JPH0633464B2 - Phosphate treatment liquid for composite structure and treatment method - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a phosphate treatment liquid and a treatment method for treating a surface of an automobile body, that is, a composite structure, which is formed by combining different materials such as steel plate, zinc and aluminum together. is there.

[Prior art]

Conventionally, when a car body, which is made of aluminum as a part of the structural body, that is, a part, is subjected to a phosphate treatment, a chromate treatment is mainly performed for performance reasons before attaching the aluminum part to the body, and then a steel is used. A method is known in which a plate and a galvanized steel plate are mounted on an automobile body, subjected to phosphate treatment again, and then subjected to cationic electrodeposition coating. The feature of this method is that the chromate film formed on the aluminum part first elutes part of the chromium and aluminum in the phosphate treatment step performed later, resulting in an incomplete chromate film state. It tends to occur, and of course, the formation of a phosphate film does not occur.

[Problems to be Solved by the Invention]

In the method of the conventional example, since the chromate-treated aluminum parts are incorporated in advance, chromium and aluminum are eluted in the phosphating solution, resulting in an incomplete film state of the chromate film and the phosphate film. However, there is a problem that the adhesion performance of the coating film subjected to the subsequent coating treatment is inferior, and particularly the water resistant secondary adhesion is inferior. Also, in the process of manufacturing an automobile body, in the series of process steps of assembly of parts → surface treatment → painting, the conventional example requires only aluminum parts as a separate process, that is, water washing treatment → chromate treatment → water washing drying treatment. After that, the process of assembly of parts → surface treatment → painting has to be performed, and there are problems in terms of workability and cost. In the case where the aluminum parts are assembled on an automobile body without chromate treatment and subjected to a phosphate treatment, a conventionally known treatment liquid produces a phosphate film having satisfactory performance on the surface of the aluminum parts, that is, a coating. It is not possible to obtain a film excellent in yarn rust resistance and water-resistant secondary adhesion afterwards, and only a film unsuitable for an automobile body requiring high film performance can be formed. At the same time, in the treatment process, aluminum ions are eluted in the phosphating solution, thereby significantly improving the performance of the phosphate film formed on the entire surface of the automobile body in which different kinds of materials are combined. It will have a big problem of decreasing.

[Means for Solving the Problems]

As a concrete means for solving various problems of the above-mentioned conventional example, the present invention provides zinc ion 0.3 to 2.0 g /, nickel ion
0.3 to 4.0 g /, manganese ion 0.3 to 2.0 g /,
Sodium ion 3 to 10 g /, potassium ion 0.1 to
10 g /, phosphate ion 5.0 to 25.0 g /, total fluorine ion 0.1 to 20 g /, nitrate ion 4.0 g / or more, and nitrite ion 0.01 to 1.0 g / as main components, pH 2.0 to
3.5, and the amount of complex fluoride ion in the total fluorine ion is 0.1 to 5 g / fluorine, and the free fluorine ion is
0.01 to 2 g / content of a phosphate treatment liquid for a composite structure, and the above-mentioned free fluorine using the treatment liquid and a mixture of acidic sodium fluoride and potassium acid fluoride as a replenishing liquid. The present invention provides a treatment method characterized by treating a composite structure while maintaining an ionic concentration. An excellent film can be formed as a coating base. It should be noted that aluminum ion in the treatment liquid is 400 ppm with time.
When it is included above, 0.01 to 2 of free fluorine ion
If maintained at g /, total fluorine ions will be in the range of 1 to 20 g /.

[Work]

In order to enable simultaneous treatment of zinc phosphate to a composite structure in which different materials such as aluminum, iron, zinc plating (including zinc alloy plating, alloyed zinc plating, etc.) are assembled together, Different materials are common, good coating performance after painting, aluminum elutes in the phosphate treatment liquid to treat aluminum, and aluminum ions accumulate, resulting in poor chemical conversion and deterioration of performance. Therefore, it is required to control aluminum ions. Therefore, in the composition of the treatment liquid, the presence of fluoride ions, that is, the complex fluoride ions in the total fluoride ions are 0.1 to 5 inclusive.
g /, free fluorine ion (total fluorine ion amount)
- (fluorine content in complex fluorine ions) - (fluorine content in AlF ₃₎ = is an indispensable condition that the free fluorine ion content is contained 0.01 to 2 g /, the treatment liquid 30
The composite structure is dipped at 1 to 5 ° C. for 1 to 5 minutes to be treated, and the zinc phosphate-based coating formed on the surface of the composite structure contains nickel and manganese at a ratio of 1 to 10% each (preferably Is about 4%). When aluminum ions elute and increase in the processing liquid,
It inhibits the film formation on the steel and aluminum surfaces of the composite structure. Especially, aluminum ion is 150 ppm
Above (approximately corresponding to the amount of free fluorine ions), it becomes extremely bad. Therefore, in performing continuous treatment using the treatment liquid, the reaction of the following formula: Al ⁺³ + 2KHF ₂ + NaHF ₂ → K ₂ NaAlF ₆ ↓ + 3H ⁺
F ₂ and NaHF ₂ are added appropriately (Al ⁺³ + 2KF
+ NaF + 3HF → K ₂ NaAlF ₆ ↓ + 3H ⁺ is the same reaction, and the same effect can be obtained by adding NaF and KF and HF), and controlling the elution aluminum ion by maintaining the free fluorine ion within a predetermined range. Thus, it becomes possible to make the phosphate film formed on the surface of the composite structure an appropriate film. In this case, the aluminum ion is controlled by controlling the amount of free fluorine ion in the treatment liquid. For that purpose, KHF ₂ and NaHF ₂ are added and the aluminum ion is precipitated in the form of K ₂ NaAlF ₆ . is there. And, what is important is that the acidic potassium fluoride is mixed in a ratio of 2 molecular weight with respect to 1 molecular weight of sodium acid fluoride, and these components are not mixed separately but mixed in advance. The above mixture is continuously or intermittently added to the treatment liquid. By doing so, precipitation of the aluminum compound is instantaneously generated, the free fluorine ion can be accurately measured, and control becomes easy. The mixture in this case may be liquid or solid. As a performance characteristic by applying the phosphating solution of the present invention, among the materials of the composite structure, for iron and galvanized material, there is almost no difference from the general zinc phosphate treatment. A non-phosphate coating can be formed, and the effect of improving the performance of the formed coating is remarkable for aluminum materials. That is, the phosphate film formed on the surface of aluminum contains Zn ₃ (PO ₄ ) even with the three components phosphoric acid, hydrofluoric acid and zinc.
_Although 2.4H ₂ O can be generated, as described above, in the present invention, since nickel and manganese are contained in the film at a ratio of 1 to 10% respectively, the film crystal is densified. In addition, the water-resistant secondary adhesion and outdoor exposure are improved. Table 1 shows the results of comparing the coating performance of the coating solution treated with the treatment liquid according to the present invention with the conventional example after coating. Conventional Zn-based treatment liquid composition Zn 1.2 g / Na 7.0 〃 PO ₄ 15 〃 NO ₃ 7 〃 SiF ₆ 3 〃 NO ₂ 0.5 〃 pH 3.2 conventional chromium-based treatment liquid composition CrO ₄ 7 g / PO ₄ 10 〃 F 2 〃 pH 1.5 Inventive treatment liquid composition Zn ²⁺ 1.4 g / Ni ²⁺ 1.5 〃 Mn ²⁺ 0.5 〃 PO ₄ ^-3 15.5 g / SiF ₆ ^-2 3 g / F ⁻ 100 ppm NO ₃ ⁻ 7 g / K ⁺ 0.5 〃 Na ⁺ 7 〃 NO ₂ ⁻ 0.2 〃 pH 3.2

【Example】

Next, some examples of the treatment liquid and the treatment method of the present invention will be given, and the effect thereof will be clarified by comparison with the conventional example. Example 1 (1) treatment solution composition ^{Zn 2+ 1.1~ 1.2 g / Ni 2+} 0.9~ 1.0 〃 Mn ²⁺ 0.4 to 0.6 〃 PO ₄ ^3- from 15.0 to 15.5 〃 SiF ₆ ^2- 2~ 3 〃 free F ^- 0.08 to 0.15 〃 NO ₃ ^-. 6 to 8 〃 K ⁺ 0.05 ~ 0.5 〃 Na ⁺ 6.8 ~ 7.8 〃 NO ₂ ^- 0.15 ~ 0.25 〃 pH 3.2 to 3.3 (2) processing conditions 45 ° C., for 2 minutes immersion the process conditions, Automobile body composed of 5000 series aluminum plate, electrogalvanized steel plate, zinc-nickel plated steel plate and steel plate (Fe: Al: Zn-Ni = 6: 1:
3), so that free fluorine is management range, free fluorine measurements (free fluorine assay ...... total fluorine content - as the amount of fluorine -alF 3 _(F in complex fluorine) = free fluorine amount) to, 2m ² / treatment while adding a 5% mixed aqueous solution of 2 molecular weight of KHF ₂ powder having a water content of 10% and 1 molecular weight of flaky NaHF ₂ and while supplementing with a replenisher so as to maintain other components as well. Table 2 shows the results of checking the performance of each test piece by. Comparative Example 1 5% NaH was used instead of the mixed solution of KHF ₂ and NaHF _2.
Table 2 shows the results obtained under the same conditions as in Example 1 except that F ₂ was used. Comparative Example 2 Table 2 shows the results obtained by the same method as in Example 1 except that the amount of free fluorine was maintained at 0 g / near. The clogging of the piping system was more than in Example 1. Comparative Example 3 KHF ₂ and instead of the mixture of NaHF ₂ 5% KHF ₂
Table 2 shows the results obtained under the same conditions as in Example 1 except that
Shown in. Comparative Example 4 The same conditions were used except that Mn ²⁺ was removed from the treatment liquid of Example 1. Comparative Example 5 The same conditions were used except that Ni ²⁺ was removed from the treatment liquid of Example 1.

【The invention's effect】

As described above, the phosphate treatment solution and treatment method for a composite structure according to the present invention include a predetermined amount of Ni ions and Mn ions in the zinc phosphate-based treatment solution, and a predetermined content of free fluorine ions. By controlling within the range, even if it is a composite structure containing aluminum parts, continuous processing is possible and workability is improved, and the phosphate film formed on the surface of the composite structure is It has an excellent effect of improving the adhesiveness of a coating film obtained by electrodeposition coating after outdoor exposure and the water-resistant secondary adhesiveness. Also, in the continuous processing of the composite structure including aluminum parts, the dissolved aluminum ions, which are harmful, are sequentially subjected to KH.
Since a mixture of F ₂ and NaHF ₂ is added and aluminum ions are precipitated and removed in the form of K ₂ NaAlF _6, an excellent effect that a good phosphate film is obtained can be obtained.

Claims (5)

[Claims] 1. Zinc ion 0.3 to 2.0 g /, nickel ion 0.3 to 4.0 g /, manganese ion 0.3 to 2.0 g /
, Sodium ion 3-10g /, potassium ion
0.1-10 g /, phosphate ion 5.0-25.0 g /, total fluorine ion 0.1-20 g /, nitrate ion 4.0 g / or more and nitrite ion 0.01-1.0 g /
Steels characterized in that they are 2.0 to 3.5, and complex fluorine ions are 0.1 to 5 g / in fluorine as total fluorine ions, and 0.01 to 2 g / in free fluorine ions represented by the following formula. A phosphating solution for a composite structure having a galvanized steel and an aluminum material. Perfluorinated ion (g /) - fluorine in complex fluorine ions (g /) - Fluorine ions in AlF ₃ (g /) = free fluorine ion (g /) 2. The phosphate treatment liquid for a composite structure according to claim 1, wherein in the treatment step, (excessive) free fluorine ions are contained with respect to the eluted aluminum ions. 3. The phosphating solution for composite structures according to claim 1, which is applied to form a film for a cationic electrodeposition coating base. 4. Zinc ion 0.3 to 2.0 g /, nickel ion 0.3 to 4.0 g /, manganese ion 0.3 to 2.0 g /
, Sodium ion 3-10g /, potassium ion
0.1-10 g /, phosphate ion 5.0-25.0 g /, total fluorine ion 0.1-20 g /, nitrate ion 4.0 g / or more and nitrite ion 0.01-1.0 g /
An acidic treatment liquid having a content of 2.0 to 3.5, a complex fluoride ion of 0.1 to 5 g / in terms of fluorine in a total fluoride ion, and a free fluoride ion of 0.01 to 2 g / is used.
A treatment method comprising treating the composite structure while maintaining the free fluorine ion concentration, using a mixture of sodium acid fluoride and potassium acid fluoride as a supplement. 5. The treatment method according to claim 4, wherein the mixture is a liquid or a solid mixed in a ratio of 2 molecular weights of potassium acid fluoride to 1 molecular weight of sodium acid fluorides.