Patent Application
20250084536
The present invention relates to a chemical treatment liquid and a method for chemical treatment of a target metal material and particularly to a chemical treatment liquid and a method for chemical treatment of a target metal material which do not require chromium.
In order to enhance corrosion resistance of a metal, chemical treatment is conducted. For this treatment, a chemical treatment liquid containing chromium and cobalt has conventionally been used; however, chromium and cobalt contained in the drainage water become sludge, which requires conducting an industrial waste treatment, making the cost of the drainage treatment very high. In addition, if a chromate treatment liquid is used, hexavalent chromium, which is toxic to the human bodies, can be eluted. For this reason, in order to avoid environmental pollutions or adverse effects on human bodies, a chromium-free chemical treatment liquid has been demanded.
Patent Literatures 1 to 4 describe chromium-free chemical treatment liquids containing a titanium complex fluoride ion and a vanadium compound ion containing pentavalent vanadium, and state that these chromium-free chemical treatment liquids are used for aluminum or an aluminum alloy. However, Patent Literatures 1 to 4 fail to describe a chromium-free chemical treatment liquid containing an oxidizing agent at a specific concentration or more.
The corrosion resistances of coatings formed in accordance with the conventional chromium-free chemical treatment liquids are not sufficient, and a chromium-free chemical treatment liquid capable of forming a coating with further improved corrosion resistance has been demanded. In view of this, an object of the present invention is to provide a chemical treatment liquid capable of forming a coating having improved corrosion resistance.
As a result of conducting earnest studies in order to solve the above-described problem, the present inventors found that a coating having a favorable corrosion resistance was able to be formed without using chromium by blending a high-concentration oxidizing agent in a chemical treatment liquid containing a water-soluble titanium complex ion and a water-soluble vanadium-containing ion, and completed the present invention. Specifically, the present invention provides a chemical treatment liquid and a method for chemical treatment of a target metal material described below.
[1] A chemical treatment liquid comprising a water-soluble titanium complex ion, a water-soluble vanadium-containing ion, and 0.03 mol/L or more of an oxidizing agent, wherein a concentration of a fluorine ion is 0 to 0.3 g/L.
[2] A chemical treatment liquid comprising a water-soluble titanium complex ion, a water-soluble vanadium-containing ion, and 0.03 mol/L or more of an oxidizing agent, wherein a fluoride that releases a fluorine ion other than a fluoro complex is not added to the chemical treatment liquid.
[3] The chemical treatment liquid according to the above [1] or [2], wherein pH is 2.0 to 5.0.
[4] The chemical treatment liquid according to any one of the above [1] to [3], wherein the oxidizing agent contains a nitrate salt that releases nitric acid and/or a nitrate ion.
[5] The chemical treatment liquid according to any one of [1] to [4], wherein the water-soluble titanium complex ion is a titanium complex fluoride ion.
[6] The chemical treatment liquid according to any one of the above [1] to [5], wherein a concentration of the water-soluble titanium complex ion in terms of titanium is 0.15 to 10 g/L.
[7] The chemical treatment liquid according to any one of the above [1] to [6], wherein the water-soluble vanadium-containing ion is a vanadium compound ion containing pentavalent vanadium.
[8] The chemical treatment liquid according to any one of the above [1] to [7], wherein a concentration of the water-soluble vanadium-containing ion in terms of vanadium is 0.4 to 15 g/L.
[9] The chemical treatment liquid according to any one of the above [1] to [8], further comprising at least one additional water-soluble metallic salt containing Zn, Co, W, Zr, Mn, Mo, Ta, Ce, Sr, or Fe.
[10] The chemical treatment liquid according to any one of the above [1] to [9], that does not contain a hexavalent chromium ion and/or a trivalent chromium ion.
[11] The chemical treatment liquid according to any one of the above [1] to [10] for use on a zinc-containing metal material.
[12] A method for chemical treatment of a target metal material, comprising a step of immersing the target metal material into the chemical treatment liquid according to any one of the above [1] to [11] or a step of spraying the chemical treatment liquid according to any one of the above [1] to [11] onto the target metal material.
[13] The method according to the above [12], wherein the target metal material is a zinc-containing metal material.
According to the present invention, it is possible to form a coating having a favorable corrosion resistance on a surface of a target metal material by blending a high-concentration oxidizing agent in a chemical treatment liquid containing a water-soluble titanium complex ion and a water-soluble vanadium-containing ion.
In this case, since it is unnecessary to blend chromium in the chemical treatment liquid, it becomes possible to provide an environmentally friendly chemical treatment liquid.
Hereinafter, the present invention will be described in further detail.
The present invention relates to a chemical treatment liquid comprising a water-soluble titanium complex ion, a water-soluble vanadium-containing ion, and 0.03 mol/L or more of an oxidizing agent. As the above water-soluble titanium complex ion, a water-soluble titanium complex ion which is normally used in the art can be employed without particular limitation, but for example, the above water-soluble titanium complex ion may be a titanium complex fluoride ion. More specifically, the above water-soluble titanium complex ion may be one derived from at least one titanium compound selected from the group consisting of hexafluorotitanic acid, sodium hexafluorotitanate, potassium hexafluorotitanate, and ammonium hexafluorotitanate, or the like. The concentration of the above water-soluble titanium complex ion is not particularly limited as long as chemical treatment can be conducted, but may be, for example, about 0.15 to about 10 g/L and is preferably about 0.3 to about 1 g/L, at concentration in terms of titanium. Note that since a fluorine ion is difficult to release from a fluoro complex such as the above titanium complex fluoride ion, the concentration of the fluorine ion derived from this fluoro complex is below 0.3 g/L as long as it is used within a normal concentration range in the chemical treatment liquid.
As the above water-soluble vanadium-containing ion, a water-soluble vanadium-containing ion which is normally used in the art can be employed without particular limitation, but for example, the above water-soluble vanadium-containing ion may be a vanadium compound ion containing pentavalent vanadium. More specifically, the above water-soluble vanadium-containing ion may be one derived from at least one vanadium compound selected from the group consisting of sodium vanadate, potassium vanadate, ammonium vanadate, sodium metavanadate, potassium metavanadate, ammonium metavanadate, and vanadium oxytrichloride, or the like. The concentration of the above water-soluble vanadium-containing ion is not particularly limited as long as chemical treatment can be conducted, but may be, for example, about 0.4 to about 15 g/L, and is preferably about 0.5 to about 1.2 g/L, at concentration in terms of vanadium.
The chemical treatment liquid of the present invention contains the above oxidizing agent at a high concentration, and specifically contains the above oxidizing agent at a concentration of about 0.03 mol/L or more or about 0.07 mol/L or more. The upper limit value of the concentration of the above oxidizing agent is not particularly limited, but may be, for example, about 0.15 mol/L or less. As the above oxidizing agent, an oxidizing agent which is normally used in the art can be employed without particular limitation, but for example, the above oxidizing agent may contain at least one selected from the group consisting of nitric acid, nitrous acid, sulfuric acid, sulfurous acid, persulfuric acid, phosphoric acid, hydrochloric acid, bromic acid, chloric acid, hypochlorous acid, hydrogen peroxide, permanganic acid, metavanadic acid, tungstic acid, molybdic acid, salts of these, and the like, and preferably contains a nitrate salt which releases nitric acid and/or a nitrate ion. The above nitrate is not particularly limited, but is preferably water-soluble, and specifically may contain ammonium nitrate, sodium nitrate, potassium nitrate, lithium nitrate, chromium nitrate, aluminum nitrate, zirconyl nitrate, cobalt nitrate, or the like. By causing the above oxidizing agent to be contained in the chemical treatment liquid, the formation of a chemical coating can be promoted, and more excellent appearance and corrosion resistance can be achieved.
The chemical treatment liquid of the present invention can form a coating having improved corrosion resistance due to the presence of the high-concentration oxidizing agent, and thus does not require chromium. That is, in a certain aspect, the above chemical treatment liquid does not contain a hexavalent chromium ion and/or a trivalent chromium ion.
The chemical treatment liquid of the present invention substantially does not contain a fluorine ion, and specifically, the concentration of a fluorine ion is 0 to about 0.3 g/L or 0 to about 0.1 g/L or a fluoride which releases a fluorine ion other than a fluoro complex is not added. The above fluorine ion is a free fluorine ion and can be clearly distinguished from a fluorine atom which has formed a complex ion with a metal. The fluoride which releases the above fluorine ion includes, for example, sodium fluoride, sodium hydrogen fluoride, potassium fluoride, potassium hydrogen fluoride, ammonium fluoride, ammonium hydrogen fluoride, hydrofluoric acid, and the like. It is considered that in the chemical treatment liquid of the present invention, it is possible to avoid excessive etching by lowering the concentration of a fluorine ion, and to thus form a coating having excellent corrosion resistance while maintaining a favorable appearance of a target metal material (particularly a zinc-containing metal material).
The chemical treatment liquid of the present invention can be used to conduct chemical treatment of various target metal materials. The above target metal material is not particularly limited, but for example, the above target metal material may be a material formed from zinc, aluminum, iron, nickel, copper, or an alloy of these, or a material plated with these metals, and is preferably a zinc-containing metal material (a zinc-plated product and a zinc alloy-plated product).
In a certain aspect, the chemical treatment liquid of the present invention further contains at least one additional water-soluble metallic salt containing Zn, Co, W, Zr, Mn, Mo, Ta, Ce, Sr, or Fe (for example, a nitrate salt, a chloride salt, a sulfate salt, or the like). Preferably, the above water-soluble metallic salt contains Zn, and a zinc ion is brought in the above chemical treatment liquid. When such a water-soluble metallic salt is contained, the corrosion resistance of the coating to be formed can be further improved. The concentration of the water-soluble metallic salt is not particularly limited as long as chemical treatment can be conducted, but may be, for example, about 0.4 to about 30.0 g/L, and is preferably about 0.8 to about 3.0 g/L.
The pH of the chemical treatment liquid of the present invention is not particularly limited, but may be, for example, about 2.0 to about 5.0, and is preferably about 3.0 to about 4.5. In addition, the chemical treatment liquid of the present invention may further contain any additive which is normally used in the art as long as the object of the present invention is not impaired.
In another aspect, the present invention relates also to a method for chemical treatment of a target metal material and comprises a step of immersing the above target metal material into the chemical treatment liquid of the present invention or a step of spraying the chemical treatment liquid of the present invention onto the above target metal material. The type of the target metal material to which the method of the present invention is applied is not particularly limited, but for example, the above target metal material may be a material formed from zinc, aluminum, iron, or an alloy of these, or a material plated with these metals, and is preferably a zinc-containing metal material (including a zinc-plated product and a zinc alloy-plated product).
In the method of the present invention, the treatment temperature and the treatment time when the above target metal is brought into contact with the above chemical treatment liquid are not particularly limited, but for example, the treatment temperature may be about 15 to about 55° C., and preferably about 25 to about 45° C., and the treatment time may be about 20 to about 400 seconds, and preferably about 30 to about 200 seconds. In addition, the method of the present invention may further include any step which is normally used in the art as long as the object of the present invention is not impaired.
Hereinafter, the present invention will be described in detail by using Examples, but the scope of the present invention is not limited to these Examples.
Ammonium hexafluorotitanate, sodium metavanadate, ammonium nitrate, and zinc sulfate were mixed, and the pH was adjusted to 4.00 by using sodium hydroxide or sulfuric acid to prepare chemical treatment liquids 1 to 6 having compositions shown in Table 1 (the concentrations of NO3+, TiF62−, VO3−, and Zn2+ were based respectively on the amounts of ammonium nitrate, ammonium hexafluorotitanate, sodium metavanadate, and zinc sulfate blended, and although these compounds are all ionized, it was assumed that F− was not generated from TiF62− and the concentration of F− was close to 0 g/L), which will be described later, in accordance with a conventional method. ZDC2 (manufactured by Nippon Testpanel Co., Ltd.), which is a zinc alloy die-cast, was degreased as a pretreatment, and washed with water, and thereafter chemical treatment was performed on the ZDC2 under conditions of 40° C. and 60 seconds by using each chemical treatment liquid. The zinc alloy die-cast after the treatment was washed with water and dried at 60° C. for 10 minutes or more. Then, the neutral salt spray test (NSS) of methods of salt spray testing (JIS Z 2371) was conducted, and the corrosion resistance of the coating formed (a ratio of the area in which a white product was attached to the surface area of the target metal material) was observed with time from loading into a salt spray testing machine, and evaluated in accordance with the following criteria. Results are shown in Table 1.
In the chemical treatment liquids containing a water-soluble titanium complex ion (TiF62−) and a water-soluble vanadium-containing ion (VO3−), a coating having a high corrosion resistance was able to be formed on the surface of the above alloy by making the concentration of the nitrate ion (oxidizing agent) higher than the conventional technique (see particularly the chemical treatment liquids 3 to 5).
Chemical treatment was conducted in the same manner as in Test Example 1 except that the chemical treatment liquids shown in Table 2 or 3 were used, and the corrosion resistance of the coating formed on the surface of the ZDC was evaluated. Results are shown in Table 2 and Table 3.
In all of the conditions shown in Table 2 and Table 3, a coating having a favorable corrosion resistance was formed. It was found that as long as the nitrate ion (oxidizing agent) was sufficiently contained, a coating having a favorable corrosion resistance was formed even when the concentrations of a water-soluble titanium complex ion (TiF62−), a water-soluble vanadium-containing ion (VO3−), and a zinc ion in the chemical treatment liquid were changed within the ranges of Table 2 and Table 3.
Chemical treatment was conducted in the same manner as in Test Example 1 except that the pH of the chemical treatment liquid 5 was changed as shown in Table 4, and the corrosion resistance of the coating formed on the surface of the ZDC was evaluated. Results are shown in Table 4.
In all of the conditions shown in Table 4, a coating having a favorable corrosion resistance was formed. It was found that as long as the nitrate ion (oxidizing agent) was sufficiently contained, a coating having a favorable corrosion resistance was formed even when the pH of the chemical treatment liquid was changed within the range of Table 4.
Chemical treatment was conducted in the same manner as in Test Example 1 except that the chemical treatment was conducted with temperatures and times shown in Table 5 by using the chemical treatment liquid 5, and the corrosion resistance of the coating formed on the surface of the ZDC was evaluated. Results are shown in Table 5.
In all of the conditions shown in Table 5, a coating having a favorable corrosion resistance was formed. It was found that as long as the nitrate ion (oxidizing agent) was sufficiently contained, a coating having a favorable corrosion resistance was formed even when the temperature and time of the chemical treatment were changed within the ranges of Table 5.
From the above, it was found that by blending a high-concentration oxidizing agent in a chemical treatment liquid containing a water-soluble titanium complex ion and a water-soluble vanadium-containing ion, a coating having a favorable corrosion resistance was able to be formed on the surface of a target metal. In this case, since it is unnecessary to blend chromium in the chemical treatment liquid, it becomes possible to provide an environmentally friendly chemical treatment liquid.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-208323 | Dec 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP22/39102 | 10/20/2022 | WO |
