JPS58193375A - Automatic management of chromating bath - Google Patents

Abstract

PURPOSE:To contrive to stabilize the quality of a chromated steel sheet, by analyzing Cr<6+> content in a chromating bath to control the amount of a new treating liquid to be replenished, and analyzing Zn<2+> content in it to control the treatment of regenerating the treating liquid. CONSTITUTION:Cr<6+> content in a chromating bath 5 is analyzed by an automatic analyzer 6, and a pump 4 is driven on the basis of the deviation between an objective concentration and the measured value to replenish a new chromating liquid from a supplementary tank 3. In addition, Zn<2+> content in the treating bath 5 is analyzed, and a pump 7 is driven on the basis of the deviation between an objective concentration and the measured value to introduce the deteriorated treating liquid into filters 8A, 8B for the removal of fine suspended matter from it. Thereafter, the treating liquid is introduced into columns 9A, 9B packed with ion-exchange resin to adsorb and catch cations, e.g. zinc and iron, and Cr<3+> accumulated in the liquid, and the regenerated liquid is returned to the chromating bath 5 again.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for automatically controlling the chromate treatment bath used in chromate treatment to impart corrosion resistance and columnarization to hot-dip galvanized steel sheets or electrogalvanized steel sheets. on how to manage it.

Chromate treatment applied to #'1km galvanized steel sheet or cloudy galvanized steel sheet.The treatment solution used is:
It is an aqueous solution containing anhydrous chromium # of several y/l to several tens of F/11, but only the violet that has been converted into a film on the object to be treated contains 6
Valent chromium ions are reduced, and Sugiyama fc is removed from the treated material.
! Cations such as lead and iron and CrM+, which is a product of the chromate film, are released into the liquid. Among these energy-saving ions, especially when the 6 degrees of Znl and Cr1+ ions become high, the chromate film forming reaction slows down, making it difficult to manufacture products with constant chromate adhesion.

For this reason, the degraded treated material is usually reduced to 3111h of hexavalent chromium for several months before being disposed of at a disposal site.

Conventionally, in order to ensure the stability of the quality of chromate-treated steel sheets and to regenerate the treatment solution, methods such as conductivity measurement and spectrophotometry have been tried to analyze chromium emv in the treatment solution. Examples of regeneration methods include a method using an ion exchange resin and an electrolytic regeneration method using an H membrane. Furthermore, it is possible to combine an analyzer for the chromic acid concentration in the processing liquid and a processing liquid regeneration system.
41 automatic processing liquid regeneration management machines are in use. However, conventionally, when removing cations from a chromate treatment solution using cation exchange 4# fat, the concentration of cations in the chromate treatment solution has not been checked.

The chromate treatment solution was supplied to an ion exchange resin column. Therefore, if a closed system is adopted in which the chromate treatment solution is regenerated and reused as a chromate treatment bath, the chromate treatment bath will have an increase in the number of Kaede ions in the chromate treatment bath, resulting in the chromate treatment being There was a time when the quality of the steel plate was unstable.

For the purpose of the present invention, the above-mentioned prior art interpharyngeal points are eliminated,
To provide an automatic management method for a chromate treatment bath that can adopt a closed 7-stem system that regenerates the chromate treatment solution and reuses it as a chromate treatment bath, while ensuring stability in the quality of chromate treatment steel sheets. be.

The process of the present invention is the result of an in-depth study of the chromate treatment bath management method VC--Cn-Cr"-Zn"+each ion a
Measuring only 1 degree makes it possible to manage the bath, which is essential, and automatic analysis is easy because measuring the concentration of these ions does not involve interfering ions or interfering substances in the processing bath. It turns out to be a friend.

This book @L4II was made based on the findings like L1, and it automatically divides the Cr@1 concentration in the chromate treatment bath and the Cr@+ concentration in the chromate treatment bath.
Sub-controlling the replenishment Mk of a new chromate treatment solution to be replenished into the chromate treatment bath based on the surface difference between the concentration and the target value, as well as controlling the amount of Zn in the chromate treatment bath.
Automatically analyze the degree of li, this minute 4? Based on the deviation value between 'r* and the target value of Zn''+ concentration of chromate treatment ms, 516''''-1! , 1 to control the amount of liquid [7].

Embodiments of the present invention will be described in detail below based on the accompanying drawings.

The drawing shows an example of the automatic management system of the present invention.
It consists of a device 6 for automatically analyzing the n k+ concentration and a regeneration system B for the chromate treatment solution. The replenishment line for the chromate treatment bath includes mixing tanks IA and IB for the chromic acid aqueous solution, and a replenishing tank 3 for the chromic acid bath solution connected to these mixing tanks via 2τ. The chromium melt solution is supplied to the chromate treatment bath via a pipe 4τ. Made by Honda 4! tb
is designed to operate at fixed time intervals according to the difference between the Cr"@[in the chromate treatment bath measured by the automatic analyzer 6 VC and the Cr@+ target concentration in the chromate treatment bath 5. Po/12 and Bonzo 3 may be made of acid-resistant resin as long as they have a pumping capacity of 91 l/min or more.The sizes of the tanks IA and IB and the replenishment tank 3 are determined by the replenishment liquid A. Although it varies depending on the temperature and chromate treatment solution size, one batch is I!0.5 rn"7M degree.

The automatic analyzer 6Fi analyzes the Cr6+ concentration in the chromate treatment bath 57 and controls the difference between these concentrations from the target value to provide L5 with proportional control for replenishment and regeneration of the chromate treatment bath. There is. The method for measuring the Cr@+ concentration and Zn2+ concentration in this automatic analysis 56 is as follows.

Cr@shi? Analysis of Is degree; chromate treatment solution (test solution)
Add a mixed acid and a sodium chloride difluoride indicator to the mixture and prepare a 1/1θN-ferrous ammonium phosphate semi-bath using a trowel.
λtanomo IJ! In addition to a few rxl of intimidation, an excess of 1/10N of standard bath solution was added to the standard solution of potassium chromate.

Analysis of Zn14 chain;
The sample was diluted and sprayed, then atomized with an air-acetylene flame, and the absorbance at a wavelength of 213.86 nm was measured. .

Regenerated yarn B-go in chromate treatment bath, Zn2+ concentration measured by automatic analyzer 6 and Zn in chromate treatment Fuchu
+Pump 7, filters 8A and 8B, ion exchange resin columns 9A and 9B, and high concentration sulfuric acid tank l
O, and a cleaning sulfuric acid tank 11^. Filters 8mm and 8mm111 polypropylene filters (4, cartridge type) are installed. The strong acidic cation exchange resin can be completely filled in the Makuio/Chichi Kankashiri columns 9A and 9B. Various types of strongly acidic cation exchange resins such as U7 can be used, but in this Example tC, a macroporous type polymerized with Sunalene and Diviny J lebenzene was used. In addition, the ion exchange resin column de^ and qB6 are pressurized and have a resin light #AI of approximately 2501, and the inner surface of the ζ column is Lined with polyvinyl chloride.

The details of the automatic management method using the automatic management system for the romate treatment bath will be explained below. The automatic analyzer 6 analyzes the Cr@+ concentration in the chromate treatment bath, calculates the deviation value from the target concentration, and operates the pump 4 in response to a signal based on this deviation value. By operating the pump 4, the chromate treatment bath 5 is replenished with a fresh chromate treatment liquid from the replenishment tank 3. The automatic analyzer 6 analyzes the Zn''+ concentration in the chromate treatment bath 5, calculates the deviation value from the target concentration, and operates the pump 7 based on a signal based on this deviation value. The chromate treatment solution can be introduced into filters 8A and 8B.
ilI/'' suspended matter is removed and then introduced into ion exchange resin columns 9A and 9B. In ion exchange resin columns 9A and 9BK, cations such as zinc and iron eluted from the treated material and Cr1+, which is the main component of the chromate film, accumulate in the liquid, so these ions are It is adsorbed and captured by the cation exchange resin.

The chromate treatment liquid thus regenerated is returned to the chromate treatment bath 5 again. The regeneration of ion exchange resin is
A trace amount of hexavalent chromium in the aqueous solution discharged from the sulfuric acid supplied from the high concentration sulfuric acid tank 10 and the pure water supplied from the pure water tank 12 is reduced to trivalent PM by a reduction device (not shown). It is discharged out of the posterior system.

As mentioned above, only Cr" and Zn" are analyzed in the automatic analyzer. pnFi in the bath is necessarily constant,
Also, if the Zn"+ concentration and Cr@+ concentration are constant, it is due to the chemical reaction accompanying the chromate treatment, Cry (h"-+ 141
("+32n==2Cr"→+3Zn++7HyO
This is because the concentration of Crm+ generated is determined. In addition, the concentration of F e I in the chromate treatment bath 5 is originally low, and the influence of F@"11 degrees on the quality of the chromate film is smaller than that of Znt + and Cr" 10 degrees.
There is no particular need to employ a process based on s'' medium concentration analysis.

Next, chromate treatment was applied to a non-alloy hot-dip galvanized steel sheet using the automatic management system shown in the figure. Table 1 shows the white rust occurrence area ratio. 1ill board as threading material!
12501m, plate thickness 0.82mm, zinc coating amount 60P/-
The material was used. From Table 1, the following facts are recognized: (The pH of the rechromate treatment solution can be kept constant.

(2) Cr'' (T, Cr-Cr''), Zn'' and T, F@concentration t < 11/1. < 0.
4f/l and 0, l P/l r can be controlled.

(3) Even if the chromate treatment solution is used for a long time, the total Cr content in the chromate film hardly changes.

(4) According to the salt spray test results of non-alloy hot-dip galvanized hook plates with chromate coating (Product H), white rust generation is less than when automatic control equipment is not used, and the time required for using chromate treatment solution is also reduced. Product quality (rust resistance) remains stable even over time.

In the above test example, an example using a hot-dip galvanized steel sheet was shown, but similar results were obtained in the case of chromate treatment of an electrogalvanized steel sheet.

From these test fruits, Cr in chromate powder was determined.
Set the target value of "8 degrees" and the target value of Zn + concentration,
Cr''+ in the chromate treatment bath by controlling the Cr'+ concentration and Zn''+ concentration in the chromate treatment bath
The concentration and Zn"4 concentration should be adjusted within a range where the quality of the chromate-treated steel sheet is stable, and in particular the rust resistance of the steel sheet does not deteriorate (Cr"f
i11 degrees = 1)/i or more T, Zn" concentration: 0.01 to 0.
5 y/l).

In addition, if an automatic analyzer is used that analyzes the concentration of cations that accumulate in the chromate treatment solution and are removed by the regeneration system in addition to the concentration of Cr a, it is possible to automatically analyze the chromate treatment solution for aluminum steel sheets. can be done, and also
The main component of the treatment liquid used to form a chromate film on tin-free steel sheets and steel plates is Cr.
Since it consists of I+, it is possible to automatically manage the romate treatment liquid in this way.

As described above, according to the present invention, (
Since the r j + concentration and the Zn''+ concentration can be automatically controlled, it becomes easy to manufacture stable and high-quality products while preventing delays in the chromate film forming reaction.

[Brief explanation of the drawing]

The drawing shows the present invention! It is an overall view showing an example of automatic management equipment for a chromate treatment bath to be treated. lA, 111...Preparation tank, 2.4.7...BO/
P. 3... Replenishment tank, 5... Chromate treatment bath. 6...Automatic analyzer, 8A-8B...Filter. 9m, 911...Ion exchange resin column, lO...
High-grade sulfuric acid tank.

Claims (1)

[Claims] (1) The chromate treatment bath is automatically analyzed for 6 degrees of Cr, and based on the deviation value between this analysis value and the target value of C% + concentration of the chromate treatment bath. In addition to controlling the amount of new chromate treatment solution replenished, the Zn''+ concentration in the chromate treatment bath is automatically analyzed, and the deviation value between this analysis value and the target value of the Zn''+ concentration in the chromate treatment bath is determined. An automatic management method for a chromate treatment bath comprising controlling the amount of chromate treatment ms supplied from the chromate treatment bath to a chromate treatment liquid regenerating device based on t-%.