JPH05195248A - Method for acid chemical conversion of metal material - Google Patents

Abstract

PURPOSE:To accurately control the film thickness of a chemical conversion film of Al-base metal material by detecting the dropping amt. of titrant to the inflection point of potential curve of F ion electrode. CONSTITUTION:When the ion concn. of fluorides in an acid chemical conversion treating liquid is measured, potentiometric titration is performed without controlling pH by using a soln. containing Al, La, Y, Zr, Ga, Ce or Be ions as a titrant and the F ion electrode as the indicator electrode. The dropping amt. of the titrant to the inflection point of the potential curve of the F ion electrode is determined, and thereby, thickness of the chemical conversion film formed on an Al-base metal material by using a fluorine-contg. acid chemical conversion liquid is accurately controlled and the effective F concn. can be measured by a simple method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acid chemical conversion treatment liquid for a metal component containing an aluminum-based metal material, specifically, a phosphate chemical conversion treatment liquid for treating the surface of automobile bodies, household electric appliances and the like, chromate. The present invention relates to a method for applying a treatment such as a treatment liquid, and more specifically to a chemical conversion treatment method capable of reproducibly controlling a chemical reaction involving fluorine contained in the chemical conversion treatment liquid. ..

It is well known that fluorine is added to an acid chemical conversion treatment solution for treating a metal component containing an aluminum-based metal material, and an example of the method is disclosed in JP-A-63-157879.

[0003]

2. Description of the Related Art Generally, the concentration of fluoride ions in an aqueous solution is directly measured by using a fluorine ion meter. As a measurement procedure in this case, as disclosed in Japanese Patent Laid-Open No. 63-157879 regarding phosphorylation treatment, a fluorine ion electrode is equilibrated with a fluorine standard solution having a known fluoride ion concentration, and an unknown sample is prepared. The method of measuring is taken. The phosphate chemical conversion treatment is performed by adjusting the bath components so that the fluoride concentration obtained by converting the value obtained as a result of the measurement falls within a predetermined range.

[0004] Fluoride, as with respect to chromate treatment disclosed in KOKOKU No. 3-48271 for example F ^-
Is maintained within a predetermined range to perform the chemical conversion treatment.

Although not intended for the chemical conversion treatment liquid, a method of measuring the fluorine concentration by potential titration using aluminum nitrate, lanthanum nitrate or the like as a titration liquid and a fluorine ion electrode as an indicator electrode is described in Z. Anal. Che
m. , 245, 67 (1969), which is a known method. This method is a measuring method for measuring total fluorine in an aqueous solution, and the pH is adjusted to 4 or more and 7 or less as a pretreatment of the sample.

[0006]

As a method for measuring the fluoride ion concentration of an acid chemical treatment solution, in the direct concentration measurement using a fluorine ion meter such as the one described above, the fluorine ion electrode deteriorates with time during use in the measurement. Therefore, there is a problem that the standard solution must be frequently equilibrated, and the deterioration of the fluoride ion electrode progresses. At present, the complicated work of is frequently performed.

Further, even if the fluoride ion concentration can be accurately measured, if the fluoride ion concentration is controlled to a predetermined value and the chemical conversion treatment is continuously carried out, in addition to the fluoride ion concentration, p
Despite the control of other control items such as H and total acidity to predetermined values, the film thickness of the chemical conversion film and the amount of adhesion per unit area fluctuated significantly. In a chemical conversion treatment such as a zinc phosphate chemical conversion treatment, the chemical conversion treatment performance appears in terms of the size of the coating film, so the value of the coating film weight can be substituted for the chemical conversion treatment performance. Therefore, when chemical conversion treatment is performed based on such a measurement method, not only the corrosion resistance and coating adhesion of the material to be treated but also the corrosion resistance and adhesion of the coating film are unstable.

Further, the method by the potentiometric titration method like the method (1) has the advantage that the fluorine ion electrode does not need to be balanced and the measurement error due to electrode deterioration is small.
The fluoride ion concentration measured by the method of previously setting the pH of the sample to 4 or more and 7 or less is the total fluorine concentration, and the fluorine concentration effective for the chemical conversion reaction cannot be measured. Since the total fluorine concentration does not always become a factor controlling the chemical conversion property in the acid chemical conversion treatment, this method is unsuitable as a control means of the acid chemical conversion treatment liquid. Therefore, it caused the same problem as in the above case.

[0009]

[Means for Solving the Problems] As a result of diligent studies for solving the problems and problems of the conventional technology,
We investigated the method of measuring the fluorine concentration, which is a component in the acid chemical treatment solution that contributes to the chemical conversion reaction and is effective for the chemical conversion reaction. Aluminum ion, lanthanum ion, yttrium ion, zirconium ion, potassium ion, cerium ion or beryllium ion An aqueous solution containing a is used as a titration liquid, a fluorine ion electrode is used as an indicator electrode, and an acid chemical treatment liquid having a pH of less than 4 is directly potentiometrically titrated without pH adjustment,
By determining the effective fluorine concentration from the titrated amount of droplets up to the inflection point of the potential curve of the fluorine ion electrode, it is possible to cope with deterioration of the fluorine ion electrode and to obtain the effective fluorine concentration that contributes to the chemical conversion reaction with good reproducibility and speed. By confirming that it can be measured, and performing chemical conversion treatment based on this measurement method,
It has been found to solve the problems of the prior art.

Further, the inventors of the present invention compared the value measured by the measuring method of the present invention with the value of the fluoride ion concentration detected as the concentration of total fluorine or the concentration of free fluorine, which has been conventionally measured, in the acid formation. It was discovered that the measured value had a higher correlation with the chemical conversion reaction in the treatment liquid.

The present invention completed on the basis of the above findings,
In a method of acidifying a metal material at least a part of which is composed of an aluminum-based metal material, an aqueous solution containing aluminum ion, lanthanum ion, yttrium ion, zirconium ion, potassium ion, cerium ion or beryllium ion is used as a titration liquid. ,
Using the fluorine ion electrode as an indicator electrode, potentiometric titration of a fluorine-containing acidic chemical conversion treatment liquid having a pH of less than 4 without adjusting the pH,
It is characterized in that the titration liquid drop amount to the inflection point of the potential curve of the fluorine ion electrode is obtained, and when the titration liquid drop amount is less than a predetermined range, a fluorine-containing drug is added.

In the present invention, the chemical conversion treatment liquid is a phosphate chemical conversion treatment liquid or a chromate treatment liquid, and the composition thereof is not particularly limited. The phosphate chemical treatment solution is disclosed in Japanese Patent Publication No. 3-38343, etc., which is filed by the present applicant, and the chromate treatment solution is also disclosed in Japanese Patent Publication No.
-66906, etc. can be used.

In the present invention, the chemical conversion treatment is carried out so that the value (that is, the effective fluorine concentration point) determined by the measuring method described in detail below is maintained within a predetermined range. This range is predetermined depending on the type of chemical conversion treatment, the composition of the bath, the metal material to be treated, and the like. If the effective fluorine concentration point exceeds the predetermined range, the etching of the metal material by fluorine proceeds too much, and a chemical conversion film having a larger amount than the predetermined amount is formed, which is not preferable. On the other hand, when the effective fluorine concentration point is less than the predetermined range, the etching of the metal material by fluorine is insufficient and the desired chemical conversion treatment does not occur. Therefore, to maintain these ranges,
It is characterized in that a fluorine-containing agent such as borofluoric acid, borofluoride, hydrofluoric acid, sodium fluoride, sodium fluorosilicate, silicofluoric acid is added.

In the chemical conversion treatment, it is necessary to carry out the measurement of pH, total acidity, oxidation-reduction potential and the like which are usually carried out and the control based on the measurement. This measuring method is known per se, and it is disclosed, for example, in Japanese Patent Publication 3-
The method described in Japanese Patent Publication No. 59989 can be used.

The method for measuring the effective fluorine concentration point will be described below. 1. A fixed amount (A [ml]) of the acid chemical treatment solution is sampled. 2. Dilute if necessary. The acid chemical conversion treatment liquid sampled in a fixed amount can be diluted with a liquid that does not form a compound with fluorine, such as pure water or ethanol, if necessary. 3. The fluorine ion electrode is contacted with the chemical conversion liquid. Also, the fluorine ion electrode used may be an aged one as long as the electromotive force changes according to the fluoride ion concentration in the treatment liquid, and this method is not a method for measuring only the fluoride ion concentration. It is not necessary to equilibrate the fluorine ion electrode with the fluorine standard solution. 4. A sample of the acid chemical treatment solution is titrated with an aqueous solution (B [mol / l]) containing aluminum ions, lanthanum ions, yttrium ions, zirconium ions, potassium ions, cerium ions or beryllium ions as the titrant. 5. The relationship between the titration amount and the electromotive force of the fluorine ion electrode is shown in the titration curve, and the titration amount up to the inflection point of the titration curve (C [m
l]). The titration curve is a graph in which the electromotive force (E [mV]) of the fluorine ion electrode and the dropping amount (V [ml]) of the titrant are plotted on both axes, and the inflection point of the titration curve is from this graph. It means the point where the value of dE / dV (differential value of electromotive force) obtained is the maximum. The values of A and B in the above measurement procedure have suitable ranges but are not particularly limited. 6. The effective fluorine concentration point is calculated from Equation 1 using the values of A, B, and C. Formula 1: Effective fluorine concentration point [pt] = 400 × B ×
C / A Therefore, for example, if A is 20 ml and B is 0.05 mol / l, the value of C [ml] becomes equal to the effective fluorine concentration point, so conversion to points becomes unnecessary.

As the water-soluble salts of metals used as the titrant, nitrates, sulfates, chlorides and the like of each metal can be used. The concentration of the water-soluble salt can be adjusted depending on the amount of sample and the concentration of fluorine in the sample, but if it is an acid chemical conversion treatment liquid such as a zinc phosphate chemical conversion treatment liquid or a chromate treatment liquid, it is 0.01 to 0.1 mol. It is preferably about 1 / l. If it is less than 0.01 mol / l, the potential change of the fluorine ion electrode with respect to the amount of the titrant to be dropped becomes slow,
On the other hand, when it exceeds 0.1 mol / l, the potential change of the electrode is too rapid, which makes it difficult to determine the inflection point of the potential curve. Considering the convenience of automatic titration, the sampling amount of the treatment liquid is preferably about 10 to 100 ml.

[0017]

The fluorine component in the acid chemical conversion treatment solution has a high contribution to the etching property of the metal to be treated, and particularly when the metal to be treated is aluminum or contains aluminum, it has a great influence on the chemical conversion reaction. However, the reactivity of the chemical conversion reaction is not simply determined by the total fluorine concentration contained in the treatment liquid, but depends on the effective fluorine concentration acting on the metal to be treated in the treatment liquid. And since this effective fluorine concentration changes its form depending on pH,
It is necessary to measure without changing the pH of the treatment liquid.

Further, a fluorine ion electrode and a fluorine ion meter are generally used to measure the fluorine concentration in the aqueous solution, and a method of equilibrating and directly measuring with a fluorine standard solution is generally used. There is a problem that the electromotive force decreases with use, so that it cannot withstand long-term use and accurate measurements cannot be obtained with aged electrodes.

That is, as in the present invention, by using the treatment liquid itself as the sample liquid, it is possible to measure the effective fluorine concentration at the treatment liquid pH, and it is also possible to cope with the deterioration of the electrode by the titration method. Of.

In the measuring method of the present invention, first, a fluorine ion electrode is brought into contact with the treatment liquid, and then an aluminum ion, lanthanum ion, yttrium ion, zirconium ion, gallium ion, cerium ion or beryllium ion aqueous solution having a known concentration is dropped. To go. Each metal salt forms a complex compound with the fluoride ion concentration in the treatment liquid. That is, the fluoride ion concentration in the treatment liquid decreases according to the amount of metal ions in the titration liquid.

Therefore, the fluorine ion electrode used as the indicator electrode in the present invention does not directly convert the fluoride ion concentration from the electromotive force of the electrode, but the fluoride ion concentration which decreases by titration Therefore, it is possible to avoid the adverse effects caused by the deterioration of the electrode electromotive force caused by the deterioration of the electrode, that is, the long-term use of the electrode.

Furthermore, by setting the inflection point of the titration curve as the end point of the titration, not only the end point can be obtained by a simple calculation process, but this also has a high correlation with the chemical conversion property in the acid chemical treatment solution. The effective fluorine concentration point can be obtained.

By adjusting the bath composition so that the effective fluorine concentration point obtained by the above method falls within a predetermined range, stable chemical conversion treatment ability can be realized.

[0024]

EXAMPLES Next, some specific examples of actual processing will be described. First, regarding four types of zinc phosphate chemical conversion treatment liquids (PB-L3020: manufactured by Nippon Parkerizing Co., Ltd.) having different fluorine component systems, effective fluorine concentration points, fluoride ion concentrations, and total fluorine concentrations were measured by the following measurement methods. did. The fluorine component system of the zinc phosphate chemical conversion treatment solution was as shown in Table 1. The measurement results of the fluorine concentration of the treatment liquid (immediately after starting the measurement and after repeating the measurement once a day for 100 times), and the coating weight measurement results of the aluminum alloy plate (JIS-5052) treated at the same time as the measurement, respectively. The results are shown in Table 2.

[0025]

[Table 1]

Effective Fluorine Concentration Point Measurement Method 1) 20 ml of the acidifying treatment liquid is sampled. 2) Dilute to 50 ml with pure water. 3) Fluoride ion electrode (7200-0.65W made by DKK)
Liquid). 4) Titrate with 0.05 mol / l aluminum nitrate aqueous solution. 5) The relationship between the titration amount and the electromotive force of the fluorine ion electrode is shown in the titration curve, and the titration amount [ml] up to the inflection point of the titration curve is displayed as the effective fluorine concentration at the point [pt].

Fluoride ion concentration measuring method 1) Sodium fluoride is added to 1.0 mol / l sodium nitrate aqueous solution to prepare 100 ppm and 1000 ppm fluorine standards. At that time, the pH is adjusted to 5 using nitric acid or sodium hydroxide. 2) Fluoride ion electrode (7200-0.65W made by DKK)
Type) with a fluorine standard solution. 3) Contact the fluoride ion electrode directly with the acid chemical treatment solution,
The fluoride ion concentration is measured from the electromotive force of the electrode. Note: However, after the second measurement, only the measurement in 3) is performed.

Total Fluorine Concentration Measurement Method 1) 20 ml of acid conversion treatment solution is sampled. 2) Adjust to pH 5 with an aqueous sodium hydroxide solution and make up to 50 ml with pure water. 3) Fluoride ion electrode (7200-0.65W made by DKK)
Liquid). 4) Titrate with 0.05 mol / l aluminum nitrate aqueous solution. 5) From the potential titration curve of the fluorine ion electrode, the titration amount until the fluorine component was completely consumed was determined, and the total fluorine concentration was calculated assuming that 3 mol of fluorine was consumed with respect to 1 mol of aluminum.

[0029]

[Table 2]

From Table 2, it can be seen that the coating weight of the aluminum alloy plate changes depending on the difference in the fluorine component in the zinc phosphate-based chemical conversion treatment liquid which is the acid conversion treatment liquid.
In addition, the fluoride ion concentration shows an extreme increase, while the total fluorine concentration shows an extreme decrease, though the coating weights hardly change at the 1st and 100th times. It can be seen that the chemical conversion treatment method based on it cannot provide stable chemical conversion treatment capacity. On the other hand, in the effective fluorine concentration measuring method, the coating weight and the measured value show similar changes.

Therefore, in order to make the above tendency clearer, the relationships between the values measured by the methods of Example 1 and Comparative Examples 1 and 2 and the coating weight are shown in FIGS. 1, 2 and 3, respectively. In addition, X in the graphs of FIGS. 1, 2 and 3 indicates a measured value immediately after the start of measurement, and Y indicates a measured value at the 100th time after the start of measurement.

According to this, the effective fluorine concentration point is
The correlation coefficient with the coating weight exceeds 0.99 for both X and Y, indicating not only a good correlation, but also a good reproducibility because the X and Y graphs are similar. .. On the other hand, in the fluoride ion concentration measuring method, although the reproducibility is recognized, the correlation coefficient is 0.20 for both X and Y.
And the correlation coefficient with the coating weight is poor and the correlation coefficient is 0.95 or more for both X and Y in the total fluorine concentration measurement method. It can be seen that there is a gap and there is a problem in the reproducibility of measurement.

Based on the above preliminary test results, an aluminum plate (70 × 150 × 6 to 8 mm zinc phosphate chemical conversion treatment was carried out by the method described below. Here, the range of effective fluorine concentration points was 1. 9 to 2.5, 0.5
Control was performed to obtain a coating weight of ˜1.5 g / m ² . (1) Degreasing Fine Cleaner-L4460 (strong alkaline type degreasing agent manufactured by Nippon Parkerizing Co., Ltd.) 43 ° C 120 seconds spray (2) Rinsing [tap water] room temperature 30 seconds spray (3) Surface adjustment Percollane-ZN (Nihon Parkerizing titanium) Colloidal surface conditioner) Normal temperature 20 seconds Spray (4) Zinc phosphate chemical conversion treatment 43 ° C 120 seconds Immersion bath composition Zn: 0.8 to 1.2 g / L Ni: 0.5 to 1.0 g / L Mn: 0.5~ 0.8g / L PO: 12 ~20 g / L NO 3: measuring the effective fluorine concentration point for each processing of 0.5 to 8.0 g / L 10 times, the effective fluorine concentration point acceleration HF when below the lower limit
0.1 g / L was added.

(5) Washing with water [tap water] Spraying at room temperature for 20 seconds (6) Washing with deionized water [Deionized water (conductivity: 0.2 μS
/ Cm)] Room temperature 20 seconds Spray (7) Draining and drying 110 ° C 180 seconds One aluminum plate per time by the above method
It was possible to obtain a coating weight within the above range by performing a 00-sheet chemical conversion treatment.

[0035]

As described above, the chemical conversion treatment method according to the present invention is an extremely excellent method for accurately and reproducibly measuring the effective fluorine concentration that contributes to the chemical conversion reaction in the acid chemical conversion treatment liquid. ..

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between effective fluorine concentration points and coating weight.

FIG. 2 is a graph showing the relationship between fluoride ion concentration and coating weight.

FIG. 3 is a graph showing the relationship between total fluorine and coating weight.

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[Procedure amendment]

[Submission date] December 16, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction content]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acid chemical conversion treatment liquid for a metal component containing an aluminum-based metal material, specifically, a phosphate chemical conversion treatment liquid for treating the surface of automobile bodies, household electric appliances and the like , chromate. it relates to a method of straining facilities the processing of the processing liquid or the like, to a method of chemical conversion treatment with fluorine contained in the chemical conversion solution stated in more detail can be controlled with good reproducibility associated chemical reactions.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

[0003]

2. Description of the Related Art Generally, the concentration of fluoride ions in an aqueous solution is directly measured by using a fluorine ion meter. As a measurement procedure in this case, as disclosed in Japanese Patent Laid-Open No. 63-157879 concerning phosphorylation treatment, a fluorine ion electrode is calibrated with a fluorine standard solution having a known fluoride ion concentration, and an unknown sample is measured. The way to do is taken. The phosphate chemical conversion treatment is performed by adjusting the bath components so that the fluoride concentration obtained by converting the value obtained as a result of the measurement falls within a predetermined range.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

As a method for measuring the fluoride ion concentration of an acid chemical treatment solution, in the direct concentration measurement using a fluorine ion meter such as the one described above, the fluorine ion electrode deteriorates with time during use in the measurement. Therefore, there is a problem that the calibration with a standard solution must be performed frequently, and there is a problem that the deterioration of the fluorine ion electrode progresses, so that the measurement of the fluoride ion concentration requires complicated electrode cleaning and calibration. The current situation is that various tasks are frequently performed.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

In addition, the method by the potentiometric titration method like the method of 1 has the advantage that the calibration of the fluorine ion electrode does not take time and the measurement error due to electrode deterioration is small .
The fluoride ion concentration measured by the method of previously setting the pH of the sample to 4 or more and 7 or less is the total fluorine concentration, and the fluorine concentration effective for the chemical conversion reaction cannot be measured. Since the total fluorine concentration does not always become a factor controlling the chemical conversion property in the acid chemical conversion treatment, this method is unsuitable as a control means of the acid chemical conversion treatment liquid. Therefore, it caused the same problem as in the above case.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

[Means for Solving the Problems] As a result of diligent studies for solving the problems and problems of the conventional technology,
We investigated the method for measuring the fluorine concentration, which is a component in the acid chemical treatment solution that contributes to the chemical conversion reaction and is effective for the chemical conversion reaction. Aluminum ion, lanthanum ion, yttrium ion, zirconium ion, gallium ion , cerium ion or beryllium ion An aqueous solution containing a is used as a titration liquid, a fluorine ion electrode is used as an indicator electrode, and an acid chemical treatment liquid having a pH of less than 4 is directly potentiometrically titrated without pH adjustment,
By determining the effective fluorine concentration from the titrated amount of droplets up to the inflection point of the potential curve of the fluorine ion electrode, it is possible to cope with deterioration of the fluorine ion electrode and also to obtain the effective fluorine concentration that contributes to the chemical conversion reaction with good reproducibility and speed. By confirming that it can be measured, and performing chemical conversion treatment based on this measurement method,
It has been found to solve the problems of the prior art.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

The present invention completed on the basis of the above findings,
In a method of acidifying a metal material at least a part of which is composed of an aluminum-based metal material, an aqueous solution containing aluminum ion, lanthanum ion, yttrium ion, zirconium ion, gallium ion , cerium ion or beryllium ion is used as a titrant. ,
Using the fluorine ion electrode as an indicator electrode, potentiometric titration of a fluorine-containing acidic chemical conversion treatment liquid having a pH of less than 4 without adjusting the pH,
It is characterized in that the titration liquid drop amount to the inflection point of the potential curve of the fluorine ion electrode is obtained, and when the titration liquid drop amount is less than a predetermined range, a fluorine-containing drug is added.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

The method for measuring the effective fluorine concentration point will be described below. 1. A fixed amount (A [ml]) of the acid chemical treatment solution is sampled. 2. Dilute if necessary. The acid chemical conversion treatment liquid sampled in a fixed amount can be diluted with a liquid that does not form a compound with fluorine, such as pure water or ethanol, if necessary. 3. The fluorine ion electrode is contacted with the chemical conversion liquid. Also, the fluorine ion electrode used may be an aged one as long as the electromotive force changes according to the fluoride ion concentration in the treatment liquid, and this method is not a method for measuring only the fluoride ion concentration. It is not necessary to calibrate the fluorine ion electrode with the fluorine standard solution. 4. A sample of the acid chemical treatment solution is titrated using an aqueous solution (B [mol / l]) containing aluminum ions, lanthanum ions, yttrium ions, zirconium ions, gallium ions , cerium ions or beryllium ions as a titration liquid. 5. The relationship between the titration amount and the electromotive force of the fluorine ion electrode is shown in the titration curve, and the titration amount up to the inflection point of the titration curve (C [m
l]). The titration curve is a graph in which the electromotive force (E [mV]) of the fluorine ion electrode and the dropping amount (V [ml]) of the titrant are plotted on both axes, and the inflection point of the titration curve is from this graph. It means the point where the value of dE / dV (differential value of electromotive force) obtained is the maximum. The values of A and B in the above measurement procedure have suitable ranges but are not particularly limited. 6. The effective fluorine concentration point is calculated from Equation 1 using the values of A, B, and C. Formula 1: Effective fluorine concentration point [pt] = 400 × B ×
C / A Therefore, for example, if A is 20 ml and B is 0.05 mol / l, the value of C [ml] becomes equal to the effective fluorine concentration point, so conversion to points becomes unnecessary.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Further, a fluorine ion electrode and a fluorine ion meter are generally used to measure the fluorine concentration in the aqueous solution, and a method of directly calibrating with a fluorine standard solution is used, but the fluorine ion electrode is used for a long time. Therefore, there is a problem that the electromotive force is lowered, and therefore it cannot withstand long-term use, and an aged electrode cannot obtain an accurate measurement value.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

Fluoride ion concentration measuring method 1) Sodium fluoride is added to 1.0 mol / l sodium nitrate aqueous solution to prepare 100 ppm and 1000 ppm fluorine standards. At that time, the pH is adjusted to 5 using nitric acid or sodium hydroxide. 2) Fluoride ion electrode (7200-0.65W made by DKK)
Type) is calibrated by fluorine standard solutions. 3) Contact the fluoride ion electrode directly with the acid chemical treatment solution,
The fluoride ion concentration is measured from the electromotive force of the electrode. Note: However, after the second measurement, only the measurement in 3) is performed.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

[0029]

[Table 2]

[Procedure Amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

Based on the above preliminary test results, an aluminum plate (70 × 150 × 6 to 8 mm zinc phosphate chemical conversion treatment was carried out by the method described below. Here, the range of effective fluorine concentration points was 1. 9 to 2.5, 0.5
Control was performed to obtain a coating weight of ˜1.5 g / m ² .
(1) Degreasing Fine Cleaner-L4460 (Nippon Parkerizing's strong alkaline degreasing agent) 43 ° C 120 seconds spray (2) Rinsing [tap water] room temperature 30 seconds spray (3) Surface preparation preparene ZN (Nihon Parkerizing titanium colloid) System surface modifier) Normal temperature 20 seconds Spray (4) Zinc phosphate chemical conversion treatment 43 ° C 120 seconds Immersion bath composition Zn: 0.8 to 1.2 g / L Ni: 0.5 to 1.0 g / L Mn: 0 0.5 to 0.8 g / L PO ₄ : 12 to 20 g / L NO ₃ : 0.5 to 8.0 g / L The effective fluorine concentration point is measured after every 10 treatments, and the effective fluorine concentration point is adjusted. HF when below the lower limit
0.1 g / L was added.

Claims (2)

[Claims] 1. A method for acid chemical conversion treatment of a metal material, at least a part of which is an aluminum-based metal material, containing aluminum ion, lanthanum ion, yttrium ion, zirconium ion, potassium ion, cerium ion or beryllium ion. Using the aqueous solution as the titrant and the fluorine ion electrode as the indicator electrode, p
Potentiometric titration of a fluorine-containing acidic chemical conversion treatment liquid of less than H4 without adjusting the pH is performed to obtain the titration droplet drop amount up to the inflection point of the potential curve of the fluorine ion electrode. When the titration drop drop amount is less than the predetermined range, A method for acid chemical conversion treatment of a metal material, which comprises adding a fluorine-containing chemical. 2. Aluminum ion, lanthanum ion, yttrium ion, zirconium ion in the titrant,
When the concentration of gallium ion, cerium ion or beryllium ion is B [mol / l] and the amount of the acid chemical treatment solution is A [ml], the effective fluorine concentration point [pt] is calculated from the titration drop amount C [ml]. = 400 x B x C / A
And the effective fluorine concentration point is maintained within a predetermined range.