JPS58211644A - Automatic control method and apparatus for concentration of fluoride in plating bath for electrolytic chromic acid treated steel plate - Google Patents

Abstract

PURPOSE:To achieve the automatic control of a plating bath by a simple method by measuring the potential of a sample with an ion electrode after the addition of a chemical agent thereto to determine the concentration of all fluorine ions and the concentration of active fluorine ions based on a calibration curve prepared. CONSTITUTION:A sample is taken into a measuring tank 8 with a pump 17 from a plating bath tank 12 and a buffer is injected into the tank 8 with a pump 19 from a tank 4. After they are mixed thoroughly, potential is measured with an ion electrode 1 and a conversion assay of the concentration of all fluorine ions is performed with a microcomputer 9. Then, a NaCl solution is fed to an assayed sample solution, sampled into a measuring tank 8' with the pump 17, from a tank 6 with a pump 20 and after they are mixed thoroughly, potential is measured with an ion electrode 2 and a conversion assay of the concentration of active fluorine ions is performed with the microcomputer 9. The measured concentrations of both the fluorides are compared with a preset target concentration and addition values of both the fluorides are calculated. Based on the results, they are fed to a plating bath tank 12 by a specified amount from chemical liquid tanks 10 and 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plating bath control method and apparatus for producing an electrolytically chromic acid treated steel sheet having metallic chromium in the lower layer and hydrated chromium oxide in the upper layer.

In recent years, electrolytic chromic acid treated steel sheets (generally referred to as tin free steel) having the above-mentioned coating have been developed.
:hereinafter abbreviated as TFS) is mainly used as a metal container material. Tin-plated steel sheets, or turtle tin, have been used as a material for metal containers for a long time, but in response to global resource depletion and in response to the demand for cheaper container materials, tin has been replaced by tin. This is a steel plate that does not use tin at all, that is, "I'F' 8 (Tin Free 8)".
TeeL)' was developed and has come to be used as a material for beer cans and carbonated beverage tins.

Unlike tin, TFS cannot be soldered at the joints, so it is used after being bonded. Metal containers include three-piece cans, categorized by composition.
Can) and Two Pieces
In addition, by processing classification, Handa Rin,
Welded cans, adhesive cans, DI cans (Drawing Iron
ingCan: Abbreviation for a can that is drawn and ironed. The following is divided into DI can (abbreviated as DI can) and bent end.

Generally, when referring to metal containers for food and beverage cans, there are four types of metal containers: semi-conical, welded cans, glued cans, and DI cans. When TFS is used as a container material, it is used for products other than solder solder, and is mainly processed as a 3-piece can with a body glued together as an adhesive can.

In recent years, DI cans have been widely used as metal containers in the field of beer cans and carbonated beverage cans due to their stable quality, good appearance, and low cost, and adhesive cans using TF8 material are , coffee cans, juice cans, and other beverage cans, or general food cans.

The adhesive can is formed by applying a paint mainly composed of epoxy resin or epoxy phenol resin to the surface of the TF8, and then heat-bonding the can body with a nylon adhesive.

Metal containers are selected depending on the type of food or beverage to be filled, but adhesive cans, due to their structure, have excellent performance as cans for low-temperature filling or storage of beer and carbonated drinks. ing. However, depending on the type of contents, high-temperature filling or sterilization may be performed, and the filled cans are exposed to high temperatures of 90°C to 130°C, which reduces the strength of the can body bond. It may deteriorate and cause damage. Particularly in recent years, many vending machines have been installed due to the rationalization of distribution, but in the case of heated drinks such as coffee, they are always stored at around 70 degrees Celsius, which deteriorates the strength of the bonded parts. is the most important concern.

An investigation of the adhesive part of the adhesive can that caused the damage accident revealed that the peeling occurred from the interface between the steel plate and the resin coating, and not from the interface between the resin coating and the nylon adhesive. In order to elucidate this peeling phenomenon, research has been conducted on the quality characteristics of the TF8 surface, particularly the adhesive characteristics, and many patents have been published. According to them, the adhesive force between the TF8 surface and the paint film interface is due to the hydrated chromium oxide film (hereinafter referred to as oxide chromium film, Oxide Cr film) formed on the TF8 surface.
It depends on the quality of the film (abbreviated as “film”). The quality of this oxide chromium film is determined by the TFS plating manufacturing method. That is, the plating bath composition characteristics.

It is said that the quality of the plating is influenced by the components present in trace amounts, and research is progressing to clarify the relationship between these plating manufacturing conditions and the quality of the oxide chromium film.

In recent years, research on the quality characteristics of solid surfaces has progressed rapidly.
Precision equipment necessary for research analysis is used. In particular, the Auger Btectron 8pe
CTroscopy: Hereafter abbreviated as Ag3) and Esca (Electron 8pectroscopy Ch)
emicatAnalysis: hereinafter f'1BscA
A device called (abbreviated as) is used.

The present invention ultimately withstands hot filling and sterilization processes,
With the aim of providing TFS with excellent surface quality properties and good adhesion properties, we have now found a method and apparatus for automatically and rapidly analyzing and controlling the plating bath composition in the plating production of TFS. be.

The manufacturing process of TF8 is divided into three steps.

The first step is a plating pre-treatment step, the second step is a plating step, and the third step is a post-treatment step. 1st
The process includes immersing the original plated plate in an alkaline solution, or washing it with water after degreasing it by electrolysis, pickling it in a sulfuric acid or hydrochloric acid solution, and then washing it with water. The second step is a step of simultaneously obtaining metallic chromium and oxide chromium films by cathodic electrolysis in a plating bath containing chromic acid as a main component and adding a necessary amount of a fluorine compound. The third step is a step in which unnecessary components contained in the oxide chromium film in the previous plating step are removed by immersion in high-temperature water and electrolytic treatment.

As mentioned above, the adhesive force between the TFS surface and the coating interface is
He stated that it depends on the quality of the oxide chromium film formed on the surface. That is, by cathodic electrolysis in the plating bath in the second step, a metallic chromium layer of about 0.015 microns and an oxide chromium film of about 200.chi. are deposited on the steel plate surface with an average thickness. The main component of the plating bath for obtaining a metallic chromium layer is chromic anhydride, with a concentration of 20 to
200 f/l, and necessary amounts of fluorine compounds and sulfuric acid groups are further added to obtain a chromium oxide film. The presence of fluorine is essential to impart excellent adhesive properties to chromium oxide films. Through cathodic electrolysis in the plating bath, fluorine is incorporated into the chromium oxide film and has an effective effect on improving adhesive properties. When manufacturing glued irons, the paint is usually baked twice for the inner and outer coats, and then heated once to bond the can body, making a total of three heating sessions at around 200°C. . Fluorine separates from the oxide chromium film when heated, improving the degree of polymerization of the film, and can be said to be an indirectly effective element for creating an insoluble film that does not easily change even during high-temperature filling and high-temperature sterilization treatment after adhesion. .

Conventionally, fluoride has been added to TFS plating baths. For example, in JP-A-56-96094, NHIF' is used as a fluoride component.

NaF SHF, KF, + Nal-lF2, K
HF'2, NH, HF2, etc. (these are collectively abbreviated as FA), Na2SiF6, H□S i F6.

K2S1Fa, (NL(4)2SiFa, IIBFiN
There are aBF, KBF, N114BF4, etc. (these are collectively abbreviated as F'B), and FA and F'B components are appropriately combined to form a plating bath. In the plating bath, for example, ammonium fluoride is added to N1 (4- and F-) and
Sodium silicofluoride is Na+! :5iFS-, and furthermore, some SiF knees are dissociated into S + (OH)a- and F-.

The inventors conducted research on fluoride-added TFS plating baths, and found that among the various forms of fluoride present in these baths, a particularly important form of fluorine is free fluorine (hereinafter abbreviated as Free F). ) and total fluorine (tota
(abbreviated as tF). In actual operation, 1. Iron ions Fe3+ generated by elution from the steel plate accumulate, and FreeF decreases conversely. The reason why Free F decreases in this way is that Fe3+ ions react with Free F in the bath to form a complex called FeFx, thereby decreasing available fluorine ('Free F). This is because the Free 7
This is also supported by the decrease in tsunium concentration. Therefore, in order to stably control the plating quality, it is necessary to
F and TotatF are constantly analyzed and grasped at a high frequency, and the decreased F”reeF is quickly analyzed and NH
It is necessary to compensate by introducing a fluorine ion source such as . In addition, calculations of the types and dosages of drugs for compensation are burdensome, and there are other problems, such as the unavoidable possibility of human error.

In order to solve these problems, the present invention uses an ion electrode to determine the potential and determine Free F and Tota.
In addition to establishing a method to rapidly analyze lF, we have also developed a method for collecting the plating solution, adding a total ion strength adjustment agent, measuring the potential,
We have invented an automatic control method and device for a fluoride-added TFS plating bath that automates each process from analytical calculations to fluorine source agent dosage calculations and dosage instructions. The purpose is to operate a tin-free steel plating bath.
The aim is to eliminate the human burden and human errors associated with ion electrode analysis and drug dosage calculations. Another purpose is to quickly measure changes in the plating bath to maintain the plating bath in a good condition at all times to prevent deterioration in the quality of TF8 products.゛The gist is that a certain amount of analysis sample is automatically collected from the electrolytic chromic acid-treated steel plate manufacturing tower containing 17 trouside, and after adding and mixing an ionic strength adjusting agent or a pH adjusting agent, it is stained with an ion electrode. The computer connected to the ion electrode calculates and stores the total fluorine concentration from the measured potential, and separately adds neutral salt to the sample collected above. After mixing II +, the potential is measured by an ion electrode, and a computer connected to the ion electrode calculates and stores the active fluorine ion concentration from the measured potential,
Next, the difference between these measured fluorine concentrations and the total fluorine target concentration and active fluorine concentration, which are pre-stored in the Conobutter, is calculated, and the required amount of fluoride replenishment solution is automatically added to the plating bath based on the calculation results. A method for automatically controlling fluoride concentration in a plating bath for electrolytic chromic acid-treated steel sheets, characterized in that the fluoride concentration is replenished in a plating bath for electrolytic chromic acid-treated steel sheets.

2. 17 stages for collecting an analysis sample from the plating bath, a reagent addition means for adding a reagent to the sample liquid, an analysis means using an ion electrode for measuring the fluorine ion concentration in the sample liquid, and a fluorine ion injected into the plating bath. The fluoride replenishment means is connected to the ion electrode and the fluoride replenishment means, and the difference between the preset fluoride ion target concentration and the actually measured fluoride ion concentration is calculated and the calculated result is calculated. 1. An automatic control device for controlling fluoride concentration in a plating bath for electrolytic chromic acid-treated steel sheets, comprising a control means for calculating and replenishing the required amount of fluoride replenishment solution based on the above-mentioned information.

It is.

The present invention will be explained in detail below. As mentioned above, the present invention was completed by establishing a method for rapidly analyzing Free F and TotatF.

First, the analysis method employed in the present invention will be explained in detail. When measuring the total amount of fluoride (hereinafter abbreviated as TotatF) existing in an electrolytic chromic acid treatment bath using an ion electrode, various error factors intervene.

For example, FIG. 1 shows the relationship between the measured potential of the ion electrode and pH. This is the potential when NaOH is added to the same mother liquor mixed with a certain amount of ammonium fluoride, ammonium fluorosilicide, and chromic acid, and the potential is adjusted stepwise from 1 to 9, and it depends on the pH. is changing. When the pH is 6 or less, the potential changes linearly, but when it becomes 6 or more, it becomes stable. Therefore, in order to eliminate the influence of fi PH, it is necessary to adjust the PH to about 58 or higher. This may be done by adding an alkali such as NaOH, but it is more desirable to use a total ionic strength adjuster (TI8ABfi) for the reasons described below. In other words, in addition to the effect of PH mentioned above, in general, in analysis using an ion electrode, the measured potential is
Another effect is the inclusion of errors due to differences in the total ionic strength of the solutions. The purpose of the total ionic strength adjusting agent is to maintain the total ionic strength of the measurement solution constant in this way and eliminate errors caused by this. Furthermore, if a total ionic strength regulator with a pH adjustment function is used, the above-mentioned P
Errors caused by H can also be eliminated at the same time. FIG. 2 shows T I S A II (T
otatIonic Strength Adjust
This is a calibration curve of Total F- created by measuring the potential with an ion electrode using ment Buffer). The composition of Tl5AH used at this time was a mixture of NaCL, sodium citrate, glacial acetic acid, and water.

Next, a method for measuring active fluorine present in the electrolytic chromic acid treatment bath will be explained. Active fluorine, or free fluorine, is an important factor that has the greatest effect on the quality of plated products. However, there are various problems in measuring this with analysis means using ion electrodes. For example, when an electrolytic chromic acid treatment solution is sampled and an ion electrode is immersed in it to measure its potential, the potential should be a value that correlates with the active fluorine concentration, but T
There are problems as shown in the example of measuring otatF.

That is, it is the effect of total ionic strength. Figure 2 shows a calibration curve for active fluorine. In this way, the calibration curve becomes an irregular curve, the potential at each measurement is unstable, economical changes are large, and measurement is difficult.

Therefore, if we try to eliminate the influence of total ion strength by using the total ion strength adjusting agent as mentioned above, it has a pH buffering function, so the pH increases and ions existing as fluorides, such as 8iF6- and FeFx, − etc. dissociate,
Since it becomes active fluorine, the value will be different from the value originally present in the bath. Therefore, a proposal was made to add neutral salts in order to stabilize only the total ionic strength without changing the pH. Figure 4 shows NaCl as one of the neutral salts added to the solution prepared under the same conditions as Figure 3.
This is a calibration curve obtained when one quantitative amount of 1 was added, and good linearity was obtained. In addition, the stability of the potential over time was also good.

The analysis method using an ion electrode described above is a simple method in which a chemical is added to a sample and mixed, the potential is measured, and the concentration is determined from the potential using a calibration curve prepared in advance. It is essential to the law and equipment.

Next, the method and apparatus of the present invention will be explained based on the drawings.

FIG. 5 shows an outline of the apparatus according to the present invention and the flow of the piping system from the plating bath. Reference numeral 12 denotes an electrolytic chromic acid treatment bath, and an underground bit tank 13 containing a plating solution is provided below it. Reference numerals 15 to 21 are liquid pumps for feeding the plating solution, additive chemical solution, and fluoride solution. 3 is a heavy lid main body. 8.8' are TotatF and FreeF measurement tanks, respectively, and each of them contains TotatF and FreeF measurement tanks.
Ion electrode for tatF and Free F measurement 1.2
will be installed. 14.14' is a magnetic stirrer. Also, 4 is a buffer tank, 5 is a standard solution tank,
6 ij NaCl solution tank. 9 is Mike.

The computer u 10S 11 is a chemical tank for supplying fluoride, which is provided to compensate plating bath additives according to the analysis results of the plating bath.

Next, a method for automatically controlling the concentration of fluorine compounds in a plating bath using the apparatus of the present invention will be explained.

First, the amount of sample necessary for Total F analysis is pumped from the plating bath 12 using the pump 17, and the piping systems a and b are
The buffer solution stored in the tank 4 is injected into the measurement tank via the piping system d by the pump 19, and then the magnetic stirrer 14 which is placed in the bottom of the cypress.
Rotate to mix the measurement solution thoroughly. The potential measured by the ion electrode I is converted into a Total value and quantified by the microcomputer-9. Also, piping system a
, c to the analysis sample bath liquid collected by the pump 17 into the measurement tank 8', the NaCL solution is supplied from the tank 6 via the piping system f by the pump 20. After sufficiently mixing the measurement liquid with the mechanical stirrer 14', the potential is measured with the ion electrode 2, and the Free F value is converted and quantified using the microcomputer 9. The amount of both fluorides to be added is calculated by the microcomputer 9 from the difference between the measured concentration of both fluorides and the preset target concentration, and the required amount of chemical solution is sent from the chemical tank 10.11 to the plating bath. Direct to pump 15.16. As a result, the necessary fluoride is supplied via the plating bath 12 piping g or h. By repeating the above cycle at regular intervals, the fluoride concentration in the plating bath is kept constant. Note that the plating solution used for measurement is discharged outside the apparatus. Next, an example using this device will be described.

〔Example〕

Continuous plating was carried out for 500 hours using the following plating bath Cry382.4 f/I N)I, F 1.11 t/l, during which time,
Using the apparatus of the present invention shown in FIG. 5, the plating bath was analyzed every 30 minutes to determine the Free F concentration and Totat F concentration at 0.2 f/1 Totat on Free F O, 45.
F was automatically controlled to be 1.6±0.1 f/l. T 200 hours and 500 hours after starting plating
As a result of testing the high temperature adhesive properties of FS products, the DI value was between 120 and 130, which is the lower limit of the control standard value of DI value 1
An excellent product far exceeding 0.00 was obtained.

In addition, as a comparative example, the plating bath was used as a free bath after a health bath.
When continuous plating was performed without particularly controlling F and Total F, the DI value decreased to 100 or less after 200 hours.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between PH and ion electrode potential. Figure 2 is the calibration curve for TotatF, Figure 3 is the calibration curve for active fluorine, and Figure 4 is the calibration curve for active fluorine (addition of NaC1).
, FIG. 5 is an explanatory diagram of the apparatus of the present invention. l Ion electrode for TF 2 Ion electrode for PF 3 Device body 4 Buffer tank 6 Standard solution tank 5 NaC1 solution tank 8 Measuring tank (1) 8' Measuring tank (2) 9
Microcomputer - 10 Chemical tank (1) 11 (2) 12 Plating bath 13 Underground bit tank 14 Magnetic stirrer 15 Liquid pump 16 Liquid pump 17 N 18# 19〃 20# 11 b) Piping for collecting analysis sample C) Chemical piping for analytical samples Fig. 2'mI/Io6mJl -4- Fig. 3-F→/lθρml→ Fig. 4 Fm4/lθθml-- Continued from page 1 0 Inventor Yokichi Sato Nakaikegami, Ota-ku, Tokyo 2-14-12 Inventor: Japan Pariki Rising Co., Ltd. Technical Research Center Inventor: Keizo Oshiba To Kitakyushu City, 4-7 Yubaramachi, Hatanishi-ku, Japan Pariki Rising Co., Ltd., Kyushu Sales Office ■Applicant: Nippon Pariki Rising Co., Ltd. Company 1-15-1 Nihonbashi, Chuo-ku, Tokyo

Claims (2)

[Claims] (1) Automatically collect a certain amount of analysis sample from the electrolytic chromic acid-treated steel sheet manufacturing bath containing fluoride, add and mix an ionic strength adjusting agent or a PH adjusting agent, and then measure the potential with an ionic electrode, A computer connected to the ion electrode calculates and stores the total fluorine concentration from the measured potential, and after separately adding and mixing a neutral salt to the sample collected above, measuring the potential with the ion electrode,
A computer connected to the ion electrode calculates and stores the active fluorine ion concentration from the measured potential, and then calculates the difference between these measured fluorine concentrations and the total fluorine target concentration and active fluorine concentration, which are stored and set in the computer in advance. The method is characterized in that the required amount of fluoride replenishment solution is automatically supplied to the plating bath based on the calculation result.
Automatic control method for fluoride concentration in a plating bath for electrolytic chromic acid treated steel sheets. (2) A means for collecting an analysis sample from the plating bath, a reagent addition means for adding a reagent to the Sanvil solution, an analysis means using an ion electrode for measuring the fluorine ion concentration in the sample solution, and a fluoride ion in the plating bath. The fluoride replenishment means is connected to the ion electrode and the fluoride replenishment means, and the difference between the preset fluoride ion target concentration and the actually measured fluoride ion concentration is calculated and the calculated result is calculated. 1. An automatic control device for controlling fluoride concentration in a plating bath for electrolytic chromic acid-treated steel sheets, comprising a control means for calculating and replenishing the required amount of fluoride replenishment solution based on the above-mentioned information.