EP0630426A1 - Process for mantaining a cathodic protection against corrosion and device for carrying out said process. - Google Patents

Process for mantaining a cathodic protection against corrosion and device for carrying out said process.

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Publication number
EP0630426A1
EP0630426A1 EP92919515A EP92919515A EP0630426A1 EP 0630426 A1 EP0630426 A1 EP 0630426A1 EP 92919515 A EP92919515 A EP 92919515A EP 92919515 A EP92919515 A EP 92919515A EP 0630426 A1 EP0630426 A1 EP 0630426A1
Authority
EP
European Patent Office
Prior art keywords
potential
current
value
anode
intensity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP92919515A
Other languages
German (de)
French (fr)
Other versions
EP0630426B1 (en
Inventor
Gino Cadignani
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cgr Di Cadignani Pi Gino
CGR DI CADIGNANI P I GINO
Original Assignee
Cgr Di Cadignani Pi Gino
CGR DI CADIGNANI P I GINO
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cgr Di Cadignani Pi Gino, CGR DI CADIGNANI P I GINO filed Critical Cgr Di Cadignani Pi Gino
Publication of EP0630426A1 publication Critical patent/EP0630426A1/en
Application granted granted Critical
Publication of EP0630426B1 publication Critical patent/EP0630426B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
    • C23F13/04—Controlling or regulating desired parameters

Definitions

  • the present invention relates to a process for mantaining a cathodic protection agaist corrosion.
  • the present invention relates to a galvanic process for mantaining a cathodic protection against corrosion on metallic objects, particularly on boilers, using an electrode acting as anode which is crossed by an external current and an electronic control potentiometer.
  • the invention relates to a device suitable for carrying out said process.
  • the invention may be mainly applied in the fields of thermo-mechanical and electrochemical industries.
  • Italian patent n. IT- A- 1.079.586 discloses a device for carrying out a method which provides for the use of two electrodes, respectively an anode and a reference electrode which, together with the boiler wall, are connected to the three input terminals of an electrical generator; more precisely, the anode is connected to the positive pole, the boiler wall is connected to the negative pole, and the reference electrode is connected to the connecting pole of a reverse feedback circuit
  • the system continuously gauges the potential difference appearing between the reference electrode and the boiler wall, without reducing nor interrupting the current.
  • the gauged potential difference is compared with a reference value which is seeked for by means of suitable adjustments of the current which is delivered between the anode and the boiler wall.
  • This system implies some disadvantages and drawbacks, since the measure of potential difference is carried out under current, comprises an ohmic term which is variable with water conductivity and with temperature, and which may therefore not be determined in advance.
  • the reference electrode is provided with a particular structure, according to which said electrode should be mounted close to the boiler wall.
  • EP-A-0 018 522 discloses a further cathodic protection method according to which a single electrode is used, acting as anode, which is connected to the positive pole of an electrical generator whose negative pole is connected to die boiler.
  • the current which is delivered is periodically interrupted (i.e. its value is set to zero) and, during this phase, the potential difference existing between anode and boiler wall is gauged.
  • the anode acts as reference electrode.
  • the gauged potential difference is compared with a reference value by means of a comparator, and the deviation between the Values is used for determining the intensity of the current to be delivered during the next phase.
  • Measuring the potential difference between anode and boiler wall during a zero current phase aims to avoid the cited drawbacks due to the presence of a ohmic drop in the water.
  • the present invention aims to obviate to the disadvantages and drawbacks of the background art, and to provide, thus, for a cathodic protection process which, while making use of a single electrode, allows a reproduceable current measurement to be carried out, and which therefore allows the intensity of the protection current to be reliably controlled.
  • the cathodic protection process against corrosion features a single electrode, the anode, which is connected to the positive pole of an electrical power supply, whose negative pole is connected to the object to be protected, e.g. to a boiler.
  • the intensity of the current necessary for mantaining the process is periodically raised or lowered for a predetermined lapse of time about a predetermined percentage value relative to the steady condition value, and during this phase in which a higher or a lower current is delivered the potential difference between boiler and anode is gauged.
  • This potential difference is compared, by means of a comparator, with a predetermined reference value, and the deviation is used for determining the cu ⁇ -ent intensity during the next steady condition phase.
  • measuring the potential difference during a phase in which a lower current is delivered allows the ohmic drop value in the water to be substantially decreased up to a negligible value; this value is otherwise difficult to be gauged, since it varies from place to place and it depends on temperature.
  • the intensity of the protection current is periodically reduced to a fraction relative to the steady condition value for a predetermined lapse of time, and a voltage measurement is carried out during this phase.
  • the result of the measurement is linearly corrected by extrapolating the zero current value, and then compared with a reference value in order to obtain a value for controlling the current during the next steady condition phase.
  • the intensity of the protection current is periodically doubled during a predetermined lapse of time, and the corresponding potential is gauged. Yet, an extrapolation of the resulting value is carried out, and the corrected value is compared with a predetermined reference value in order to carry out the current control during the next cycle.
  • reference sign 10 generally indicates a block diagram representing the component parts of a device suitable for carrying out a process according to the invention.
  • Device 10 generally cooperates with an object 11 to be protected against corrosion, having a metallic surface which contacts water.
  • object 11 is constituted by a boiler; however, the process according to the invention may be also applied to other metallic surfaces which are suitable for being corroded by water, such as boat parts, pipelines, gutters etc. .
  • Boiler 11 which is filled with water consituting the electrolyte solution, houses an electrode 12 belonging to device 10, and which is connected to the positive pole of a current generator 20, whose negative pole is connected to the wall of boiler 11.
  • This electrode is generally constituted by a titanium bar activated by noble metals.
  • the electrical power supply for the whole circuit is delivered by a suitable DC source (not shown in the figure), which is generally constituted by a feeder which is connected to the AC mains and which is provided with a transformer, a rectifier circuit and suitable filters.
  • current generator 20 and electrode 10 are connected to a pair of Sample and Hold cells 14, 15, which are push-pull controlled by an oscillator 19.
  • cell 15 is rendered conductive, by means of a suitable control, relative to a current intensity equal to 100% of the steady condition current, while cell 14 is rendered conductive relative to a current intensity equal to 50% of the steady condition current.
  • V ⁇ oo% Vi
  • V50% V2
  • values Vi and V2 are used for carrying out a linear correction according to the following formula:
  • Value V3 corresponds to an extrapolated value of the potential corresponding to zero current, and is compared with a potential reference value Vr which is predetermined and stored in a memory.
  • device 10 comprises a first differential amplifier 16 which carries out the substraction (V1-V2) and which, by a suitable choice of the resistance values, is set in order to obtain a total gain equal to two; in this way, the output voltage of differential amplifier 16 is equal to 2(V ⁇ -V2).
  • This potential is applied to one of the input terminals of a second differential amplifier 17, which substracts said value from the steadi condition potential Vi.
  • a potential equal to V3 may be found at the output of amplifier 17.
  • potential V3 is applied to an input terminal of a third differential amplifier 18, at the other input terminal of which being applied reference potential Vr, which is obtained from a divider module 22 by dividing the supply voltage; the output voltage of amplifier 18 is then applied to current generator 20.
  • module 20 generates a current which is proportional to the output voltage of amplifier 18.
  • the circuit is completed by an electronic switch 21 which, by means of a control signal generated by oscillator 19, and timed with the conduction period (Sample) of cell 14, halves the output current of generator 20 and sets it to a value corresponding to 50% of the steady condition value. The process described above is then periodically repeated and the current intensity is suitably controlled.
  • the potential value V2 corresponds to a 50% reduction of the current intensity. This fact does not involve a limitation of the process according to the invention, since value V2 may be choosed within wide limits, corresponding to values of current intensity comprised between 10% and 50% of the steady condition current intensity; in any case, very reliable controls of the current intensity are achieved.
  • the current is delivered to one cell with an intensity equal to 100% relative to the steady condition value, and to the other cell with an intensity equal to 200% relative to the steady condition value, for a short period; at the output terminal of amplifier 17 is then present a potential equal to
  • V Vl-(V2-Vl) and this value is compared with reference value Vr.
  • divider 22 is connected to a water temperature sensor (not shown in the figure).
  • the insertion of a water temperature sensor has the purpose of compensating the potential variation on the anode, due to a water temperature change.
  • reference potential Vr is generated by divider 22, which reduces the potential which is stabilized by a Zener diode (not shown in the figure); since Vr is fixed, it happens that, by controlling the current delivered by the circuit, the potential between anode and cathode varies in accordance with the different behaviour of the electrolyte solution interposed between anode and cathode at different operating temperatures.
  • Vr when Vr is also controlled, by providing a water temperature sensor cooperating with the divider circuit 22, this reference potential may be varied in accordance with temperature changes in the electrolyte solution.
  • the potential between anode and cathode is characterised by .a more constant behaviour; this limited possibility of ranging of the potential allows a more reliable and homogeneous protection to be achieved; the danger of corrosion due to an ove ⁇ rotection in the case where passive protection materials (enamels, paintings etc.) are used, is also greatly reduced.
  • a indicating device (not shown in the figure), which is generally constituted by a LED display, is connected to current generator 20.
  • This device has the purpose of delivering a visible indication of the operation of the protection circuit against corrosion.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Prevention Of Electric Corrosion (AREA)

Abstract

Selon le procédé de protection cathodique contre la corrosion présenté, on utilise une seule électrode (12), l'anode, qui est reliée au pôle positif d'un dispositif d'alimentation en courant électrique dont le pôle négatif est relié à l'objet à protéger, par exemple à une chaudière. Une caractéristique essentielle de l'invention est que l'intensité de courant nécessaire pour maintenir la protection est périodiquement augmentée ou abaissée pendant un temps prédéterminé et d'une valeur prédéterminée représentant un pourcentage de la valeur de régime permanent, et qu'au cours de cette phase, phase pendant laquelle un courant d'intensité plus élevée ou plus basse est fourni, la différence de potentiel entre la chaudière et l'anode est mesurée. Cette différence de potentiel est comparée, au moyen d'un comparateur, avec une valeur de référence prédéterminée, et l'écart trouvé est utilisé pour déterminer l'intensité de courant à fournir pendant la prochaine phase de régime permanent.According to the method of cathodic protection against corrosion presented, a single electrode (12), the anode, is used, which is connected to the positive pole of an electrical current supply device whose negative pole is connected to the object to be protected, for example a boiler. An essential characteristic of the invention is that the current intensity necessary to maintain the protection is periodically increased or decreased for a predetermined time and by a predetermined value representing a percentage of the steady state value, and that during this phase, during which a current of higher or lower intensity is supplied, the potential difference between the boiler and the anode is measured. This potential difference is compared, by means of a comparator, with a predetermined reference value, and the difference found is used to determine the current intensity to be supplied during the next steady state phase.

Description

"PROCESS FOR MANTAINING A CATHODIC PROTECTION AGAINST CORROSION AND DEVICE FOR CARRYING OUT SAID PROCESS."
The present invention relates to a process for mantaining a cathodic protection agaist corrosion.
More particularly, the present invention relates to a galvanic process for mantaining a cathodic protection against corrosion on metallic objects, particularly on boilers, using an electrode acting as anode which is crossed by an external current and an electronic control potentiometer.
Furthermore, the invention relates to a device suitable for carrying out said process.
The invention may be mainly applied in the fields of thermo-mechanical and electrochemical industries.
Cathodic protection processes against corrosion in boilers or water heaters are known since long time.
Italian patent n. IT- A- 1.079.586 discloses a device for carrying out a method which provides for the use of two electrodes, respectively an anode and a reference electrode which, together with the boiler wall, are connected to the three input terminals of an electrical generator; more precisely, the anode is connected to the positive pole, the boiler wall is connected to the negative pole, and the reference electrode is connected to the connecting pole of a reverse feedback circuit
The system continuously gauges the potential difference appearing between the reference electrode and the boiler wall, without reducing nor interrupting the current.
The gauged potential difference is compared with a reference value which is seeked for by means of suitable adjustments of the current which is delivered between the anode and the boiler wall. This system implies some disadvantages and drawbacks, since the measure of potential difference is carried out under current, comprises an ohmic term which is variable with water conductivity and with temperature, and which may therefore not be determined in advance. In order to overcome this problem, the reference electrode is provided with a particular structure, according to which said electrode should be mounted close to the boiler wall.
However, this causes further drawbacks for assemblying the boiler structure. EP-A-0 018 522 discloses a further cathodic protection method according to which a single electrode is used, acting as anode, which is connected to the positive pole of an electrical generator whose negative pole is connected to die boiler.
According to this method, the current which is delivered is periodically interrupted (i.e. its value is set to zero) and, during this phase, the potential difference existing between anode and boiler wall is gauged. During the zero current phase, the anode acts as reference electrode.
In a similar way as that disclosed in the italian patent cited above, the gauged potential difference is compared with a reference value by means of a comparator, and the deviation between the Values is used for determining the intensity of the current to be delivered during the next phase. Measuring the potential difference between anode and boiler wall during a zero current phase aims to avoid the cited drawbacks due to the presence of a ohmic drop in the water.
However, this method provides for disadvantages and drawbacks too; in fact, when the delivered current is interrupted, the anode potential quickly drops from its value under current towards the zero current value, which is remarkably lower than the former. This drop depends on intermediate desorbing processes which are carried out during the normal current operation, and on a superficial pH variation, the pH passing from an acid value, which is typical of the situation when current is flowing, to an alkaline value, which is typical of water. This potential drop, which has a remarkably high value and which is very fast, causes the measurement which is carried out during the zero current phase to be scarcerly reproduceable; thus, the following control of the current intensity is not fully reliable.
The present invention aims to obviate to the disadvantages and drawbacks of the background art, and to provide, thus, for a cathodic protection process which, while making use of a single electrode, allows a reproduceable current measurement to be carried out, and which therefore allows the intensity of the protection current to be reliably controlled.
This is achieved by carrying out a cathodic protection process against corrosion having the features disclosed in the main claim.
The dependent claims disclose particularly advantageous forms of embodiment of the invention.
Furthermore, claims 6 to 9 describe a device suitable for carrying out the process according to the invention. According to the invention, the cathodic protection process against corrosion features a single electrode, the anode, which is connected to the positive pole of an electrical power supply, whose negative pole is connected to the object to be protected, e.g. to a boiler.
According to an essential feature of the invention, the intensity of the current necessary for mantaining the process is periodically raised or lowered for a predetermined lapse of time about a predetermined percentage value relative to the steady condition value, and during this phase in which a higher or a lower current is delivered the potential difference between boiler and anode is gauged.
This potential difference is compared, by means of a comparator, with a predetermined reference value, and the deviation is used for determining the cuπ-ent intensity during the next steady condition phase.
In this way several advantages may be achieved relative to the known processes.
In fact, measuring the potential difference during a phase in which a lower current is delivered allows the ohmic drop value in the water to be substantially decreased up to a negligible value; this value is otherwise difficult to be gauged, since it varies from place to place and it depends on temperature.
Furthermore, the fact of simply reducing, and of not interrupting the intensity of the protection current, greatly reduces the dropping effect of the anode potential towards the zero current steady value; this fact allows a continuously reproduceable measurement to be carried out and a highly reliable controlling operation of the current intensity to be obtained.
According to another form of embodiment of the process according to the invention, the intensity of the protection current is periodically reduced to a fraction relative to the steady condition value for a predetermined lapse of time, and a voltage measurement is carried out during this phase.
By means of a suitable control electronics, the result of the measurement is linearly corrected by extrapolating the zero current value, and then compared with a reference value in order to obtain a value for controlling the current during the next steady condition phase.
According to a further form of embodiment of the process according to the invention, the intensity of the protection current is periodically doubled during a predetermined lapse of time, and the corresponding potential is gauged. Yet, an extrapolation of the resulting value is carried out, and the corrected value is compared with a predetermined reference value in order to carry out the current control during the next cycle.
Other features and advantages of the invention will become apparent by reading the folowing description of a form of embodiment of the invention, given as a non- limiting example, with the help of the figure illustrated in the attached sheet, which shows a block diagram of a device suitable for carrying out a process for mantaining a cathodic protection current against corrosion according to the present invention.
In the figure, reference sign 10 generally indicates a block diagram representing the component parts of a device suitable for carrying out a process according to the invention.
Device 10 generally cooperates with an object 11 to be protected against corrosion, having a metallic surface which contacts water.
Commonly, object 11 is constituted by a boiler; however, the process according to the invention may be also applied to other metallic surfaces which are suitable for being corroded by water, such as boat parts, pipelines, gutters etc. .
Boiler 11, which is filled with water consituting the electrolyte solution, houses an electrode 12 belonging to device 10, and which is connected to the positive pole of a current generator 20, whose negative pole is connected to the wall of boiler 11.
This electrode is generally constituted by a titanium bar activated by noble metals. The electrical power supply for the whole circuit is delivered by a suitable DC source (not shown in the figure), which is generally constituted by a feeder which is connected to the AC mains and which is provided with a transformer, a rectifier circuit and suitable filters. Furthermore, current generator 20 and electrode 10 are connected to a pair of Sample and Hold cells 14, 15, which are push-pull controlled by an oscillator 19.
According to this form of embodiment, cell 15 is rendered conductive, by means of a suitable control, relative to a current intensity equal to 100% of the steady condition current, while cell 14 is rendered conductive relative to a current intensity equal to 50% of the steady condition current.
Thus, in cell 15 a value Vιoo% (Vi) is stored, which represents the potential value which is present on anode 12 when the current intensity is equal to the steady condition current Iι∞% (Ii), while in cell 14 a value V50% (V2) is stored which represents the potential value which is present on anode 12 when the current intensity is equal to 50% of the steady condition current I50%(Ϊ2).
According to a feature of the invention, values Vi and V2 are used for carrying out a linear correction according to the following formula: Value V3 corresponds to an extrapolated value of the potential corresponding to zero current, and is compared with a potential reference value Vr which is predetermined and stored in a memory.
In order to practically implement said formula, device 10 comprises a first differential amplifier 16 which carries out the substraction (V1-V2) and which, by a suitable choice of the resistance values, is set in order to obtain a total gain equal to two; in this way, the output voltage of differential amplifier 16 is equal to 2(Vι-V2).
This potential is applied to one of the input terminals of a second differential amplifier 17, which substracts said value from the steadi condition potential Vi. Thus, a potential equal to V3 may be found at the output of amplifier 17. Thereafter, potential V3 is applied to an input terminal of a third differential amplifier 18, at the other input terminal of which being applied reference potential Vr, which is obtained from a divider module 22 by dividing the supply voltage; the output voltage of amplifier 18 is then applied to current generator 20.
As a consequence thereof, module 20 generates a current which is proportional to the output voltage of amplifier 18.
The circuit is completed by an electronic switch 21 which, by means of a control signal generated by oscillator 19, and timed with the conduction period (Sample) of cell 14, halves the output current of generator 20 and sets it to a value corresponding to 50% of the steady condition value. The process described above is then periodically repeated and the current intensity is suitably controlled.
According to this form of embodiment, the potential value V2 corresponds to a 50% reduction of the current intensity. This fact does not involve a limitation of the process according to the invention, since value V2 may be choosed within wide limits, corresponding to values of current intensity comprised between 10% and 50% of the steady condition current intensity; in any case, very reliable controls of the current intensity are achieved.
According to a second form of embodiment of the invention, it is possible to invert the inputs of differential amplifier 16, and to set it in order to obtain a gain equal to one, as well as to connect electronic switch 21 in such a way that the inversion causes the current which is generated at the output to be doubled.
In this case, the current is delivered to one cell with an intensity equal to 100% relative to the steady condition value, and to the other cell with an intensity equal to 200% relative to the steady condition value, for a short period; at the output terminal of amplifier 17 is then present a potential equal to
V =Vl-(V2-Vl) and this value is compared with reference value Vr.
According to a third form of embodiment of the invention, divider 22 is connected to a water temperature sensor (not shown in the figure).
The insertion of a water temperature sensor has the purpose of compensating the potential variation on the anode, due to a water temperature change.
In the applications which are not provided with this sensor, reference potential Vr is generated by divider 22, which reduces the potential which is stabilized by a Zener diode (not shown in the figure); since Vr is fixed, it happens that, by controlling the current delivered by the circuit, the potential between anode and cathode varies in accordance with the different behaviour of the electrolyte solution interposed between anode and cathode at different operating temperatures.
However, when Vr is also controlled, by providing a water temperature sensor cooperating with the divider circuit 22, this reference potential may be varied in accordance with temperature changes in the electrolyte solution.
Therefore, by suitably rating the sensor in order to obtain a variation of reference potential Vr, the potential between anode and cathode is characterised by .a more constant behaviour; this limited possibility of ranging of the potential allows a more reliable and homogeneous protection to be achieved; the danger of corrosion due to an oveφrotection in the case where passive protection materials (enamels, paintings etc.) are used, is also greatly reduced.
According to a fourth form of embodiment of the invention, a indicating device (not shown in the figure), which is generally constituted by a LED display, is connected to current generator 20.
This device has the purpose of delivering a visible indication of the operation of the protection circuit against corrosion.

Claims

CLAIMS 1. Process for mantaining a cathodic protection agaist corrosion, in which an electrode (12) acting as anode in which flows an external current is immerged in an electrolyte solution contacting a metallic object (11) to be protected, acting as cathode, said process using a module (22) at the terminals of which a reference potential (Vr) is present, and an electronic circuit suitable for comparing data relative to the potential difference which is present between anode and cathode with said reference potential (Vr), characterised in that it comprises: a phase, which is periodically repeated in the time, in which the steady condition of the intensity of the protecion current (Iιoo ) is raised or lowered to a predetermined value which is never equal to zero, said value being either comprised between 10% and
50% relative to the value of the steady condition current value, or equal to 200% relative to the steady condition current value; a phase in which the potential difference (V2) which is present between anode (12) and cathode is gauged during this condition in which the current intensity is varied relative to the steady condition intensity, and a phase in which said potential difference and said reference potential (Vr) are compared to each other, the difference of values obtained in this way being used as control quantity for controlling the intensity of the protection current.
2. Process according to claim 1, characterised in that the potential values which respectively correspond to a steady condition current intensity (V and to a reduced current intensity (V2) are processed by said electronic circuit by operating a linear correction extrapolation of the potential value (V3) corresponding to a current equal to zero in the anode (12), said potential (V3) being then compared with the reference potential (Vr).
3. Process according to claim 2, characterised in that the potential value (V3) corresponding to a current intensity equal to zero in the anode (12) which is extrapolated by said electronic circuit is obtained by implementation of the following formula:
V3=Vι-2(Vι-V2) in which Vi represents the potential corresponding to the steady condition current intensity and V2 represents the potential corresponding to the reduced current intensity.
4. Process according to claim 1, characterised in that the potential values which respectively correspond to a steady condition current intensity (Vi) and to a reduced current intensity (V2) are processed by said electronic circuit by operating a linear correction extrapolation of the potential value (V- , this potential (V-+) being then compared with the reference potential (Vr).
5. Process according to claim 4, characterised in that said linearly corrected potential value (V-4) is obtained by the implementation of the following formula: in which Vi represents the potential corresponding to the steady condition current intensity and V2 represents the potential corresponding to the raised current intensity.
6. Device (10) for carrying out a process according to anyone of the preceding claims, comprising an electrode (12) acting as anode immerged in an electrolyte solution contacting an object (11) to be protected against corrosion which acts as cathode, characterised in that it further comprises a pair of Sample and Hold cells (14, 15) for recording and storing data relative to the potential difference existing between anode and cathode under different conditions of intensity of the current which flows through the anode, a reference potential (Vr) source (22), first means (16, 17) for processing said data, second means (18) suitable for comparing the processed data with said reference potential (Vr), a current generator (20) controlled by said second means (18), and third, timing, means (19, 21).
7. Device (10) according to claim 6, characterised in that said first means (16, 17) comprise a pair of differential amplifiers which are serially connected with respect to each other and which are suitably connected to said cells ( 14, 15).
8. Device (10) according to anyone of claims 6 and 7, characterised in that said second means comprise a differential amplifier (18), an input terminal of which is connected to the output terminal of said first means (16, 17), the other input terminal of which is connected to said reference potential (Vr) source, the output terminal of said amplifier (18) being connected to said current generator (20).
9. Device according to anyone of claims 6 to 8, characterised in that said third, timing, means (19, 21) comprise an electronic switch (21) and an oscillator (19).
10. Device (10) according to anyone of claims 6 to 9, characterised in that it is further provided with an electrolyte solution temperature sensor cooperating with said reference potential (Vr) source (22) in order to control the value of said reference potential (Vr) in accordance with temperature changes intervening in the electrolyte solution during operation.
11. Device (10) according to anyone of claims 6 to 10, characterised in that it is further provided with an indicating device for displaying the state of the protection process.
EP92919515A 1991-08-14 1992-08-12 Process for mantaining a cathodic protection against corrosion and device for carrying out said process Expired - Lifetime EP0630426B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
ITVR91007 1991-08-14
ITVR910070A IT1253258B (en) 1991-08-14 1991-08-14 PROCESS OF MAINTENANCE OF A CATHODIC PROTECTION AGAINST CORROSION AND DEVICE FOR THE IMPLEMENTATION OF SUCH PROCESS
PCT/IT1992/000105 WO1993004218A1 (en) 1991-08-14 1992-08-12 Process for mantaining a cathodic protection against corrosion and device for carrying out said process

Publications (2)

Publication Number Publication Date
EP0630426A1 true EP0630426A1 (en) 1994-12-28
EP0630426B1 EP0630426B1 (en) 1995-11-15

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EP92919515A Expired - Lifetime EP0630426B1 (en) 1991-08-14 1992-08-12 Process for mantaining a cathodic protection against corrosion and device for carrying out said process

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Country Link
EP (1) EP0630426B1 (en)
DE (1) DE69206157T2 (en)
DK (1) DK0630426T3 (en)
ES (1) ES2082500T3 (en)
GR (1) GR3018985T3 (en)
IT (1) IT1253258B (en)
WO (1) WO1993004218A1 (en)

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DE102008013943B4 (en) 2008-03-12 2018-09-13 Stiebel Eltron Gmbh & Co. Kg Hot water storage and test device for testing an anode in a hot water tank
WO2009116901A1 (en) * 2008-03-19 2009-09-24 Ab Volvo Penta Control of a corrosion protection system
ES2409938B1 (en) * 2011-12-28 2014-08-22 Fagor, S. Coop. Method and device for cathodic corrosion protection
CN104818487B (en) * 2015-04-22 2017-11-14 中交四航工程研究院有限公司 Interruptedly supplying power Switching Power Supply Combined constant potentiometer

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3477931A (en) * 1965-03-30 1969-11-11 Mitsubishi Heavy Ind Ltd Method and apparatus for automatic electric corrosion-proofing
AT344816B (en) 1976-02-10 1978-08-10 Westfael Elekt Werke DEVICE FOR CATHODIC CORROSION PROTECTION WITH EXTERNAL CURRENT MANODE
DE2916934C2 (en) 1979-04-26 1981-05-07 Vereinigte Elektrizitätswerke Westfalen AG, 4600 Dortmund Method and device for maintaining cathodic protection against corrosion
US4823072A (en) 1986-09-04 1989-04-18 Walcott Kenneth J Measurement of the polarized potential of buried pipeline having impressed current cathodic protection
DE3707791C1 (en) * 1987-03-11 1988-03-31 Ver Elek Zitaetswerke Westfale Method and device for maintaining cathodic corrosion protection for metallic surfaces with external current

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9304218A1 *

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ES2082500T3 (en) 1996-03-16
ITVR910070A1 (en) 1993-02-14
DE69206157T2 (en) 1996-07-18
DK0630426T3 (en) 1996-05-06
DE69206157D1 (en) 1995-12-21
ITVR910070A0 (en) 1991-08-14
EP0630426B1 (en) 1995-11-15
IT1253258B (en) 1995-07-14
GR3018985T3 (en) 1996-05-31
WO1993004218A1 (en) 1993-03-04

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