DE1621535A1 - Device and method for monitoring acidic solutions - Google Patents

Description

Device and method for monitoring acidic solutions W rrr rr. @,.,. . @ rm The present invention relates to methods and devices for monitoring acidic solutions which erzugsverfahren as washing solutions for metal surfaces after their treatment in%, in particular after the Hk Contro l with a usual PhosphatUberzugelöaung be used. The usual coating with phosphate or phosphate is carried out in a treatment sequence which consists of. Cleaning, washing with water, coating with phosphate, washing with water and washing with chemical solutions Ad.h. acidic solutions). The final washing of the phosphated surfaces with acidic solutions is carried out with a dilute solution which contains hexavalent chromium ions and / or phosphoric acid and gives the surface a quick, optimal resistance to corrosion and color absorption. A lrtthea American patent, US Patent 2,403,126, who taught the use of a säurrrhaltigen Waachlösung which comprises 30 to 450 g Ghromsäur (Cr03) contained in 380 liters of solution and was maintained at a pH from 2.0 to 4.6 . It was later found that the corrosion resistance can be increased if this washing solution is still further . contains dissolved ions, according to the teaching of German Patent 896 892, for example, ions.

However, these very dilute acid solutions are still so acidic that they dissolve parts of the phosphate coating and dissolved ionic constituents. accumulate in the solution, although this can be reduced by the presence of sufficient kaiionischen ingredients for preventing the presence of free acid. Thus, for example, US Patent 2,634,225 the use of Aromoniumionen and the use proposed by the French Patent 1,141,925 of polyvalent metal ions such as Ca, .cd, Al and / or Zn in the solution.

More recently O was 63,877 describes the use of mixtures of chromium compounds with both hexavalent chromium and reduced chromium forms in the wash solution to increase the Korrosionabeständigkeit in US Pat. 3

However Hei current use of such wash solutions increases its salt content, partially entrained salt impurities and partly by-evaporation so that often a point is reached at which the Norroeionsbeständigkeit reduced rather the examination by Salzepritz- and humidity tests as will be improved. Changes experienced by this acid-containing washing solutions, in use, are firstly in the depletion of active ingredients such as chromic acid and phosphoric acid and secondly in the enrichment with unierwünschten ingredients such as tonic impurities. The first of these changes takes place with decreasing frequency and significance through the entrainment of solution with the workpiece (especially in not emptied depressions or cavities, the overflow of solution, through corresponding entrainments from the previous water washing stages or other introduction of water and the chemical action of the solution on the coating of the workpiece.

The second change is also with decreasing frequency and significance, by the entrainment of the preceding Lösung.aus Behandlungsstufen- (for example, the Phosphatüberzugslüsung itself, although a Wasserwasehatute in between), in particular in the treatment of Werkstffaken with cavities, the chemical action of the solution to the about coated metal and partially evapo- the wash solution, in particular tei use of heated washing baths (to assist the drying of the treated: caused.

Various agents are used alone or in combination to reduce the changes described above. Changes in the level of the solution herds offset by Wasserzuftyhrventil which is actuated by a float or other level changes responsive device, though diluted by such addition of water, the content of the solution of active substances. The gewtfnsahte concentration of active substances is generally prepared by the addition of concentrated solutions of the same by hand or by running pumping from a container again and checked by random chemical analysis.

For the satisfactory elimination of an increased ion concentration, the solutions are used (sometimes only in part) discarded h externa fig completely and replaced by fresh solutions; This results, however, at. Processes with high production rates (e.g. "strip-line process") represent a significant production bottleneck: It is very difficult to determine the "degree of contamination" of the solution and thus to use a better controlled process for removing the contaminants, since many contaminants have an unfavorable influence on the coated metal surface, in particular its corrosion and blister resistance and its ability to be bonded to organic films . It has been found, however, that the strength of the ionic contamination (which, along with suspended solids and organic foams, is the most serious contaminant ) affects the electrical conductivity of the solution. For example, based on measurements of the electrical conductivity, fresh water can be introduced into the solution and a corresponding amount of the solution can be drained off. However, this monitoring procedure alone is completely unsuitable, since it does not provide any information about the quantities of active substances present.

For a suitable control of the addition of active substances , at least one of these substances ( e.g. chromic acid) must be monitored . This can be one for the light absorption in certain Spektre- -rich sensitive electro-optia®he device take place, but such devices are expensive and with considerable complications of Anlagebwie example, the solution to the optical absorption cells (Uhrenden circuit lines and FlUssigkeitafilter for .the light diffusing solids ], respectively. However, although important monitoring the recent acidic wash solution does not justify the use of such expensive and complicated equipment. therefore, the present invention has the object to create in production and operation relatively simple and inexpensive methods and devices with which in a . acid-containing washing solution optimum conditions can been substantially maintained automatically proportionate. Thus, an apparatus for monitoring the composition of the invention on the one hand an acidic Wasohbädes of the be Treatment of metal surfaces used type proposed, soft an electrically operated chemical supply device for introducing concentrated chemical refill solution from a supply source into the bath, an electrically operated Wasserzuftihrvorriohtung for introducing water from another supply source into the bath and three signals each for the power supply to the two supply devices Switches, of which the first is a switch that is periodically actuated by a timer , the second a switch that responds to the conductivity, when the electrical conductivity of the bath rises above a certain value , and the third - a switch that responds to the level of fluidity, by decreasing is the liquid level in the bath falls below a certain value-actuated switch, comprising.

With such a device , active chemicals and water are accordingly added separately, but more or less simultaneously, at specific time intervals, which are normally sufficient to limit the concentration of active chemicals within suitable limits and to keep the content of ionic detergents below a permissible maximum value and at the same DAS occurrence of supernatant foams and organic impurities by Uberlließen the solution from the Bäd to maintain very low. Since the concentration of active chemicals is not overly critical upper, slight variations thereof are permissible so that an addition at intervals of small fractions of an hour has been found to be adequate under normal conditions. If any occurrences during the process lead to a temporarily faster introduction of contaminants into the bath or if the volume never drops due to evaporation or other causes, the second or third switch is actuated regardless of the timed addition of the refill materials to get the optimal conditions in the bathroom right to call.

Preferably, the system includes stopping devices between the switches and the feed devices, which a signal from one of the switches in a. sustained signal of a certain duration transformed, creating a Obersä @ 8 *. is traveling to 1Nachfiilimaterialien and 8adbedingungen during most not to have come to the allowable optimum conditions. Such stop means expediently consist of an electric motor for rotating a wool with three cams, one of which maintains the power supply to the motor during a ° revolution of the shaft and the other two power supply to the Zuführvorriehtungen, preferably (but adjustable) in beatimte fractions of 9ignsldaner, ie a turn of a while, steer. Because if a bath of a rotation of the full one of the three switches still gives a signal, the shaft will of course start a new rotation.

Expediently, the ChemikalienzufUhrvorriohtung is arranged so they daae upon actuation of the first switch longer under power held as the WasserzufUhrvorrichtals e $ upon actuation of the two other switches is the case. In this way upon actuation of the Zeitauslöaeraohal.ters introduced a stronger solution than during the remaining time ,; this is useful. as this one by normal single country Ausschleppen'-vex, # urcaohter .. concentration drop again. is filled up and the addition of Mrkeren would lead solution at the rise of the reading Leitfehigkeit tTAER the allowable value to the distortion unerwttrmohten Leitfähigkeittsmessungen. Such appropriate means may consist in pressing the chemical feed device through a first of the signal-on a switch responsive fourth cams on the Vel_le. Thus, the first switch may be set to d-ate it a Vielkamtaktrelais with a first kotakt, softer the engine was connected to the current source "a second contact, which can connect the Chemikalienzutührvorriohtung to the power source together with the fourth cam, and a third contact which, together with a fifth cam on the shaft , can keep the relay in the energized state during one revolution of the shaft . Yorzugßw- "'". The MfUhrvorrlohtungen exist in each case also a pump driven by an electric motor or an electrically controlled valve. The second switch can have a conductance measuring cell and one of these ..; operated shift relay, and preferably also a device for injecting the parts of the cell measured words. to one that is sufficient to actuate the switching relay Value ent = w: that. The third switch is expediently through a Sohwi sea device operated in the bathroom . On the other hand, a process for the tiberwaahung Zuoameneetsung is proposed an acidified washing bathing of the kind used for the treatment of Metallobertläohen with the invention, in one welöhem FTIR from a supply source is a tonzentrierte Haohfüllösung the chemicals in the bath and separated therefrom ,. However, substantially simultaneously added from another source of supply of water, wherein the additive periodically at regular time intervals and unabhäagig of this periodic addition to a the increase in the electrical conductivity of the Baden tlber a certain value erzeigendes signal, or Saut a decay of the Radniveaus under a certain. Signal indicating the level takes place. . Preferably, the last periodic additions to the bath or on one of the signals towards a ertölgenden additions beetimte time reached 'even though the latter additions can be as long pause "stops until the entspreohendQ.Signal. It is also preferably set from the above. 0ründen at the periodic Addition of a higher concentration of active chemicals introduced into the bath than with the additions made in response to one of the signals.

The invention is explained in more detail below with reference to the accompanying drawings; it, in which: Figure 1 - a block diagram showing the basic elements einer.erfindungsgemäßen device z to checking and replenishing the solution in one. Wohbad sv, igur 2 - the elements of the device according to Figure 1 in detail in a schematic representation; FIG. 3 - a somewhat more complicated device than that shown in FIG. 2 in a schematic representation; FIG. 4 - a further modification of the devices shown in FIGS. 2 and 3 in a schematic representation. The device shown in FIG. 1 comprises a tank 1 with an acidic washing solution 2, into which a conductivity sensor 3 responsive to changes in electrical conductivity and a level sensor 4 responsive to changes in the liquid level are immersed. The sensors 3 and 4 and an appealing to the timing time trigger 5 respectively actuate an associated signal transmitter 6, 7 or B. This signal generator 6 to 8 may be any suitable devices such as switches consist barren relay, preferably signal generators are used which when actuated generate the rest of the system without further amplification operating an electrical signal. This signal can consist only of a simple electrical impulse or possibly also of a sustained signal, or the signal transmitter can also be designed in such a way that it normally sends out a sustained signal which is interrupted when it is actuated.

The signals from the three signal generators 6 to 8 become. a control unit 9, where they are evaluated and used to generate output signals which control the supply of the refill materials into the container 1. The unit 9 can consist of a simple wire circuit which forwards the signals from the signal transmitters directly to the feed mechanism; However, in the preferred embodiments shown in FIGS. 2 to 4 , the unit 9 contains elements which the. Convert input signals into sustained output signals of a certain duration. The output signals from the unit 9 are fed to two feed control devices 10 and 11, which are each connected to a reservoir 12 or 13 containing the filling chemicals or water. The two actuating devices 10 and 11, which effect the supply of the refill materials to the container 1, can for example consist of electrically driven pumps or valves.

In the arrangements shown in detail in FIGS. 2 to 4 according to the block diagram in FIG. 1, the same reference numbers are used, as far as possible, for the same elements.

In the device shown in FIG. 2, a conductivity sensor 3 'in the form of a conductivity measuring cell and a level sensor 4 in the form of a float are immersed in the washing solution 2 located in the container 1. The conductivity measuring cell 3 controls a relay 14 (which is one of the three switching mechanisms of the circuit) and this relay 14 closes whenever the conductance of the solution 2 rises above a certain value, for example by means of a balanced pointer on a scale. 15 is displayed . The second switching mechanism contains a switch 16 which is actuated by a lever 17 connected to the float 4 via a rod 18 whenever the level of the solution 2 fills below a certain height. The level "-when the switch 16 is actuated , - k @ -: h Adjustment of the length of the rod 18 changed will. "le the second switching mechanism can, however For example , a pressure-sensitive switch actuated by changing the pressure level of solution 2 can also be used. Her third switching mechanism consists of a time release 5 (which includes the signal transmitter 8 in FIG. 1 ), which repeatedly opens and closes a switch at certain time intervals. The relay 14 and de2 @ time release 5 are each connected to the two poles 1g and 20 of an electrical O #; romquelie, and whenever an aor c12.ohalter 14, 16. or 5 is actuated , the one pole 2p ' 1 is connected to a common point X in the electrical circuit shown in FIG. Rin motor 21 is connected with one input to the point X and with its other ring to the pole 19r, so that each time one of the switching mechanisms is actuated, the motor 21 drives a pump 22, which with a relatively concentrated solution of the Chemicals for the storage container (not shown) containing washing solution 2 is connected and this concentrated solution is then pumped into the container 1. Simultaneously with the power supply to the motor 21, a relay or other device 23 is energized in the same way , which opens a valve 24 and thereby allowing water to flow into the container 1 from another reservoir (not shown).

It is of course also possible, if necessary , to understand a relay / valve arrangement for the chemical solution and / or a motor / pump arrangement for the water supply. The pump and valve must of course be arranged so that they supply the chemical solution and water at a precisely regulated rate so that any necessary metering pumps and / or flow regulators must be used.

The timer g works automatically in the gecshten @@ lt @ b @ t @@ p @@, @ i @ e las @@@ c @ @ = ° '@, terialnachfü @ ..- lumit ®occCig @ it to ensure da® b3: 1 j "-a-op mode of operation largely the same Together with the solution 2 in the container 1 is maintained . If, in spite of this normal refilling, the content of the Löd * 2 of fonisehen impurities is too high , the conductivity measuring cell 4 activates the relay 14 and this the lpe 22 and the valve. 24 to add concentrated chemical solution and water in addition to the amounts normally given. This additional Naohttlllen normally continues as long, until the solution flows over 2 irr container 1 to a certain extent and carries away a portion of the available ionic impurities and above floating foams and organic impurities. If the level of the solution 2 falls below the usual level , a subsequent precipitation of the wet and concentrated chemical solution is of course also brought about by actuating the switch 16. The simultaneous addition of water und'konzentrierten chemicals Uaung 2 by the actuation of one of the three switches 16 1k and 5, thus preventing not only an increase in the concentration of undesirable impurities but also the! Decrease in the concentration of erwUnsahten chemicals.

The device shown in FIG. 3 contains .the same elements never the. Cam 3.n Figure 2 and also shown not yet a periodically operating time tripping device 25 with a synchronous motor 26 having a shaft 27 (shown by dashed line) drives, on which drei.untersahiedliche 28, 29 and are thirtieth The cams 28 to 30 can each actuate the plugs of three holders 31 to 33. The motor 26 is connected between the power source 19 of the gene insamen point X and the pole, so that hot pressing to the cam 28 to rotate one of the switches 14, IG or the motor 5 is started 26 to 30. All three switches 31 to 33 are closed immediately. The switch 31 remains closed for a full turn and keeps the motor 26 in motion, since it is connected on one side to point X and on the other side to the pole 19 of the power source . The switch 32 remains closed for only half a turn, ie. as long as the part of the #oekene 29 3.n with the larger radius makes contact with the plug of the switch 32, and during this time it establishes the connection to the relay 2, 3 in order to feed water from a storage container through the valve 24 To let the container 1 flow, the Sehalter 33 remains closed somewhat longer under the action of the Nookene 30 and establishes the connection to the motor 21 so that the pump 22 pumps nutrient chemicals into the container 1. After a complete revolution of the shaft of the 2'j StOpeedes switch 31 falls into the notch in the cam 28, so that the motor 26 is stopped, if necessary, to represent time is not just one of the switches A, 16 or .5 in operation, the duration one revolution of the shaft 27 can be made adjustable by installing a variable transmission in the drive from the motor 26 to the shaft 27 and the ratio of large to small radius in deal cams 29 and 30 is also adjustable, so that during one revolution of the timer device 25 The quantities of chemicals and water reaching the container 1 can be varied. The arrangement shown in FIG. 3 is advantageous when a constant, but not easy to distribute, ratio of the feeds is required .

The IM ijur 4 shown device comprises essentially the glex..e elements as that shown in Figure 3 and a few other. It firstly includes a non-periodically operating Zeltauslösevorriohtung 34, which corresponds to the device 25 in Figure 3, but still contains two or more cams 35 and 36; which press the pegs of two sofa ages 3'7 and 3 $. Furthermore , the time trigger 5 is with a 39 (which when the switch of the Zeitsaun -., 4ers 5 is excited) with three normally open contacts 40 '' 41 and 42 and a further line system, the switches 3'1 and 38, the relay 39 and 61e contacts 40, 41 and 42 in the electrical circuit. The switches 31 to 33 with the associated cams 26 to 30 and 26 operate in the same hdcor Wise SSN as the embodiment shown in Figure 3, device;.?, the switch 37 may also operate the motor 21, but thin as the switch 33. the switch 3 but is not connected to the engine 21 side when the Relaiakontakt 42 the time the trigger switch 5 is closed not by the action.

The Zeitausiö®esohalter 5 sets a. Connection between the poles 19 and 20 here, so DALI the relay 39, the contacts 40 to 42 closes. -Aut ° -these wines is the motor 26 via the point X ud the contact 40 with the pole 20 is connected, so that °. - all cams 28, 299, 30y 35 and 36 go and among other things the switch 38 is closed by the cam 36 and the relay 39 by the current from the pole. "1g is kept closed by the relay 39, the switch 38 and the contact 41 to the pole 20 until the plug of the switch 38 falls into the notch Aes cam 36 after one revolution of the shaft 2T. During this time, the pumping of Nachtfllmateriala.en through the PE 22 into the container 1 by the cam 35 and the switch 37 connected to the contact 42 with the power source controlled. By o31 -o * tti -. The switches 5, 14 or 16 has been thus chemicals and water in the Beh_ter '1 naohgelt but ° d 5, a larger amount NSCH £ üilehmikalien Ih the container 1 introduced by operation of the Zeiesehalters as upon actuation of the switches 14 and 16. the profiles of the Nookoa 28.9 29, 30, 35 and 36 may be changed as desired to the optimal fl NsohfUllverhältnisse be able to set various conditions r -. the addition of larger quantities of the container 1 under NachfUlllohemikalen Control of the timer $ .5 than when the switch 14 or 16 is actuated has the following purpose: In some metal treatment plants , a relatively large amount of water from a previous process stage is dragged into the container with the container with the container and a correspondingly large amount of the treatment solution is drained out with it, ao that the active cold content of the washing solution is reduced significantly more than is normally the case.

The addition of further refill solution is not always a satisfactory remedy, since it leads to undisguised distortions of the conductance stresses if it occurs in response to a signal that indicates too high an electrical conductivity. These Difficult * ince but can be i8berwunden when the concentration of active Chmikalien in Nachfilllstrcm when actuated by a Signa? the switch # 1 or @ 16 corresponds approximately to the gewttnsahten Badiconzentration and b ei operation by 'a signal of the time triggers --5 hUher is. When using the preferred devices according to FIGS. 1 to 4, the post-filling materials are added in a fraction of a period of time of about 15 minutes, since it is difficult to change the overall chemical composition in the container 1 . Who but at the end of this short refills is one of the $ etätigungssahaiter still in operation, the Naohftillung continues until none of the switches is longer in operation.

Claims (1)

ete @ @ a @; epr tt a 1n e 1. Device for determining the composition of an acidic wash bath of the type used for the treatment of metal surfaces, characterized by an electrically operated chemical feed device. (1O br # - 21/22) for introducing concentrated chemical solution from a storage source (12) into the bath (2), an electrically operated water supply device (11 or: 23/24) for introducing water from a storage tank (13) into the Bad (2) and three switches (6, 7, 8 or 5, 14, 16) giving signals for the power supply to the two ZufUhrvorriohtungen (10 or ". 21/22, 11 or 23/2 #) The first (8 or 5) is a switch that is periodically operated by a timer (5) , the second (6 or 14) is a switch that responds to the conductivity and is operated by increasing the electrical conductivity of the bath (2) above a certain value Switch and the third switch (7 or 16) is a switch that responds to the fluid level and is operated by the liquid ketan level of Hades (2) falling below a certain level. Re Vorriahtuah Anspxuab 1! »16) _ and the Zuftvorribtuen (21 / 2e 23 / '4) an AWaltvorri oht (25r 34), which contains a signal: from: one of the switches in a sustained signal of permanent umwdel t R 3. Device according to claim 2, characterized in that the stopping device (23 or 34) is an electric motor ( 2i), which rotates a shaft (2?) With three cams (28, 29, 34) , one of which receives the power supply to the motor (2ö) during one revolution of the shaft (27) and the other to the power supply Control the feed devices (21/22, 23/24). 4. Apparatus according to claim 2 or 3, characterized in that the stopping device (25 or 34) the Zuf`txhrvorriohtungen (21/22, 23/24) can keep a certain fraction of the duration of the sustained signal under power for a long time. 5. Device according to claims 3 and 4, characterized in that the cams (29, 30) maintaining the power supply to the feed devices (21 / 229-23 / 24) for changing the amount of material carried out during one revolution of the shaft (27) are adjustable. 6. Yorsiohtung - tach --- Ar @ saying ;: or 5,.: Characterized in that the $: - stopping device (25 or ) _bet- actuation of the first ßohalter :(, 5) .die..ChemkallenzuftDhrvorrichtung, (21/22) -: longer under Strsa: holds. ala the water supply device (23 / 2e as: when actuated, one of the two other switches (14, 16). a device went to -the. claims 3 and 6 ,. thereby -marked # -does the Chemikallenzuführvorrichtung (21/22) - to a 8lgnel the first switch (5) back through a fourth Noekea- (35) -on the shaft (27) actuated wird.-ß. nach.Ampruch@7 device, characterized in that - the first switch (5) a multi-contact relay (39) -with a first contact (4Q), which can connect the motor (26) to a power source- (19/20) , a second contact (42), which together with the fourth cam (35) can connect the chemical feed device (21/22) to the power source (i9 / 24), and a third contact (41) which, together with a fit cam (36) on the shaft (27), the relay (39 ) can keep in operation during one revolution of the shaft (27); actuated. g. Device according to Claims 1 to $, characterized in that the two feed devices n (21/22, 23/24) consist of a pump operated by an electric motor or an electrically controlled valve. 10. Device according to Anaprtichen 1 to 9, characterized in that the third switch (1ö) actuated by a float device (4) in the bathroom (2) . . 11. Device according to claims 1 to 10, - characterized in that the second switch (14) comprises a Leituertmeßzelle (3) and a switching relay (14) actuated by this. 12. The device according to claim 11, characterized in that it has means for adjusting the Me®wert of the line (3) . contains a value sufficient to operate the switching relay (i4). 13. A method for monitoring of the composition of an acid-containing washing bathing FILR the treatment of metal surfaces used Type "characterized, one däß from a supply source a concentrated NaahfUllösungfür the chemicals in the bath and separately, but substantially simultaneously, water is added from another source of supply, wherein Where added periodically at regular time intervals and independently of this periodic addition to a the increase in the electrical conductivity of the Hades above a certain value indicative signal, or to a decay of the Badnivesus below a certain level indicating signal. 14. the method according to claim 13 characterized DAB take, the periodic additions to the bath or on one of the signals towards additions taking place for a certain time. 15. the method of claim 13, and a, characterized in that Daiss mm in periodic additions of a higher concentration of active chemicals introducing into the bath than in the one of the signals taking place towards additions.