JPS5881980A - Aluminum surface cleaning method and device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION It is known that aluminum products, such as cans, can be cleaned by contacting the aluminum surface with an acidic solution containing fluoride. For example, Hess (
Hess et al. are published in the Journal of the American Welding Society (Journa).
l of the American Weld
ing Society) Addendum (September 1944)
For example, on pages 417-423 of J.D., he describes a method using a solution containing fluoride and sulfuric acid, and such a method is described in British Patent Specification No.
7 It is also stated in No. 4.

The practice of such methods requires supplementing the solution with acid and fluoride during use. Hess points out on page 420 of said document that there is no easy way to measure and maintain bath activity, as described for example in U.S. Pat. No. 3,431,182. The development of fluoride sensing electrodes provides a method for very precisely controlling fluoride content. The use of such electrodes is described in British Patent Specification No. 1,4 5 4,9
7 No. 4, it is described as a method for measuring fluoride content and determining the amount of supplementation.

When replenishing acid to a bath system, the acidity of the solution is usually measured and acid is added according to this measurement. The most common method of measuring acidity is the potential one-electrode method. This method is also described in British Patent Specification No. 1,
4 5 4, 9 7 4.

Said Hess and British Patent Specification No. 1,4 5 4,9
The method as described by No. 7 No. 4 actually involves maintaining the temperature of the working solution at a constant value by suitable heating and/or cooling devices, extracting and analyzing a sample from this working solution, and It appears that this is done commercially by replenishing the solution used according to the analysis results.
That is, the content of fluoride ions is maintained constant by measuring the content of free fluoride ions in the solution and automatically adding fluoride according to the deviation of this measured content with respect to a predetermined value. , the content of tri-acid is maintained constant by measuring the μ value of the solution in one go and automatically adding acid according to the deviation of this μ value from a predetermined value. Although these methods are widely used commercially,
In practice it has proven extremely difficult to control these contents so as to obtain uniform results.

Many other control systems are known for many chemical processes, one example of which is disclosed by the applicant in his British Patent Specification No. 2,050,64.
There is a control system primarily intended for the control of zinc phosphate solutions described in No. 5.

The present invention measures the actual free fluoride ion content when cleaning aluminum surfaces by contact with an aqueous solution of acid containing fluoride and supplemented with fluoride during use. The present invention relates to an improved method for cleaning aluminum surfaces in which said replenishment is carried out automatically by automatically adding fluoride depending on the deviation of the actual fluoride content from a desired predetermined value.

It was unexpectedly discovered that, in this method, if acid is replenished according to a fixed potential value, erroneous results may occur and the content of the solution cannot be maintained stably. Therefore, in the present invention, acidity is The potential standard is not used.

It was unexpectedly discovered that the measurement of acidic conductivity gives good results, whereas one measurement gives a false result, and therefore in the present invention we measure the acidic conductivity of the solution and change this actual acidic conductivity. Preferably, acid is added automatically in response to deviations from a desired predetermined value. - The reasons for this surprising finding that measurements of acidic conductivity give reliable results whereas measurements give erroneous results are not always fully elucidated.

However, whereas the recorded 100,000,000 tends to "follow" the free fluoride content, or vice versa, acidic conductivity appears to be unrelated to the fluoride content. That is, the − electrode is υ
It has been eroded and recorded 100 million, which is higher than the original value. Therefore, acid supplementation will be required. The addition of this extra acid causes the measured fluoride content to be lower than it should be, thus causing the fluoride sensor to automatically add more hydrogen fluoride.

As the fluoride content increases in this way, the glass electrode is further eroded. However, it was unexpectedly discovered that acidic conductivity is a reliable measurement measure independent of fluoride content.

In order to very precisely control the acidity, the acid conductivity must be used as described above to control the acid feed, but in most cases the appropriate control for the purpose is simply the amount of fluoride added. It has also been unexpectedly discovered that this can be achieved by adding acid in a predetermined and constant relationship to .

In such a method, replenishment cycles are started at regular time intervals, and during each cycle the fluoride ion content is measured and a first pump adds fluoride replenishment solution and a second pump adds acid. Add replenishment solution,
Replenishment is accomplished by operating these pumps at a predetermined delivery rate during each cycle for a period of time that is automatically controlled depending on the deviation of the fluoride ion content from the desired value. It is done cyclically.

This cyclical replenishment includes a timer to start each replenishment cycle and a first den to deliver a predetermined rate of fluoride replenishment solution. a second pump for delivering an acid replenishment solution at a predetermined rate; and a second pump for measuring the fluoride ion content of the treatment solution and generating a signal responsive to the deviation of this measured content from a desired value. and a device for automatically operating the first pump in each cycle for a time automatically controlled in response to said signal and operating the second pump together with the first pump. controlled by the device. The second sonde may alternatively be operated in conjunction with the first pump in an otherwise similar cyclic process depending on the acid conductivity.

It is known that the effectiveness of a solution is dependent on its temperature, and therefore great care is usually taken to keep the temperature of the kernels as constant as possible.

In the present invention, it is preferred that the temperature of the solution is measured and the desired predetermined value of free fluoride is automatically varied and compensated for depending on the deviation of the actual temperature from the predetermined temperature.

Because the effect of temperature on solution effectiveness is critical, it is important to perform all measurements in the actual working solution to obtain good performance, and therefore measurements are performed on samples taken from solution. Do not follow.

The degree of attack of aluminum by a given acidic fluoride solution increases with increasing temperature, and this degree approximately doubles for every 25° C. increase in temperature. Therefore, in the present invention, the desired predetermined value of free fluoride is reduced as the temperature rises above a predetermined temperature (to compensate for the increase in reaction rate that would otherwise occur) and the temperature is reduced to a predetermined temperature. It is preferable to increase it when decreasing below.

In one simple embodiment of this method, the fluoride concentration device records a concentration that is doubled for every 25°C increase in temperature such that the actual concentration decreases to V2 for every 25°C increase in temperature. is set to give. On the other hand, 25℃
For each drop in , the registered concentration must also be decreased by some equal value compared to the actual concentration, thereby increasing the actual concentration. In this case, the device for measuring the fluoride ion content of the solution and generating a signal depending on its deviation from the desired value is equipped with a visual indicator, such as a meter with a pointer. The means for measuring the temperature and adjusting said predetermined value in response to changes in temperature, which may be of the form Means may be provided for indicating and recording elevated fluoride ion concentrations.

In order to obtain the most accurate operation using this method,
Determine the exact relationship between temperature and concentration of fluoride ions, store this in a suitable storage device, and use this stored information to adjust the desired predetermined value of free fluoride to a temperature change. It is preferable to automatically defecate the food.

In addition to the invention of the method described above, the present application includes an invention of an apparatus having means for carrying out the method. The device maintains the acid number within the optimum value of 511 during normal operation when supplementing the acid in a predetermined constant relationship to the amount of fluoride actually added to the heptafluoride in solution. It turned out to be a compliment. However, it is generally preferable to monitor the acidity from time to time even during stable processing, so that acid is added when necessary depending on the deviation of the acidity υ from a predetermined value. Acidity can be measured vocally, but is preferably measured by the acidic conductivity scale as described above.

Although acid replenishment in a constant relationship to the amount of heptadide is good in steady-state operation, the surfaces of the aluminum to be treated may be affected as a result of stoppages of the conveyors transporting them, etc. False results can occur if little or no solution is supplied or the amount of solution varies abnormally. This is because little or no fluoride is used.
This is because while the line is in operation, acid continues to be used as cleaning solution is pumped into the pre-clean tank. Therefore, during such measurements of fluoride ions, the pump is only operated for a very short period of time, and in fact, the bonder may not operate at all.

At that time, it is preferable to cancel the normal operation of the acid replenishment control system so that acid replenishment can be carried out separately, that is, it is generally preferable to add acid at time intervals not exceeding a predetermined value. The device is therefore further provided with a release timer for adding acid at predetermined time intervals even when fluoride is not being added. That is, when sufficient acid has been added during a normal replenishment cycle to maintain the acid content properly, the release timer will not activate the second pump to add acid replenishment solution. but,
When the amount of acid replenishment solution added in response to a fluoride ion measurement by normal operation of the controller is insufficient to maintain the preset degree of acid addition, the release timer disables the acid addition. The second pump is operated occasionally for sufficient extra time to maintain the appropriate volume. The setting time of this release timer can be easily determined by experiment.

This set time is determined primarily by the normal losses per cycle of working solution, the content of free acid in the working solution, the concentration of the acid make-up solution, and the flow rate of the second 47 days.

Instead of or in addition to the timer-based release device, a release device may also be provided which includes a device for measuring the acidity, preferably by means of acid conductivity or by means of one electrode.

That is, a release device is provided for measuring the acidity and automatically adding an acid replenishing solution by the operation of the second bonder when the acidity of arsenic changes from a set value by more than a predetermined degree. It will be done.

The control device used in the present invention preferably uses electronic components, namely a variable mark/space ratio circuit as a tie to determine when to switch on the 4-way switch that supplies the fluoride replenishment solution during normal operation. A configured electronic control device. If the acid is supplied in a predetermined constant relationship to the fluoride, the bomb f for supplying the acid make-up solution is controlled in response to this timer. If the acid is added in response to the measurement of acid conductivity, the control housing includes a control device for measuring this conductivity and for using the signal obtained thereby to control the four rings for the supply of acid. Appropriate equipment is provided. The point at which this four-channel switch is turned ON may also be controlled according to a variable mark/space ratio circuit or other timing mechanism.

A control device is associated with the cleaning device and is trapped to operate for the entire period of time whenever the cleaning device is in operation.

For example, if a metal surface is preferably contacted with an aqueous solution by sugray, it is preferred that a control device be associated with the spray pump to operate the device for the entire period when the spray pump is in operation. The mark/scan ratio circuit turns ON the operation of metering I7f at regular intervals which determines the replenishment cycle via the output relay and determines the actual content of fluoride ions or the content compensated for temperature changes. The metering pump is set to turn off after a period of time corresponding to the desired value.

The metering pumps deliver sufficient fluoride replenishment solution and acid replenishment to maintain the bath at the desired concentration when their operation is ON for a predetermined portion of the cycle period, preferably the IA period. The solution is preset to be added to the bath. If the operating conditions change, the recorded content of fluoride ions will generally increase from its predetermined reference value, represented by the zero potential of the indicator scale, and the mark/space ratio circuit will respond accordingly. Turn on the fluoride supply pump
Change the time accordingly. Therefore, as the aluminum surface feed rate decreases, the fluoride ion content of the processing solution tends to increase and the fluoride feed pump @ON1 time is automatically reduced for the next replenishment cycle. Historically, the time for this replenishment cycle is 4 minutes, and the normal operation of the fluoride replenishment pump is approximately 1/2 of this time.
It is convenient to set it to /2.

The controller may be provided with means to prevent the operation of these pumps from being turned off too quickly, for example when approaching an abnormal condition, for example if the operation of the feed pumps is not turned off for most or part of the replenishment cycle. A warning light that indicates an undesirable condition such as when the fluoride ion content increases or decreases excessively and the mark/space ratio circuit operates abnormally, such as when it is turned on for the entire period. One or more alarm devices may be provided, such as.

Devices for measuring acid conductivity and fluoride ion concentration are both well known. An example of an electrode device for measuring fluoride ions is described in US Pat. No. 3,431,182. As is usual in this electrode arrangement, a reference electrode in a sealed reference electrode or a salt bridge is provided. Salt bridges are commonly used in other ion concentration measurement devices, such as certain types of measurement devices. While this salt bridge device has many advantages, it also has the disadvantage of giving false indications due to unobserved loss of salt from the salt bridge.

The present application also includes an invention relating to a salt bridge ion measuring device that has been improved to automatically issue a warning when a malfunction occurs in the salt bridge.

According to this feature of the invention, there is provided a salt bridge for the measurement of ion concentration in a solution, the salt bridge comprising a container containing a salt electrolyte and a container which is immersable in a solution and which contains a salt electrolyte. a permeable member connected to the container so as to be able to come into electrolytic contact with the solution without substantially leaking out; a round reference electrode provided in the container for use in measuring the concentration of ions in the solution; , an alarm electrode electrically connected to the reference electrode and positioned in the container to generate an alarm signal when the level of salt electrolyte in the container falls below a predetermined level.

The ion concentration measuring device comprises an ion concentration electrode positioned in the container with the salt bridge and electrolytically connected to a reference electrode to generate a signal depending on the concentration of a desired ion in the solution. It is equipped with

The container is usually adapted to contain a bath of salt electrolyte with both a reference electrode and an alarm electrode provided in the bath. The lowest end of the alarm electrode is placed above the point where the reference electrode no longer functions as a reference electrode.During normal operation, there is no electrical connection between the alarm electrode and the reference electrode by the salt electrolyte. A strong contact is formed.

However, after prolonged use or under abnormal conditions, salt electrolyte may be lost from the container, for example as a result of salt electrolyte leaching through the permeable member. When the level of the salt electrolyte drops to such an extent that the lowest end of the alarm electrode is no longer immersed in the electrolyte, the potential difference between the reference electrode and the alarm electrode increases steadily, and this change in potential difference is used to An appropriate signal is generated. This signal may be in the form of an audible or visible sound, or may be expressed using the solution whose concentration is being measured! It may also be used for the operation of some control mechanism related to the process.

The permeable member is generally a porous plug made of a ceramic material and connected to the container by a tube.

As the salt electrolyte, an aqueous solution of potassium chloride is often used. The alarm electrode may be stainless steel. The reference electrode is selected in consideration of the ion concentration control device in which it is used, and may be, for example, a calomel electrode encapsulated in glass.

In other parts of the ion concentration device, the ion concentration electrode is selected according to the solution and the ion concentration to be measured. The probe may for example be a voice measuring device, in which case electrodes of the type customary in salt bridge measuring devices can be used.

However, this feature of the invention is particularly useful when applied to the measurement of free fluoride ions in solutions, particularly the acidic fluoride solutions. The ion concentration electrode may therefore be a fluoride ion concentration electrode of known construction, for example an elastic glass member whose ends are edged with metal fluoride or the like.

A preferred method and apparatus of the invention is schematically illustrated in the accompanying drawings. An acidic, fluoride solution or bath 1 is used in a conventional tank and sprayed by means not shown onto the aluminum light surface at the solution's working temperature. The tank is equipped with a device (not shown) to maintain a constant temperature.

Since these are all common, further detailed explanation will be omitted.

A fluoride ion selective electrode 2 is immersed in the bath 1 and connected via a conventional fluoride measurement device 4 to a reference electrode 3 formed by calomel in glass, thereby detecting free fluoride in the bath. The content of chemical substances can be measured. The reference electrode 3 is housed in a salt bridge vessel 6 and immersed in an aqueous solution of potassium chloride electrolyte, and a tube 7 provided in this vessel is connected to a ceramic porous stopper 8 immersed in the service bath. It is connected. A rod-shaped alarm electrode 9 made of stainless steel is immersed in the salt electrolyte solution 5, with its lowermost end positioned at a height indicated by the dotted line 22 seen above the outwardly extending end of the reference electrode 3. It's a shame. An electrical contact is made between the reference electrode 3 and the alarm electrode 9 by an alarm control device 10 equipped with a suitable alarm device which gives an alarm when the potential difference between these electrodes 3 and 90 increases to an unfavorable value. is formed.

As an alternative embodiment, this salt bridge and the associated parts 3, 5, 6, 7, 8, 9, 10 may be replaced by an encapsulated reference electrode of conventional construction.

A temperature sensor 13 is also provided in the bath 'sl to generate a signal in response to a change in temperature from a predetermined value, wherein the optimum operating temperature of the solution is typically about 50°C.
Usually set around ℃. This signal predetermines the relationship between temperature and desired fluoride content! It is sent to the control device 11 which is a controller. This control device 11 sends a signal corresponding to the measured value of fluoride to the fluoride measuring device 4.
Calculate this from
5 provides an output signal to a control f14 feeding into the bath via conduit 16. The control device 11 also generates a signal to cause the digital display 12 to display the actual fluoride content.

A conventional acidic conductivity measuring device 17 was immersed in the air and connected to a numerical control device 18.

This device generates a signal in response to a change in acidic conductivity from a predetermined value, and when the acidity decreases below a predetermined value, an I
Operate yp19. Pump 7''19 supplies acid make-up solution from inlet 20 through discharge tube 21 into the bath.

The effective operation of controllers 11 and 18 and sensors 13 and 17 is controlled by a timer 23 that includes a mark/space ratio circuit. This timer 23 starts each replenishment cycle every four minutes. During each cycle, the inductor 14 is operated at a predetermined rate, controlled by the controller 11, and delivering the fluoride replenishment solution for a period of time dependent on the fluoride content and temperature values to increase the concentration of fluoride ions. is maintained at a constant desired temperature compensated value. The tank 7'19 supplies a replenishing solution of sulfuric acid or other acid, also at a predetermined rate, over a period of time controlled in response to signals from the controller 18. Also, the control device 1
8 and the conductivity sensor 17 may be omitted, and the timer 23 may be operated in a constant relationship with the operating time of the bonder 14. It is provided to initiate each replenishment cycle and is determined by the respective replenishment amount.The fluoride concentration is displayed on the display device 12 and the temperature is also displayed on this device.

The bath is generally initially at a temperature of 30-70°C, with -3
below, in most cases 1 to 2.5, but preferably about 1.5, and the free fluoride content is 0.
00005~o, xll/Is preferably 0.0001
~0.0051/l, and most preferably about 0.0
00811/I. Such baths can be readily prepared using appropriate amounts of hydrofluoric acid or other fluoride-providing substances and sulfuric acid, and the baths may also contain anionic surfactants. Okay, this bath is used to spray clean aluminum cans in the usual way.

[Brief explanation of drawings]

The drawing is an explanatory diagram showing an outline of an apparatus for carrying out the method of the present invention. DESCRIPTION OF SYMBOLS 1... Acid solution containing fluoride, 2... Fluoride ion selective electrode, 3... Reference electrode, 4... Fluoride measuring device, 5... Salt electrolyte, 6... Salt bridge Container, 9...
Alarm electrode, lO... Alarm control device, 11... Control device, 13... Temperature sensor, 14.19... Bonde,
17... Acidic conductivity measuring device, 18... Acid control device, 23... Timer. Agent Patent Attorney Minoru Kinoshita

Claims (1)

[Claims] (1) Contact the aluminum surface with an acidic aqueous solution containing heptadide, which is replenished during use, and measure the content of active free ions to determine the desired actual content of free fluoride. In a method of cleaning aluminum surfaces by replenishing Schiffide by automatically adding fluoride in response to deviation from a predetermined value, Φ) Adding acid in an amount that is in a predetermined constant relationship to the amount of fluoride added. A method for cleaning an aluminum surface, characterized in that acid is supplied by: (2) A method for cleaning an aluminum surface according to item 1 of the patent scope, characterized in that acid is replenished by adding acid in a predetermined and constant relationship to the amount of fluoride added. (3) Contact the aluminum surface with an acidic aqueous solution containing fluoride that is replenished during use, and measure the content of active free ions to determine the deviation of the actual content of free fluoride from the desired predetermined value. In a method for cleaning aluminum surfaces by replenishing Schiffide by automatically adding fluoride according to the temperature of said solution and measuring the temperature of said solution according to the deviation of this actual temperature from a predetermined temperature. A method for cleaning aluminum surfaces, characterized in that the desired predetermined value of free fluoride is automatically varied and compensated for. (4) (a) Measuring the acidic conductivity of the solution and automatically adding acid according to the deviation of the actual acidic conductivity from the desired predetermined value; or (b) the amount of fluoride added. 4. The method of cleaning an aluminum surface according to claim 3, wherein the acid is replenished by adding acid in a predetermined and constant amount to the aluminum surface. (5) The method for cleaning an aluminum surface described in Patent Section 3 or 4, which is characterized by visually displaying the actual free fluoride ion content (6) Amount of fluoride added 5. The method of cleaning an aluminum surface according to claim 4, wherein the acid is replenished by adding the acid in a predetermined and constant relationship to the aluminum surface. (A method for cleaning an aluminum surface according to claim 6, characterized in that the acid is added at time intervals not exceeding a predetermined value. (8) Measuring acidity and determining the deviation of this acidity from a desired value. Claim 6, characterized in that an acid is added depending on the condition.
Aluminum surface cleaning method described in Section O (9) i! ! ? ! 9. The method for cleaning an aluminum surface according to claim 8, wherein acid is added depending on the deviation of the acidic conductivity from a predetermined value. a [A device for measuring the content of free fluoride ions,
an apparatus for adding fluoride depending on the deviation of the actual content of free fluoride from a desired predetermined value; (a)! A device that measures the acidic conductivity of the liquid and automatically adds acid depending on the deviation of the actual acidic conductivity from the desired predetermined value; and a device for acid replenishment consisting of a device for adding acid in related quantities. aυ The device for measuring the content of free fluoride ions is
a container containing a salt electrolyte; a permeable member immersed in the solution and connected to the container to permit electrolytic contact with the solution without substantially allowing the salt electrolyte to escape out of the container; a reference electrode for use in measuring the ion concentration in the solution; and a reference electrode electrically connected to the reference electrode to issue an alarm signal when the rail in the salt electrolyte container falls below a predetermined level. Aluminum according to claim 10, characterized in that it is a vertical measuring device for # of ions in solution, comprising a salt bridge consisting of an alarm electrode positioned in the container so as to occur. Surface cleaning equipment. The device that measures the content of free fluoride ions is
further comprising an ion concentration electrode as a free fluoride ion electrode disposed in the solution and electrolytically connected to the reference electrode to generate a signal responsive to the concentration of desired ions in the solution. An apparatus for cleaning an aluminum surface according to claim 11. (1 m content of free fluoride), a device to add fluoride according to the deviation of the actual content of free fluoride from a desired predetermined value, and a device to measure the temperature of the solution and measure the actual content of free fluoride. A device for automatically changing and compensating for a desired predetermined value of free fluoride in accordance with deviation of the temperature of the aluminum surface from a predetermined temperature. The device for measuring the content of oxide ions comprises a container containing a salt electrolyte and a container such that it is immersed in the solution and can be brought into electrolytic contact with the solution without substantially allowing the salt electrolyte to flow out of the container. a reference electrode provided in the container for use in measuring the ion concentration in the solution; and a reference electrode electrically connected to the reference electrode and connected to the salt electrolyte in the container. and a salt bridge consisting of an alarm electrode located in the container so as to generate an alarm signal when the concentration of ions falls below a predetermined level. An apparatus for cleaning an aluminum surface according to claim 13, characterized in that the apparatus for measuring the content of α9 free fluoride ions comprises:
further comprising an ion concentration electrode as a free fluoride ion electrode disposed in the solution and electrolytically connected to the reference electrode to generate a signal responsive to the concentration of desired ions in the solution. An apparatus for cleaning an aluminum surface according to claim 14. a container containing an αe salt electrolyte; a permeable member immersed in the solution and connected to the container in a manner that allows the salt electrolyte to be brought into electrolytic contact with the solution without substantially escaping the container; a reference electrode provided in the container for use in measuring the ion concentration in the solution, and electrically connected to the reference electrode, when the level of the salt electrolyte in the container falls below a predetermined level; An apparatus for measuring the concentration of ions in a solution, characterized in that it comprises a salt bridge consisting of an alarm electrode placed in the container so as to generate an alarm signal. alpha force further comprising an ion concentration electrode, such as a free fluoride ion electrode, disposed in the solution and electrolytically connected to a reference electrode to generate a signal responsive to the concentration of a desired ion in the solution. Features a patented concentration measuring device.