JPH0665756A - Treatment of chromic phosphate film - Google Patents

Abstract

PURPOSE:To lessen the need for spending the useless time, cost and equipment for a waste liquid treatment, etc., after a chemical conversion treatment by specifying the effective concn. of a chemical conversion agent in the chemical conversion treatment. CONSTITUTION:A chromic phosphate treatment is executed by subjecting a sample of an aluminum material to the chemical conversion treatment after a degreasing treatment. The effective concn. of the chemical conversion agent (H3PO4, CrO3) is specified within a 0.5 to 4 point range, more preferably to 2 points in the chemical conversion treatment. As a result, the film forming speed is increased and, on the other hand, the corrosion preventive performance is improved. Further, the amt. of the auxiliary material (HF) to be used is decreased with a decrease in the amt. of the chemical conversion agent to be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical conversion treatment method for aluminum materials, particularly aluminum cans.

[0002]

2. Description of the Related Art A treatment method for forming an oxide film or an insoluble metal salt film of an inorganic salt on a metal surface by a chemical / electrochemical reaction between a metal and a solution is called chemical conversion treatment. Phosphate treatment, chromate treatment, oxide film treatment, oxalate treatment, etc. are known for this method, and rust prevention of metal, coating base, cold work lubrication film of metal, sliding part of metal Widely used for wear-resistant coatings and electrical insulation coatings. For example, in the phosphate coating method, a metal is allowed to act on a phosphate aqueous solution to form a metal phosphate coating on the surface thereof, and the metal to be treated is steel, Zr, Al, Mg, etc. Widely used as a coating for steel, Zr-plated steel sheets, and as a lubricating coating for cold working of steel. The chemical conversion treatment aqueous solution generally contains alkali metal, ammonium, M
Primary phosphate consisting of one or two of g, Zn and Ca, free phosphoric acid as a reaction accelerator, heavy metals such as Ni, Co and Cu, oxidizing agents such as nitric acid, nitrous acid and chlorate, and fluorine And the like are used depending on the purpose and application. The chromate treatment liquid includes an alkaline bath system and an acid bath system.

In the chemical conversion treatment, the concentration and composition are analyzed periodically to adjust and reinforce the chemical concentration and composition, and accumulated interfering ions and sludge are continuously removed from the bath or periodically renewed. There is a need to. At present, the concentration and composition of all processes of degreasing, washing with water, film formation, and post-treatment are automatically measured and recorded by electrical conductivity, oxidation-reduction potential, and neutralization titration, and at the same time, automatic management is performed in conjunction with an automatic device for chemicals and water supply. Central control of management is in place. For more detailed information on chemical conversion treatment, please refer to the textbooks or reference books in that field (Chemical Handbook Application, published by Maruzen Co., Ltd., etc.).

The present application refers to a chemical conversion treatment method for aluminum cans. The chemical conversion treatment method in this case is roughly classified into a phosphoric acid chromic acid coating treatment (Cr-based chemical conversion treatment) and a Zr composite oxide conversion coating treatment (Zr-based chemical conversion treatment). For example, the phosphoric acid chromic acid film treatment is usually performed using a chemical conversion main agent composed of CrO ₃ and H ₃ PO ₄ and a chemical conversion auxiliary agent composed of HF. In this treatment, it cannot be said that the relationship between the film formation rate and the corrosion resistance has been sufficiently clarified, and as a result, it is difficult to judge the appropriate amount of the chemical conversion treatment agent, and it is inappropriate to use an excessive amount of chemical conversion treatment agent. There is a problem in that wasteful time, cost and equipment have to be spent for chemical conversion treatment or waste liquid treatment after chemical conversion treatment. Therefore, for example, it is required to clarify the basic characteristics of the phosphoric acid chromic acid film treatment by adding an approach not only to the new bath but also to the chemical bath composition in the actual process. . Further, as shown in Table 1, since the chemical conversion treatment liquid contains HF, this HF
One of the problems is how to reduce it.

[0005]

Therefore, in view of the above circumstances, the present invention derives optimum chemical conversion treatment conditions,
Moreover, it aims at reducing the amount of HF used for chemical conversion treatment compared with the conventional one.

[0006]

[Means for Solving the Problems] By forming a coating film with a chemical conversion treatment main agent concentration as low as 1/2 of the conventional concentration, the coating formation rate is accelerated, while the corrosion resistance is improved. That is, the effective concentration of the chemical conversion agents (H ₃ PO ₄ , CrO ₃ ) used in the phosphoric acid chromic acid film treatment method, in which a sample made of an aluminum material is degreased and then subjected to chemical conversion treatment, is 0.5
Within the range from 4 points to 4 points, preferably 2 points.

[0007]

【Example】

<Example 1> 1. Sample preparation An aluminum coil material (34004-MR368) was cut into a size of 30 mm x 60 mm x 0.38 mm to prepare a sample. This sample was degreased and then subjected to chemical conversion treatment.

Specifically, the sample was first washed by sonication with acetone (5 minutes), passed through ethanol and washed with pure water, and then the washed sample was naturally dried.
Next, a degreasing agent (trade name:
It was dipped in a surf cleaner NHC100 (A / M) = 3.5% / 0.8% solution amount, 1 liter, manufactured by Nippon Paint Co., Ltd.) and treated with a stirrer at 70 ° C. for 1 minute.

The degreasing agent-treated sample was collected and washed with tap water. This washing was performed by running tap water for 30 seconds. Subsequently, the washed sample was subjected to chemical conversion treatment. This chemical conversion treatment is performed by Nippon Paint Co., Ltd. Alsurf 401/45 solution (base agent: Alsuf 40
1. Adjunct: Alusf 45) was used. Soak the sample in this solution (1 liter) and stir with a stirrer.
It was treated at 40 ° C for 2 minutes. The stirring speed in this case is about 250 rpm.

Chemical conversion agent 4 points (= 15 mS / cm, Cr
⁶⁺ = 1350mg / m ² ) 3mS / cm lower chemical conversion agent concentration confirmation result is 3 points, 3mS / cm decrease is 1 point reduction of chemical conversion agent concentration, so concentration 2 points In order to achieve this, a further decrease of 3 mS / cm is required.

The chemical conversion treated sample was washed with tap water.
This washing was performed by running tap water for 30 seconds. After washing with tap water, further washing with distilled water was performed (30 seconds). The sample for which the chemical conversion treatment was completed was dried at 200 ° C. for 120 seconds.

2. Evaluation method (1) With respect to the sample (n = 3) subjected to the conversion coating treatment, the amount of Cr deposited in the conversion coating was measured by mini-X under the following conditions, and the average value thereof was evaluated. mini-X measurement conditions: measurement time = 500 seconds and number of repetitions = 1 time.

(2) Corrosion resistance evaluation method A sample (n = 3) that had been subjected to a chemical conversion coating treatment was subjected to retort treatment under the following conditions, and the white-stained state of the treated sample surface was visually confirmed. In addition, the amount of Cr deposited in the chemical conversion coating was measured by mini-X for the sample after visual confirmation.

Retort treatment conditions: An autoclave was used as a retort apparatus, the treatment temperature was 115 ° C., and the treatment time was 30 minutes.

Chemical conversion treatment concentration: Alsuf401 = 4.0 points and Alsuf45 = 200 points.

3. Results FIG. 1 shows the film formation rate, and FIG. 2 shows the results relating to corrosion resistance. In these figures, the vertical axis represents the Cr adhesion amount (mg / ml ² ), and the horizontal axis represents the Alsuf401 (Cr ⁶⁺ ) concentration. From FIG. 1, a negative correlation that the amount of deposited Cr decreases as the Alsuf401 (Cr ⁶⁺ ) concentration increases in any F-concentration region was observed. A positive correlation was observed for F-concentration.

Further, when the Alsuf401 concentration was 5.0 points or more, the Cr deposition amount hardly changed. On the other hand, Alsu
When the f401 concentration is lower than 5.0 points, an effect on the Cr deposition amount is recognized.

Regarding the corrosion resistance, as shown in FIG.
A change in corrosion resistance was observed at the Alsuf401 concentration of 4.0 points. That is, the corrosion resistance performance was remarkably deteriorated at 4.0 points or higher, while the corrosion resistance performance was high at 4.0 points or lower. In addition,
A site considered to be discolored was observed in the sample judged to have no white stain, but when the site was observed with a scanning electron microscope, it was confirmed that there was no change.

<Example 2> The above Example 1 was based on the dipping treatment (plate). Here, the relationship between the rate of film formation and the corrosion resistance depending on the concentration of the chemical conversion treatment main agent (Alsuf 401 = Cr ⁶⁺ ). It was investigated by the spray treatment (can) method.

1. Sample preparation A bucket (2
It was collected in a 0 liter container). Next, this sample was degreased. Degreasing condition: Treatment agent ・ ・ ・ ・ ・ SC419 / SC446 = 1.2% / 0.025% Equipment ・ ・ ・ ・ ・ Can Tester No.1 Nozzle type ・ ・ ・ ・ ・ Top = KSS-0465, Bottom = KSS-0440 Treatment Time: 90 minutes Processing pressure: 3.0 kgf / cm ² Table rotation speed: 10 rpm

After the degreasing treatment, the sample was washed with tap water and naturally dried. Subsequently, the sample was subjected to chemical conversion treatment. Equipment: Can tester No.2 Nozzle type: Upper = KSS-0465, Lower = KSS-0440 Processing temperature: 40 ° C Processing time: <Reaction speed check> New bath : 20, 40, 60, 120, 180 seconds (5 levels) Hold time constant 10 seconds Equilibration bath: 120 seconds (1 level) Hold time constant 10 seconds <Corrosion resistance check> Cr adhesion amount = 15 mg / m ³ Processing by time Processing pressure ・ ・ ・ ・ 3.0 kgf / cm ² Table rotation speed: 10 rpm Chemical conversion treatment liquid: New bath = 2 levels, equilibration bath = 3 levels Alusf 401 (4 points and 2 points)

The chemical conversion treated sample was washed again with tap water and further with distilled water. Finally, the washed sample was dried in an oven (200 ° C, 2 minutes).

2. Evaluation method (1) With respect to the sample (n = 2) subjected to the chemical conversion coating treatment, the amount of Cr deposited in the chemical conversion coating was measured by mini-X under the following conditions, and the average value was evaluated. mini-X measurement conditions: measurement time = 500 seconds and number of repetitions = 1 time.

(2) Corrosion resistance performance evaluation method With respect to the sample (n = 5) which was subjected to the chemical conversion coating treatment, a black change test was conducted under the following conditions, and the black change state of the sample surface after the treatment was visually confirmed. Black test condition: Treatment water: Black evaluation water, Evaluation sample: Can with Cr deposit of about 15 mg / m ² , Treatment temperature: 100 ° C, Treatment time: 30 minutes

3. Results FIG. 3 shows the results of experiments on the rate of film formation. As is clear from this figure, in the spray process (can),
Similar results to the experimental results of the immersion treatment (plate) were obtained, in which the film formation reaction was faster at 2.0 points than the Alsuf401 (Cr ⁶⁺ ) concentration of 4.0 points. Regarding the corrosion resistance, for samples with a Cr deposit of about 15 mg / m ² , both Alsuf 401 concentration of 4 points and 2 points discolored slightly to blackened water, and both samples showed a slight discoloration. Was confirmed, though slightly (results not shown).

[0026] The (managed by 1/2 concentration Kasei main agent) by low concentrations of the chemical conversion main agent, such as variations in pH occurs, the sub-agent concentration ^- from the display value true value surf Progard of (F) takes the deviation value, the sub-agent concentration (F ^-) is view that there is a possibility of causing confusion to the concentration management, which is a sufficiently adaptable by changing the standard solution Fukuzai (results shown No). Therefore, in the present invention, by changing the chemical conversion agent concentration from 4 points to 2 points, the auxiliary agent concentration could be reduced from 0.12% to 0.09% as a result.

[0027]

INDUSTRIAL APPLICABILITY In the present invention, the chemical conversion treatment main agent concentration is reduced to 1 /
2 low concentration, that is, the effectiveness of the chemical conversion agents (H ₃ PO ₄ , CrO ₃ ) used in the phosphoric acid chromic acid film treatment method in which the sample made of aluminum material is degreased and then chemical conversion treated.
By setting it within the range of 0.5 to 4 points, preferably 2 points, the film formation rate is increased, while the corrosion resistance performance is improved, and the auxiliary agent (HF) is reduced due to the decrease in the amount of the chemical conversion agent used. Since the usage amount of is also reduced, it becomes possible to reduce the need for wasting time, cost and equipment for waste liquid treatment after chemical conversion treatment as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an Alsuf 401 concentration and a Cr adhesion amount.

FIG. 2 is a diagram showing a relationship between Alsuf401 concentration in a chemical conversion treatment bath and coating corrosion resistance.

FIG. 3 is a diagram showing a relationship between a chemical conversion agent concentration and a film formation rate.

Claims (1)

[Claims] 1. A method for treating a phosphoric acid chromic acid film, which comprises degreasing a sample made of an aluminum material and then performing chemical conversion treatment,
In this chemical conversion treatment, the chemical conversion main agent (H ₃ PO ₄ , Cr
A method for treating a chromic acid phosphate coating, characterized in that the effective concentration of O ₃ ) is within the range of 0.5 to 4 points, preferably 2 points.