JPH0674507B2 - Management method of surface conditioning liquid for phosphate coating chemical conversion treatment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a phosphate film chemical conversion treatment (hereinafter referred to as “phosphate chemical conversion treatment”) on a metal surface of steel, zinc, etc. The present invention relates to a method for controlling a surface conditioning liquid that is used and contains titanium colloid as a main component.

[Conventional technology]

In phosphate chemical conversion treatment of metal surfaces such as steel and zinc,
A method in which steel is washed with water and the surface is adjusted with a surface adjusting solution containing titanium colloid as a main component to form a phosphate-treated film of fine crystals is generally used.

For example, the surface conditioning solution disclosed in JP-B-39-7125 is dissolved by adding an excess of sulfuric acid to titanium oxide,
It is manufactured by adding one or more kinds of phosphoric acid, polymerized phosphoric acid, alkali phosphate, or polymerized alkali phosphate at 1 or less to prepare a slurry, and then aging and drying the slurry at pH 6.5 to 8.5. .

Further, the surface conditioning solution disclosed in Japanese Examined Patent Publication No. 58-55229 contains titanium ions, phosphate root ions, pyrophosphate root ions, and carbonate root ions as essential components, pH 8.
It is adjusted to 5 to 9.5. This surface conditioning solution uses a carbonate ion as one component of the surface conditioning solution in order to eliminate the drawback that it is difficult to carry out stable surface conditioning with a conventional surface conditioning solution, which tends to cause a decrease in pH over time. It is characterized by that.

In order to prevent deterioration of performance of this type of surface conditioning liquid over time,
For example, as disclosed in Japanese Examined Patent Publication No. 58-55229, there is a proposal to modify the components of the surface conditioning liquid, but the component modification alone cannot actually completely prevent the deterioration of performance over time. Conditioning solution must be constantly updated. As the method, continuous partial waste renewal from the container is usually performed.

Heretofore, as a method for controlling this type of surface conditioning solution, the measurement of pH of the surface conditioning solution and the measurement of total alkalinity which is almost proportional to the titanium ion content have been performed in a timely manner. Based on these measurement results, a new surface conditioner containing a pH adjuster and a titanium compound as the main component was added, and at the same time, the auto-drain was used to continuously and partially update the surface adjuster solution, which is equivalent to the amount of waste update. It was replenished with water.

[Problems to be Solved by the Invention]

The conventional method of managing the surface conditioning solution for phosphate chemical conversion treatment, which adjusts the amount of continuous partial waste renewal based on the measured values of pH and total alkalinity of the surface conditioning solution, is to stabilize the performance of the surface conditioning solution There was a flaw in lack of accuracy in terms of maintenance. That is, in order to make the amount of the finally formed phosphate coating within the predetermined coating weight range small, even if the above-mentioned measured value is referred to, the determination of the continuous partial waste renewal amount will be made by an expert. There was a problem that I had to rely on my experience.

The composition research of the phosphate chemical conversion treatment solution, which reduces the variation in coating weight, has been advanced, and it is certain that it has been improved considerably. However, the use of the phosphate chemical conversion treatment liquid having such a specific composition has a drawback that the range of selection of the phosphate chemical conversion treatment liquid is narrowed accordingly.

Regardless of which of the above-mentioned surface preparation solutions is used, the adjustment of the continuous partial waste renewal amount cannot depend only on the measured values of pH and total alkalinity, and further depends entirely on the experience of a skilled person. I had no choice.

The present invention is intended to provide a management method capable of appropriately controlling a surface conditioning solution for a phosphate coating chemical conversion treatment without depending on the experience of a skilled person.

[Means for Solving the Problems]

In order to solve these drawbacks, the present invention focuses on the fact that titanium colloid is produced from the titanium compound in the surface conditioning liquid, and investigates the correlation between the average particle size of titanium colloid and the surface conditioning performance. , And various studies were carried out for the purpose of applying this to the control method of the surface conditioning liquid. as a result,
The present inventors have used for pretreatment of phosphate chemical conversion treatment,
In the performance control of the surface conditioning solution containing a titanium compound as the main component, the average particle size of the titanium colloid in the surface conditioning solution was measured, and based on this measurement value, the average particle size was adjusted to 60
The present invention has been completed by finding that a sufficient and stable adjusting function can be exerted by controlling the amount of the surface conditioning solution to be discarded and updated so that the surface conditioning solution is stored at 0 nm or less.

The management method of the surface conditioning solution for phosphate film chemical conversion treatment of the present invention is a pretreatment for the phosphate film chemical conversion treatment of a metal material, which is performed on the metal material with a surface conditioning solution containing a phosphoric acid compound and a titanium compound. In the surface conditioning treatment performed, a part of the surface conditioning solution is substantially continuously discarded, and when it is renewed to control the surface conditioning performance of the surface conditioning solution, it is generated in the surface conditioning solution. The average particle size of the titanium colloid is measured, and the amount of renewal of waste of the surface conditioning solution is adjusted according to the measured value, thereby controlling the average particle size of the titanium colloid to 600 nm or less. It is what

In the above method of the present invention, it is preferable to control the average particle size of the titanium colloid in the surface conditioning liquid within the range of 200 to 600 nm.

[Work]

 Hereinafter, the present invention will be described in detail.

In the present invention, as in the conventional method, the titanium compound content and pH are controlled to predetermined values during the construction bath.

In the method of the present invention, the average particle size of the titanium colloid generated in the surface conditioning solution during the surface conditioning step is measured, and the amount of renewed waste of the surface conditioning solution is adjusted based on the average particle size value.
As a result, the plane particle size of titanium colloid is 600 nm or less,
It is preferably controlled and controlled within the range of 200 to 600 nm. As will be described later in detail, when a part of the surface conditioning liquid is substantially continuously discarded and renewed from the storage container, the average particle diameter of the titanium colloid is measured so that the measured value falls within the above range. Control and manage the amount of renewal of the surface conditioning solution that is discarded and maintain the proper performance of the surface conditioning solution.

Incidentally, the pH of the surface conditioning solution is within a predetermined range due to the composition determination of the surface conditioning agent before the prescribed chemical conversion treatment, and since there is little change over time, the pH measurement frequency is the average particle size measurement frequency of the titanium compound colloid. May be less. The titanium content may be measured by quantitative analysis of titanium in liquid, but since it is almost proportional to the total alkalinity, the measurement of total alkalinity may be used instead of the measurement of titanium content. Good. The frequency of measuring titanium content is at least much better than the frequency of measuring pH.

The average particle size of titanium colloid can be measured by using a submicron particle analyzer.

〔Example〕

In the following experimental example, the average particle size of titanium colloid is 600 nm.
After that, the partial conditioning of the surface conditioning solution was renewed continuously so as to preferably control to 200 to 600 nm.

1 to 4 show experimental data obtained by the following test materials, treatment methods and measurement methods.

1. Specimen steel plate SPCC JIS-G-3141 2. Preparation of each treatment liquid (1) Alkaline degreasing liquid Phicleaner 4326TA (Nihon Parkerizing Co., Ltd.)
1.8kg / 100 Total alkalinity 15 ± 1 point (10ml sample, bromphenol blue indicator, titration value with titration solution 0.1N H ₂ SO ₄ ) (2) Surface preparation solution A Surface preparation agent A: Sulfuric acid Surface conditioning agent obtained by heating while mixing titanyl, sodium phosphate, sodium pyrophosphate and water and adjusting the pH with an alkali Concentration: 100g / 100 (solvent uses tap water of Tokyo with conductivity 196μs / cm) Total alkalinity: 6.2 ± 0.5 points (100 ml sample, titration value of bromphenol blue indicator titration solution 0.1 normal H ₂ SO ₄ ) pH: 8.2 ± 0.2 (3) Phosphate chemical treatment liquid Palbond 3030 (Nippon Parkerizing ) -Main component: primary phosphate, oxidizer (chlorate, sulfate, sulfite)) Concentration: 5kg / 100 Total acidity: 18 ± 1 point (10ml sample, phenolphthalein indicator, titrant)
Free acidity: 0.9 ± 0.1 point (100 ml sample, bromphenol blue indicator titration solution 0.1 N NaOH titration value) Accelerator concentration: 1.2 ± 0.1 points (according to saccharometer method) 3. Treatment method (1) Alkaline degreasing: 50 ± 2 ℃, 180 seconds immersion (2) Rinse: tap water, room temperature, 20 seconds spray (3) Surface preparation: room temperature, 30 seconds immersion (4) Phosphate conversion treatment: 53 ± 2 ℃, 120 seconds immersion (5) Rinse: tap water, room temperature, 20 seconds spray (6) Deionized water: Deionized water (conductivity 0.2μs / cm), 20 seconds spray (7) Drain dry: 110 ℃ 180 seconds 4. Coating weight measurement method The phosphate chemical conversion treated test piece was immersed in a 5% chromic anhydride aqueous solution at 75 ° C for 15 minutes to peel off the chemical conversion coating. The weight of the chemical conversion coating was calculated from the weight difference before and after peeling. Unit: g / m ² 5. Colloid average particle size measuring method Coulter N4 type manufactured by US Coulter Co. is used as a submicron particle analyzer.

Measurement conditions: 20 ° C, scattering angle 90 °, sample time, prescale, run time in automatic mode Measurement unit: nm The experimental results obtained by the above test materials, surface treatment methods, and measurement methods are shown in Figs. It is shown in FIG.

A 100 solution containing 100 g of the surface conditioning solution A was treated with the same surface conditioning solution for 10 days while measuring the coating weight and the average particle size of the titanium colloid every two days from the time of new construction. The graph of FIG. 1 is a graph in which the weight of the chemical conversion coating when the deterioration over time in use is investigated is plotted, and the graph of FIG. 2 is a graph in which the average particle diameter of titanium colloid is plotted. The pH for 10 days was within the range of 8.2 ± 0.2, and the total alkalinity was maintained within the range of 6.2 ± 0.5 points.

As shown in FIG. 1, the effect of the surface conditioning liquid deteriorates over time, and as a result, the coating weight increases. In the case of the Palbond 3030 chemical conversion coating used in this experimental example, the standard coating weight is usually 2.0 to 2.5 g / m ² . Therefore, it is recognized from FIG. 1 that 5 days is the limit of the elapsed time of use of the surface conditioning solution. The fluctuation of the average particle size of titanium colloid in Fig. 2 is
The figure shows similar behavior of the coating weight variation.

The same behavior was observed for the surface conditioning liquid and the chemical conversion treatment liquid other than the above. As a result, the present inventors have found that the deterioration of the surface conditioning liquid over time can be captured by increasing the average particle size of the colloid. That is, it was confirmed that when the average particle diameter of the colloid generated in the surface conditioning liquid exceeds 600 nm, deterioration of the surface conditioning liquid over time exceeds the limit.

Considering the significant increase in coating weight and average particle size from 4 days to 6 days in Fig. 1 and Fig. 2, if the average particle size is controlled to 400 nm or less in consideration of safety, the film Since the weight is about 2.4 g / m ² or less, the coating weight can be stabilized. There is no particular need to control the average particle size of the colloid during the new bath. This is because the surface conditioning liquid at the time of new building bath is determined so as to obtain a predetermined coating weight. In the experimental examples whose results are shown in FIGS. 1 and 2, the average particle diameter of the colloid in the newly constructed bath is about 200 nm, and by this surface adjustment, the conversion coating weight of 2.0 g / m ² is obtained.
Therefore, the lower limit of the average particle diameter of colloid may be adjusted to the optimum value when a new bath is built.

Similar to FIG. 2, FIG. 3 is a graph showing changes over time in the average particle size of titanium colloid. However, in Fig. 3, the continuous partial waste renewal amount is 960
ml / hr (-○-), 480 ml / hr (-△-), 240 ml / hr (-
×-), the treatment with the surface conditioning solution and the chemical conversion treatment were continuously performed for 10 days while changing in three ways. The same amount of tap water as the amount of partial waste renewal was supplied. In this experimental example, total alkali stopping was measured several times a day during the surface conditioning treatment by continuous partial waste renewal, and surface conditioning solution A was replenished so that the total alkalinity did not deviate from the range of 6.2 ± 0.5 points. It was It was also confirmed that the pH of the surface conditioning solution at this time was in the range of 8.2 ± 0.2.

As shown in FIG. 3, it can be seen that the change in the average particle size of the colloid can be controlled by controlling the partial waste renewal amount with respect to the total amount of 100. conventionally,
Based on experience, the amount of renewal of partial disposal of surface conditioning solution was set, but the amount of renewal of partial disposal is 480 ml / hr.
Or when it corresponds to 240 ml / hr, after about 4 to 6 days, the weight of the chemical conversion coating on this surface-conditioned surface exceeds the standard value, and if the amount of partial waste renewal is more than 960 ml / hr, the surface conditioning agent becomes useless. It has been discarded. The average particle size of titanium colloid is maintained at an almost appropriate value at the partial waste renewal amount of 960 ml / hr, but in the conventional empirical method, finding such a partial waste renewal amount is entirely coincidental and has no reproducibility. It was According to the present invention, it is possible to continuously monitor the average particle size of the colloid in the surface conditioning liquid and detect from the measured value whether the surface conditioning liquid is stable or deteriorated with time.

FIG. 4 plots the relationship between the number of days elapsed when the average particle size was measured in FIG. 3 and the coating weight after the phosphate chemical conversion treatment. The aging days-chemical conversion film weight relationship curve shown in FIG. 4 shows the same tendency as the aging days-titanium colloid average particle size relationship curve in FIG. That is, it can be seen that the fluctuation of the weight of the chemical conversion coating can be suppressed by measuring the average particle size of the titanium colloid during surface preparation and controlling the amount of renewal of the surface preparation solution discarded so that it is maintained at the set value of 600 nm or less. .

Further, when the average particle size of the titanium colloid in the surface conditioning liquid deviates from the set value, the partial waste renewal amount may be controlled. In this way, in FIGS. 3 and 4,
Even if the specified conversion coating cannot be obtained after 6 to 8 days of use (partial waste renewal amount = 480 ml / hr, 240 ml / hr),
By appropriately changing the partial disposal renewal amount, it becomes possible to further extend the usable days of the adjustment liquid.

The frequency of measuring the average particle size of the colloid when carrying out the method of the present invention is not particularly limited, but is preferably once or more per hour.

5 to 8 show experimental data obtained by the following test materials and measuring methods. Only the points different from the above experiment are shown.

1. Test steel plate Double-sided electrogalvanized steel plate 2. Coating weight measurement method 20 g of ammonium dichromate and 480 g of concentrated ammonia water were added to distilled water to remove the solution as 1 and then calculated from the weight difference before and after the removal. Unit: g / m ² 3. Treatment liquid Surface preparation liquid B: Same composition as the surface preparation liquid Concentration: 200g / 100 Total alkalinity: 13.5 ± 1.0 points pH: 8.2 ± 0.2 Phosphate conversion treatment liquid: Palbond 3004 (manufactured by Nippon Parkerizing Co., Ltd.) Main components: primary zinc phosphate, fluoride oxidizer (nitrate, nitrite) Concentration: 5kg / 100 (same) Total acidity: 23 ± 1 points Release strength: 1.0 ± 0.1 point Accelerator concentration: 1.5 ± 0.1 points FIGS. 5 to 8 are graphs corresponding to FIGS. 1 to 4, respectively. In addition,-○-in Fig. 7 and Fig. 8 indicates that the partial disposal renewal amount of the surface conditioning solution is 1400 ml / hr, and-△-is 700 ml / h.
r and -x- indicate the case of 350 ml / hr. From these graphs, by controlling the partial disposal renewal amount of the surface conditioning solution so that the average particle size of the titanium colloid is 600 nm or less, the weight of the chemical conversion coating is almost 3.25 even after 3 days.
It can be seen that it can be maintained at g / m ² .

Further, it can be seen that the above management method is also effective when the types and compositions of the surface conditioner and the phosphate treatment liquid are changed.

〔The invention's effect〕

As described above, since the management method of the present invention can accurately set the continuous partial discard update amount, which has relied on experience so far, the number of trials for setting this partial discard update amount. Can be significantly reduced, and the control accuracy of the surface conditioning solution in the phosphate chemical conversion treatment line can be improved.

In the case of an actual phosphate chemical conversion treatment line, the amount of continuous partial disposal and renewal of the surface conditioning solution may not always be constant due to fluctuations in water pressure on the water supply side, but the average particle size of the colloid is measured appropriately. As a result, it is possible to prevent abnormalities in the surface conditioning liquid, and to adjust the water amount with higher accuracy, thus eliminating waste over time.

In addition, since the titanium colloid of the surface conditioning liquid is negatively charged as a whole, the charge of the colloid is discharged when water containing excess Mg ²⁺ , Ca ²⁺ ions in water is used. The colloid is agglomerated, that is, the colloid particle size is increased, and the surface conditioning performance is deteriorated. However, by using the control method by measuring the colloid average particle diameter according to the present invention, it becomes possible to appropriately deal with the above-mentioned fluctuations in water quality.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the number of days of the surface conditioning solution and the weight of the chemical conversion coating, and FIG. 2 is the number of days of the surface conditioning solution shown in FIG. 1 and the average particle size of the titanium colloid. FIG. 3 is a graph showing the relationship between the number of days elapsed and the average particle size of titanium colloid in various continuous partial waste renewal amounts, and FIG. It is a graph which shows the relationship between the number of days elapsed and the conversion coating weight in the continuous partial waste renewal amount. FIGS. 5 to 8 are graphs when the compositions of the surface conditioning liquid and the chemical conversion treatment liquid are changed in FIGS. 1 to 4, respectively. [Explanation of Codes]-○-○-: Partial waste renewal amount of surface conditioning solution = 1400 ml / hr- △-△-: Partial waste renewal amount of surface conditioning solution = 700 ml / hr- ×-×-: Surface conditioning liquid Partial disposal renewal amount = 350ml / hr

Claims (2)

[Claims] 1. A surface conditioning treatment performed on a metal material with a surface conditioning solution containing a phosphoric acid compound and a titanium compound as a pretreatment for a phosphate coating chemical conversion treatment on a metal material, comprising: Part to be substantially continuously discarded, and when renewed to control the surface conditioning performance of the surface conditioning solution, the average particle size of the titanium colloid generated in the surface conditioning solution is measured. According to the measured value, the amount of renewal of waste of the surface conditioning solution is adjusted, thereby controlling the average particle size of the titanium colloid to 600 nm or less, a surface conditioning solution for phosphate coating chemical conversion treatment. Management method. 2. The method according to claim 1, wherein the average particle size of the titanium colloid in the surface conditioning liquid is controlled within the range of 200 to 600 nm.