WO2022050079A1

WO2022050079A1 - Method for producing rust-proof member

Info

Publication number: WO2022050079A1
Application number: PCT/JP2021/030556
Authority: WO
Inventors: 司丹羽; 寿裕杉浦; 良規平松; 裕輝吉田
Original assignee: ユケン工業株式会社
Priority date: 2020-09-04
Filing date: 2021-08-20
Publication date: 2022-03-10
Also published as: EP4123051A1; CN115362284A; EP4123051A4; US20230140575A1; JP2022043493A; JP6868313B1

Abstract

Provided is a reactive chemical conversion treatment solution characterized by: comprising colloidal silica, a water-soluble substance containing trivalent chromium, and a water-soluble substance containing an organic acid having a high pKa value such as a hydroxymonocarboxylic acid; being capable of further containing a film-formable metal-containing water-soluble substance in a preferred embodiment; and having a pH value of 3.0 or more. This chemical conversion treatment solution enables the formation of an Si-containing chemical conversion film.

Description

Manufacturing method of rust preventive material

The present invention relates to a method for manufacturing a rust preventive member.

Patent Document 1 includes a two-layer structure conversion treatment film 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 provided with a zinc or zinc alloy plating layer. Corrosion resistant substrate is 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. do.

The present invention provided to solve the above-mentioned problems is, in one embodiment, a method for manufacturing a rust-preventive member, in which a chemical conversion treatment liquid is brought into contact with a member to be treated containing zinc on the surface, and then the treatment is performed. The chemical treatment liquid comprises colloidal silica and trivalent chromium which is an ionic substance containing trivalent chromium, which comprises a chemical conversion treatment step of forming a chemical conversion film on the member to be treated, including cleaning the member. It contains a water-soluble substance and a high pKa organic acid-containing water-soluble substance which is a water-soluble substance containing a high pKa organic acid which is an organic acid having the lowest pKa of 3.5 or more, and is in contact with the member to be treated. The pH is 3.0 or more and 4.5 or less in the state before the above, and the high pKa organic acid contains glycolic acid (allylamine, polyallylamine, aromatic sulfonic acid, aromatic sulfonic acid-formaldehyde condensate and It is a method for manufacturing a rust preventive member, which comprises at least one selected from these derivatives). That is, the above chemical conversion treatment liquid does not contain allylamine, polyallylamine, aromatic sulfonic acid, aromatic sulfonic acid-formaldehyde condensate and derivatives thereof as active ingredients.

In the above production method, the chemical conversion treatment liquid may satisfy at least one of the following requirements.
-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.
The high pKa organic acid equivalent content of the high pKa organic acid-containing water-soluble substance is 0.2 or more and 2 or less as the molar ratio to the trivalent chromium equivalent content of the trivalent chromium-containing water-soluble substance.
-The 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, is further contained.
The ratio of the content (unit: g / L) of colloidal silica to the high pKa organic acid equivalent content (unit: g / L) of the high pKa organic acid-containing water-soluble substance (coloidal silica / high pKa organic acid) is , 0.5 to 10.
The 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 the lowest pKa of 1.27 or more and less than 3.5, is further contained, and the high pKa organic acid-containing water-soluble substance is further contained. The molar ratio of the low pKa organic acid equivalent content of the low pKa organic acid-containing water-soluble substance to the high pKa organic acid equivalent content of the sex substance is 1 or less.

In the above manufacturing method, it is preferable that the member to be treated has a zinc-based plating layer formed on a base material.

In the above manufacturing method, the base material may be 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 manufacturing 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 the 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 liquid 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 containing this gel in the vicinity of the surface of the member to be treated, mass transfer to the bulk region is reduced due to gelation of colloidal silica, so that the pH of the chemical conversion treatment liquid can be easily maintained at a high pH. 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 constituent element 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 the above, 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 embodiment can easily have a thickness of 200 nm or more, and is to be treated. By adjusting the contact time between the member and the chemical conversion treatment liquid, it is possible to grow to a thickness of about 1 μm.

The content of colloidal silica in the chemical conversion treatment liquid according to this 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 to use 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 use / 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 increase in pH is relatively easy to be maintained. This is one of the reasons why a high pH region is formed when the chemical conversion treatment liquid according to this 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 the zinc ion generated by the 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 by the type of 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. The following may be preferable, 0.25 or more and 2 or less may be more preferable, and 0.5 or more and 1.2 or less may be particularly preferable. 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, preferably 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. Also 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 (coloidal silica / high pKa organic acid) 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 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 A water-soluble substance may be contained. By containing 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 (lowest pKa: 1.27), succinic acid (lowest pKa: 3.09), malic acid (lowest 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 of the high pKa organic acid-containing water-soluble substance may be 3 or less. preferable. From the viewpoint of increasing the corrosion resistance more stably, the organic acid molar ratio 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 formable 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 more preferably 0.06 g / L or more and 0.20 g / L or less. 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. It is more preferably 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 higher. 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 manufacturing a rust-preventive member according to an embodiment of the present invention uses the above-mentioned chemical conversion treatment liquid according to the present embodiment, 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, molding, etc. such as rolling, cutting, and pressing. 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 of the base material (steps, unevenness, etc.) and the surface texture (surface roughness, etc.). 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 becoming high, and therefore the member to be treated has the 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, a brightener (primary brightener, secondary brightener) is 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 concentration of the brightener 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 chemical conversion treatment liquid according to the present embodiment with the chemical conversion treatment liquid, and then cleaning the chemical conversion treatment member to form a chemical conversion film on the chemical conversion treatment member. 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 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 near 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 is performed. The increase in the pH of the liquid is limited.

On the other hand, in the chemical conversion treatment liquid according to the present embodiment, as described above, since zinc is dissolved from the surface of the member to be treated to cause gelation of colloidal silica, the chemical conversion treatment liquid in the vicinity of the surface of the member to be treated is used. The fluidity 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 general reaction type chemical conversion treatment liquids. 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. If the chemical conversion treatment temperature is in the range of 30 ° C to 55 ° C, it is possible to suppress the deterioration of workability in the chemical conversion treatment step, and if 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.

After 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 improved 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 of the chemical conversion treatment liquid located in the high pH region is higher than the zinc-equivalent concentration of the zinc-containing substance of 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 this embodiment has high robustness against zinc contamination.

Similarly, iron-containing substances (iron ions, iron complex ion, etc.) derived from the base material, etc. are dissolved in the chemical conversion treatment liquid being used. 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.

The present invention includes the following aspects.
(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 the pH of the chemical conversion treatment liquid is 3.0 or higher. ..

(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 the molar ratio with respect to the trivalent chromium equivalent content of the trivalent chromium-containing water-soluble substance. The chemical 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) The low pKa organic acid-containing water-soluble substance is further contained, and the high pKa organic acid-containing water-soluble substance has a high 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.

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: Electrogalvanized ("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 the 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 pH organic acid, and hydrochloric acid, sodium hydroxide, and potassium hydroxide were used. Was used to adjust the pH. 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 electrozinc plating was changed. The results are shown in Table 3.

(Example 5-2) Brightening agent concentration The composition of the brightening agent in the plating solution for forming the electrozinc plating 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 for chemical conversion processing 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 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 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 a 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 area, the white rust occurrence area ratio was more than 5% and 10% or less in only two places. In Table 12, these results are shown in the frame of the two-dot chain 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 treatment liquid according to Example 4, a part of the high pKa organic acid was used as a part of oxalic acid (lowest pKa) which is a kind of low pKa organic acid. Was changed to 1.27) to prepare chemical treatment 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 row of "Mole ratio of organic acid" in 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. (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 differ 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 manufactured 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

It is a manufacturing method of 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 member to be treated containing zinc on the surface with a chemical conversion treatment liquid and then cleaning the member to be treated.
The chemical conversion treatment liquid is
Colloidal silica, a trivalent chromium-containing water-soluble substance that is an ionic substance containing trivalent chromium, and a high pKa organic acid-containing water-soluble substance that has the lowest pKa of 3.5 or more. Contains pKa organic acid-containing water-soluble substances and
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 allylamine, polyallylamine, aromatic sulfonic acid, aromatic sulfonic acid-formaldehyde condensate and at least one selected from these derivatives).
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.
Claimed that the high pKa organic acid equivalent content of the high 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 method for manufacturing a rust preventive member according to 1.
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, according to claim 1 or claim. Item 2. The method for manufacturing a rust preventive member according to Item 2.
In the chemical treatment liquid, the ratio of the content (unit: g / L) of colloidal silica to the high pKa organic acid equivalent content (unit: g / L) of the high pKa organic acid-containing water-soluble substance (coloidal silica / high). pKa organic acid) is the method for producing a rust-preventive member according to any one of claims 1 to 3, which is in the range of 0.5 to 10.
The chemical treatment liquid 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 high amount. Claim 1 to claim 1, wherein the molar ratio of the low pKa organic acid equivalent content of the low pKa organic acid-containing water-soluble substance to the high pKa organic acid equivalent content of the pKa organic acid-containing water-soluble substance is 1 or less. The method for manufacturing a rust preventive member according to any one of 4.
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.