JPWO2012137677A1 - Composition for chemical conversion treatment and method for producing member comprising chemical conversion film formed by the composition - Google Patents

Abstract

As a chemical conversion treatment liquid capable of forming a chemical conversion film having excellent corrosion resistance and appearance and suppressing the elution amount of hexavalent chromium, 0.05 mol / L or more of a water-soluble trivalent chromium-containing substance in terms of chromium with respect to the entire composition; A water-soluble acidic composition comprising one or more water-soluble hydroxycarboxylic acid substances selected from the group consisting of hydroxycarboxylic acids and their ions, salts and coordination compounds, There is provided a chemical conversion treatment liquid in which the ratio of the molar concentration of hydroxycarboxylic acid in terms of hydroxycarboxylic acid to the molar concentration of chromium in water-soluble trivalent chromium-containing material is 0.4 or more and less than 2.5.

Description

  The present invention relates to a composition for chemical conversion treatment capable of forming a chemical conversion film in which elution of hexavalent chromium harmful to the natural environment is suppressed, and to a member having a chemical conversion film formed by the treatment. The present invention relates to a composition for chemical conversion treatment, a liquid composition for preparing the composition, and a method for producing a member having a chemical conversion film formed from the composition.

  In recent years, environmental regulations such as RoHS (Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment) Directive and ELV (End of Life Vehicles) Directive have been introduced. It has been required to regulate the use of substances (lead, mercury, cadmium, hexavalent chromium, etc.).

  In response to this trend, a chromate coating effective as a chemical conversion coating for corrosion protection of a member having a metal surface such as a galvanized member is a composition for chemical conversion treatment using a chromate containing hexavalent chromium (hereinafter, chemical conversion treatment). The composition for the above is not called “chemical conversion treatment liquid”), but is formed by chemical conversion treatment liquid containing trivalent chromium. A chemical conversion film obtained by a conventional chemical conversion treatment solution containing hexavalent chromium contains soluble hexavalent chromium in the film. For this reason, such a film is subject to regulation by the above-mentioned directive.

Thus, although chromate by chemical conversion treatment liquid containing trivalent chromium has become common, it has become clear that a very small amount of hexavalent chromium is detected from the chemical conversion film obtained by this chemical conversion treatment solution. I came. Although the amount of elution from the film depends on the measurement method, it is generally 0.1 μg / cm ² or less, which is far greater than the amount of elution from the chemical film obtained with the chemical conversion treatment solution containing hexavalent chromium. small.

  However, since the movement to reduce the environmental load is expected to become more severe in the future, it elutes from the chemical conversion film (hereinafter simply referred to as “chemical conversion film”) obtained by the chemical conversion treatment liquid containing trivalent chromium 6. Means for reducing the concentration of valent chromium have been studied.

  In Patent Document 1, a metal part on which a chemical conversion film is formed is immersed in a reduction treatment solution of a predetermined concentration in a reduction treatment process of hexavalent chromium for a predetermined set time, and dried to reduce the amount of elution of hexavalent chromium. Is disclosed. The reducing agent preferably used in this means is L-ascorbic acid.

  Patent Document 2 discloses a method of adding a reducing agent that reduces hexavalent chromium to trivalent chromium in the chemical conversion treatment solution. The reducing agent preferably used in this means is sodium bisulfite, and the addition of the reducing agent is performed before and after the addition of the supporting salt.

JP-A-2005-240084 JP 2006-28547 A

  However, the reason why hexavalent chromium is eluted from the chemical conversion film obtained by the chemical conversion treatment solution containing trivalent chromium has not been clarified yet. For this reason, it is unclear whether the addition of a reducing agent as described above is the optimal means for suppressing hexavalent chromium elution.

  Further, the effect of suppressing elution of hexavalent chromium needs to be realized over a long period of time. However, in Patent Document 2, only the amount of elution immediately after the formation of the conversion film is evaluated. The amount of elution after the degree is maintained is only evaluated. Therefore, it is unclear whether the effect of suppressing hexavalent chromium elution is maintained over a long period of time. In this regard, the inventors measured the elution amount of the chemical conversion film after being stored in a high temperature and high humidity environment (80 ° C., 100% RH) as an accelerated test environment for elution of hexavalent chromium. As a result, for substances that have been conventionally recognized as significant substances for suppressing the elution of hexavalent chromium (hereinafter, such substances are collectively referred to as “elution inhibitors”), a short period (about 1 day) It was revealed that hexavalent chromium was rapidly eluted during the period. Moreover, it has been clarified that when such an elution inhibitor according to the prior art is added to the chemical conversion solution, the obtained chemical conversion film is colored yellow or brown.

  Therefore, in the present invention, it is possible to form a new hexavalent chromium elution suppressing means for the chemical conversion film, particularly a chemical conversion film capable of suppressing elution of hexavalent chromium even when stored in a high temperature and high humidity environment. It aims at providing a chemical conversion treatment means.

  The present inventor has studied to solve the above-mentioned problem by an approach different from the prior art. That is, in the conventional technology, a material having a function of suppressing elution of hexavalent chromium (hereinafter referred to as “a conventional chemical conversion solution”) (hereinafter referred to as “a conventional chemical conversion solution”) containing a trivalent chromium existing in the past. An approach that solves the above-mentioned problems has been adopted by attaching an “elution inhibitor”. In the case of such attachment, along with the addition of new components, an increase in the cost of the product and an increase in the management load in the manufacturing process are inevitable. Therefore, the present inventors have solved the above problem with a new approach of suppressing elution of hexavalent chromium by reviewing the type of organic acid compound that is a basic component of the chemical conversion treatment liquid containing trivalent chromium. Aimed.

  As a result of such an approach, in the conventional chemical conversion treatment liquid, a water-soluble dicarboxylic acid compound typified by oxalic acid is generally used as the organic acid compound, but instead of the water-soluble dicarboxylic acid compound, water-soluble dicarboxylic acid compound is used. It has been found that by using a hydroxycarboxylic acid-based substance, elution of hexavalent chromium can be suppressed even when stored in a high-temperature and high-humidity environment. In this specification, the water-soluble hydroxycarboxylic acid-based substance is selected from the group consisting of hydroxycarboxylic acids, hydroxycarboxylic acid ions, hydroxycarboxylic acid salts, and coordination compounds containing hydroxycarboxylic acid and / or hydroxycarboxylic acid ions. It means one or two or more selected substances that are soluble in a chemical conversion treatment solution that is an aqueous composition.

  One aspect of the present invention provided on the basis of the above knowledge is an aqueous acidic composition (chemical conversion solution) comprising a water-soluble trivalent chromium-containing substance and a water-soluble hydroxycarboxylic acid-based substance, and is water-soluble trivalent chromium. The molar molar concentration in terms of chromium with respect to the total composition of the contained substances is 0.05 mol / L or more, and the molar concentration in terms of hydroxycarboxylic acids of the water-soluble hydroxycarboxylic acid-based substance is relative to the molar equivalent of chromium in the water-soluble trivalent chromium-containing substance. It is a composition for chemical conversion treatment characterized by having a ratio of 0.4 or more and less than 2.5.

  The composition is a water-soluble cobalt-containing substance having a concentration of 2 mmol / L or more and 50 mmol / L or less in terms of cobalt and / or pyrogallol having a conversion in the range of 0.05 g / L or less and 3.0 g / L or less in terms of pyrogallol relative to the total composition. A compound may be contained.

  The pH of the composition can be stably used within a wide range of 2.0 or more and 4.0 or less.

  Moreover, the present invention provides, as another aspect, obtaining a member having a chemical conversion film on zinc-based plating by bringing the composition for chemical conversion treatment into contact with the member subjected to zinc-based plating. Provided is a method for producing a member having a characteristic chemical conversion film.

  Furthermore, this invention is another one aspect | mode, It is a water-system acidic composition for manufacturing said composition (chemical conversion liquid), Comprising: A water-soluble trivalent chromium containing material and a water-soluble hydroxycarboxylic acid-type material And the water-soluble trivalent chromium-containing molar concentration of the water-soluble trivalent chromium-containing material is 0.25 mol / L or more, A composition (concentrated liquid for chemical conversion treatment) is also provided in which the ratio of the contained substance to the chromium equivalent molar concentration is 0.4 or more and less than 2.5.

  According to said invention, without mix | blending a special elution inhibitor with a chemical conversion liquid, the hexavalent chromium elution amount from the chemical conversion film excellent in the corrosion resistance and external appearance obtained by the chemical conversion liquid is high temperature, high humidity. Even after exposure to the environment, it can be suppressed to a particularly low level. Moreover, since the chemical conversion liquid which concerns on this invention has a wide pH range which can form a favorable chemical conversion film stably compared with the chemical conversion liquid concerning a prior art, it is excellent in productivity.

1. Composition for chemical conversion treatment A composition for chemical conversion treatment (chemical conversion treatment liquid) according to an embodiment of the present invention is an aqueous acidic composition comprising a water-soluble trivalent chromium-containing substance and a water-soluble hydroxycarboxylic acid-based substance. And the water-soluble trivalent chromium-based molar concentration of the water-soluble trivalent chromium-containing material is 0.05 mol / L or more, and the water-soluble trivalent water-soluble tricarboxylic acid-based molar concentration of the water-soluble hydroxycarboxylic acid-based material. The ratio of the chromium-containing substance to the chromium equivalent molar concentration is 0.4 or more and less than 2.5.

By performing a treatment in which a chemical conversion treatment liquid according to this embodiment is brought into contact with a member having a metal surface (for example, galvanization), a chemical conversion film having excellent corrosion resistance is formed while elution of hexavalent chromium is suppressed. Hereinafter, the member subjected to the chemical conversion treatment is also referred to as a “processed member”. Since the treatment temperature depends on the concentration, pH, etc., it cannot be determined definitely. When temperature is 20 degreeC or more, it is preferable to perform the process made to contact for 10 seconds or more, and when it is 40 degreeC or more, the contact for 5 to 50 seconds is especially preferable. A contact method is not specifically limited, What is necessary is just to immerse a to-be-processed member in the chemical conversion liquid which concerns on this embodiment, or to spray the chemical conversion liquid on a to-be-processed member. When the contact with the chemical conversion treatment is completed, the member is rinsed with water or the like, and further dried to form a chemical conversion film on the metal surface of the member to be processed. That is, the chemical conversion treatment liquid according to the present embodiment is a coating type (a system in which a coating liquid layer formed of components of the processing liquid is formed on a member to be processed and a coating film obtained by drying the coating liquid layer is used as a chemical conversion film). After the contact between the member to be treated and the chemical conversion treatment liquid, the coating liquid layer remaining on the member is removed by rinsing, and the chemical conversion treatment liquid and the member to be treated are in contact with each other while the chemical conversion treatment liquid and the member to be treated are in contact with each other. It is a reaction type chemical conversion treatment liquid in which a chemical conversion film is mainly formed by the deposited components and / or formed components.
Below, the component of the chemical conversion liquid which concerns on this embodiment is demonstrated in detail.

(1) Water-soluble trivalent chromium-containing substance The chemical conversion treatment liquid according to the present embodiment contains at least one water-soluble trivalent chromium-containing substance. The water-soluble trivalent chromium-containing substance is selected from the group consisting of trivalent chromium (Cr ³⁺ ) and a water-soluble substance containing the same. An example of the water-soluble substance containing trivalent chromium is Cr [H ₂ O] ₆ ³⁺ .

  It is possible to produce a water-soluble trivalent chromium-containing substance in water as a material blended to contain the water-soluble trivalent chromium-containing substance in the chemical conversion liquid, that is, as a raw material of the water-soluble trivalent chromium-containing substance. It is preferable to use a water-soluble compound (hereinafter referred to as “water-soluble trivalent chromium compound”).

  Examples of water-soluble trivalent chromium compounds include reduction of hexavalent chromium compounds such as chromic acid and dichromate in addition to trivalent chromium salts such as chromium chloride, chromium sulfate, chromium nitrate, chromium phosphate and chromium acetate. Examples thereof include compounds reduced to trivalent by an agent. The water-soluble trivalent chromium compound may be composed of only one kind of compound, or may be composed of a plurality of kinds. In addition, since the hexavalent chromium compound is not positively added as a raw material with respect to the chemical conversion liquid which concerns on this embodiment, the chemical conversion liquid which concerns on this embodiment does not contain hexavalent chromium substantially.

  The content of the water-soluble trivalent chromium compound is 0.05 mol / L or more and preferably 0.07 mol / L or more in terms of chromium from the viewpoint of ease of formation of the chemical conversion film. In addition, content of this water-soluble trivalent chromium compound means content of the component melt | dissolved in the chemical conversion liquid among water-soluble trivalent chromium compounds. The upper limit of the content of the water-soluble trivalent chromium compound is not particularly limited. However, if excessively contained, there is a possibility of causing a problem from the viewpoint of economy or waste liquid treatment, so the upper limit is about 0.5 mol / L. It is preferable to do. From the viewpoint of stably suppressing the hexavalent chromium elution amount, it is more preferably 0.25 mol / L or less.

(2) Water-soluble hydroxycarboxylic acid-based material The chemical conversion treatment liquid according to this embodiment contains a water-soluble hydroxycarboxylic acid-based material. Here, the “water-soluble hydroxycarboxylic acid-based substance” means a hydroxycarboxylic acid, a hydroxycarboxylic acid ion, a hydroxycarboxylic acid salt, and a hydroxycarboxylic acid and / or hydroxycarboxylic acid having at least one hydroxyl group in the molecule. It means one or two or more substances selected from the group consisting of coordination compounds containing carboxylic acid ions, which are compounds that are soluble in a chemical conversion treatment solution that is an aqueous composition. Therefore, it is not necessary for all of them to be dissolved in the chemical conversion solution, and a part of them may be dispersed or precipitated in the chemical conversion solution.

  The chemical conversion film obtained from the chemical conversion treatment liquid according to the present embodiment contains a water-soluble dicarboxylic acid compound (in this embodiment, “dicarboxylic acid” is a carboxylic acid) because the chemical conversion treatment liquid contains a water-soluble hydroxycarboxylic compound. An organic compound having two groups and having no hydroxyl group, and “dicarboxylic acid compound” means dicarboxylic acid, dicarboxylic acid ion, dicarboxylic acid salt and dicarboxylic acid and / or dicarboxylic acid ion based on this definition. As compared with a chemical conversion film obtained from a conventional chemical conversion treatment liquid generally containing as a basic component one or two or more water-soluble substances selected from the group consisting of coordination compounds containing The elution amount of hexavalent chromium when placed in a hot and humid environment is significantly reduced. Further, even when placed in such a high-temperature and high-humidity environment, deterioration of the appearance of the chemical conversion film, specifically, discoloration to yellow or brown hardly occurs. That is, the chemical conversion treatment liquid according to the present embodiment can form a chemical conversion film having particularly excellent temporal stability by using a water-soluble hydroxycarboxylic acid-based substance as a basic component instead of the water-soluble dicarboxylic acid compound. It is.

  Hydroxycarboxylic acids can be broadly classified into aliphatic hydroxycarboxylic acids and aromatic hydroxycarboxylic acids. Examples of aliphatic hydroxycarboxylic acids include glycolic acid, lactic acid, β-hydroxypropionic acid, tartronic acid, glyceric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, malic acid, tartaric acid, citramalic acid, Examples include citric acid, isocitric acid, leucine acid, mevalonic acid, pantoic acid, ricinoleic acid, ricinaleic acid, cerebric acid, quinic acid and shikimic acid. Examples of aromatic hydroxy acids include monohydroxybenzoic acid derivatives such as salicylic acid, creosote acid, vanillic acid, and syringic acid; dihydroxybenzoic acid derivatives such as pyrocatechuic acid, resorcylic acid, protocatechuic acid, gentisic acid, and orthoric acid; gallic acid Trihydroxybenzoic acid derivatives such as acids; phenylacetic acid derivatives such as atrolactic acid, benzylic acid and mandelic acid; cinnamic acids such as melirotoic acid, furoretic acid, coumaric acid, umberic acid, caffeic acid, ferulic acid and sinapinic acid And acid derivatives.

  The hydroxycarboxylic acid according to the present embodiment is preferably an aliphatic hydroxycarboxylic acid from the viewpoint of the solubility in the chemical conversion treatment liquid according to the present embodiment, which is an aqueous composition, and the difficulty of generating by-products. The number is preferably small. Further, the ratio of the number of carboxylic acid groups (including the case of ionization) in the molecule to the number of hydroxyl groups (number of carboxylic acid groups / number of hydroxyl groups) is preferably close to 1, and this ratio is 1, that is, It is particularly preferable that the number of carboxylic acid groups is equal to the number of hydroxyl groups. From these viewpoints, particularly preferable compounds as the hydroxycarboxylic acid according to the present embodiment are aliphatic monohydroxymonocarboxylic acids having 4 or less carbon atoms such as glycolic acid, hydroxypropionic acid, and hydroxybutyric acid.

  In addition, the kind of metal ion which comprises a hydroxycarboxylate is not specifically limited. Further, the specific structure of the coordination compound of hydroxycarboxylic acid is not particularly limited. Any substance may be dissolved in the chemical conversion liquid which is an aqueous composition.

  The molar concentration in terms of hydroxycarboxylic acid of the water-soluble hydroxycarboxylic acid-based material according to the present embodiment is 0 as a ratio (hereinafter also referred to as “HC / Cr ratio”) to the molar concentration in terms of chromium of the water-soluble trivalent chromium-containing material. 4 to less than 2.5. The molar concentration of water-soluble hydroxycarboxylic acid-based substance in terms of hydroxycarboxylic acid is the hydroxycarboxylic acid equivalent of the component dissolved in the chemical conversion treatment liquid among the water-soluble hydroxycarboxylic acid-type substances present in the chemical conversion treatment liquid. Mean molar concentration. When the HC / Cr ratio is excessively small, the deterioration of the appearance and the deterioration of the corrosion resistance become remarkable. On the other hand, when the HC / Cr ratio is excessively large, there is a high possibility that the liquid stability is lowered, a by-product is easily generated, and a defect such as a poor appearance occurs. From the viewpoint of stably achieving the corrosion resistance and liquid stability of the treated product, the HC / Cr ratio is preferably in the range of 0.8 to 2.2.

  The water-soluble hydroxycarboxylic acid-based material according to the present embodiment may be added as hydroxycarboxylic acid, or may be added as a hydroxycarboxylic acid salt or a coordination compound in preparing the chemical conversion treatment liquid. Alternatively, it may be added as a lactone or a derivative such as an ester.

(3) Optional addition component (A) Water-soluble cobalt-containing substance The chemical conversion treatment liquid according to this embodiment may contain a cobalt-containing substance. The water-soluble cobalt-containing material is selected from the group consisting of cobalt ions (Co ²⁺ ) and water-soluble materials containing the same. Examples of water-soluble cobalt-containing substances include Co [H ₂ O] ₆ ²⁺ , coordination compounds of cobalt ions and carboxylic acid compounds, and the like.

  A water-soluble compound capable of producing a water-soluble cobalt-containing substance in water (hereinafter referred to as “a water-soluble cobalt-containing substance”) as a raw material for the water-soluble cobalt-containing substance, It is preferable to use "water-soluble cobalt compound").

  Examples of water-soluble cobalt compounds include cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt phosphate, and cobalt acetate. The water-soluble cobalt compound may be composed of only one kind of compound, or may be composed of a plurality of kinds.

  The content of the water-soluble cobalt-containing substance is preferably 50 mmol / L or less in terms of cobalt. In addition, content of this water-soluble cobalt compound means content of the component melt | dissolved in the chemical conversion liquid among water-soluble cobalt compounds. When the content exceeds 50 mmol / L, the effect of increasing the elution amount of hexavalent chromium may be superior to the effect of improving the corrosion resistance. Moreover, since it may show the tendency for corrosion resistance to fall rather when it contains a water-soluble cobalt containing substance excessively, it shall be 20 mmol / L or less in cobalt conversion from a viewpoint of ensuring the effect which improves corrosion resistance stably. In this range, it is particularly preferable to set the content to a minimum that can achieve the purpose of ensuring the corrosion resistance determined by the application.

  When applied to general purposes, the content of the water-soluble cobalt-containing substance may be in the range of 4 mmol / L or more and 20 mmol / L or less in terms of cobalt, and a salt spray test in accordance with JIS Z2371 is performed for 72 hours. Even after performing, it is achieved that the white rust area ratio in the obtained chemical conversion film is 5% or less of the whole.

(B) Pyrogallol compound The chemical conversion treatment liquid according to the present embodiment may contain a pyrogallol compound in order to further suppress the elution of hexavalent chromium from the chemical conversion film obtained by the chemical conversion treatment liquid. In the present specification, the “pyrogallol compound” means one or more compounds selected from pyrogallol and alkylpyrogallol having 3 or less carbon atoms. Alkyl pyrogallols such as 5-methyl pyrogallol and 5-ethyl pyrogallol also exhibit performance equivalent to that of pyrogallol as long as the carbon number of the alkyl group is 3 or less.

  The concentration of the pyrogallol compound in the chemical conversion treatment liquid is not particularly limited, but is preferably 0.05 g / L or more and 3.0 g / L or less. In addition, the concentration of the pyrogallol compound in the chemical conversion treatment liquid means the content of a component dissolved in the chemical conversion treatment liquid out of the concentration of the pyrogallol compound present in the chemical conversion treatment liquid. When the concentration of the pyrogallol compound is excessively low, the effect of addition cannot be obtained. On the other hand, if it is excessively high, the appearance of the treatment becomes darker than yellow and becomes brownish, and an undissolved component is easily generated in the concentrated liquid described later.

(C) Other components The chemical conversion treatment liquid according to this embodiment is selected from the group consisting of metal ions, inorganic acids and their anions, inorganic colloids, silane coupling agents, organophosphorus compounds, and fluorine compounds in addition to the above substances. One or two or more selected may be included. Also, a kind selected from the group consisting of polymers such as waxes, corrosion inhibitors, surfactants such as diols, triols, amines, plastic dispersions, dye generators such as dyes, pigments and metal dye generators, desiccants and dispersants Or you may contain the 2 or more types of material further.

  Examples of metal ions include Al, Si, Ni, Na, K, Ag, Fe, Ca, Mg, Zr, Sc, Ti, Mn, Cu, Zn, Sn, Mo, V, and W ions. It may be present in the form of oxyacid ions such as ions.

  Inorganic acids include hydrohalic acid such as hydrochloric acid, hydrofluoric acid, hydrobromic acid, chloric acid, perchloric acid, chlorous acid, hypochlorous acid, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, Illustrative are phosphoric acid (orthophosphoric acid), polyphosphoric acid, metaphosphoric acid, pyrophosphoric acid, ultraphosphoric acid, hypophosphorous acid, and superphosphoric acid, especially from hydrohalic acid, sulfuric acid, nitric acid and phosphoric acid (orthophosphoric acid) It is preferable that 1 type, or 2 or more types chosen from the group which consists of is comprised as an anion.

  The concentration of these acids and / or acid ions in the chemical conversion solution is not particularly limited. Generally, the ratio of the total acid equivalent molar concentration to the total molar concentration of trivalent chromium and the above metal ions is 0.1 to 10, and preferably 0.5 to 3.

  Examples of the inorganic colloid include silica sol, alumina sol, titanium sol, and zirconia sol, and examples of the silane coupling agent include vinyltriethoxysilane and γ-methacryloxypropyltrimethoxysilane.

As the organic phosphorus compound, an organic phosphonic acid compound is particularly preferable. In the present specification, the “organic phosphonic acid compound” means a compound composed of one or more selected from the group consisting of organic phosphonic acid, organic phosphonic acid ions, and organic phosphonates. In the formula, R—P (═O) (OH) ₂ (R is an organic group) means an organic group bonded to a phosphonic group. As organic phosphonic acids, 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane 1,2,4-tricarboxylic acid, amino (trimethylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic) Acid). As salts of these organic phosphonic acids, 1-hydroxyethylidene-1,1-diphosphonic acid tetrasodium salt, 1-hydroxyethylidene-1,1-diphosphonic acid trisodium salt, ethylenediaminetetra (methylenephosphonic acid) pentasodium salt, Examples include diethylenetriaminepenta (methylenephosphonic acid) 7 sodium salt. In these salts, sodium ions are often dissociated in the chemical conversion solution.

  In addition, since the chemical conversion treatment liquid according to the present embodiment contains a water-soluble hydroxycarboxylic acid-based substance instead of the water-soluble dicarboxylic acid compound that is generally contained in the conventional chemical conversion treatment liquid as one of the basic components, It is preferable not to contain a water-soluble organic acid compound other than the water-soluble hydroxycarboxylic acid compound. However, a water-soluble organic acid compound other than the water-soluble hydroxycarboxylic acid substance may be contained as long as the elution amount of hexavalent chromium is not significantly increased. However, also in this case, it is preferable not to contain a water-soluble dicarboxylic acid compound. Moreover, it is preferable that the chemical conversion liquid which concerns on this embodiment does not contain organic film-forming components, such as an organic resin material and its precursor (a monomer, an oligomer, etc.) substantially. Here, “substantially” means that a very small amount of the corresponding component is inevitably mixed. It is preferable that the chemical conversion treatment liquid according to the present embodiment does not substantially contain a fluorine-based substance such as a hexafluoro ion of a metal such as titanium or aluminum in consideration of the environment. In addition, since the chemical conversion liquid which concerns on this embodiment forms a chemical conversion film with few amounts of hexavalent chromium to elute, it does not contain a water-soluble hexavalent chromium containing substance substantially.

(4) Solvent, pH
The solvent of the chemical conversion treatment liquid according to the present embodiment contains water as a main component. As a solvent other than water, an organic solvent having high solubility in water, such as alcohol, ether, and ketone, may be mixed. In this case, it is preferable that the ratio shall be 10 volume% or less with respect to all the solvents from a viewpoint of stability of the whole chemical conversion liquid.

  Further, the chemical conversion treatment solution is made acidic from the viewpoint of proceeding with the chemical conversion treatment, and therefore the pH is set to less than 7.

  As described above, since the chemical conversion treatment liquid according to the present embodiment contains a water-soluble hydroxycarboxylic acid-based material instead of the water-soluble dicarboxylic acid compound, compared to the conventional chemical conversion treatment liquid containing the water-soluble dicarboxylic acid compound. Wide pH range that can stably provide a chemical conversion film having excellent appearance and corrosion resistance. Specifically, the practical pH control range in the conventional chemical conversion treatment liquid is less than 1.0, but the chemical conversion treatment liquid according to the present embodiment is from 2 to 4 and specifically 2.0 or more. It is possible to stably provide a chemical conversion film having excellent characteristics over a wide range of 4.0 or less.

  In addition, the composition according to this embodiment is a composition particularly suitable for forming a chemical conversion film on a zinc plating obtained by a chloride bath by adjusting the pH to 2.5 or more and 3.5 or less. By setting the ratio to 3.0 or more and 4.0 or less, the composition is particularly suitable for forming a chemical conversion film on the zinc plating obtained by the zincate bath.

2. Concentrated composition for preparing a chemical conversion liquid A composition having fluidity having a composition in which the main components of the chemical conversion liquid are concentrated about 5 to 20 times (hereinafter referred to as “concentrated liquid for chemical conversion”). ) Is preferable because it saves the trouble of individually preparing the content of each component and facilitates storage. When preparing this concentrated solution for chemical conversion treatment, the upper limit is set for the content in consideration of the solubility of each of the above components.

  Specifically, a water-soluble trivalent chromium-containing material and a water-soluble hydroxycarboxylic acid-based material are provided, and the molar molar concentration in terms of chromium with respect to the total composition of the water-soluble trivalent chromium-containing material is 0.25 mol / L or more. Chemical conversion treatment of a water-based acidic composition in which a ratio of the water-soluble hydroxycarboxylic acid-based substance to the hydroxycarboxylic acid-converted molar concentration of the water-soluble trivalent chromium-containing substance is 0.4 to 2.5 If prepared as a concentrated solution for use, a chemical conversion treatment liquid according to the present embodiment is easily obtained by a preparation step including a step of diluting with a predetermined solvent, usually water, at an appropriate magnification of 5 to 20 times. Is realized.

3. Method for Analyzing Hexavalent Chromium in Chemical Conversion Film The hexavalent chromium concentration per unit surface area of the chemical conversion film obtained from the chemical conversion liquid according to this embodiment is diphenylcarbazide described in EN (European Norm) 15205: 2006. Obtained by the following analysis method based on the colorimetric method.

The test member is cut so that the surface of the chemical conversion film is 50 ± 5 cm ² , and the cut member is put into a beaker. At this time, unlike EN15205: 2006, the member after cutting is not heated in advance and is kept at room temperature. Put 55 mL of water that has been reduced to less than 1 μS / cm by passing through an ion exchange column, distillation, etc. into this beaker, add no zeolite, heat the beaker opening covered with a film, and boil for 10 minutes . After boiling, the beaker is air-cooled to room temperature, and the member is taken out to a constant volume of 50 mL. 1 mL each of 75% orthophosphoric acid and diphenylcarbazide solution is added to the solution after this constant volume. This diphenylcarbazide solution is prepared by dissolving 1.0 g of 1,5-diphenylcarbazide in 70 mL acetone and making up to 100 mL. This diphenylcarbazide solution should be stored in a cool and dark place and used only within 4 weeks after preparation. The liquid after the addition is allowed to stand for 10 minutes, and then the absorbance is measured. On the other hand, a standard solution in which 0.113 g of potassium chromate was dissolved in 1000 mL of water was prepared, and 1 mL of each of the above 75% orthophosphoric acid and diphenylcarbazide solution was added thereto, and allowed to stand for 10 minutes. Measure. The hexavalent chromium concentration of the test solution is calculated based on the absorbance of the standard solution, and the hexavalent chromium concentration per unit area of the test member is obtained from the result.

  Here, the chemical conversion film to be subjected to the above analysis is exposed to a high-temperature and high-humidity environment for a predetermined period, and analysis is performed after the hexavalent chromium is easily eluted from the chemical conversion film. Specifically, the exposure to the high temperature and high humidity environment is stored for 72 hours in a constant temperature bath maintained at 80 ° C. and 90% RH for each member on which the chemical conversion film is formed. Thus, it becomes possible to grasp | ascertain reliably the effect of elution suppression over a long period of time by analyzing the chemical conversion film in the state in which the formation of hexavalent chromium was promoted to some extent. In addition, products containing components with chemical conversion coatings may be placed in high-temperature and high-humidity environments in Southeast Asia and the like, so exposure to such high-temperature and high-humidity environments is not only an accelerated test, It also has a reproduction aspect.

Exposure to a high-temperature and high-humidity environment as the above-described pretreatment for analysis, specifically at 80 ° C., for the member subjected to the chemical conversion treatment with the chemical conversion treatment solution containing the water-soluble hydroxycarboxylic acid compound according to this embodiment. By holding for 72 hours in an environment of 90% RH and then carrying out the above analysis method, it is possible to stably obtain 0.007 μg / cm ² or less as the hexavalent chromium concentration per unit surface area.
Thus, the chemical conversion film obtained from the chemical conversion treatment liquid according to the present embodiment can suppress the elution of hexavalent chromium over a long period even in a harsh environment.

The hexavalent chromium concentration per unit surface area in a chemical conversion film obtained by performing treatment with a conventional chemical conversion treatment solution is typically about 0.025 μg / cm ² or more as a result of performing the above-described pretreatment and analysis method. Therefore, by the chemical conversion treatment using the chemical conversion treatment liquid according to the present embodiment, it is possible to realize an elution amount of 30% or less as compared with a normal chemical conversion coating.

  When other analysis methods such as JIS H8625 or the so-called VOLVO method are used, since the elution process is different, the numerical value obtained as the hexavalent chromium concentration is naturally different. However, regardless of which analysis method is used, if the chemical conversion treatment is performed using the chemical conversion solution according to the present embodiment, it is possible to significantly reduce the hexavalent chromium concentration compared to the case where the chemical conversion treatment is not performed.

4). Member subjected to chemical conversion treatment (member to be treated)
Since the chemical conversion treatment using the chemical conversion treatment liquid according to the present embodiment is for suppressing elution of hexavalent chromium in the chromate film by the chemical conversion treatment liquid containing trivalent chromium, the member subjected to the chemical conversion treatment (processed) The material of the member is not particularly limited as long as it is a member having a metal surface capable of forming this chromate film. A preferable material for the member to be processed is a metal, and particularly a steel plate on which zinc-based plating is applied is particularly preferable. The composition of the zinc-based plating may be pure zinc or, for example, a zinc alloy containing aluminum. The plating method may be electroplating or hot dipping. In the case of electroplating, any of a cyan bath, a chloride bath, a sulfuric acid bath and a zincate bath may be used. In the case of hot dipping, alloying treatment may be performed after plating.

  Here, the chemical conversion treatment liquid according to the present embodiment can stably provide a chemical conversion film having excellent corrosion resistance and appearance regardless of the type of galvanization by electroplating. Specifically, even if the surface of the base material to be subjected to chemical conversion treatment is galvanized formed by either a chloride bath or a zincate bath, it is excellent in corrosion resistance and appearance, and hexavalent chromium elution is suppressed over a long period of time. A chemical conversion film can be formed. It is preferable that the chemical conversion film formed from the chemical conversion liquid which concerns on this embodiment does not contain the metal salt of inorganic oxygen acid containing phosphorus, such as phosphoric acid. That is, it is preferable that the chemical conversion liquid which concerns on this embodiment does not contain the component based on the inorganic type oxygen acid containing phosphorus as a film-forming component.

Hereinafter, although the effect of the present invention is explained based on an example, the present invention is not limited to this.
[Example 1]
(1) Preparation of test member First, chromium nitrate as a water-soluble trivalent chromium compound is 0.76 mol / L in terms of chromium, and cobalt (II) hexahydrate as a water-soluble cobalt compound is 57 g / L. A concentrated liquid for chemical conversion treatment containing 1 g / L of pyrogallol, 100 g / L of sodium nitrate and 1.0 mol / L of the organic acid of the type shown in Table 1 was prepared. A chemical conversion treatment solution containing 100 mL / L of this concentrated solution and having a pH of 3.2 was prepared using nitric acid and sodium hydroxide.

Subsequently, the steel sheet (5 cm × 5 cm × t1 mm, surface area 50 cm ² ) subjected to electrogalvanization (zincate bath) was washed with water according to a conventional method, and then immersed in nitric acid (67.5% nitric acid 3 ml / L, liquid temperature was room temperature) The surface was activated by performing an immersion time of 10 seconds. The test member was further washed with water at room temperature for 10 seconds, and then immersed in the above chemical conversion solution (pH is 3.2) maintained at 30 ° C. and stirred for 30 seconds. The test member pulled up from the treatment liquid was washed with water (normal temperature, 10 seconds) and then dried at 80 ± 10 ° C. for 10 minutes.

(2) Evaluation method The following evaluation was performed about the concentrated liquid for chemical conversion liquids, and the test member after drying.
(A) Properties of concentrated liquid for chemical conversion liquid The prepared concentrated liquid for chemical conversion liquid was visually observed, and the characteristics were evaluated according to the following criteria:
A (excellent): Neither precipitation nor suspended matter was observed in the concentrated liquid for chemical conversion treatment liquid, and autolysis was not observed.
B (good): Self-decomposition was not observed in the concentrated liquid for chemical conversion treatment, but gas was generated during long-term storage.
C (Poor): Self-decomposition occurred at the stage of preparing the concentrated liquid for chemical conversion treatment, and the liquid properties were poor.

(B) Hexavalent chromium elution amount First, the test member after drying was stored for 72 hours in a thermostatic bath maintained at 80 ° C. and 90% RH to promote elution of hexavalent chromium from the chemical conversion film. Subsequently, the concentration of hexavalent chromium contained in the chemical conversion film formed on the test member after storage was measured by the evaluation method based on EN15205 described above.

(C) Corrosion resistance A salt spray test was conducted for 96 hours in accordance with JIS Z2371, and the white rust area ratio of the test member after the test was measured.

(D) Appearance The color tone of the surface of the test member after drying was visually observed and evaluated according to the following criteria:
A (excellent): Blue to white silver
B (good): light yellow to yellow,
C (defect): Brown to purple black.

(E) Discoloration with time The color tone of the surface of the test member stored in the thermostatic bath for the evaluation of the amount of elution of hexavalent chromium described above was visually observed and evaluated according to the following criteria:
A (excellent): Blue to white silver
B (good): light yellow to yellow,
C (defect): Brown to purple black.

(3) Evaluation results Table 1 shows the evaluation results. In addition, "-" in the table means that the chemical conversion treatment liquid is inferior in quality or the quality of the chemical conversion film is inferior, so that the evaluation cannot be performed or need not be performed. doing.

[Example 2]
Chromium nitrate as water-soluble trivalent chromium compound is 0.76 mol / L in terms of chromium, cobalt nitrate (II) hexahydrate as water-soluble cobalt compound is 57 g / L, pyrogallol is 1 g / L, sodium nitrate is A concentrated liquid for chemical conversion treatment containing 100 g / L and 1.0 mol / L of the organic acid of the type shown in Table 2 was prepared. A chemical conversion treatment solution containing 100 mL / L of this concentrated solution and having a pH of 3.2 was prepared using nitric acid and sodium hydroxide.

A steel plate (5 cm × 5 cm × t1 mm, surface area 50 cm ² ) subjected to electrogalvanization (zincate bath) according to a conventional method was washed with water, and then immersed in nitric acid (67.5% nitric acid 3 ml / L, liquid temperature was room temperature, soaking time) The surface was activated by performing (for 10 seconds). The test member was further washed with water at room temperature for 10 seconds, and then immersed in the above chemical conversion solution (pH is 3.2) maintained at 30 ° C. and stirred for 30 seconds. The test member pulled up from the treatment liquid was washed with water (normal temperature, 10 seconds) and then dried at 80 ± 10 ° C. for 10 minutes.
Evaluation similar to Example 1 was performed with respect to the obtained test member.
The evaluation results are shown in Table 2.

[Example 3]
Chromium nitrate as water-soluble trivalent chromium compound is 0.76 mol / L in terms of chromium, cobalt nitrate (II) hexahydrate as water-soluble cobalt compound is 57 g / L, pyrogallol is 1 g / L, sodium nitrate is A concentrated solution for a chemical conversion treatment solution containing 100 g / L and lactic acid at concentrations shown in Table 3 was prepared. A chemical conversion treatment solution containing 100 mL / L of this concentrated solution and having a pH of 3.2 was prepared using nitric acid and sodium hydroxide.

A steel plate (5 cm × 5 cm × t1 mm, surface area 50 cm ² ) subjected to electrogalvanization (zincate bath) according to a conventional method was washed with water, and then immersed in nitric acid (67.5% nitric acid 3 ml / L, liquid temperature was room temperature, soaking time) The surface was activated by performing (for 10 seconds). The test member was further washed with water at room temperature for 10 seconds, and then immersed in the above chemical conversion solution (pH is 3.2) maintained at 30 ° C. and stirred for 30 seconds. The test member pulled up from the treatment liquid was washed with water (normal temperature, 10 seconds) and then dried at 80 ± 10 ° C. for 10 minutes.
Evaluation similar to Example 1 was performed with respect to the obtained test member. However, the test time of the salt spray test was 72 hours.
The evaluation results are shown in Table 3.

[Example 4]
Chromium nitrate as a water-soluble trivalent chromium compound is 0.76 mol / L in terms of chromium, cobalt nitrate (II) hexahydrate as a water-soluble cobalt compound is 57 g / L, and sodium nitrate is 100 g / L. As shown in FIG. 4, a concentrated solution for a chemical conversion treatment solution containing an organic acid and, if necessary, pyrogallol was prepared. A chemical conversion treatment solution containing 100 mL / L of this concentrated solution and having a pH of 3.2 was prepared using nitric acid and sodium hydroxide.

A steel plate (5 cm × 5 cm × t1 mm, surface area 50 cm ² ) subjected to electrogalvanization (zincate bath) according to a conventional method was washed with water, and then immersed in nitric acid (67.5% nitric acid 3 ml / L, liquid temperature was room temperature, soaking time) The surface was activated by performing (for 10 seconds). The test member was further washed with water at room temperature for 10 seconds, and then immersed in the above chemical conversion solution (pH is 3.2) maintained at 30 ° C. and stirred for 30 seconds. The test member pulled up from the treatment liquid was washed with water (normal temperature, 10 seconds) and then dried at 80 ± 10 ° C. for 10 minutes.
Evaluation similar to Example 1 was performed with respect to the obtained test member. However, the test time of the salt spray test was 72 hours.
The evaluation results are shown in Table 4.

[Example 5]
As a water-soluble trivalent chromium compound, chromium nitrate is 0.76 mol / L in terms of chromium, cobalt nitrate (II) hexahydrate as a water-soluble cobalt compound is the amount shown in Table 5 in terms of cobalt, and pyrogallol. A concentrated solution for chemical conversion solution containing 1 g / L, 100 g / L of sodium nitrate and 1.0 mol / L of lactic acid was prepared. A chemical conversion treatment solution containing 100 mL / L of this concentrated solution and having a pH of 3.2 was prepared using nitric acid and sodium hydroxide.

A steel plate (5 cm × 5 cm × t1 mm, surface area 50 cm ² ) subjected to electrogalvanization (zincate bath) according to a conventional method was washed with water, and then immersed in nitric acid (67.5% nitric acid 3 ml / L, liquid temperature was room temperature, soaking time) The surface was activated by performing (for 10 seconds). The test member was further washed with water at room temperature for 10 seconds, and then immersed in the above chemical conversion solution (pH is 3.2) maintained at 30 ° C. and stirred for 30 seconds. The test member pulled up from the treatment liquid was washed with water (normal temperature, 10 seconds) and then dried at 80 ± 10 ° C. for 10 minutes.
Evaluation similar to Example 1 was performed with respect to the obtained test member. However, the test time of the salt spray test was 72 hours.
The evaluation results are shown in Table 5.

One aspect of the present invention provided on the basis of the above knowledge is an aqueous acidic composition (chemical conversion solution) comprising a water-soluble trivalent chromium-containing substance and a water-soluble hydroxycarboxylic acid-based substance, and is water-soluble trivalent chromium. The molar molar concentration in terms of chromium with respect to the total composition of the contained substances is 0.05 mol / L or more, and the molar concentration in terms of hydroxycarboxylic acids of the water-soluble hydroxycarboxylic acid-based substance is relative to the molar equivalent of chromium in the water-soluble trivalent chromium-containing substance. ratio Ri der 0.4 or more and less than 2.5, hydroxy carboxylic acids to give water-soluble hydroxycarboxylic acid-based material is characterized by more than four aliphatic monohydroxy monocarboxylic acids der Rukoto carbon atoms Chemical A composition for treatment.

Furthermore, this invention is another one aspect | mode, It is a water-system acidic composition for manufacturing said composition (chemical conversion liquid), Comprising: A water-soluble trivalent chromium containing material and a water-soluble hydroxycarboxylic acid-type material And the water-soluble trivalent chromium-containing molar concentration of the water-soluble trivalent chromium-containing material is 0.25 mol / L or more, Ri der less than the ratio of 0.4 to 2.5 to chromium in terms of the molar concentration of the contained substance, hydroxy carboxylic acids to give water-soluble hydroxycarboxylic acid-based material has a carbon number of 4 or less of aliphatic monohydroxy monocarboxylic acid Oh Rukoto composition characterized (chemical conversion treatment concentrate) is also provided.

Claims (6)

A water-based acidic composition comprising a water-soluble trivalent chromium-containing material and a water-soluble hydroxycarboxylic acid-based material,
Chromium conversion molar concentration with respect to the whole composition of the said water-soluble trivalent chromium containing substance is 0.05 mol / L or more,
The ratio of the molar concentration of the water-soluble hydroxycarboxylic acid-based substance in terms of hydroxycarboxylic acid to the molar equivalent of chromium in the water-soluble trivalent chromium-containing material is 0.4 or more and less than 2.5. Composition for.   The composition according to claim 1, comprising 2 mmol / L or more and 50 mmol / L or less of a water-soluble cobalt-containing substance in terms of cobalt with respect to the entire composition.   The composition according to claim 1, comprising 0.05 to 3.0 g / L of pyrogallol compound in terms of pyrogallol relative to the total composition.   The composition according to claim 1, wherein the pH is 2.0 or more and 4.0 or less.   A component having a chemical conversion film on a zinc-based plating is obtained by bringing the composition according to any one of claims 1 to 4 into contact with a member that has been subjected to zinc-based plating. Manufacturing method of member.   An aqueous acidic composition that can be used in producing the composition according to any one of claims 1 to 4, comprising a water-soluble trivalent chromium-containing substance and a water-soluble hydroxycarboxylic acid substance, The water-soluble trivalent chromium-containing substance having a molar concentration in terms of chromium with respect to the total composition of the water-soluble trivalent chromium-containing substance of 0.25 mol / L or more, The ratio with respect to the chromium conversion molar concentration is 0.4 or more and less than 2.5.