JP6868313B1 - Method for manufacturing reaction type chemical conversion treatment liquid and rust preventive member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reaction type chemical conversion treatment liquid capable of forming a chemical conversion film containing Si, and a method for producing a rust preventive member using the chemical conversion treatment liquid. A colloidal silica, a trivalent chromium-containing water-soluble substance, and a high-pKa organic acid-containing water-soluble substance such as hydroxymonocarboxylic acid are contained, and the pH of the chemical conversion treatment solution is 3.0 or more. Reaction type chemical conversion treatment liquid. The content of colloidal silica is 2 g / L or more and 25 g / L or less, and the trivalent chromium equivalent content of the trivalent chromium-containing water-soluble substance is 1 g / L or more and 6 g / L or less, and is highly pKa organic acid-containing water-soluble. The high pKa organic acid equivalent content of the substance is a chemical conversion treatment solution in which the molar ratio of the trivalent chromium-containing water-soluble substance to the trivalent chromium equivalent content is 0.2 or more and 2 or less. [Selection diagram] None

Description

The present invention relates to a reaction-type chemical conversion treatment liquid and a method for producing a rust preventive member using the chemical conversion treatment liquid.

Patent Document 1 includes a two-layer structure conversion treatment film formed by a one-component treatment consisting of _{a lower layer containing Cr and an upper layer containing SiO 2} on the surface layer of a base material to be treated, which is provided with a zinc or zinc alloy plating layer. Corrosion resistant substrates are described.

Japanese Patent No. 362510

An object of the present invention is to provide a reaction-type chemical conversion treatment liquid capable of forming a Si-containing chemical conversion coating as described in Patent Document 1, and a method for producing a rust preventive member using such a chemical conversion treatment liquid. To do.

(1) A chemical conversion treatment liquid containing colloidal silica, a trivalent chromium-containing water-soluble substance, and a high pKa organic acid-containing water-soluble substance, and having a pH of the chemical conversion treatment liquid of 3.0 or more. ..
(2) The content of the colloidal silica is 2 g / L or more and 25 g / L or less, and the trivalent chromium equivalent content of the trivalent chromium-containing water-soluble substance is 1 g / L or more and 6 g / L or less, which is high. The high pKa organic acid equivalent content of the pKa organic acid-containing water-soluble substance is 0.2 or more and 2 or less as a molar ratio to the trivalent chromium equivalent content of the trivalent chromium-containing water-soluble substance. The chemical conversion treatment liquid according to.
(3) The chemical conversion treatment solution according to (1) or (2) above, wherein the high pKa organic acid contained in the high pKa organic acid-containing water-soluble substance contains a hydroxymonocarboxylic acid.
(4) The chemical conversion treatment liquid according to any one of (1) to (3) above, which further contains a film-forming metal-containing water-soluble substance.
(5) Ratio of colloidal silica content (unit: g / L) to high pKa organic acid equivalent content (unit: g / L) of high pKa organic acid-containing water-soluble substance (coloidal silica / high pKa organic acid) Is the chemical conversion treatment liquid according to any one of the above (1) to (4), which is in the range of 0.5 to 10.
(6) Further containing a low pKa organic acid-containing water-soluble substance, and a high pKa organic acid equivalent content of the high pKa organic acid-containing water-soluble substance having a low pKa organic acid equivalent content of the low pKa organic acid-containing water-soluble substance. The chemical conversion treatment solution according to any one of (1) to (5) above, wherein the molar ratio to the amount is 3 or less.
(7) The chemical conversion treatment liquid according to any one of (1) to (6) above, which is a reaction type.
(8) A method for manufacturing a rust preventive member, which comprises a plating step of forming the zinc-based plating layer on the base material to obtain a member to be treated having the base material and the zinc-based plating layer, and the above-mentioned (8). A chemical conversion treatment step of contacting the member to be treated with the chemical conversion treatment liquid described in 7) and then cleaning the member to be treated is provided to form the chemical conversion film on the member to be treated. A method for manufacturing a rust preventive member.
(9) The method for manufacturing a rust preventive member according to (8) above, wherein the base material is a cast product.

According to the present invention, there is provided a reaction type chemical conversion treatment liquid capable of forming a chemical conversion film containing Si, and a method for producing a rust preventive member using such a chemical conversion treatment liquid.

Hereinafter, embodiments of the present invention will be described.

The chemical conversion treatment liquid according to one embodiment of the present invention contains colloidal silica, a trivalent chromium-containing water-soluble substance, a film-forming metal-containing water-soluble substance, and a high-pKa organic acid-containing water-soluble substance. The pH of the chemical conversion treatment solution is 3.0 or higher. The chemical conversion treatment liquid according to the present embodiment preferably further contains a film-forming metal-containing water-soluble substance.

Colloidal silica is silica dispersed as a colloid in a chemical conversion treatment liquid, and typically has a primary particle size on the order of subnm to subμm. In the chemical conversion treatment liquid according to the present embodiment, as will be described later, a high pH region in which the pH tends to be high is generated in the vicinity of the surface of the member to be treated. Therefore, colloidal silica contained in the chemical conversion treatment liquid near the surface of the member to be treated tends to gel. In the region near the surface of the member to be treated containing this gel, the gelation of colloidal silica reduces the mass transfer to the bulk region, so that the pH of the chemical conversion treatment liquid is likely to be maintained at a high level. Therefore, zinc dissolved from the member to be treated does not easily diffuse into the bulk region and tends to stay in the high pH region. Therefore, in the chemical conversion treatment liquid according to the present embodiment, zinc dissolved from the member to be treated tends to be a component of the chemical conversion coating as a hydroxide.

Further, the colloidal silica that has diffused and moved from the bulk region to the high pH region gels rapidly due to the high pH in the high pH region and the mobility decreases. Therefore, the reaction-type chemical conversion treatment liquid according to the present embodiment. By using, a thick chemical conversion film is likely to be formed. The thickness of the chemical conversion coating formed by using a general reaction-type chemical conversion treatment liquid is less than 100 nm, but the chemical conversion coating according to the present invention can easily have a thickness of 200 nm or more, and the member to be treated By adjusting the contact time between the compound and the chemical conversion treatment liquid, it is possible to grow the film to a thickness of about 1 μm.

The content of colloidal silica in the chemical conversion treatment liquid according to the present embodiment is preferably 2 g / L or more and 25 g / L or less. If the content of colloidal silica is excessively low, there is a concern that the formation rate of the chemical conversion film may be slowed down or the corrosion resistance of the chemical conversion film may be lowered. If the content of colloidal silica is excessively high, there is a concern that the viscosity of the chemical conversion treatment liquid may increase or the life of the chemical conversion treatment liquid may be shortened. From the viewpoint of ensuring the corrosion resistance of the chemical conversion coating while ensuring the stability of the chemical conversion treatment liquid, the content of colloidal silica in the chemical conversion coating may be preferably 4 g / L or more and 20 g / L or less, and 6 g / L. It may be more preferable that the amount is 20 g / L or less.

The trivalent chromium-containing water-soluble substance is an ionic substance containing ^{trivalent chromium (Cr 3+).} The trivalent chromium-equivalent content of the trivalent chromium-containing water-soluble substance (hereinafter referred to as "trivalent chromium content") is preferably 1 g / L or more and 6 g / L or less. If the trivalent chromium content is excessively low, there is a concern that the formation rate of the chemical conversion film may be slowed down or the corrosion resistance of the chemical conversion film may be lowered. If the trivalent chromium content is excessively high, there is a concern that the viscosity of the chemical conversion treatment liquid may increase or the life of the chemical conversion treatment liquid may be shortened. From the viewpoint of ensuring the corrosion resistance of the chemical conversion coating while ensuring the stability of the chemical conversion treatment liquid, the trivalent chromium content in the chemical conversion coating may be preferably 1 g / L or more and 5 g / L or less, and is 1.2 g. It may be more preferable to set / L or more and 4.1 g / L or less.

A high pKa organic acid-containing water-soluble substance is a water-soluble substance containing an organic acid (high pKa organic acid) having the lowest pKa of 3.5 or more, and the high pKa organic acid, its ions and a complex containing the ions. including. Since the high pKa organic acid-containing water-soluble substance has a high pH buffer range due to the height of the pKa, the chemical conversion treatment liquid located in the region near the surface of the member to be treated was generated due to the dissolution of the member to be treated. The pH rise is relatively easy to maintain. This is one of the reasons why a high pH region is formed when the chemical conversion treatment liquid according to the present embodiment is used. Specifically, in the high pH region, the chemical conversion treatment liquid may have a pH of about 6 or higher at which colloidal silica is likely to gel. From the viewpoint of enhancing the stability of the chemical conversion treatment liquid, the lowest pKa of the high pKa organic acid may be preferably 4.5 or less, and more preferably 4.0 or less.

Further, since the high pKa organic acid-containing water-soluble substance has a high pKa, it is difficult to form a complex with zinc ions generated by dissolution of the member to be treated. Therefore, zinc ions generated in the chemical conversion treatment liquid near the surface of the member to be treated are less likely to be confused and tend to exist in the state of zinc hydrated ions. Therefore, in the chemical conversion treatment using the chemical conversion treatment liquid according to the present embodiment, the zinc ions generated by the dissolution of the member to be treated tend to become hydroxides and become constituent elements of the chemical conversion coating.

Specific examples of the high pKa organic acid related to the high pKa organic acid-containing water-soluble substance include glycolic acid (3.83), lactic acid (3.86), (±) -3-hydroxybutyric acid (4.70), and glyceric acid. Examples thereof include hydroxymonocarboxylic acids such as (3.64). The high pKa organic acid related to the high pKa organic acid-containing water-soluble substance may be one kind or a plurality of kinds. Considering the difficulty of interaction with zinc ions, the organic acid according to the high pKa organic acid-containing water-soluble substance preferably contains lactic acid or glycolic acid.

The content of the high pKa organic acid-containing water-soluble substance in the chemical conversion treatment liquid according to the present embodiment is set according to the type of the high pKa organic acid, the desired film characteristics (corrosion resistance, film appearance, film formation rate), and the like. By way of example without limitation, the high pKa organic acid equivalent content of the high pKa organic acid-containing water-soluble substance is 0.2 or more as the molar ratio (high pKa organic acid / trivalent chromium) to the trivalent chromium content. In some cases, it is preferably 0.25 or more and 2 or less, and in some cases it is particularly preferable that it is 0.5 or more and 1.2 or less. When glycolic acid is contained as the high pKa organic acid, the glycolic acid equivalent content of the high pKa organic acid-containing water-soluble substance composed of glycolic acid is preferably 1 g / L or more and 10 g / L or less, and 2 g / L. It is more preferably 7 g / L or more, and particularly preferably 3 g / L or more and 6 g / L or less. Even in this case, the high pKa organic acid-containing water-soluble substance may contain a high pKa organic acid (for example, lactic acid) other than glycolic acid.

The ratio (colloidal silica / high pKa organic acid) of the colloidal silica content (unit: g / L) to the high pKa organic acid equivalent content (unit: g / L) of the high pKa organic acid-containing water-soluble substance is 0. It is preferably in the range of .5 to 10, and more preferably 0.6 or more and 9 or less. If this ratio is excessively large, it may be difficult to obtain the effect of containing a water-soluble substance containing a high pKa organic acid. If this ratio is excessively small, the formation rate of the chemical conversion film becomes slow, and the possibility that the film thickness becomes thin may increase.

The chemical conversion treatment liquid according to the present embodiment is a low pKa organic acid which is a water-soluble substance containing a low pKa organic acid which is an organic acid having the lowest pKa of less than 3.5 in addition to a high pKa organic acid-containing water-soluble substance. Contains Water-soluble substances may be contained. By incorporating a water-soluble substance containing a low pKa organic acid, the appearance (particularly the degree of gloss) of the chemical conversion film may be adjusted. As low pKa organic acids related to low pKa organic acid-containing water-soluble substances, oxalic acid (minimum pKa: 1.27), succinic acid (minimum pKa: 3.09), malic acid (minimum pKa: 3.4). ) Etc. are exemplified. The molar ratio (organic acid molar ratio) of the low pKa organic acid-containing water-soluble substance to the high pKa organic acid-containing water-soluble substance to the high pKa organic acid equivalent content is 3 or less. preferable. From the viewpoint of more stably enhancing the corrosion resistance, the molar ratio of organic acids is preferably 1 or less, more preferably 1/2 or less, further preferably 1/3 or less, and 1/10 or less. Is particularly preferable.

The film-forming metal-containing water-soluble substance is a water-soluble substance containing ions of a metal (film-forming metal) capable of forming a film by interacting with oxygen or the like. Specifically, Ti, Al, V, Nb, Ta, W, Zr and the like are exemplified as the film-forming metal. Ti and Al are exemplified as more preferable comparatively forming metals. The type of the film-forming metal constituting the film-forming metal-containing water-soluble substance contained in the chemical conversion treatment liquid may be one type or a plurality of types.

The content of the film-forming metal-containing water-soluble substance in the chemical conversion treatment liquid according to the present embodiment is set according to the type of the film-forming metal, the desired film characteristics (corrosion resistance, film appearance, film formation rate, etc.) and the like. By way of example without limitation, when the comparatively forming metal is Ti and Al, the Ti equivalent content of the film-forming metal-containing water-soluble substance containing Ti is 0.03 g / L or more and 0.45 g / L or less. It is preferably 0.05 g / L or more and 0.30 g / L or less, and 0.06 g / L or more and 0.20 g / L or less is particularly preferable. Further, in this case, the Al equivalent content of the film-forming metal-containing water-soluble substance containing Al is preferably 2 mg / L or more and 50 mg / L or less, and preferably 3 mg / L or more and 30 mg / L or less. More preferably, it is 4 mg / L or more and 15 mg / L or less.

The chemical conversion treatment liquid according to the present embodiment may contain the following optional additive components in addition to the above essential components. As such an optional additive component, one selected from the group consisting of P, B, C, S, Li, Ca, Mg, Fe, Ni, Co, Cu, Si, Zn, Al, Sn and Bi and lanthanoids or Examples thereof include film-forming element-containing substances containing two or more kinds of elements. The element-equivalent content of the film-forming element-containing substance is appropriately set within a range that fulfills the purpose of containing the element.

The pH of the chemical conversion treatment liquid according to this embodiment is 3.0 or more. Since the pH of the chemical conversion treatment liquid is relatively high and, as described above, a high pKa organic acid-containing water-soluble substance having a high pH buffer range is contained, the chemical conversion treatment liquid according to the present embodiment is a member to be treated. A high pH region is likely to be formed near the surface of the surface. Therefore, the colloidal silica contained in the chemical conversion treatment liquid according to the present embodiment is likely to gel in the vicinity of the surface of the member to be treated, and a thick chemical conversion film is likely to be formed.

The pH of the chemical conversion treatment solution according to the present embodiment is adjusted by using an inorganic acid such as hydrochloric acid or nitric acid, an organic acid such as acetic acid, an inorganic base such as sodium hydroxide or potassium hydroxide, or an organic base such as amines. Can be done by. The upper limit of the pH of the chemical conversion treatment liquid according to the present embodiment is not set as long as it functions as the chemical conversion treatment liquid. From the viewpoint of ensuring the ease of forming a chemical conversion film and the stability of the chemical conversion treatment liquid, the pH of the chemical conversion treatment liquid according to the present embodiment may be preferably 4.5 or less, and is 4.0 or less. May be more preferred.

The method for producing a rust-preventive member according to an embodiment of the present invention uses the chemical conversion treatment liquid according to the present embodiment described above, and includes a plating step and a chemical conversion treatment step described below.

In the plating step, a zinc-based plating layer is formed on the base material to obtain a member to be treated having the base material and the zinc-based plating layer. In the present specification, "zinc-based plating" means a general term for zinc plating and zinc alloy plating. The base material is made of, for example, an iron-based material, is manufactured by rolling, casting, extrusion, etc., and has a shape created by machining such as rolling, cutting, pressing, or molding. The zinc-based plating layer may be formed by electroplating or may be formed by another method.

The chemical conversion film formed from the chemical conversion treatment liquid according to the present embodiment is not easily affected by the shape (steps, irregularities, etc.) and surface texture (surface roughness, etc.) of the base material. Since the pH of the chemical conversion treatment liquid according to the present embodiment is relatively high as described above, when a general chemical conversion treatment liquid having a pH of less than 3 (specifically, 2.0 to 2.5) is used. Compared, the weight loss of the zinc-based plating layer is small. For this reason, the surface texture of the base material varies widely, such as the base material having a stepped shape and the surface roughness being high. Therefore, the member to be treated has a thickness of the zinc-based plating layer. Even when has a thin portion, it is possible to stably form a chemical conversion film. A specific example of such a base material is a cast product. If the thickness of the zinc-based plating layer is 10 μm or more, the possibility that the corrosion resistance is locally lowered is stably avoided. When the thickness of the zinc-based plating layer is 5 μm or more, it is possible to suppress a local decrease in corrosion resistance.

As described above, the chemical conversion film formed from the chemical conversion treatment liquid according to the present embodiment is not easily affected by the zinc-based plating (thickness, composition), and therefore the chemical conversion film according to the present embodiment forms the zinc-based plating. It is not easily affected by the composition of the plating solution. When forming zinc-based plating, brighteners (primary brightener, secondary brightener) are added to the plating solution from the viewpoint of adjusting the film thickness and surface texture (glossiness, etc.) of the formed zinc-based plating layer. Will be done. Since this brightener is consumed when the plating solution is used, the brightener concentration in the plating solution constantly fluctuates. In order to suppress this fluctuation range, the plating solution is used while periodically adding a brightener to the plating solution. Since the chemical conversion film according to the present embodiment is not easily affected by the composition of the plating solution, it is not necessary to strictly control the brightener concentration.

The chemical conversion treatment step includes contacting the member to be treated with the chemical conversion treatment liquid according to the present embodiment and then cleaning the member to be treated to form a chemical conversion film on the member to be treated. Examples of the contact method between the chemical conversion treatment liquid and the member to be treated include immersion of the member to be treated in the chemical conversion treatment liquid, spray spraying of the chemical conversion liquid onto the member to be treated, and the like.

In the reaction type chemical conversion treatment, in general, the tendency that the fluidity of the chemical conversion treatment liquid in the vicinity of the surface of the member to be treated decreases is not remarkable due to the dissolution of zinc from the surface of the member to be treated. Therefore, through the chemical conversion treatment, mutual diffusion between the chemical conversion treatment liquid near the surface of the member to be treated and the bulk chemical conversion treatment liquid is continuously generated. Therefore, even if the pH of the chemical conversion treatment liquid near the surface rises due to the dissolution of zinc from the surface of the member to be treated, the bulk chemical conversion treatment liquid diffuses to the vicinity of the surface, so that the chemical conversion treatment near the surface The increase in pH of the liquid is limited.

On the other hand, in the chemical conversion treatment liquid according to the present embodiment, as described above, zinc is dissolved from the surface of the member to be treated to cause gelation of colloidal silica. Liquidity decreases. Moreover, when the bulk chemical conversion treatment liquid comes into contact with the gelled colloidal silica, the colloidal silica contained in the bulk chemical conversion treatment liquid is further gelled. Therefore, in the reaction type chemical conversion treatment liquid according to the present embodiment, the thickness of the chemical conversion coating tends to increase as the treatment time becomes longer. This point is significantly different from the general reaction type chemical conversion treatment liquid. As the thickness of the chemical conversion film increases, the corrosion resistance of the rust preventive member tends to improve. Therefore, when the chemical conversion treatment liquid according to the present embodiment is used, the corrosion resistance is controlled by adjusting the treatment time. be able to.

The chemical conversion treatment temperature when the chemical conversion treatment liquid is brought into contact with the member to be treated may be set in the range of 20 ° C. to 60 ° C. Since the chemical conversion treatment liquid in the present embodiment is not easily affected by the treatment temperature, a rust preventive member having good corrosion resistance can be stably produced within the above range. If the temperature of the chemical conversion treatment liquid is excessively low, there is a concern that the liquid viscosity will decrease and the workload such as stirring will increase. When the temperature of the chemical conversion treatment liquid is excessively high, the amount of volatilization of water as a solvent increases, and the workload (water injection, stirring) for stabilizing the composition and viscosity of the chemical conversion treatment liquid may increase. I am concerned. When the chemical conversion treatment temperature is in the range of 30 ° C. to 55 ° C., it is possible to suppress a decrease in workability of the chemical conversion treatment process, and when the chemical conversion treatment temperature is in the range of 35 ° C. to 50 ° C., the chemical conversion treatment step It is stably realized to manufacture a rust preventive member having good corrosion resistance while ensuring good workability.

When the contact between the chemical conversion treatment liquid and the member to be treated is completed, the chemical conversion treatment liquid remaining on the surface of the member to be treated is washed and removed and dried. The cleaning method is not limited, but generally, a pool rinse followed by a running water rinse is performed. Drying conditions are set as appropriate. It is expected that the stability of the chemical conversion film will be enhanced by increasing the drying temperature and the drying time. By way of example without limitation, the drying temperature is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and particularly preferably 70 ° C. or higher. The drying time may be set in relation to the drying temperature. By way of example, when the drying temperature is 40 ° C, the drying time can be 20 minutes, when the drying temperature is 50 ° C, the drying time can be 10 minutes, and when the drying temperature is 70 ° C. Can have a drying time of 5 minutes.

Since the chemical conversion treatment forms a substance constituting the chemical conversion film by increasing the pH of the chemical conversion treatment liquid near the surface generated when zinc is dissolved from the surface of the member to be treated, it is inevitable for the chemical conversion treatment liquid in use. Zinc-containing substances (zinc ions, zinc complex ions, etc.) are dissolved. The zinc-equivalent concentration of this zinc-containing substance affects the process of dissolving zinc from the member to be treated, and may affect the film thickness and film quality of the chemical conversion film. However, in the chemical conversion treatment liquid according to the present embodiment, as described above, colloidal silica gels in the high pH region, the fluidity of the chemical conversion treatment liquid decreases, and mass transfer with the chemical conversion treatment liquid in the bulk region decreases. .. Therefore, the zinc-equivalent concentration of the zinc-containing substance in the chemical conversion treatment liquid located in the high pH region is higher than the zinc-equivalent concentration of the zinc-containing substance in the bulk chemical conversion treatment liquid. Therefore, as a result, in the chemical conversion treatment liquid according to the present embodiment, the zinc-equivalent concentration of the zinc-containing substance does not easily affect the characteristics (film thickness, composition, etc.) of the chemical conversion film. That is, the chemical conversion treatment liquid according to the present embodiment has high robustness against zinc contamination.

Similarly, iron-containing substances (iron ions, iron complex ions, etc.) derived from a base material or the like are dissolved in the chemical conversion treatment liquid in use. Its content tends to increase with increasing usage time. As described above, the chemical conversion treatment liquid according to the present embodiment is suitable for iron contamination because the region where the chemical conversion film is formed near the surface of the member to be treated is not easily affected by the composition of the bulk chemical conversion treatment liquid. On the other hand, it has high robustness.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention. For example, the chemical conversion film may contain an organic binder component. In this case, a component that gives an organic binder component may be contained in the chemical conversion treatment liquid, and a region that can be positioned as an organic overcoat of the above-mentioned inorganic chemical conversion coating is formed on the Si-rich region. You may.

Hereinafter, the effects of the present invention will be described based on examples, but the present invention is not limited thereto.

(Examples 1 to 4)
A rust preventive member was produced under the following conditions.
(1) Base material: Iron-based cast member (100 mm × 50 mm, thickness 8.0 mm)
(2) Zinc-based plating layer: Electrogalvanization ("FZ-77A1 (primary brightener) / GC1 (secondary brightener)" manufactured by Yuken Kogyo Co., Ltd.), plating film thickness 10 μm
(3) Chemical conversion treatment liquid: Composition shown in Table 1 (4) Chemical conversion treatment: Immerse in chemical conversion treatment liquid at 45 ° C. for 40 seconds while bubbling (air stirring) (only in Example 1, further stop bubbling for 30 seconds). Immersion), washing with water (washing with running water after rinsing), drying (80 ° C, 10 minutes)

In the preparation of the chemical conversion treatment solution, chromium chloride was used as the chromium source, titanium tetrachloride was used as the titanium source, aluminum chloride was used as the aluminum source, glycolic acid was used as the high pKa organic acid, and hydrochloric acid, sodium hydroxide, and potassium hydroxide were used. The pH was adjusted using. As shown in Table 1, with respect to the treated appearance, the gloss was not remarkable in any of the examples, and the appearance color was white to blue. This appearance could be adjusted by changing the content of the film-forming metal-containing water-soluble substance containing Ti and Al. Specifically, by increasing the content of the film-forming metal-containing water-soluble substance containing Ti and Al, the treated appearance could be made blue.

A rust preventive member was provided in the neutral salt spray test (SST) described in JIS Z2371: 2015, and the time until white rust occurred (white rust generation time) was measured by visually observing at predetermined time intervals. .. Specifically, the surface of the rust preventive member is visually observed every 12 hours from the start of the test, and when white rust is observed in 1% or more of the measurement area, the test time related to the observation is the white rust occurrence time. And said. The measurement results are shown in Table 2. In addition, Comparative Example 1 is a general reaction type chemical conversion treatment liquid (manufactured by Yuken Kogyo Co., Ltd.) on the same base material (iron-based cast member subjected to zinc electroplating) as in the case of Example 1 above. It is a rust preventive member obtained by immersing it in "YFA-S / 30HR") for 40 seconds under standard conditions.

(Example 5)
The robustness of the chemical conversion treatment was evaluated using the chemical conversion treatment liquid according to Example 1.
A rust preventive member was provided for the neutral salt spray test described in JIS Z2371: 2015, and the rust preventive member was visually observed after the test time of 480 hours and evaluated according to the following criteria.
A: No white rust was observed in the measurement area.
B: The white rust generation area ratio in the measurement area was less than 5%.
C: The white rust generation area ratio in the measurement area was 5% or more.

(Example 5-1) Plating film thickness The film thickness of electrogalvanization was changed. The results are shown in Table 3.

(Example 5-2) Brightener concentration The composition of the brightener in the plating solution for forming electrogalvanization was changed. The results are shown in Table 4. The display in the column of "brightener ratio" in Table 4 means "addition amount of primary brightener (unit: mL / L) / addition amount of secondary brightener (unit: mL / L)".

(Example 5-3) Chemical conversion processing time The processing time of chemical conversion treatment was changed. The results are shown in Table 5.

(Example 5-4) Chemical conversion treatment temperature The treatment temperature for chemical conversion treatment was changed. The results are shown in Table 6.

(Example 5-5) pH of chemical conversion treatment liquid
The pH of the chemical conversion treatment solution was changed. The results are shown in Table 7.

(Example 5-6) Drying temperature The drying temperature after the chemical conversion treatment was changed. The results are shown in Table 8.

(Example 5-7) Zinc concentration of chemical conversion treatment liquid When preparing the chemical conversion treatment liquid, zinc chloride was added to change the zinc equivalent concentration of the zinc-containing substance in the chemical conversion treatment liquid. The results are shown in Table 9.

(Example 5-8) Iron concentration of chemical conversion treatment liquid When preparing the chemical conversion treatment liquid, iron chloride was added to change the zinc-iron equivalent concentration of the iron-containing substance in the chemical conversion treatment liquid. The results are shown in Table 10.

(Example 6) Composition of chemical conversion treatment liquid Based on the composition of Example 4, the content of components other than colloidal silica (Cr, Ti, Al, high pKa organic acid) and the content of colloidal silica are shown in Table 11. A plurality of chemical conversion treatment liquids were prepared (treatment liquids 4-1 to 4-36). The treatment liquid 4-22 had the same composition as the chemical conversion treatment liquid according to Example 4, and the pH of each treatment liquid was 3.3. The same chemical conversion treatment as in Example 4 was carried out, and SST was carried out on the obtained rust preventive member. The rust preventive member was visually observed at the test time of 72 hours, 168 hours and 264 hours, and the white rust generation area ratio (unit:%) was measured. Table 11 shows the measurement results of the white rust generation area ratio.

As shown in Table 11, up to the test time of 168 hours, the rust preventive member formed by using any of the treatment liquids has a white rust generation area ratio of 5% or less and has good corrosion resistance. Was confirmed.

The results with a test time of 264 hours are shown in a matrix (Table 12). In Table 12, the area where the white rust generation area ratio is 5% or less is surrounded by a thick line. In this region, the white rust occurrence rate was more than 5% and 10% or less in only two places. In Table 12, these results are shown in the frame of the alternate long and short dash line.

It was confirmed that when the content of colloidal silica is relatively large, a rust preventive film having excellent corrosion resistance can be stably obtained even if the content of components other than colloidal silica fluctuates to some extent.

(Example 7) Effect of organic acid type As shown in Table 13, in the chemical conversion treatment liquid according to Example 4, a part of the high pKa organic acid was used as a part of the oxalic acid (lowest pKa) which is a kind of low pKa organic acid. Was changed to 1.27) to prepare chemical conversion liquids 4-37 to 4-40. Further, all of the high pKa organic acids in the chemical conversion treatment liquid according to Example 4 were changed to oxalic acid to prepare the chemical conversion treatment liquid according to Comparative Example 2. In the "Organic acid molar ratio" row of Table 13, the molar ratio of the low pKa organic acid-containing water-soluble substance to the high pKa organic acid equivalent content of the high pKa organic acid-containing water-soluble substance to the high pKa organic acid equivalent content. (Low pKa organic acid / high pKa organic acid) is shown. As shown in Table 13, the chemical conversion treatment liquids 4-37 to 4-40 differed in the organic acid molar ratio in the range of 0.1 to 3 with respect to the chemical conversion treatment liquid according to Example 4.

A rust preventive member was manufactured using these chemical conversion treatment liquids. The obtained rust preventive member was subjected to the same test as in Example 6. Table 14 shows the measurement results of the white rust generation area ratio (unit:%) at each measurement time.

The rust preventive member produced by using the chemical conversion treatment liquid according to Comparative Example 2 had a white rust generation area ratio of 2% in 72 hours.

Claims (7)

It is a method of manufacturing rust preventive members.
A chemical conversion treatment step of forming a chemical conversion film on the member to be treated is provided, which comprises contacting a chemical conversion treatment liquid with a member to be treated containing zinc on the surface and then cleaning the member to be treated.
The chemical conversion treatment liquid is
Colloidal silica, trivalent chromium-containing water-soluble substance which is an ionic substance containing trivalent chromium, and high pKa which is a water-soluble substance containing high pKa organic acid which is an organic acid having the lowest pKa of 3.5 or more. Contains pKa organic acid-containing water-soluble substances,
The pH is 3.0 or more and 4.5 or less in the state before contacting with the member to be treated.
The high pKa organic acid contains glycolic acid (except when it contains at least one selected from allylamine, polyallylamine, aromatic sulfonic acid, aromatic sulfonic acid-formaldehyde condensate and derivatives thereof).
A method for manufacturing a rust preventive member. The chemical conversion treatment liquid is
The content of the colloidal silica is 2 g / L or more and 25 g / L or less.
The trivalent chromium-equivalent content of the trivalent chromium-containing water-soluble substance is 1 g / L or more and 6 g / L or less.
High pKa organic acid in terms of the content of the high pKa organic acid-containing water-soluble material, as the molar ratio of trivalent chromium conversion amount of the trivalent chromium-containing water-soluble substance, 0.2 to 2, claim The method for manufacturing a rust preventive member according to 1. Claim 1 or claim , wherein the chemical conversion treatment liquid further contains a film-forming metal-containing water-soluble substance which is a water-soluble substance containing metal ions capable of forming a film by interacting with oxygen. Item 2. The method for manufacturing a rust preventive member according to Item 2. In the chemical conversion treatment solution, the ratio of the content of colloidal silica (unit: g / L) to the high pKa organic acid equivalent content (unit: g / L) of the water-soluble substance containing high pKa organic acid (coloidal silica / high pKa). The method for producing a rust preventive member according to any one of claims 1 to 3 , wherein the organic acid) is in the range of 0.5 to 10. The chemical conversion treatment solution further contains a low pKa organic acid-containing water-soluble substance which is a water-soluble substance containing a low pKa organic acid which is an organic acid having a lowest pKa of 1.27 or more and less than 3.5, and the low pKa is said. The molar ratio of the low pKa organic acid equivalent content of the pKa organic acid-containing water-soluble substance to the high pKa organic acid equivalent content of the high pKa organic acid-containing water-soluble substance is 1 or less , claims 1 to 4 The method for manufacturing a rust preventive member according to any one of the above. The method for manufacturing a rust-preventive member according to any one of claims 1 to 5, wherein the member to be treated has a zinc-based plating layer formed on a base material. The method for manufacturing a rust preventive member according to claim 6 , wherein the base material is a cast product.