalent chromium salt having a function of forming a chromate film, and dichromic acid ( K ₂ Cr ₂ O ₇ ) Cathodic electrolytic treatment (electrolytic chromate) in aqueous solution is often performed.

  However, when these treatment methods are employed, even when a plating film is formed using a plating solution containing trivalent chromium, in order to use a treatment solution containing hexavalent chromium in the post-treatment step, Work environment problems cannot be resolved.

  Further, although the hexavalent chromium plating film is excellent in corrosion resistance as compared with the trivalent chromium plating film, it may be required to further improve the corrosion resistance.

  For this reason, the novel processing method which can improve corrosion resistance not only about a trivalent chromium plating film but about a hexavalent chromium plating film is desired.

JP 2002-285375 A

Surface technology Vol.56, No.6, 2005 302p "Development of chromium plating and environmental problems"

  The present invention has been made in view of the above-mentioned problems of the prior art, and its main purpose is to greatly improve the corrosion resistance not only for trivalent chromium plating films but also for hexavalent chromium plating films. It is possible to provide a novel anti-rust treatment liquid and treatment method that does not contain a hexavalent chromium compound and that is less harmful to the environment.

  As a result of intensive studies to achieve the above object, the present inventor immerses an article having a chromium plating film in the aqueous solution when an aqueous solution containing chromium (III) phosphate is used as the treatment liquid. It has been found that the corrosion resistance of the chromium plating film can be greatly improved by a simple method. Furthermore, the present inventor performs electrolytic treatment in an aqueous solution containing a water-soluble trivalent chromium compound before or after the treatment in addition to the immersion treatment with the aqueous solution containing chromium phosphate. It has been found that the corrosion resistance of the chromium plating film can be further improved. The present invention has been completed as a result of repeated studies based on these findings.

That is, the present invention provides the following rust-preventing immersion treatment liquid and rust-proofing method for a chromium plating film.
1. An immersion treatment solution for rust prevention of a chromium plating film, comprising an aqueous solution containing chromium phosphate.
2. The immersion treatment solution for rust prevention of a chromium plating film according to claim 1, which is an aqueous solution of pH 1 to 3 containing chromium phosphate in a trivalent chromium ion concentration of 1 to 50 g / l.
3. Furthermore, the immersion treatment liquid for rust prevention of the chromium plating film | membrane of the said claim | item 1 or 2 characterized by including the compound which has pH buffer ability.
4). Item 4. The immersion treatment solution for rust prevention of a chromium plating film according to Item 3, wherein the compound having a pH buffering capacity is a water-soluble aliphatic carboxylic acid.
5). Furthermore, it is a transition metal element having a plurality of valences, and contains a compound containing a transition metal element in a high valence state. Treatment liquid.
6). 6. An antirust treatment method for a chromium plating film, comprising immersing an article having a chromium plating film in the antirust corrosion treatment solution for a chromium plating film according to any one of items 1 to 5.
7). Chromium plating characterized by cathodic electrolysis of an article having a chromium plating film in an electrolytic solution comprising an aqueous solution containing a water-soluble trivalent chromium compound before or after the immersion treatment according to the method of item 6 above Rust prevention treatment method for film.
8). Item 8. The rust prevention treatment method according to Item 7, wherein the electrolytic solution is an aqueous solution having a pH of 2 to 8 and containing 5 to 50 g / L of a water-soluble trivalent chromium compound as a trivalent chromium ion concentration.
9. Item 9. The antirust treatment method according to Item 8, wherein the electrolytic solution is an aqueous solution further containing a compound having a pH buffering ability.

  Hereinafter, the immersion treatment liquid for rust prevention and the rust prevention treatment method of the chromium plating film of the present invention will be specifically described.

Rust-proof immersion treatment solution The chromium plating rust-proof immersion treatment solution of the present invention is an aqueous solution containing chromium (III) phosphate as an active ingredient.

  In the rust-proofing immersion liquid of the present invention, the concentration of chromium phosphate is preferably about 1 to 50 g / L, more preferably about 2 to 30 g / L, as the concentration of trivalent chromium ions. . When the chromium phosphate ion concentration is too low, the corrosion resistance of the chromium plating film cannot be sufficiently improved even when the immersion treatment is performed under the conditions described later. In addition, by increasing the chromium phosphate ion concentration, it becomes possible to impart good corrosion resistance by immersion treatment. However, if the concentration is too high, the surface of the chromium plating film is discolored yellow and the appearance is impaired. May be.

  The immersion treatment liquid for rust prevention of the present invention preferably has a pH in the range of about 1 to 3, more preferably in the range of 1 to 1.5. When the pH is within this range, good corrosion resistance can be imparted without impairing the appearance of the plating film by performing immersion treatment under the conditions described later. On the other hand, if the pH is too low, a chromium plating film, particularly a trivalent chromium plating film may be dissolved in the treatment liquid, which is not preferable. On the other hand, if the pH is too high, precipitation of chromium phosphate occurs in the treatment solution, which is also not preferable.

  If necessary, a compound having a pH buffering ability in the above pH range may be added to the rust prevention immersion treatment liquid of the present invention. Examples of the compound having pH buffering ability include water-soluble aliphatic carboxylic acids, boric acid, borax, phosphoric acid, potassium dihydrogen phosphate, glycine, tartaric acid, phthalic acid and the like. In particular, the water-soluble aliphatic carboxylic acids can act as a pH buffering agent and at the same time act as a complexing agent for trivalent chromium ions to suppress the formation of hydroxide that occurs during pH adjustment. Examples of such aliphatic carboxylic acids include aliphatic monocarboxylic acids such as formic acid and acetic acid; aliphatic dicarboxylic acids such as oxalic acid, malonic acid and succinic acid; aliphatic hydroxymonocarboxylic acids such as gluconic acid; malic acid Examples thereof include aliphatic hydroxydicarboxylic acids such as carboxylic acids; carboxylic acids such as aliphatic hydroxytricarboxylic acids such as citric acid; and water-soluble salts of these carboxylic acids such as sodium salts and potassium salts. These compounds having pH buffering ability can be used singly or in combination of two or more.

  The amount of the compound having a pH buffering ability is not particularly limited, but can be usually about 10 to 100 g / L, and preferably about 20 to 50 g / L.

  In the rust prevention immersion treatment liquid of the present invention, if necessary, a compound containing a transition metal element having a plurality of valences and having a high valence (hereinafter referred to as “expensive number”). Transition metal compounds ”). By adding an expensive transition metal compound, it is possible to further improve the rust prevention effect of the rust prevention immersion treatment liquid of the present invention. Moreover, since favorable corrosion resistance can be provided even when the chromium phosphate ion concentration is relatively low, it is advantageous in terms of cost.

The metal element contained in the expensive transition metal compound is not particularly limited. For example, Ce (IV), Sm (III), V (V), Fe (III), Co (III), Mn (VII ) And the like. The expensive transition metal compound containing these metal elements may be a water-soluble compound. For example, nitrates, sulfates, hydrochlorides, ammonium salts, oxo acid salts, and the like can be used. The addition amount is not particularly limited, but in order to exert a sufficient addition effect, for example, the amount of the expensive transition metal element is 0.0005 to 0 with respect to 1 mol of trivalent chromium contained in the treatment liquid. About 1 mol is preferable, and about 0.001 to 0.05 mol is more preferable. By adding such a small amount of an expensive transition metal compound, the formation of a rust-preventing film mainly composed of phosphoric acid is promoted, and the thickness of the rust-preventing film increases, thereby improving the rust-preventing performance it is conceivable that. If the addition amount is less than this range, the improvement of the rust prevention effect by adding an expensive transition metal compound is not sufficiently observed, and even if the addition amount exceeds this range, the rust prevention effect may be further improved. There is no cost disadvantage.

Rust prevention treatment method In the rust prevention treatment method of the present invention, the object to be treated is an article having a chromium plating film. The type of the chromium plating film is not particularly limited, and is formed from a chromium plating film formed from a chromium plating bath containing hexavalent chromium (hexavalent chromium plating film) or a chromium plating bath containing trivalent chromium. Any of chromium plating films (trivalent chromium plating films) may be used. In particular, when using the treatment liquid of the present invention for the rust prevention treatment for a trivalent chromium plating film formed from a chromium plating bath containing trivalent chromium, without using any treatment liquid containing hexavalent chromium, A hexavalent chromium-free process makes it possible to obtain a chromium-plated product with excellent corrosion resistance, which is extremely advantageous in terms of working environment, wastewater treatment, and the like.

  The trivalent chromium plating solution used for forming the chromium plating film on the article to be treated may be a chromium plating bath containing a trivalent chromium compound as a chromium component, and the specific composition is not particularly limited. An example of a trivalent chromium plating bath includes an aqueous trivalent chromium compound such as chromium sulfate, basic chromium sulfate, chromium chloride, and chromium acetate as a chromium component, and sodium sulfate, potassium sulfate, and ammonium sulfate as conductive salts. , Sodium chloride, potassium chloride, ammonium chloride, etc., as complexing agents, monocarboxylic acids such as formic acid and acetic acid or salts thereof, dicarboxylic acids such as oxalic acid, malonic acid, maleic acid, citric acid, malic acid, glycol Examples thereof include a plating bath containing a hydroxycarboxylic acid such as an acid or a salt thereof, an inorganic compound such as urea, thiocyanate, and cyanic acid. Further, boric acid, sodium borate, aluminum chloride or the like may be included as a pH buffer. The concentration of each of these components is not particularly limited, but for example, about 10 to 100 g / L for trivalent chromium compounds, about 30 to 300 g / L for conductive salts, and about complexing agents. About 5 to 50 g / L, and a pH buffering agent, a trivalent chromium plating bath of about 10 to 100 g / L can be exemplified. The conditions for forming the chromium plating film are not particularly limited, and the plating conditions may be determined according to the trivalent chromium plating solution used.

  The hexavalent chromium plating bath may be a chromium plating bath containing a hexavalent chromium compound as a chromium component, and the specific composition is not particularly limited. As an example of a hexavalent chromium plating bath, a chromic acid-sulfuric acid bath containing about 100 g / L to 500 g / L of chromic anhydride and sulfuric acid having a concentration of about 1/100 of chromic anhydride; An ammonium fluoride bath containing about 250 to 400 g / L of acid, about 1.5 to 4 g / L of chromium sulfate, and about 1 to 4 g / L of ammonium fluoride; about 250 to 400 g / L of chromic anhydride, 0.5 to 1.5 g / liter of sulfuric acid A silicofluorination bath containing about L and about 2-10 g / L of silicofluoric acid; a borofluorination bath containing about 250 g / L of sodium dichromate, about 150 g / L of anhydrous chromic acid, and about 9 g / L of borofluoride Can be mentioned. The conditions for forming the hexavalent chromium plating film are not particularly limited, and the plating conditions may be appropriately determined in accordance with the hexavalent chromium plating solution to be used within the range of known plating conditions.

  In the rust prevention treatment method of the present invention, an article having a chromium plating film formed from the above-described trivalent chromium plating solution or hexavalent chromium plating solution is used as an object to be treated, and the aforementioned rust prevention immersion treatment solution of the present invention described above. What is necessary is just to immerse a to-be-processed object in it. Thereby, the corrosion resistance of the chromium plating film of a to-be-processed object can be improved significantly.

  The immersion treatment temperature is not particularly limited. However, when the bath temperature is high, precipitation and gelation of chromium phosphate occur in the treatment solution, and therefore, the temperature is preferably in the range of about 20 ° C to 50 ° C.

  Regarding the immersion treatment time, when the treatment time is extremely short, sufficient improvement in corrosion resistance is not recognized. In addition, when the treatment time is longer than necessary, a yellow film is formed on the surface of the chromium plating film, which may be unfavorable. For this reason, the immersion time is usually about 10 seconds to 5 minutes, preferably about 30 seconds to 2 minutes.

Electrolytic treatment Further, in the present invention, in addition to the above immersion treatment, as a pretreatment or posttreatment of the immersion treatment, an electrolytic treatment using an article having a chromium plating film as an anode in an aqueous solution containing a water-soluble trivalent chromium compound. By carrying out, the corrosion resistance of the chromium plating film can be further improved. Hereinafter, the content of the electrolytic treatment will be specifically described.

(1) Electrolytic treatment liquid An aqueous solution containing a water-soluble trivalent chromium compound is used as the electrolytic treatment liquid. As the water-soluble trivalent chromium compound, any aqueous solution compound containing trivalent chromium as a chromium component can be used without particular limitation. Examples of such aqueous trivalent chromium compounds include chromium sulfate, basic chromium sulfate, chromium nitrate, chromium acetate, chromium chloride, and chromium phosphate. These water-soluble trivalent chromium compounds can be used singly or in combination of two or more.

  In the electrolytic treatment solution used in the present invention, when the trivalent chromium ion concentration is too low, the corrosion resistance of the chromium plating film cannot be sufficiently improved. In addition, by increasing the trivalent chromium ion concentration, it is possible to impart good corrosion resistance by electrolytic treatment. However, if the concentration is too high, the surface of the chromium plating film is discolored yellow and the appearance is impaired. May be. Therefore, from such a viewpoint, the concentration of the water-soluble trivalent chromium compound is preferably about 5 to 50 g / L, more preferably about 10 to 30 g / L as the concentration of the trivalent chromium ions. .

  The pH of the electrolytic treatment liquid is preferably in the range of about 2-8. When the pH is within this range, the corrosion resistance can be greatly improved without deteriorating the appearance of the plating film by performing cathodic electrolysis under the conditions described later. On the other hand, if the pH is too low, the chromium plating film may be dissolved in the treatment liquid, which is not preferable. On the other hand, if the pH is too high, green chromium oxide may adhere to the surface of the object to be treated by cathodic electrolysis, which is also not preferable.

  If necessary, a pH variation of the electrolytic treatment solution can be suppressed by adding a compound having a pH buffering ability in a predetermined pH range to the electrolytic treatment solution. Examples of the compound having such pH buffering ability include water-soluble aliphatic carboxylic acid, boric acid, borax, phosphoric acid, potassium dihydrogen phosphate, glycine, tartaric acid, phthalic acid and the like. In particular, the water-soluble aliphatic carboxylic acids can act as a pH buffering agent and simultaneously act as a complexing agent for trivalent chromium ions to suppress the formation of hydroxide during pH adjustment. Examples of such aliphatic carboxylic acids include aliphatic monocarboxylic acids such as formic acid and acetic acid; aliphatic dicarboxylic acids such as oxalic acid, malonic acid and succinic acid; aliphatic hydroxymonocarboxylic acids such as gluconic acid; malic acid Examples thereof include aliphatic hydroxydicarboxylic acids such as carboxylic acids; carboxylic acids such as aliphatic hydroxytricarboxylic acids such as citric acid; and water-soluble salts of these carboxylic acids such as sodium salts and potassium salts. These aqueous aliphatic carboxylic acids can be used singly or in combination of two or more.

  The addition amount of the compound having pH buffering ability is not particularly limited, but can be usually about 5 to 200 g / L, and preferably about 10 to 100 g / L.

  In addition, since the electrolytic treatment solution performs cathodic electrolysis in a weakly acidic region (pH is in the range of 2.0 to 8.0), conductive salts such as sodium sulfate, potassium sulfate, and chloride are used to suppress an increase in bath voltage. Potassium, sodium chloride, ammonium sulfate and the like may be added. The amount of these conductive salts added is not particularly limited, but is usually preferably about 5 to 100 g / L, and more preferably about 10 to 50 g / L.

(2) Electrolytic treatment method The electrolytic treatment using the above-described electrolytic treatment liquid can be performed before or after the immersion treatment in the rust prevention immersion treatment liquid. In particular, it is preferable to perform an electrolytic treatment after the immersion treatment. Normally, a water washing treatment is performed between the immersion treatment and the electrolytic treatment.

  As an electrolytic treatment method, an article having a chromium plating film may be immersed in an electrolytic treatment solution, and the electrolytic treatment may be performed using the article as a cathode. Thereby, the corrosion resistance of the chromium plating film of a to-be-processed object can be improved significantly.

There are no particular limitations on the electrolysis conditions, but it is desirable to apply a current density or potential at which metal chromium does not precipitate from the electrolytic treatment solution. Even in the current density range in which metallic chromium does not precipitate, if the current density is too high, a yellow film may be formed on the surface of the object to be processed and the appearance may be impaired. Therefore, the cathode current density is preferably in a 0.1~5A / dm ² about, and more preferably a 0.3~2A / dm ² about.

  Although there is no particular limitation on the electrolytic treatment temperature, for example, a temperature range of about 20 ° C to 60 ° C may be used.

  Regarding the electrolytic treatment time, when the treatment time is extremely short, sufficient improvement in corrosion resistance is not recognized. In addition, when the treatment time is longer than necessary, a yellow film is formed on the surface of the chromium plating film, which may be unfavorable. For this reason, the electrolytic treatment time is usually about 10 seconds to 10 minutes, preferably about 30 seconds to 2 minutes.

  The anode used for the electrolytic treatment is not particularly limited. However, when stainless steel or the like is used, elution of metal components (Fe, Ni, Cr, etc.) may occur in the electrolytic treatment solution due to long-term electrolytic treatment. Since the eluted various metal components (especially Fe, Ni) are noble metals than chromium, there is a concern about deposition on the surface of the trivalent chromium plating film on the cathode side during the electrolytic treatment. For this reason, it is desirable to use an insoluble anode as the anode. For example, insoluble electrodes such as carbon, Ti—Pt, and DSA electrodes (Ru oxide type, Ir oxide type) are preferably used.

  In addition, there exists a tendency for pH of a process liquid to fall by performing a cathodic electrolysis process. For this reason, when performing electrolytic treatment continuously, it is necessary to control the pH so that the pH of the electrolytic treatment solution is in the range of 2-8. In this case, an alkaline aqueous solution such as NaOH can be used to adjust the pH, but when adding the alkaline aqueous solution, it is necessary to gradually add it so as to suppress the formation of chromium hydroxide.

  The immersion treatment liquid for rust prevention of the present invention is a treatment liquid that does not contain a hexavalent chromium compound, and does not impair the appearance of chromium plating films such as a trivalent chromium plating film and a hexavalent chromium plating film. Good corrosion resistance can be imparted.

  In particular, the chromium plating film formed from the trivalent chromium plating solution is subjected to a rust prevention treatment using the treatment solution of the present invention, so that chromium having excellent appearance and corrosion resistance is obtained by a hexavalent chromium-free plating process. A plating film can be formed.

  Moreover, the corrosion resistance of the chromium plating film can be further improved by performing an electrolytic treatment in an aqueous solution containing a water-soluble trivalent chromium compound as a pretreatment or a posttreatment of the immersion treatment.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Examples 1-4
Using a commercially available trivalent chromium plating solution (trade name: Top Fine Chrome, manufactured by Okuno Pharmaceutical Co., Ltd.) on a brass plate on which a bright nickel plating film with a film thickness of 5 μm is formed, the liquid temperature is 45 ° C., and the current density is 8 A. A trivalent chromium plating film having a film thickness of about 0.1 μm was formed under the conditions of / dm ² .

  Using the sample on which the trivalent chromium plating film was formed by the above-described method as a test piece, using the rust-preventing immersion liquids of Examples 1 to 4 having the compositions described in Table 1 below, under the conditions described in Table 1 Immersion treatment was performed. In addition, each immersion treatment liquid described in the table was prepared by dissolving a 2 mol / L chromium phosphate aqueous solution manufactured by Nippon Chemical Industry Co., Ltd. in water.

  Each test piece after the immersion treatment was subjected to a corrosion resistance test by a salt spray test method according to JIS 2371, and the corrosion resistance was evaluated by the time until the occurrence of white rust.

  Moreover, the external appearance of the chromium plating film after immersion treatment was evaluated visually. A test piece that is not changed from the plated state is indicated by ◯, a test piece that has turned slightly yellow after the immersion treatment is indicated by Δ, and a test piece that has turned brown after the immersion treatment is indicated by ×.

  The above results are shown in Table 1 below. In the table, as Comparative Example 1, the result of the test piece not subjected to the immersion treatment with the treatment liquid of the present invention is also described.

  As is clear from the above results, when immersion treatment was performed using the rust prevention immersion treatment liquids of Examples 1 to 4, the time until white rust was generated by the salt spray test method was 120 hours or more. It became. On the other hand, when the immersion treatment was not performed, white rust was generated in the trivalent chromium plating film about 72 hours after the start of the salt spray test, and the immersion treatment was performed using the treatment liquid of the present invention. It was confirmed that the corrosion resistance of the trivalent chromium plating film can be greatly improved.

  Further, in Examples 3 and 4 in which the chromium concentration in the treatment liquid was high and the immersion treatment time was extended, the time until the occurrence of white rust was 216 hours, and it was confirmed that the corrosion resistance could be further greatly extended.

  In Examples 1 to 4, the film appearance after the immersion treatment was good.

  Therefore, it is clear that the corrosion resistance can be greatly improved without deteriorating the appearance of the trivalent chromium plating film by performing the immersion treatment using the rust prevention immersion liquid for the chromium plating film of the present invention.

Example 5
Using a hexavalent chromium plating bath containing 250 g / L of chromic acid and 2.5 g / L of 98% sulfuric acid on a brass plate with a bright nickel plating film with a thickness of 5 μm, bath temperature: 40 ° C, current density: 15A / A hexavalent chromium plating film having a film thickness of about 0.2 μm was formed under the conditions of dm ² and film formation time: 3 minutes.

  A chromium phosphate (2M) aqueous solution for a sample in which a hexavalent chromium plating film was formed by the above-described method and a sample in which a trivalent chromium plating film having a film thickness of about 0.1 μm was formed under the same conditions as in Examples 1 to 4. Rust prevention treatment was performed by immersion for 2 minutes at 25 ° C. in an immersion treatment solution of pH 1.3 containing 150 g / L (trivalent chromium ion concentration 10 g / L) and 89% phosphoric acid 20 ml / L.

The salt damage resistance test was performed by the following method about each sample after the above-mentioned rust prevention treatment and the sample which was not subjected to the rust prevention treatment. The results are shown in Table 2 below.
(experimental method)
(1) Mix 50 ml of saturated calcium chloride solution with 30 g of kaolin.
(2) The mixture obtained in (1) above is uniformly applied to each sample.
(3) Put in a 60 ° C thermostat and hold.
(4) After 24 hours, wash with water and measure the rust generation area.

  As is apparent from the above results, the corrosion resistance of both the trivalent chromium plating film and the hexavalent chromium plating film can be greatly improved by performing the immersion treatment using the rust prevention immersion treatment liquid of the present invention. it is obvious.

Examples 6-11
Using a sample in which a trivalent chromium plating film was formed by the same method as in Examples 1 to 4 as a test piece, each rust-preventing immersion liquid of Examples 6 to 11 having the composition described in Table 3 below was used. The immersion treatment was performed under the conditions described in 3. In addition, each immersion treatment liquid described in the table was prepared by dissolving a 2 mol / L chromium phosphate aqueous solution manufactured by Nippon Chemical Industry Co., Ltd. in water.

About each test piece after immersion treatment, it carried out similarly to Examples 1-4, the corrosion resistance test by the salt spray test method and the external appearance evaluation of the chromium plating film were performed, and salt damage resistance was evaluated similarly to Example 5. . The results are shown in Table 3 below.

  As is apparent from the above results, when the immersion treatment is performed using the rust prevention immersion treatment liquids of Examples 6 to 11 including the expensive transition metal compound, white rust is not generated by the salt spray test method. The time was longer than 250 hours, and an improvement in rust prevention performance was observed. In addition, as a result of performing XPS measurement for each of these samples, it was confirmed that the thickness of the rust-preventing film containing phosphoric acid as a main component was increased as compared with the samples obtained in Examples 1 to 4. .

  Moreover, according to the treatment liquid to which the expensive transition metal compound was added, good salt damage resistance could be confirmed. Particularly, in Examples 9 to 10 using the treatment liquid in which the addition amount of the expensive transition metal compound was increased, it was confirmed that the salt damage resistance was greatly improved.

Examples 12-15
Using the sample in which the trivalent chromium plating film was formed by the same method as in Examples 1 to 4 as a test piece, each of the immersion treatment solutions for rust prevention of Examples 12 to 15 described in the column of immersion treatment in Table 4 below was used. After performing the immersion treatment under the conditions described in Table 4, the substrate was washed with water, and subsequently, the immersion treatment was performed under the conditions described in Table 4 using the electrolytic treatment liquid described in the column of the electrolytic treatment in Table 4. In addition, each immersion treatment liquid described in the table was prepared by dissolving a 2 mol / L chromium phosphate aqueous solution manufactured by Nippon Chemical Industry Co., Ltd. in water.

  Each test piece subjected to the above immersion treatment and electrolytic treatment is subjected to the corrosion resistance test by the salt spray test method (JIS Z2371) and the corrosion resistance test by the CASS test method (JIS H8502). evaluated. The results are shown in Table 4 below.

  As is clear from the above results, according to the method of performing the electrolytic treatment after the immersion treatment, the time until the occurrence of white rust by the salt spray test is longer than 230 hours, and only the immersion treatment was performed. Compared with the samples obtained in Examples 1 to 4, further improvement in rust prevention performance was observed.

Claims (9)

An immersion treatment solution for rust prevention of a chromium plating film, comprising an aqueous solution containing chromium phosphate. The immersion treatment solution for rust prevention of a chromium plating film according to claim 1, which is an aqueous solution of pH 1 to 3 containing chromium phosphate in a trivalent chromium ion concentration of 1 to 50 g / l. Furthermore, the compound which has pH buffer ability contains the immersion treatment liquid for rust prevention of the chromium plating film of Claim 1 or 2 characterized by the above-mentioned. The immersion treatment solution for rust prevention of a chromium plating film according to claim 3, wherein the compound having a pH buffering capacity is a water-soluble aliphatic carboxylic acid. Furthermore, it is a transition metal element having a plurality of valences, and contains a compound containing a transition metal element in a high valence state. Treatment liquid. A method for rust-proofing a chromium plating film, comprising immersing an article having a chromium plating film in the rust-proof immersion treatment liquid for a chromium plating film according to any one of claims 1 to 5. Chromium plating characterized by cathodic electrolysis of an article having a chromium plating film in an electrolytic solution comprising an aqueous solution containing a water-soluble trivalent chromium compound before or after the immersion treatment by the method according to claim 6. Rust prevention treatment method for film. The rust preventive treatment method according to claim 7, wherein the electrolytic solution is an aqueous solution having a pH of 2 to 8 containing 5 to 50 g / L of a water-soluble trivalent chromium compound as a trivalent chromium ion concentration. The rust prevention method according to claim 8, wherein the electrolytic solution is an aqueous solution further containing a compound having a pH buffering ability.