Patent Application
20210071304
The present invention relates to a surface treatment agent used for surface treatment of an aluminum or an aluminum alloy material, an aluminum or an aluminum alloy material which has a surface treatment coating formed by the surface treatment agent, and a method of producing the aluminum or the aluminum alloy material.
Conventionally, metallic material surface treatment agents containing trivalent chromium have been developed as surface treatment agents for aluminum and aluminum alloy materials in a wide range of fields, such as aircraft materials, construction materials, and automobile parts.
For example, Patent Document 1 discloses a chemical conversion treatment liquid for metallic materials, which contains a component (A) comprising a water-soluble trivalent chromium compound, a component (B) comprising at least one selected from a water-soluble titanium compound and a water-soluble zirconium compound, a component (C) comprising a water-soluble nitrate compound, a component (D) comprising a water-soluble aluminum compound and a component (E) comprising a fluorine compound, and which has pH controlled in a range of 2.3 to 5.0.
Patent Document 2 discloses a chemical conversion treatment liquid which contains a predetermined amount of a specific trivalent chromium compound, a specific zirconium compound, and a specific dicarboxylic acid compound.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-328501
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2006-316334
However, according to the coatings formed on aluminum or aluminum alloy materials using the respective surface treatment agents disclosed in the Patent Documents 1 and 2, the corrosion resistance may be reduced due to exposure to a high temperature environment, depending on the use of the aluminum or the aluminum alloy materials.
An object of the present invention is to provide a surface treatment agent capable of forming, on an aluminum or an aluminum alloy material, a surface treatment coating that has excellent corrosion resistance and has excellent corrosion resistance even when the coating is exposed to a high temperature, an aluminum or an aluminum alloy material which has a surface treatment coating formed by the surface treatment agent, and a method of producing the aluminum or the aluminum alloy material.
The present inventors intensively studied to solve the above-described problems and consequently discovered that a surface treatment agent containing a trivalent chromium-containing ion (A), at least one ion (B) selected from a titanium-containing ion and a zirconium-containing ion, a zinc-containing ion (C), a free fluorine ion (D), and a nitrate ion (E) is capable of forming, on an aluminum or aluminum alloy material, a surface treatment coating that has excellent corrosion resistance and has excellent corrosion resistance even when the coating is exposed to a high temperature, thereby completing the present invention.
In order to solve the above-described problems, the present invention encompasses the followings:
(1) A surface treatment agent used for surface treatment of an aluminum or an aluminum alloy material, wherein the surface treatment agent contains a trivalent chromium-containing ion (A), at least one ion (B) selected from a titanium-containing ion and a zirconium-containing ion, a zinc-containing ion (C), a free fluorine ion (D), and a nitrate ion (E);
(2) A method of producing an aluminum or an aluminum alloy material having a surface treatment coating, the method including a contact step of contacting the surface treatment agent according to (1) on or over a surface of an aluminum or an aluminum alloy material; and
(3) An aluminum or an aluminum alloy material having a surface treatment coating obtainable by the method according to (2).
According to the present invention, the followings can be provided: a surface treatment agent capable of forming, on an aluminum or an aluminum alloy material, a surface treatment coating that has excellent corrosion resistance and has excellent corrosion resistance even when the coating is exposed to a high temperature; an aluminum or an aluminum alloy material which has a surface treatment coating formed by the surface treatment agent; and a method of producing the aluminum or the aluminum alloy material.
The surface treatment agent of the present embodiment is a treatment agent for performing a surface treatment of an aluminum or an aluminum alloy material. The surface treatment agent can also be utilized as a chemical conversion treatment agent. The surface treatment agent contains a trivalent chromium-containing ion (A), at least one ion (B) selected from a titanium-containing ion and a zirconium-containing ion, a zinc-containing ion (C), a free fluorine ion (D), and a nitrate ion (E). The surface treatment agent may be obtained by mixing an aqueous medium with sources of these ions exclusively, or by mixing an aqueous medium with sources of these ions and other components. The respective components, formulations (contents) thereof, and liquid properties are described below in detail. Examples of the above-described metal-containing ions include metal ions, metal oxide ions, metal hydroxide ions, and metal complex ions.
In the surface treatment agent, a supply source of the trivalent chromium-containing ion (A) is not particularly limited as long as it is capable of providing the ion (A) by mixing with an aqueous medium. Examples of the supply source include chromium fluoride, chromium nitrate, chromium sulfate, and chromium phosphate. These supply sources may be used singly, or in combination of two or more thereof. The content of the ion (A) in the surface treatment agent is not particularly limited, however, it is usually in a range of 5 to 1,000 mg/L, preferably in a range of 20 to 700 mg/L, in terms of chromium-equivalent mass concentration. In the present embodiment, it is preferred that the surface treatment agent does not contain hexavalent chromium ions. It is noted here that “does not contain hexavalent chromium ions” does not mean that the content of the hexavalent chromium ions is 0, but unavoidable incorporation of hexavalent chromium ions is acceptable. Specifically, the content of hexavalent chromium ions may be 10 mg/L or less, 5 mg/L or less, 1 mg/L or less, 0.5 mg/L or less, or 0.1 mg/L or less.
(At Least One Ion Selected from Titanium-Containing Ion and Zirconium-Containing Ion)
In the surface treatment agent, a supply source of at least one ion (B) selected from a titanium-containing ion and a zirconium-containing ion is not particularly limited as long as it is capable of providing the ion (B) by mixing with an aqueous medium. Examples of the supply source include titanium sulfate, titanium oxysulfate, titanium ammonium sulfate, titanium nitrate, titanium oxynitrate, titanium ammonium nitrate, hexafluorotitanic acid, hexafluorotitanium complex salts, zirconium sulfate, zirconium oxynitrate, zirconium ammonium sulfate, zirconium nitrate, zirconium oxynitrate, zirconium ammonium nitrate, hexafluorozirconic acid, hexafluorozirconium complex salts, titanium lactate, titanium acetylacetonate, titanium triethanolaminate, titanium octyl glycolate, tetraisopropyl titanate, tetra-n-butyl titanate, zirconyl acetate, zirconyl lactate, zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, tetra-n-butoxy zirconium, and tetra-n-propoxy zirconium. These supply sources may be used singly, or in combination of two or more thereof. The content of the ion (B) in the surface treatment agent is not particularly limited, however, it is usually in a range of 5 to 1,000 mg/L, preferably in a range of 20 to 700 mg/L, in terms of metal-equivalent mass concentration (total metal-equivalent mass concentration when two or more supply sources are combined).
In the surface treatment agent, a supply source of the zinc-containing ion (C) is not particularly limited as long as as it is capable of providing the ion (C) by mixing with an aqueous medium. Examples of the supply source include metallic zinc, zinc oxide, zinc carbonate, zinc nitrate, zinc chloride, zinc sulfate, zinc fluoride, zinc iodide, zinc dihydrogen phosphate, and zinc acetylacetonate. These supply sources may be used singly, or in combination of two or more thereof. The content of the ion (C) in the surface treatment agent is not particularly limited, however, it is usually in a range of 20 to 10,000 mg/L and may be in a range of 50 to 10,000 mg/L, preferably in a range of 300 to 8,000 mg/L, more preferably in a range of 700 to 5,000 mg/L, in terms of zinc-equivalent mass concentration.
In the surface treatment agent, a supply source of the free fluorine ion (D) is not particularly limited as long as it is capable of providing the free fluorine ion (D) by mixing with an aqueous medium. Examples of the supply source include hydrofluoric acid, ammonium fluoride, chromium fluoride, hexafluorotitanic acid, hexafluorotitanium complex salts, hexafluorozirconic acid, hexafluorozirconium complex salts, magnesium fluoride, aluminum fluoride, hexafluorosilicic acid, sodium fluoride, potassium fluoride, and zinc fluoride. These supply sources may be used singly, or in combination of two or more thereof. The free fluorine ion (D) may be provided by the same compound as the above-described supply source(s) of (A), (B) and/or (C), or may be provided by a different compound. In the surface treatment agent, the fluorine-equivalent mass concentration of the free fluorine ion (D) is preferably 3 to 100 mg/L, more preferably 5 to 70 mg/L.
In the surface treatment agent, a supply source of the nitrate ion (E) is not particularly limited as long as it is capable of providing the nitrate ion (E) by mixing with an aqueous medium. Examples of the supply source include nitric acid, sodium nitrate, potassium nitrate, magnesium nitrate, ammonium nitrate, cerium nitrate, manganese nitrate, strontium nitrate, calcium nitrate, cobalt nitrate, aluminum nitrate, and zinc nitrate. These supply sources may be used singly, or in combination of two or more thereof. The nitrate ion (E) may be provided by the same compound as the above-described supply source(s) of (A), (B) and/or (C), or may be provided by a different compound. The content of the nitrate ion (E) in the surface treatment agent is not particularly limited, however, it is usually in a range of 100 to 30,000 mg/L in terms of nitric acid-equivalent mass concentration.
In the surface treatment agent of the present embodiment, a variety of metal components and additives may be incorporated as long as they do not impair the effects of the present invention. Examples of the metal components include vanadium, molybdenum, tungsten, manganese, cerium, magnesium, calcium, cobalt, nickel, strontium, lithium, niobium, yttrium, and bismuth. Examples of the additives include hydroxy group-containing compounds, formyl group-containing compounds, benzoyl group-containing compounds, amino group-containing compounds, imino group-containing compounds, cyano group-containing compounds, azo group-containing compounds, thiol group-containing compounds, sulfo group-containing compounds, nitro group-containing compounds, and urethane bond-containing compounds. These metal components and additives may be used singly, or in combination of two or more thereof. These additives are incorporated within a range that does not impair the effects of the present invention, therefore, the content thereof is at most several percent by mass with respect to a total amount of the surface treatment agent.
Meanwhile, the surface treatment agent of the present embodiment preferably does not contain carboxyl group-containing compounds, preferably does not contain amidino group-containing compounds, preferably does not contain aromatic ring-containing compounds, and more preferably does not contain organic matters. By using the surface treatment agent which does not contain organic matters, a reduction in the corrosion resistance of the resulting coating can be suppressed. It is noted here that “does not contain organic matters” does not necessarily mean that the content of organic matters is 0, and it is acceptable that the surface treatment agent contains organic matters within a range that does not significantly impair the effects of the present invention. Specifically, the content of organic matters may be 10 mg/L or less, 5 mg/L or less, 1 mg/L or less, 0.5 mg/L or less, or 0.1 mg/L or less, or 0 mg/L. The term “organic matters” used herein refers to compounds containing carbon as a main component, and may encompass derivatives of such compounds.
The pH of the surface treatment agent of the present embodiment is not particularly limited, however, it is preferably 2.3 to 5.0, more preferably 3.0 to 4.5. In the present specification, the pH means a value measured at a temperature at which the surface treatment agent is contacted on or over a surface of an aluminum or an aluminum alloy material. The pH can be measured using, for example, a portable electrical conductivity/pH meter (WM-32EP, manufactured by DKK-TOA Corporation).
Thus far, formulations of the surface treatment agent of the present embodiment have been described, moreover, another aspect of the present invention is a surface treatment agent which is used for surface treatment of an aluminum or an aluminum alloy material, and which is obtainable by mixing a source of a trivalent chromium-containing ion (A), a supply source of at least one ion (B) selected from a titanium-containing ion and a zirconium-containing ion, a supply source of a zinc-containing ion (C), a supply source of a free fluorine ion (D), and a supply source of a nitrate ion (E). The supply source of the free fluorine ion (D) may be the same compound as the supply source(s) of (A), (B) and/or (C), or may be a different compound. Further, the supply source of the nitrate ion (E) may be the same compound as the supply source(s) of (A), (B) and/or (C), or may be a different compound.
The surface treatment agent of the present embodiment can be obtained by mixing an aqueous medium with appropriate amounts of supply sources of the above-described trivalent chromium-containing ion (A), at least one ion (B) selected from a titanium-containing ion and a zirconium-containing ion, zinc-containing ion (C), free fluorine ion (D), and nitrate ion (E), and stirring the resulting mixture. In the production, solid supply sources may be added to the aqueous medium, or the solid supply sources may be dissolved in the aqueous medium in advance and then added as an aqueous medium solution. The pH of the resulting surface treatment agent is preferably adjusted to be in the above-described range using a pH modifier, such as nitric acid, hydrofluoric acid, ammonium hydrogen carbonate, or aqueous ammonia, however, the pH modifier is not limited to these components. Such a pH modifier may be used singly, or two or more thereof may be used in combination.
As the aqueous medium, water is typically used. The aqueous medium may contain a water-miscible organic solvent within a range that does not impair the effects of the present invention, however, the aqueous medium is preferably water. When the aqueous medium contains a water-miscible organic solvent, the content thereof may be 10 mg/L or less, 5 mg/L or less, 1 mg/L or less, 0.5 mg/L or less, or 0.1 mg/L or less.
A method of producing an aluminum or an aluminum alloy material having a coating formed by the surface treatment agent of the present embodiment includes a contact step of contacting the surface treatment agent of the present embodiment on or over a surface of an aluminum or an aluminum alloy material. By this step, a surface treatment coating is formed on or over the surface of the aluminum or an aluminum alloy material. Pretreatment steps, such as the degreasing step, the pickling step, and the like may also be performed prior to the contact step. The water-washing step may be performed after each step, and the drying step may be performed after each water-washing step.
An aluminum or an aluminum alloy material to be treated with the surface treatment agent is not particularly limited, and the surface treatment agent is particularly effective for aluminum die-cast materials which have a thick surface oxide film and in which an alloy component is segregated. The use of the aluminum or the aluminum alloy material is not particularly limited, and examples thereof include ship propulsion engines and peripherals thereof, as well as components of motorcycle internal combustion engines.
In the production method of the present embodiment, it is preferred to perform, prior to the contact step, the degreasing step of contacting a known degreasing agent on or over the surface of the aluminum or the aluminum alloy material. A degreasing method is not particularly limited, and examples thereof include solvent degreasing and alkali degreasing.
In the contact step of the production method of the present embodiment, the contact temperature and the contact time are not particularly limited, however, usually, the surface treatment agent is contacted on or over the surface of the aluminum or the aluminum alloy material at 30 to 80° C., preferably at 40 to 70° C., for 10 to 600 seconds. After this step, as required, the aluminum or the aluminum alloy material may be washed with water and then with deionized water, followed by drying. The drying temperature is not particularly limited, however, it is preferably 50 to 140° C. A method of contacting the surface treatment agent on or over the surface of the aluminum or the aluminum alloy material is not particularly limited, and examples thereof include an immersion method, a spray method, and a flow-coating method.
An aluminum or an aluminum alloy material having a surface treatment coating, which is produced by the above-described production method, is another embodiment of the present invention. The amount of the adhered surface treatment coating on the aluminum or the aluminum alloy material is not particularly limited, however, a total mass of Cr, Ti, and/or Zr, Zn that are contained in the surface treatment coating per unit area is preferably 1 to 200 mg/m2.
The aluminum or the aluminum alloy material having the surface treatment coating according to the present embodiment has excellent corrosion resistance even without performing a painting step of applying paintings onto the surface treatment coating, and has excellent corrosion resistance even when the coating is exposed to a high temperature, however, a painting step may be performed as well.
The painting step is not particularly limited and can be performed by, for example, a painting method such as aqueous painting, solvent painting, powder painting, anionic electrodeposition painting, cationic electrodeposition painting, or the like using a known painting composition.
Examples and Comparative Examples of the present invention will now be described. It is noted here, however, that the present invention is not limited to the below-described Examples by any means.
Aluminum die-cast material (JIS ADC12)
The supply sources shown in Tables 1 to 5 were mixed with water to obtain surface treatment agents of Examples 1 to 20 and Comparative Examples 1 to 3 which had the respective ion concentration values shown in Table 6. As a pH modifier, aqueous ammonia was used. The free fluorine ion concentration was measured using a commercially available fluorine ion meter [ion electrode: fluoride ion composite electrode F-2021 (manufactured by DKK-TOA Corporation)].
Using each of the surface treatment agents of Examples 1 to 20 and Comparative Examples 1 to 3, aluminum die-cast materials having surface treatment coatings were produced as test pieces 1 to 23.
Specifically, the above-described aluminum die-cast material was immersed in an alkali degreasing agent [20-g/L aqueous solution of FINE CLEANER 315E (manufactured by Nihon Parkerizing Co., Ltd.)] at 60° C. for 2 minutes, and the surface thereof was cleaned by rinsing with tap water. Subsequently, each surface treatment agent was sprayed onto or over the surface of the aluminum die-cast material at the contact temperature shown in Table 6 to perform the contact step. Thereafter, the aluminum die-cast material was washed with running tap water (at normal temperature for 30 seconds) and then washed with deionized water (at normal temperature for 30 seconds), followed by drying in an electric oven (at 80° C. for 5 minutes), whereby aluminum die-cast materials having surface treatment coatings (test pieces 1 to 23) were each produced.
With regard to the amount of the adhered surface treatment coating on each of the thus obtained test pieces 1 to 23, a total mass of Cr, Ti, and/or Zr, Zn that were contained in the surface treatment coating was measured using a scanning X-ray fluorescence spectrometer (ZSX Primus II, manufactured by Rigaku Corporation). The measurement results are shown in Table 7.
Further, for the test pieces 1 to 23, the following tests were conducted to determine the corrosion resistance and the post-heating corrosion resistance of each surface treatment coating were evaluated. The results thereof are shown in Table 8.
A 240-hour neutral salt spray test (JIS Z2371:2015) was performed on the test pieces 1 to 23. After the test pieces 1 to 23 were dried, the ratio of white rust generated on the surface of each test piece was visually measured. The ratio of white rust is the ratio of the area of generated white rust with respect to the area of the observed part. The evaluation criteria were as follows. The evaluation results are shown in Table 8.
5: Ratio of white rust=10% or lower
4: Ratio of white rust=higher than 10% but 30% or lower
3: Ratio of white rust=higher than 30% but 50% or lower
2: Ratio of white rust=higher than 50% but 70% or lower
1: Ratio of white rust=higher than 70%
The test pieces were each heated in an electric oven (at 180° C. for 20 minutes) and then subjected to a 240-hour neutral salt spray test (JIS Z2371:2015). After the test pieces were dried, the ratio of white rust generated on the surface of each test piece was visually measured. The ratio of white rust is the ratio of the area of generated white rust with respect to the area of the observed part. The evaluation criteria were as follows. The evaluation results are shown in Table 8.
5: Ratio of white rust=10% or lower
4: Ratio of white rust=higher than 10% but 30% or lower
3: Ratio of white rust=higher than 30% but 50% or lower
2: Ratio of white rust=higher than 50% but 70% or lower
1: Ratio of white rust=higher than 70%
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-065075 | Mar 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/011666 | 3/20/2019 | WO | 00 |
