JPH05230669A - Continuous phosphate chemical conversion treatment for steel-aluminum containing metal composite material - Google Patents

Abstract

PURPOSE:To provide a method capable of stable phosphate chemical conversion treatment to a steel-aluminum contg. metal composite material while maintaining good chemical conversion effect even if aluminum ions eluted in phosphate chemical conversion treating solution are accumulated. CONSTITUTION:In the case of applying the continuous chemical conversion treatment by phosphate chemical treating solution to a composite material of steel material and aluminum or its alloy material, nitrate ions and free fluoride ions are added corresponding to the increase of aluminum ion concentration in the chemical conversion treating solution to adjust the molar ratios of Al to (NO3+F) to <=1/3 and those of NO3 to F to 1:2-2:1 and simultaneously free fluoride ion concentration is kept in the range of 50-500ppm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous phosphate chemical conversion treatment method for steel-aluminum-containing metal composite materials. More specifically, the present invention is directed to a case where a composite material containing both a steel material and an aluminum-containing metal material is continuously treated with a phosphate chemical conversion treatment solution, and aluminum ions eluted and accumulated in the treatment solution are accumulated. The present invention relates to a continuous phosphate chemical conversion treatment of a steel-aluminum-containing metal composite material capable of preventing the adverse effect of the above and forming a good phosphate chemical conversion film on the composite material.

[0002]

2. Description of the Related Art In recent years, for example, in the automobile industry, in order to reduce the weight of a vehicle body, some or all of steel materials are replaced with aluminum or aluminum-containing metal materials such as aluminum-containing alloys. Is becoming When such a steel material and a composite material containing both an aluminum-containing metal material are subjected to continuous chemical conversion treatment with a phosphate chemical conversion treatment liquid by a conventional method,
Aluminum ions are eluted from the composite material in the treatment liquid,
It is accumulated, which hinders the uniform formation of the phosphate conversion coating on the composite material, making it difficult to impart sufficient coating performance and corrosion resistance to the composite material.

In order to solve the above-mentioned problems, for example, a special phosphate chemical conversion treatment method as described in JP-B-63-157879 and JP-B-64-6881 is combined. Method of applying to material, method of subjecting composite material to phosphate chemical treatment while removing aluminum ion in phosphate chemical treatment solution using ion exchange resin, and aluminum ion in phosphate chemical treatment solution A method of selectively precipitating only the above with a special treating agent has been attempted.

However, in the above-mentioned conventional method, the phosphate conversion treatment effect on the steel material portion in the composite material can be maintained well, but the phosphate conversion treatment effect on the aluminum-containing metal material portion in the composite material is maintained. There is a problem that is insufficient. That is, in the above-mentioned conventional method, the formation of the phosphate chemical conversion film on the surface of the aluminum-containing metal material portion is unstable, and in some cases, a good phosphate chemical conversion film is formed. However, there is a problem that the phosphate conversion coating is hardly formed, and therefore the coating property and corrosion resistance of this portion are poor.

In the method using the above special ion exchange resin, the processing equipment becomes large in scale and the equipment cost thereof is high,
In addition, there is a drawback that the operating cost, especially the cost of regenerating the ion-exchange resin, is high, and that it is economically unprofitable when it is carried out on an industrial scale.

Further, as the above-mentioned aluminum ion precipitation method, aluminum ions are converted into elpasolite (K ₂₎ by using the following reaction: Al ³⁺ + 2K ⁺ + Na ⁺ + 6F ⁻ → K ₂ NaAlF _6.
A method of precipitating as NaAlF ₆ ) is known.

In order to perform the above elpasolite precipitation method on a phosphate chemical conversion treatment solution containing aluminum ions,
The sodium compound and the potassium compound must be added to the chemical conversion treatment solution so that the total ion equivalent of sodium and potassium ions becomes equal to the ion equivalent of aluminum ion. Specifically, a precipitation forming treatment liquid containing sodium acid fluoride and potassium acid fluoride in a molar ratio of 1: 2 is added to the chemical conversion treatment liquid, and this is combined with aluminum ions to form elpaso. A light precipitate needs to be formed.

In the above elpasolite precipitation method, when alkali (sodium and potassium) in an amount equal to or more than the equivalent of aluminum ions is added to the chemical conversion treatment liquid, the residual alkali ions form a phosphate chemical conversion film of the chemical conversion treatment liquid. Noh changes and stable chemical conversion becomes impossible.
Further, when the fluoride ion concentration in the treatment liquid becomes excessive by the addition of the acidic alkali fluoride, the chemical conversion film forming property of the aluminum-containing metal material part in the composite material deteriorates, and the chemical conversion processability of the steel material part also deteriorates. There are drawbacks such as

As described above, in the conventional method, it was extremely difficult to stably perform the phosphate chemical conversion treatment on the composite material.

[0010]

DISCLOSURE OF THE INVENTION The present invention provides a composite material containing both a steel material and an aluminum-containing metal material, which is continuously treated with a phosphate chemical conversion treatment solution in the treatment solution. Steel capable of stably forming a good phosphate conversion coating on both the steel material portion and the aluminum-containing metal material portion in the composite material without removing the eluted aluminum ions.
It is intended to provide a continuous phosphate chemical conversion treatment method for an aluminum-containing metal composite material.

[0011]

According to the present invention, when a composite material containing both a steel material and an aluminum-containing metal material is subjected to continuous chemical conversion treatment with a phosphate chemical conversion treatment solution, aluminum ions eluted in the treatment solution are provided. Control the molar ratio of the total amount of nitrate group ions and total fluorine added to the treatment liquid and the molar ratio of nitrate ions to total fluorine within the specified range, and maintain the free fluoride ion concentration within the specified value range. By doing so, the above-mentioned problems were successfully achieved.

That is, the continuous phosphate chemical conversion treatment method of a steel-aluminum-containing metal composite material of the present invention is a method of continuously producing a composite material containing both a steel material and an aluminum-containing metal material in a phosphate chemical conversion treatment liquid. In the case of the treatment with the above, the nitrate group ion (N
O ₃ ^-), and free fluorine ion (F ^-) is contained,
The amount of aluminum ions (Al ³⁺ ) eluted and contained in the phosphate chemical conversion treatment liquid is detected from the composite material, and the nitrate group ions (NO ³ ) of the aluminum ions (Al ³⁺ ) are detected. ₃ ^-) and the total fluorine (the molar ratio to the total amount of F) Al: the (NO ₃ + F), in 1/3 or less, and a molar ratio to the total fluorine nitrate group ions 1:
It is characterized in that it is controlled to 2 to 2: 1 and the concentration of the free fluorine ion (F ⁻ ) is maintained at 50 to 500 ppm (measured value by a fluorine ion sensitive electrode).

In the above method of the present invention, when the phosphate chemical conversion treatment is started, the phosphate chemical conversion treatment liquid contains ions of the following types and concentrations: zinc ion 0.2 to 5.0 g / liter nickel ion 0 1 to 4.0 g / liter Manganese ion 0.1 to 2.0 g / liter Phosphate group ion 5 to 30 g / liter Nitrate group ion 1 to 20 g / liter Nitrite group ion 0.01 to 1.0 g / liter and It is preferable to contain free fluorine ions in an amount of 50 to 500 ppm (measured value by a fluorine ion sensitive electrode).

[0014]

The composite material used in the method of the present invention contains both a steel material and an aluminum-containing metal material. Steel material is not particularly limited as long as it can be subjected to phosphate chemical conversion treatment, for example, cold-rolled steel sheet, electrogalvanized steel sheet, hot-dip galvanized steel sheet, alloyed hot-dip galvanized steel sheet, It also includes a two-layer plated steel sheet and the like. The aluminum-containing metal material is an aluminum material, for example, a pure aluminum series No. 1000 series material, a metal material plated with aluminum or an aluminum alloy, and an aluminum-containing alloy material such as an aluminum-copper alloy (for example, A
1-Cu-based 2018), aluminum-manganese-based alloy (for example, Al-Mn-based 3003), aluminum-
Magnesium-based alloy (for example, Al-Mg-based 505
2), aluminum-magnesium-silicon alloy (for example, Al-Mg-Si alloy 6063) and the like, and the type thereof is not particularly limited as long as it can be subjected to the phosphate chemical conversion treatment.

In the method of the present invention, nitric acid is added to the chemical conversion treatment solution in order to prevent the adverse effects of aluminum ions eluted from the aluminum-containing metal material portion in the composite material into the phosphate chemical conversion treatment solution and accumulated. Base ion (N
O ₃ ^-) and fluorine (F) is contained, to detect the amount of aluminum ions (Al ³⁺⁾ in the chemical conversion treatment solution, these aluminum ions, the molar ratio to the total amount of nitrate groups ion and total fluorine Al: (NO ₃ + F) is controlled to 1/3 or less, the molar ratio of nitrate group ions to total fluorine is controlled to 1: 2 to 2: 1, and the concentration of the free fluorine ions is 50 to 500 ppm (fluorine). (Measured by an ion sensitive electrode).

In the method of the present invention, a particularly important point is Al: (NO ₃ + F) in the phosphate chemical conversion treatment solution in order to prevent the adverse effect due to the accumulation of aluminum ions.
It is to control the molar ratio to 1/3 or less. Al: (N
When the O ₃ + F) molar ratio becomes larger than 1/3, the amount of sludge (precipitate) generated increases, and the crystallinity of the phosphate chemical conversion coating film formed deteriorates (roughening of crystals, denseness). There are adverse effects such as chipping and deterioration of adhesion. Al:
By controlling the (NO ₃ + F) molar ratio to 1/3 or less, the amount of suspended sludge can be reduced,
This is presumed to be the effect of increasing the dissolved capacity of aluminum.

In the method of the present invention, the molar ratio of nitrate ion (NO ₃ ⁻ ) to total fluorine is 1/2 to 2 /.
Control to 1. When the molar ratio is less than 1/2, insoluble sludge increases, which causes inconvenience such as deterioration of maintainability of equipment. When the molar ratio is higher than 2/1, normal phosphoric acid productivity Is inhibited, which is presumed to be due to the reduced formation of complex fluoride ions.

As described above, the aluminum ions eluted and accumulated in the treatment liquid are treated by chemical conversion treatment of the phosphate chemical conversion treatment liquid when the concentration of free fluorine ions in the chemical conversion treatment liquid is maintained at 50 to 500 ppm. It does not adversely affect the performance and does not deteriorate the phosphate chemical conversion film forming properties on the surfaces of the steel materials and the aluminum-containing metal materials. Therefore, both the surface of the steel material portion and the surface of the aluminum-containing metal material in the composite material can be stably subjected to favorable phosphate chemical conversion treatment in the aluminum-containing phosphate chemical conversion treatment liquid.

In the method of the present invention, the concentrations of aluminum ion and nitrate group ion in the phosphate chemical conversion treatment solution are
Each can be measured by a conventionally used method, that is, an atomic absorption spectrophotometric method and an ion chromat method.

The concentration of free fluorine ions in the phosphate chemical conversion treatment solution can be measured using a fluorine ion sensitive electrode as follows. That is, a fixed amount of sodium fluoride (for example, 10 ppm, 100 ppm, or 1000 ppm) is added to an IN-sodium nitrate aqueous solution,
The pH of this mixed solution is adjusted to 5 to 6 by adding nitric acid or sodium hydroxide, if necessary, to prepare a standard solution of each concentration of free fluorine. Using these standard solutions, a fluorine ion sensitive electrode (fluorine: F-125, comparison: HS-305DP, manufactured by Toa Denpa Kogyo KK) and a fluorine ion meter (IM-40S, manufactured by Toa Denpa Kogyo KK) Calibrate the indicated value of fluorine ion concentration by.
In this case, the indicated value of the fluorine ion sensitive electrode is defined to indicate the total amount of fluorine derived from sodium fluoride contained in the standard solution. The free fluorine ion concentration in the test phosphate chemical conversion treatment solution is measured using the fluorine ion sensitive electrode and the above-mentioned calibrated fluorine ion meter, and the indicated value is taken as the indicated value of the fluorine ion sensitive electrode.

The fluorine content in the phosphate chemical conversion treatment solution can be measured by a conventionally used method, that is, a fluorine distillation method, an ion chromat method, or the above fluorine ion sensitive electrode method.

In the method of the present invention, the concentration of nitrate group ions in the phosphate chemical conversion treatment liquid is adjusted by adding at least one selected from nitric acid and nitrates to the treatment liquid, and free fluorine ion Concentration is NaF, K
F, NH ₄ F, HF, NH ₄ HF ₂ , and H ₂ SiF
It is adjusted by adding at least one selected from _{6 and the} like.

In the method of the present invention, the free fluorine ion concentration in the phosphate chemical conversion treatment solution must be maintained at 50 to 500 ppm, preferably 100 to 300 ppm. When the concentration of fluorine in the chemical conversion treatment liquid is less than 50 ppm, the amount of phosphate film formed in the aluminum-containing metal material portion of the composite material decreases, and therefore its coatability,
And corrosion resistance deteriorates. Further, if it exceeds 500 ppm and becomes excessive, the etching action of the composite material on the steel material and the aluminum-containing metal material becomes excessive, and the precipitation amount of phosphate crystals on the surface of these materials decreases, and further, the aluminum-containing metal material. Deposition of AlF ₃ occurs on the surface of the material part, which reduces the effect of phosphate chemical conversion treatment on this part, resulting in a phosphate film (crystal).
Causes inconvenience such as insufficient formation of
The overall appearance of the composite material will be poor, and its paintability and corrosion resistance after painting will be reduced.

There is no strict limitation on the concentration of nitrate group ions in the phosphate chemical conversion treatment solution, but it is generally preferable that the concentration is 20 g / liter or less. That is, if the nitrate group ion concentration exceeds 20 g / liter and becomes excessive, the chemical conversion effect of the phosphate chemical conversion treatment liquid decreases, and the paintability and corrosion resistance of the obtained product become insufficient.

In the method of the present invention, the phosphate chemical conversion treatment liquid at the start of the phosphate chemical conversion treatment has the following types and concentrations of ions: zinc ion 0.2 to 5.0 g / liter nickel ion 0.1 to 4. 0.0 g / liter Manganese ion 0.1-2.0 g / liter Phosphate group ion 5-30 g / liter Nitrate group ion 1-20 g / liter Nitrite group ion 0.01-1.0 g / liter and free fluorine ion 50 ˜500 ppm (measured value by a fluorine ion sensitive electrode) is preferable.

[0026]

The method of the present invention will be further described with reference to the following examples.

Example 1 and Comparative Example 1 In each of Example 1 and Comparative Example, a composite material of a steel material and an aluminum material was continuously subjected to phosphate chemical conversion treatment at 40 ° C. for 2 minutes. The chemical conversion treatment liquid at the start of the treatment (trademark: Palbond L3080, manufactured by Nippon Parkerizing Co., Ltd.) contained the following types and concentrations of ions. Zn ion 0.8 g / liter PO ₄ ion 15 g / liter NO ₃ ion 5 g / liter Ni ion 10 g / liter Mn ion 0.8 g / liter Perfluorine free fluorine ion 120 ppm NO ₂ ion 120 ppm The pH of this treatment solution is determined by a conventional method. Was adjusted to about 2.9 to 3.0 and maintained.

In Comparative Example 1, only the phosphate chemical conversion treatment liquid was replenished without replenishing only the free fluorine ion in accordance with the lapse of treatment time. For a while after the start of the treatment, it was confirmed that both the steel material portion and the aluminum material portion of the composite material were covered with the dense phosphate conversion film (crystal). However, as the concentration of aluminum ions in the treatment liquid increased, the phosphate conversion treatment effect decreased, and when the concentration exceeded about 100 ppm, a phosphate conversion film was formed on the aluminum material part. Was not observed, and the phosphate crystals formed on the steel part gradually became coarse. When the aluminum ion concentration reached about 150 ppm, the phosphate crystals on the steel material became extremely coarse and the chemical conversion treatment effect became poor.

In Example 1, the aluminum ion concentration in the phosphate chemical conversion treatment solution was sequentially measured with the passage of the chemical conversion treatment time, and nitric acid and sodium acid fluoride were added together with the chemical conversion treatment solution replenishment solution for treatment. The molar ratio Al: (NO ₃ + F) in the liquid is controlled to 1/3 or less, and the molar ratio NO ₃ : F is controlled to 1: 2 to 2: 1 and the free fluorine ion concentration is maintained at 150 ppm. did. Then, regardless of the increase in the aluminum ion concentration, the effect of forming a phosphate film on the steel material portion and the aluminum material portion was good and unchanged, and the aluminum ion concentration was about 5%.
Even when the amount reached 00 ppm, a good phosphate chemical conversion treatment effect was obtained.

Example 2 and Comparative Examples 2 and 3 In each of Example 2 and Comparative Example 2, a composite material including a steel material and an aluminum alloy (JIS A5030) material was phosphatized by immersion at 40 ° C. for 2 minutes. The growing treatment was continuously performed. The phosphate chemical conversion treatment liquid at the start of the treatment contained components of the following types and concentrations. Zn ion 1.0 g / liter PO ₄ ion 20 g / liter NO ₃ ion 6 g / liter Ni 0.8 g / liter Mn 0.6 g / liter Total fluorine 0.8 g / liter Free fluorine ion 220 ppm NO ₂ ion 100 ppm The pH was adjusted and maintained at about 2.9-3.0 by conventional methods.

In Comparative Example 2, the chemical conversion treatment was continuously carried out while replenishing the treatment liquid so that the concentration of free fluorine ions was removed and other ions were maintained at the above concentrations. Until the aluminum ion concentration in the chemical conversion treatment liquid reached about 200 ppm, the chemical conversion treatment of the steel material portion of the composite material was performed without any problem. However, as the aluminum ion concentration increases, the chemical conversion treatment effect on the aluminum alloy material part gradually declines, and when the aluminum ion concentration exceeds 300 ppm, the chemical conversion treatment effect on the aluminum alloy material part remarkably decreases and it is formed on the steel material part. The resulting phosphate crystals were also coarse, and the quality of the obtained product was poor.

In Comparative Example 3, the chemical conversion treatment solution was replenished, and sodium acid fluoride was added to the chemical conversion treatment solution.
While maintaining the free fluorine ion concentration at 230 ppm, the same phosphate conversion treatment as in Comparative Example 2 was continuously applied to the composite material. Until the concentration of aluminum ions in the chemical conversion treatment solution reaches about 200 ppm, dense phosphate crystals are formed on the steel material part and aluminum alloy part of the composite material, and the paintability and corrosion resistance of the obtained product are improved. Was also good. However, when the aluminum ion concentration exceeds about 300 ppm, the chemical conversion treatment effect on the steel material portion and the aluminum alloy portion rapidly declines, and the paintability and corrosion resistance of the obtained product become poor.

Example 3 Using the same phosphate chemical conversion treatment liquid as in Comparative Examples 2 and 3, the composite material was subjected to continuous chemical conversion treatment. However, sodium acid fluoride and nitric acid are added to the chemical conversion treatment solution together with the replenishment solution, and the molar ratio of aluminum ions in the chemical conversion treatment solution to the total amount of nitrate group ions and fluorine is Al: (NO ₃ + F). Is controlled to 1/3 or less, and the molar ratio NO ₃ : F is controlled to 1: 2 to 2: 1.
The free fluoride ion concentration was maintained at 230 ppm. Then, even if the aluminum ion concentration in the chemical conversion treatment liquid increased, the phosphate chemical conversion coating was sufficiently formed on the steel material portion and the aluminum composite material portion of the composite material. Even when the aluminum ion concentration reached about 1000 ppm, a satisfactory chemical conversion treatment effect was obtained on the steel and aluminum alloy material portions, and the paintability and corrosion resistance of the product were good.

[0034]

According to the method of the present invention, continuous chemical conversion treatment of a steel-aluminum-containing metal composite material with a phosphate chemical conversion treatment liquid is stabilized even if the concentration of aluminum ions eluted and accumulated in the treatment liquid increases. Then, it became possible to continue, and it became possible to continuously produce a chemical conversion treatment composite material having good paintability and corrosion resistance.

Front Page Continuation (72) Inventor Osamu Furuyama 1-15-1 Nihonbashi, Chuo-ku, Tokyo Inside Parkerizing Co., Ltd. Japan (72) Inventor Asao Mochizuki 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Automobile Co., Ltd. (72 ) Inventor Haruo Kojima 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (2)

[Claims] 1. When continuously treating a composite material containing both a steel material and an aluminum-containing metal material in a phosphate chemical conversion treatment solution, a nitrate group ion (N
O ₃ ⁻ ) and free fluorine ion (F ⁻ ) are contained, and the amount of aluminum ion (Al ³⁺ ) eluted and accumulated in the phosphate chemical conversion treatment solution is detected from the composite material, and The molar ratio Al: (NO ₃ + F) of the aluminum ions (Al ³⁺ ) to the total amount of the nitrate group ions (NO ₃ ⁻ ) and total fluorine (F) is 1/3 or less, and the nitric acid is The molar ratio of the basic ion (NO ₃ ⁻ ) to total fluorine is controlled to 1: 2 to 2: 1 and the concentration of the free fluorine ion (F ⁻ ) is 50 to 500 ppm.
(Measured value by a fluorine ion sensitive electrode) is maintained, and the continuous phosphate chemical conversion treatment method of a steel-aluminum-containing metal composite material. 2. At the start of the phosphate chemical conversion treatment, the phosphate chemical conversion treatment liquid contains ions of the following types and concentrations: zinc ion 0.2 to 5.0 g / liter nickel ion 0.1 to 4. 0.0 g / liter Manganese ion 0.1-2.0 g / liter Phosphate group ion 5-30 g / liter Nitrate group ion 1-20 g / liter Nitrite group ion 0.01-1.0 g / liter and free fluorine ion 50 The method according to claim 1, which contains ˜500 ppm (measured value by a fluorine ion sensitive electrode).