JPH02277781A - Phosphating solution for combined structure and phosphating method - Google Patents

Abstract

PURPOSE:To improve the adhesion and waterproof secondary adhesion of a coating film by using a phosphating soln. of a specified pH having specified concns. of Zn ions, Ni ions, Mn ions, Na or K ions, phosphate ions, total F ions, nitrate ions, nitrite ions, complex F ions and free F ions. CONSTITUTION:A phosphating soln. of pH2-3.5 contg. 0.3-2g/l Zn ions, 0.3-4g/l Ni ions, 0.3-2g/l Mn ions, 0.1-10g/l Na ions, 5-25g/l phosphate ions, 0.1-20g/l total F ions, >=4g/l nitrate ions and 0.01-1g/l nitrite ions is used. The total F ions include 0.1-5g/l (expressed in terms of F) complex F ions and 0.01-2g/l free F ions. Even a combined structure contg. Al parts can be continuously phosphated and a formed phosphate coating film improves the adhesion of a coating film formed by cationic electrodeposition after exposure to the open air and the waterproof secondary adhesion.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a phosphate treatment solution and treatment method for treating the surface of an automobile body, that is, a composite structure, which is constructed by combining different materials such as steel plates, zinc, and aluminum. be.

[Prior art]

Conventionally, when phosphating a car body that is made of aluminum unilam, the aluminum part is chromate treated primarily for performance reasons before being attached to the body, and then the aluminum part is treated with chromate for performance reasons. Assembled into an automobile body made of sheet and galvanized steel sheet,
A well-known method is to perform phosphate treatment again, followed by cationic electrodeposition coating. The feature of this method is that the chromate film that is first formed on the aluminum part is
In the subsequent phosphate treatment step, some of the chromium and aluminum are eluted, which tends to leave the chromate film incomplete, and as a matter of course, no phosphate film is formed. It is.

[Problem to be solved by the invention]

In the conventional method, since aluminum parts that have been previously chromate-treated are incorporated, chromium and aluminum are leached into the phosphate treatment solution, resulting in incomplete chromate and phosphate coatings. However, there is a problem in that the adhesion performance of the coating film after subsequent painting treatment is poor, especially the water resistant secondary adhesion is poor. In addition, in the manufacturing process of automobile bodies, in the series of flow steps of parts assembly → surface treatment → painting, the conventional process described above requires a separate process for aluminum parts, which includes water washing → chromate treatment → water washing and drying. However, it is necessary to go through the steps of parts assembly, surface treatment, and painting, which poses problems in terms of workability and cost. When the above-mentioned aluminum parts are assembled into an automobile body and subjected to phosphate treatment without being subjected to chromate treatment, conventionally known treatment liquids do not produce a film with satisfactory performance on the surface of the aluminum parts, that is, the durability after painting. It is not possible to obtain a film with excellent thread rust resistance and water-resistant secondary adhesion, and only a film can be formed that is unsuitable for automobile bodies that require high coating film performance. At the same time, during the treatment process, aluminum ions are eluted into the phosphate treatment solution, which significantly reduces the performance of the coating that is chemically formed over the entire surface of the automobile body, which is made of a combination of different materials. This will pose major challenges.

[Means to solve the problem]

As a specific means for solving the various problems of the conventional example, the present invention provides zinc ions of 0.3 to 2.0 fi/l2, nickel ions of 0.3 to 4.0 g/l, and manganese ions of 0.3
~2.0g/l, sodium ion 3~10g/fl,
Potassium ion 0.1-10g/l! , phosphate ion 5
,0~25.09/λ, total fluorine ion 0.1~20
g/l2, nitrate ion 4.0g/n or more and nitrite ion 0.01-1.09/β as main components, pH2,
0 to 3.5, complex fluorine ions are 0.1 to 55 F/β as fluorine in total fluorine ions, and free fluorine ions are contained in an amount of 0.01 to 2 g/i. A phosphate treatment solution for composite structures, and treating a composite structure using the treatment solution and using a mixture of acidic sodium fluoride and acidic potassium fluoride as a replenishing solution while maintaining the free fluorine ion concentration. The present invention provides a treatment method that is characterized by the following, and even when applied without changing the general manufacturing process, it is possible to form a film on the surface of a composite structure that is excellent as a base for cationic electrodeposition coating. It is. In addition, if over 400 ppm of aluminum ions are included over time, free fluorine ions should be reduced by 0.01 to 29 ppm.
/l, the total fluorine ions will be in the range of 1-20g/l.

[For use]

Different materials e.g. aluminum, iron, galvanized (
In order to be able to simultaneously treat zinc phosphate on composite structures assembled with zinc alloy plating, alloyed zinc plating, etc., it is necessary to: - In order to treat aluminum, aluminum is eluted into the phosphate treatment solution, and the accumulation of aluminum ions worsens the chemical formation properties and causes performance deterioration, so it is necessary to control aluminum ions. is required. Therefore, in the treatment liquid composition, the presence of fluorine ions, that is, 0.1 to 5 complex fluorine ions in the total fluorine ions.
fJ/l2, free fluorine ions (total fluorine ion amount) - (fluorine amount in complex fluorine ions) - (/l F3
(amount of fluorine in) = amount of free fluorine ions is 0.01 to 2 g
/It is an essential condition, and the treatment solution is heated to 30 to 55°C and the composite structure is immersed for 1 to 5 minutes. The zinc oxide film is characterized in that nickel and manganese are each contained in a ratio of 1 to 10% (preferably about 4%). When aluminum ions elute and increase in the processing solution,
Inhibits film formation on the surfaces of steel plates and aluminum cum of composite structures. In particular, aluminum ions are 150D
When it exceeds Dm (approximately corresponds to m of M-separated fluorine ion), it becomes extremely bad. Therefore, when performing continuous treatment using the treatment liquid, the following formula, AI+3+2KHF2+NaHF2-+K NaAl
Due to the reaction of F6 ↓ and 3H+, KH corresponding to the amount of eluted aluminum ions is generated.
By adding F and Na1-IF2 appropriately and maintaining free fluorine ions within a predetermined range, eluted aluminum ions can be controlled and the phosphate film formed on the surface of the composite structure can be made into an appropriate film. It becomes possible. In this case, aluminum ions are controlled by controlling the amount of free fluorine ions in the treatment solution, and for this purpose KHF2 and NaHF2 are added to precipitate aluminum ions in the form of 2NaAIF6. What is important is that the ratio of two molecular weight molecules of acidic potassium fluoride to one molecular weight of acidic sodium fluoride is mixed. Rather than adding these components separately, they are mixed in advance. The mixture is added continuously or intermittently to the processing solution. By doing so, aluminum compound precipitates are instantaneously formed, free fluorine ions can be measured accurately, and control becomes easy. The mixture in this case may be liquid or solid. The performance characteristics of applying the phosphating solution of the present invention are that among the materials of composite structures, there is almost no difference in performance for iron and galvanized materials compared to that obtained by general zinc phosphate treatment. It is possible to form a film that does not require the use of aluminum, and the effect of improving the performance of the formed film on aluminum materials is remarkable. That is,
The phosphate film that forms on the aluminum surface is caused by phosphoric acid,
Even with the three components of hydrofluoric acid and zinc, Zn (, PO) "4H
Although it is possible to produce nickel and manganese in the film, as mentioned above, in the present invention, nickel and manganese are each added to the film.
By containing it at a ratio of ~10%, the film crystal becomes dense and water resistant secondary adhesion and outdoor SII properties are improved. Table 1 shows the results of comparing the performance of the film treated with the treatment liquid according to the present invention in this case with that of the conventional example after painting. Table 1 (Performance results after painting) Conventional example Zn-based treatment liquid composition Zn 1.29/l! Na 7.0n PO415/F N O37n S n Fe 3 〃 NO20,5n PH3,2p Conventional chromium-based treatment liquid composition CrO27g7tt PO410n F 2 n PH1,5n Invention treatment liquid composition Z n ” L4g/I Nt2+1.5 /F Mn” 0.5 n −31s, sg/I O4 SiF 3 g/l! 1" 100 ppm NO37g/IK" 0.5/l Na 7 No2 0.2 PH3,2 (Example) Next, some examples of the treatment liquid and treatment method of the present invention will be given and compared with conventional examples. Example 1 (1) Treatment liquid composition Zn2" 1.1-1.2 9/βN i "
0.9~l, QnMn”
0.4-0.6 n3-15.0-15.5 7 2-2-3 S i F s Free FO, 08-0.15 O3 to Na O2 PH (2) Processing test material 5000 series Aluminum material (3) Processing conditions 45°C, 2 minute immersion 6-8 0.05-0.5 6.8-7.8 0.15-0.25 3.2-3.3 11 Under the above processing conditions, Automobile body (Fe:AJ:Zn-Ni-6:1:
3), measure free fluorine so that free fluorine is within the control range (free fluorine measurement method...total fluorine m-
Amount of fluorine in the fluorine complex - 8βF3 (as F) - free fluorine 11) In L, a 5% mixed aqueous solution with 10% water content K) IF2F2 powder 2 quantum amounts of lake-like Na)-IF2 1 molecule m is added. Table 2 shows the results of checking the performance of each test piece at that point. Comparative Example 1 5% NaH instead of a mixture of KHF2 and NaHF2
Table 2 shows the results obtained under the same conditions as in Example 1 except that F2 was used. Comparative Example 2 Table 2 shows the results of the same method as in Example 1, except that the free fluorine was maintained at around O'9/l. The piping system was more clogged than in Example 1. Comparative Example 3 5% KH instead of a mixed solution of KHF2 and NaHF2
Table 2 shows the results obtained under the same conditions as in Example 1 except that F. *V1 mounting conditions: cationic electrodeposition: 175°C, 20 minutes baking, which is an excellent effect.

Claims (1)

[Claims] (1) Zinc ions 0.3 to 2.0 g/l, nickel ions 0.3 to 4.0 g/l, manganese ions 0.3 to 2.0 g/l.
0g/l, sodium ion 3-10g/l, potassium ion 0.1-10g/l, phosphate ion 5.0-25
．． 0g/l, total fluorine ion 0.1-20g/l, nitrate ion 4.0g/l or more and nitrite ion 0.01-1
．． The main component is 0 g/l, the pH is 2.0 to 3.5, and the total fluorine ions contain 0.0 g/l of complex fluorine ions as fluorine.
For composite structures containing steel, galvanized steel, and aluminum materials, characterized by containing 1 to 5 g/l and 0.01 to 2 g/l of free fluorine ions expressed by the following formula: Phosphating solution. Total fluorine ions (g/l) - Fluorine in complex fluorine ions (g/l) - Fluorine ions in AlF_3 (g/l) =
Free fluorine ions (g/l) (2) For the composite structure according to claim (1), wherein in the treatment step, free fluorine ions are contained (in excess) relative to the aluminum ions eluted. Phosphating solution. (3) The phosphate treatment solution for composite structures according to claim (1), which is applied to form a base film for cationic electrodeposition coating. (4) Zinc ion 0.3-2.0g/l, nickel ion 0.3-4.0g/l, manganese ion 0.3-2.
0g/l, sodium ion 3-10g/l, potassium ion 0.1-10g/l, phosphate ion 5.0-25
．． 0g/l, total fluorine ion 0.1-20g/l, nitrate ion 4.0g/l or more and nitrite ion 0.01-1
．． The main component is 0 g/l, the pH is 2.0 to 3.5, and the total fluorine ions contain 0.0 g/l of complex fluorine ions as fluorine.
1 to 5 g/l, and free fluorine ions are 0.01 to 2
Using an acidic treatment solution containing g/l and using a mixture of acidic sodium fluoride and acidic potassium fluoride as a replenishing agent,
A processing method characterized in that the composite structure is processed while maintaining the free fluorine ion concentration. (5) The treatment method according to claim (4), wherein the mixture is a liquid or solid in which 1 molecular weight of acidic sodium fluoride is mixed with 2 molecular weights of acidic potassium fluoride.