JPH0931675A - Electric corrosion protection method using multiple booster type anodic protection and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable complete corrosion protection of an object to be protected in a high resistance environment by inputting generated voltage into a DC-DC converter and boosting or decreasing the input voltage. SOLUTION: In this method, an electric corrosion protection equipment cell 1 comprising an auxiliary cathode 2 (or auxiliary sacrificial anode 2') and a metallic equipment 3 under electric corrosion protection is placed in an environment 4 and the equipment 3 is subjected to electric corrosion protection with a sacrificial anode 5. At this time, when the environmental resistance between the sacrificial anode 5 and an object to be protected 41 is such a high value that the corrosion protective current is insufficient, the voltage generated between the auxiliary cathode 2 (or auxiliary sacrificial anode 2') and the metallic equipment 3 under electric corrosion protection in the vicinity of the object 41 is inputted into a switching type DC-DC converter 6. Then, an optional output voltage value obtained by increasing or decreasing the input voltage with the converter 6 is applied between the object to be protected 41 that is connected or unconnected to the metallic equipment 3, and the sacrificial anode 5 and the effective potential difference of the sacrificial anode 5 is increased and accordingly, the corrosion protective current is enhanced to completely protect the object 41 from corrosion. Thus, the device for this method is also utilized as a power source for an external power source type electric corrosion protection method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an auxiliary cathode or auxiliary galvanic anode to a metal facility which is currently cathodic protected, and increases or decreases the voltage generated between the facility and the attached auxiliary electrode. The present invention relates to a cathodic protection method using a galvanic anode of a composite pressure-increasing system in which the obtained voltage of any value is used as a cathodic protection power source for an adjacent structure, and a device therefor.

[0002]

2. Description of the Related Art The cathodic protection method is a chemical device in contact with metal structures or buried pipes installed in seawater, river water, underground, etc., or reinforcing bars in concrete structures, industrial water and organic or inorganic liquids. It is used as a method to prevent the corrosion of buildings, etc. and has a great effect on the corrosion protection in infrastructure such as ports and bridges and in industries in each field.

As one of the application forms of the cathodic protection method, a potential difference between a galvanic anode having a base potential such as magnesium, aluminum, zinc, or an alloy of each of these, and a target corrosion-preventing substance having a noble potential higher than that ( An anticorrosion current is supplied from the galvanic anode to the anticorrosion body by using the effective potential difference) as a driving force. This galvanic anode method is now widely used in place of the external power source method because of its ease of construction work and maintenance, and its low risk of failure, and is especially applicable to facilities in seawater. It can be said to be 100%. Since an insoluble anode is used in the external power supply method, a strong oxidizing gas such as chlorine or oxygen is often generated and the cable is often damaged.
Furthermore, there is a problem of troublesome maintenance and reliability such as corrosion protection due to unexpected power failure, but it is applied to corrosion protection of buried pipes that require high voltage.

However, since the unique anode potential is determined by the type of galvanic anode, there is a limit to the anticorrosion ability based on that. Typical values of the anode potential of galvanic anodes are -1.0V, -1.1V and -1.5V for zinc-based, aluminum-based and magnesium-based anodes (potentials are based on the saturated sweet potato electrode, respectively). On the other hand, since the anticorrosion potential when the object to be protected is a steel structure is -0.8 V, the effective potential difference which is the driving force of the anticorrosion current for the galvanic anode is 0.2 V, respectively. , 0.3V and 0.7
V. When the environmental resistance is as low as seawater, any anode can be used because a sufficient anticorrosion current can flow with these effective potential differences. However, for corrosion protection of locks, water supply lines, buried pipes, etc. when the resistivity of the environment is several hundred to several thousand Ωcm or more like brackish water, fresh water, or soil, the most anodic magnesium anode is used. Even if is used, the effective potential difference is insufficient and it is often impossible to secure a sufficient anticorrosion current. Moreover, since the current distribution is localized, it is necessary to dispose a large number of anodes.

Many harbor facilities have reinforced concrete structures such as quays and piers, but they are always exposed to splashes of seawater and corrosion of the rebars, so-called salt damage, occurs due to an increase in chloride concentration in the concrete. Salt damage occurs to bridge floor boards and buildings using sea sand due to heavy use of snow melting salt, but it is well known that cathodic protection is effective for preventing rebar corrosion at this time, and concrete structures with salt damage are well known. After the repair, the cathodic protection method has come to be applied to prevent corrosion from occurring again or to prevent salt damage at the time of new construction or at the early stage of service. At this time, in the case of ordinary Portland cement, since the electric resistance of concrete is not so high, it is possible to improve the anticorrosion effect with a potential difference of about 0.6 V between zinc and the reinforcing bar by using a zinc-based anode. Recently, however, cement with good anticorrosive properties has come to be used, and particularly when organic polymer cement or the like is used, the resistance of concrete increases remarkably. Insufficient protection current can be applied due to lack. It is difficult to obtain thin plate-shaped products with aluminum-based or magnesium-based anodes that have a low anode potential. In order to cope with such an increase in the resistance of the use environment, although a galvanic anode having a lower base potential has been demanded, an expected anode has not been found until now.

There is a method of utilizing an external power supply when the problem cannot be solved even by changing the anode to a more base potential. That is, in the normal galvanic anode method, if the anode, which is directly connected, is disconnected from the body to be protected and a rectifying power source or battery is connected between them and a necessary voltage (polarity is positive on the anode side) is applied,
Since the potential of the galvanic anode apparently shifts in the base direction as much as the voltage of the corrosion-prevented body, the effective potential difference increases.

However, if the voltage source is a primary battery, a long-term life cannot be expected, and if it is very expensive, a secondary battery requires troublesome maintenance such as charging and replenishment of electrolyte. In addition, there is an unexpected power outage in the rectification power source by commercial AC, and it is necessary to monitor without corrosion. Therefore, the emergence of a maintenance-free uninterruptible power supply is desired.

In the vicinity of a jetty, a harbor facility and the like, there are facilities for steel structures such as steel sheet piles and steel pipe piles to which cathodic protection is applied. Since these facilities are maintained at an anticorrosion potential of about -0.8 V, a passive metal, such as copper or a copper alloy, in which an oxygen reduction reaction proceeds at a noble potential in the environment near the facility.
When stainless steel, titanium, a titanium alloy, a conductive coating film, or a carbonaceous material is immersed as an auxiliary cathode, these become cathodes to the steel structure and current can be taken out at a polarization potential of about -0.5 V. About 0.3V between structure
The voltage of can be taken out. 0.3V obtained by using corrosion resistant metals such as titanium, tantalum, niobium and copper
Has already been proposed (corresponding to Japanese Patent Publication No. 3-77280), in which the above voltage is used as it is for the corrosion protection of the portion of the steel structure in contact with the atmospheric environment (Japanese Patent Publication No. 3-77280). It is insufficient for anticorrosion, and it is desired to obtain a larger voltage.

[0009]

SUMMARY OF THE INVENTION The present invention solves these problems of the prior art, and in the cathodic protection of the galvanic anode system, the environmental resistance is high and the existing galvanic anode is effective as a driving force for the corrosion current. It is an object of the present invention to provide a cathodic protection method using a galvanic composite pressure increasing type galvanic anode capable of increasing the effective electric potential difference to completely prevent corrosion of a body to be protected when the potential difference is insufficient, and an apparatus therefor.

[0010]

SUMMARY OF THE INVENTION According to the present invention, when the environment resistance of the body to be protected by cathodic protection is high and the existing current electrode lacks an effective potential difference and a sufficient protection current cannot flow, Auxiliary electrodes are attached to a metal facility where cathodic protection is currently being applied near the anticorrosion body, and the electrodes generated between the two are used to increase the effective potential difference of the galvanic electrodes to increase the environmental resistance. It overcomes and supplies the necessary anticorrosion current to achieve complete anticorrosion.

For example, in the cathodic protection method of the galvanic electrode system for the reinforcing bars of the concrete facilities on the ocean coast such as a harbor pier, since high-resistance polymer cement is used, the environmental resistance is high and the current zinc-based flow is high. When the effective potential difference is insufficient at the electrolytic anode and the necessary anticorrosion current cannot be applied, the insufficient voltage is applied to the steel facilities such as steel sheet piles and steel pipe piles where electrical protection is currently being applied near the anticorrosion target as described above. Such as copper, copper alloy, stainless steel, titanium, titanium alloy or a conductive coating or an auxiliary cathode of carbonaceous material, or
Alternatively, a zinc-based, aluminum-based, or magnesium-based auxiliary galvanic anode is attached, and the voltage generated between the auxiliary cathode or auxiliary galvanic anode and the metal facility is boosted or depressurized by a DC / DC converter to obtain an arbitrary value. Obtain a DC voltage and apply it between galvanic anode and rebar to increase the effective potential difference of galvanic anode by this voltage to overcome high environmental resistance and supply necessary anticorrosion current, or to prevent power failure. It is intended to supply an anticorrosion current as a power supply for an external power supply without fear.

When the existing or newly installed facility for applying cathodic protection is steel sheet piles or steel pipe piles in seawater, the auxiliary cathode of the above-mentioned material is approximately 0.3 V (the voltage is based on the steel structure grounded to the ground). Can generate a generated current of about 0.1 A / m ² . However, when the auxiliary galvanic anode is attached, the anode current density of 1 A / m ² or more can be taken out, so that the electrode becomes a much smaller electrode than the auxiliary cathode and the attachment becomes easy. Moreover, if a magnesium-based anode is used, a voltage of about -0.7 V can be obtained, and a voltage about 2.5 times that of the auxiliary cathode can be obtained, but the polarity is negative. Since concrete reinforcing bars and other objects to be protected against corrosion that use this voltage are almost grounded, it is necessary to reverse the polarity of the voltage or to prevent short-circuiting between the voltages by isolating them from the facility of the voltage source. is there. Therefore, at present, only the voltage of 0.3 V taken out from the auxiliary cathode can be used, and it is desired that a larger voltage can be used.

The present inventor remodels the DC / DC converter for a low input voltage in order to amplify the voltage from the auxiliary cathode greatly and to invert the polarity of the voltage of the auxiliary galvanic anode so that it can be used. The above problems have been solved by utilizing the above, and an electrocorrosion method for completely corroding the corrosion-prevented body was established by using another facility for applying the corrosion protection adjacent to the target corrosion-prevented body.

The DC / DC converter converts a DC input voltage into an AC by a high frequency switching circuit, boosts or depressurizes it, and then rectifies it, smoothes it, and isolates it from an input circuit (input voltage) of arbitrary magnitude and polarity. A power converter that can output a constant DC output voltage that can be
% Conversion efficiency is obtained. Therefore, by converting the voltage generated between the adjacent cathodic protection facility and the auxiliary electrode with this DC / DC converter, the galvanic anode at the target facility can be used regardless of whether the auxiliary cathode or the auxiliary galvanic anode is used. It can also be used as a power source for an external power source system and an increase in the effective potential difference.

However, since the DC / DC converter is usually designed so that the entire circuit operates by using the input as a power source, it does not operate at a low input voltage. Currently, the lowest input voltage that can be converted is generally around 1V, and no one can convert a voltage as low as 0.3V. The inventor is DC / DC
In order to make the converter for low input, the input switch circuit and its drive circuit are separated, the drive circuit is operated normally by a backup secondary battery with sufficient operating voltage, and the low input voltage is low input resistance switch circuit. To reliably and efficiently convert and transform, while at the same time charging a low voltage input by boosting a low voltage input with a separate small DC / DC converter (the driving circuit of which also operates with the secondary battery). Has designed and developed an improved DC-DC converter that can continuously convert a low voltage of about 0.3V.

The inventor of the present invention is a facility in which a metal facility (mainly a steel structure) being applied to cathodic protection is combined with an auxiliary cathode or an auxiliary galvanic anode of the above-mentioned metal or the like (hereinafter, referred to as an electric protection facility. A low voltage of -0.7 to +0.3 V that can be taken out from a battery) is applied to the above improved DC / DC converter device (hereinafter,
(Here, abbreviated as “converter”) is used to increase the voltage of the effective potential difference of galvanic anodes of other facilities by using that voltage. It was confirmed that complete corrosion protection was possible.

That is, according to the present invention, in the cathodic protection of the galvanic anode method, when the galvanic anode and the object to be corroded have a large environmental resistance and thus the anticorrosion current is insufficient, the anticorrosion is actually performed near the object to be corroded. The voltage generated between either the auxiliary cathode or auxiliary galvanic anode attached to the environment of the metal facility to which cathodic protection is applied and the metal facility is input to a switching DC / DC converter to boost the voltage. Or an output voltage of any value obtained by decompressing is applied between the metal facility and the continuous or discontinuous corrosion-protected object and the galvanic anode to increase the effective potential difference of the galvanic anode, This is a galvanic protection method using a galvanic anode with a composite pressure-increasing method, which is characterized by increasing the anticorrosion current to completely corrode the body to be protected.

Further, in the present invention, the DC / DC converter includes a secondary battery which is composed of a voltage conversion section and a power source configuration section, and which operates a drive section of a switching transistor in the both sections. After converting the input DC voltage into AC, boosting and rectifying the DC voltage to charge the secondary battery, the voltage conversion unit is stably operated continuously, and the input DC voltage lower than the secondary battery voltage is converted into the voltage. Switching method for voltage conversion, characterized in that, after being converted to AC by the unit, it is continuously output as a DC voltage that has been boosted or depressurized and is insulated from the input circuit or connected to the input circuit. DC / DC converter.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a circuit diagram showing the principle of a cathodic protection method using a method of increasing the effective potential difference of a galvanic anode by converting the voltage of an electric protection facility battery according to the present invention.

The electric protection facility battery 1 is composed of an auxiliary cathode 2 (or auxiliary galvanic anode 2 ') and a facility 3 which is under cathodic protection, and is installed in an environment 4. Reference numeral 5 is a galvanic anode for galvanic protection of the facility 3. The auxiliary cathode 2 is an electron conductor having a dissolved oxygen reducing ability at a noble potential selected from metals such as copper, copper alloys, stainless steel, titanium, and titanium alloys, conductive coatings, or carbonaceous substances. Auxiliary galvanic anode 2 '
Is a galvanic anode selected from zinc, aluminum, magnesium, or alloys containing each of these as the base metal. In terms of the generated voltage of the electric protection facility battery 1,
Magnesium galvanic anodes are preferred. Most of the facilities 3 that are applying cathodic protection are steel sheet piles, steel pipe piles, locks, steel structures between water transmission lines and buried pipes. Environment 4 is an electrolytic medium such as seawater, brackish water or freshwater, or soil, and is most preferably seawater having high conductivity and dissolved oxygen concentration, but brackish water, freshwater, and soil also do not reach seawater due to generated current or electromotive force. Though
The environment for installing the battery 1 of the anti-defense facility can be set. The output voltage of this protection facility battery 1 in seawater varies depending on the type of the attached electrode (2 or 2 '), but is usually -0.7V to + 0.3V.
It is a degree. An aluminum-based galvanic anode is often used as the cathodic protection anode 5 of the facility 3.

6 is capable of automatically adjusting the voltage generated in the electric protection facility battery 1 to a constant value by boosting or reducing the voltage so that the output voltage has an appropriate value, and isolating the output voltage from the input. It also has a function), and is composed of voltage converters 11 to 17 and power supply components 21 to 27.

Although there are various types of converters, the flyback transformer type is preferable as a small anticorrosive power source because the circuit configuration is simple, and this type is used for the voltage conversion section and the inductance is used for the power source configuration section. The forward method using a coil is suitable.

The voltage generated by the electric protection facility battery 1 depends on the input conductor 3
The input voltage is input to the converter 6 at 1 and 32, and the input voltage is added to the series circuit of the flyback transformer 11 and the low-on resistance switching transistor 12 of the voltage conversion unit. The switching transistor 12 is driven by an alternating current of a driving unit 13 composed of a high-frequency oscillator of a pulse width control system and repeatedly turned on and off to generate an alternating voltage on the secondary side of the flyback transformer 11, which rectifies the rectifying unit 14. The output voltage is converted into direct current by the smoothing unit 15 and is normally boosted and sometimes reduced in comparison with the input voltage. This output voltage is divided by the resistor 16, and a part of the voltage is fed back to the drive unit 13 via the coupler 17 and controlled so that the output voltage becomes constant by the frequency change due to the pulse width modulation of the oscillation circuit. The coupler is provided to transmit the feedback voltage to the driving unit while insulating the output voltage from the input circuit.

The power source of the drive unit 13 is 1.5V to several V.
The above is necessary, and this is supplied from the backup secondary battery 27 of the power supply component. On the other hand, the secondary battery 27 is charged with a voltage obtained by boosting the low voltage input from the electric protection facility battery 1 by a small capacity forward type converter. Therefore, the switching transistor 22 in series with the inductance coil 21 switches the input voltage by the high frequency alternating current from the drive unit 23, and the output alternating current is the diode 24 and the capacitor 2.
The DC voltage becomes smooth at 5, and the voltage is controlled to the voltage required for charging the secondary battery 27 by setting the feedback resistor 26.

On the low impedance side (common) of the input circuit of the converter 6, the auxiliary electrode 2
Alternatively, it is not preferable to connect to 2 ', and it is necessary to always connect to the grounded facility 3 by the input conductor 32. Therefore, a positive voltage is applied to the input conductor 31 when the laid electrode is the auxiliary cathode 2, and a negative voltage is applied when the auxiliary galvanic anode 2'is used. Since the converter 6 is unipolar, it is necessary to change the circuit depending on the polarity of the input voltage. FIG. 1 is for a positive voltage when the auxiliary cathode 2 is attached. In this case, the transistor of the switch circuit is
An N-type bipolar type or an N-channel field effect type is used, and the driving units 13 and 23 operate with a positive voltage secondary battery. On the other hand, when the auxiliary galvanic anode 2'is attached, the input voltage is -0.2V (zinc type anode) to -0.7V.
Since it becomes a (magnesium-based anode), it is necessary to change the switching transistor to the P-type bipolar type or the P-channel field effect type, and at the same time, to change the driving units 13 and 23 and the secondary battery 27 to those operating at a negative voltage. . In addition, the diode 34 and the capacitor 35 also output a negative voltage. When the auxiliary cathode 2 is used, the input and output of the converter have the same polarity, and therefore the input and output do not need to be insulated, and a forward type switch circuit may be used for the voltage conversion unit.

The converter 6 is a power converter. When the input voltage is boosted, the output current decreases in inverse proportion to the boosting ratio. Therefore, when the boosted output voltage is required,
The voltage generation system needs to have a current capacity capable of supplying sufficient electric power.

As described above, since the low input voltage can be efficiently boosted up to several V or more by the improvement of the converter, the external power source type cathodic protection can be performed with this voltage, for example, the splash of steel sheet pile or the like. It can also be used as a maintenance-free power source that is free from the risk of blackouts, such as for erosion protection.

It is well known that the current is continuously generated in the battery 1 of the electric protection facility. However, since the calcareous scale is formed and adheres to the surface of the auxiliary cathode 2, the current generated by the auxiliary cathode 2 is lowered. The required current cannot be secured. Especially in seawater, this scale formation is remarkable, and even in brackish water and fresh water, the same gradual decrease in generated current occurs according to the concentrations of Ca ²⁺ and Mg ²⁺ . Therefore, in order to prevent the scale from being deposited on the surface of the auxiliary cathode 2, prevent the decrease of the current generated by the positive electrode, and extend the life of the auxiliary cathode 2, the present inventor has found that the seawater in contact with a certain water-absorbing polymer is Cl ^−. Although there was no change in any way the concentration of anions such as SO ^2- _4, Ca ²⁺ and Mg ²⁺ and N
Experimental results have been obtained that the concentration of cations such as a ⁺ is reduced by 10 to 25%. Therefore, in order to reduce the concentration of alkaline earth metal ions and reduce scale deposition by utilizing the ion selectivity of this water-absorbing polymer, in the present invention, the auxiliary cathode 2 is made of this type of ion-selective substance. It is also characterized by coating the surface.

The potential of the auxiliary cathode 2 and the amount of generated current differ depending on the amount of dissolved oxygen in the environment 4 and the current density at the auxiliary cathode 2. Usually, the current density of the cathode used in seawater is about 0.1 A / m ² , and it is necessary to install a considerably large cathode in order to obtain a generated current of amperes order. Therefore, in the present invention,
As a small-sized auxiliary cathode with a large surface area, a carbonaceous filler electrode having an expanded surface area using granular activated carbon is also characterized in that the current capacity and electromotive force of the voltage generating system are increased. The filler electrode may be entirely submerged in the environment 4, or a part thereof may be exposed to the atmosphere.

[0030]

[Function] In cathodic protection of metal structures in brackish water, fresh water or soil or concrete with high environmental resistance, auxiliary cathodic or auxiliary galvanic current of precious potential metal or the like is installed in a facility for applying cathodic protection adjacent to the metal structure to be protected. Installed on either of the anodes, the voltage generated between the facility and the auxiliary electrode is transformed by a DC / DC converter improved for low input and added between the metal structure and the galvanic anode, and the voltage corresponding to that voltage is applied. It makes the potential of the current anode apparently base and increases the lacking effective potential difference of the current current anode, and makes it possible to completely prevent corrosion in the existing current anode against high environmental resistance.

[0031]

EXAMPLES Next, the present invention will be specifically described based on examples. EXAMPLE A concrete beam, which was made of high-resistance concrete and could not completely prevent corrosion of reinforcing bars even when a zinc alloy galvanic anode was used, was used as a test specimen, and as shown in FIG. The steel sheet pile 3 in seawater is used as the negative electrode of the electric protection facility battery 1, and the stainless steel plate as the auxiliary cathode 2 is used as the positive electrode.
The generated voltage is boosted by the converter 6, and the zinc alloy anode 44
The effective potential difference was increased.

As the auxiliary cathode 2, five stainless steel plates (surface area: 2 m ² ) and ^two below-mentioned filler electrodes are used.
It faced the steel sheet pile quay for cathodic protection. The surface of four stainless steel sheets is a water-absorbing polymer "Aqualic CS"
Was covered with a sheet-shaped anion-selective membrane (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) thinly spread on water-resistant paper, and one sheet was used naked for comparison. This membrane is a polyacrylic acid salt-based water-absorbing polymer, but the present inventor has recognized that the polymer adsorbs alkaline earth metal ions in seawater as described above. Is experimentally confirmed to be a diaphragm having anion selectivity that does not allow passage of calcium ions and magnesium ions and has low electric resistance.

Next, in order to evaluate the effect of a filler electrode having a surface area enlarged by granular activated carbon as a small auxiliary cathode,
A carbon rod (1 cmφ x 100 cm) was used as the center electrode, and this was placed in a cloth bag (7 cmφ x 100 cm), and the gap was tightly filled with granular activated carbon of 3 to 7 mm, and both ends of the bag were closed. A test using a cathode was performed. The total apparent surface area of this filler electrode is 0.4 m ² . However, it has been evaluated from the measurement of the cathode polarization curve that the effective surface area of this electrode is about 15 times that of a smooth electrode having the same apparent surface area, although it depends on the particle size and packing density of the packing material. At this time, the individual shared current of each auxiliary electrode can be measured.

Further, the cathodic protection test piece of the concrete beam was an RC concrete beam 41 made of high resistance polymer cement, and the reinforcing bars 42 were arranged at a normal density while confirming mutual conduction. On the concrete surface, 10 m of a semi-solid backfill 43 obtained by kneading a mixture of bentonite, gypsum and sodium sulfate in a ratio of 6: 3: 1 with water.
m thickness, and the zinc alloy anode plate 44 (0.2
10 sheets of (× 100 × 100 cm) were placed. Each anode was connected to the positive terminal of the output of the converter 6 via the conductor 45 via the distributor 45, for equal distribution of the current, while the negative terminal of the converter 6 was connected to the rebar by the conductor 52. Note that the distributor 45 is an element having a constant current characteristic for evenly distributing the current to each anode, and is a simple constant current device that adjusts the resistance of 5Ω and the voltage between the base and emitter of the transistor with a variable resistor, the transistor. The stability of current distribution was also tested by using a precision constant current device or the like that adjusts the base voltage of the device with an operational amplifier.

In the anticorrosion test, it was found in a separate test that an effective potential difference of 1.7 V or more (external applied voltage: 1.1 V) is required to obtain a sufficient anticorrosion current with this concrete. The output voltage of the converter 6 was set to 1.3V. The judgment of complete anticorrosion was based on the fact that the temporary current was cut off during the energization test and that the repolarization potential of 100 mV or more was recognized by 4 hours later.

Immediately after the start of the energization test, the passing current of each anode was in the range of 13 to 14 mA, and one recovery pole test was conducted every week during the 6-month test period.
A reversion value of mV was obtained, and it was found that the corrosion was completely prevented. Therefore, the galvanic anode effective potential difference pressure increasing method of the present invention,
It became clear that it worked effectively.

During the test period, the generated voltage of the electric protection facility battery 1 was maintained at about 0.3 V, and the total generated current was about 800 mA. The shared current of each electrode was about 110 mA / sheet for the stainless steel plate, but was 230 for the filler electrode.
A generated current of about mA was observed. Therefore, it was found that the filler electrode has a large effective surface area and a large current capacity.

Further, when the stainless steel plate electrode was pulled up from seawater at the 3rd and 6th months and the adhesion condition of the calcareous scale was examined, scale deposition was observed on the stainless steel surface on which the anion selective membrane was not adhered. The amount of precipitation increased with the passage of the test time. On the other hand, almost no scale deposition was observed on the stainless steel surface below the anion selective membrane.

Next, two magnesium alloy anodes (surface area: 0.5 m ² ) were installed as the auxiliary galvanic anodes 2 ′, converted by the P-type converter 6, and the corrosion test of the concrete beam test body was also conducted. . As a result, in the 6-month test,
The 00 mV depolarization was secured, and complete corrosion protection was confirmed. During this period, the average value of the current generated by the electric protection facility battery 1 is 450 mA.
The generated voltage was about 0.55V.

[0040]

As described above, an auxiliary cathode or an auxiliary galvanic anode is installed in a facility for applying anticorrosion adjacent to a body to be protected in a high resistance environment, and the generated voltage is simply transformed by a DC / DC converter. An inexpensive uninterruptible power supply with long life and maintenance-free can be obtained, and the effective potential difference of the galvanic anode can be easily increased. Therefore, it becomes possible to completely prevent corrosion of the object to be protected in a high resistance environment where the existing galvanic anode cannot prevent corrosion due to lack of effective potential difference. And get a few volts more voltage,
It can also be used as a power source for an external power supply type cathodic protection method.

[Brief description of drawings]

FIG. 1 is a principle circuit diagram of a method of increasing the effective potential difference of a galvanic anode by a battery voltage of an electric protection facility according to the present invention.

[Explanation of symbols]

1: Battery of anti-electrostatic facility, 2: Auxiliary cathode, 2 ': Auxiliary galvanic anode, 3: Electrostatic protective facility, 4: Environment, 5: Electrostatic protective facility galvanic anode for corrosion protection, 6: Low input DC / DC converter, 1
1: flyback transformer, 12: switching transistor, 13: drive unit, 14: rectification unit, 15: smoothing unit,
16: feedback voltage setting unit, 17: coupler, 2
1: Inductance coil, 22: Switching transistor, 23: Driving part, 24: Diode, 25: Capacitor, 26: Feedback voltage setting part, 27: Backup secondary battery, 31: Input lead wire, 32: Input lead wire,
41: concrete structure, 42: rebar, 43: backfill, 44: zinc alloy anode, 45: distributor, 51: converter output plus lead wire, 52: converter output minus lead wire.

Claims (6)

[Claims] 1. In cathodic protection of galvanic anode method,
When the environmental resistance between the galvanic anode and the object to be protected is large and the anticorrosion current is insufficient, an auxiliary cathode attached in the environment of a metal facility currently being applied with anticorrosion in the vicinity of the object to be protected or The voltage generated between any of the auxiliary galvanic anodes and the metal facility is input to a switching DC / DC converter, and the output voltage of an arbitrary value obtained by boosting or reducing the pressure is used as the metal facility. Is applied between the corrosion-prevented material which is continuous or discontinuous with the galvanic anode and the galvanic anode to increase the effective potential difference of the galvanic anode, thereby increasing the anticorrosion current to completely corrode the corrosion-protected material. Cathodic protection method with composite booster galvanic anode. 2. The auxiliary cathode is selected from copper, copper alloys, stainless steel, titanium, titanium alloys, conductive coatings and carbonaceous materials, and the auxiliary galvanic anode is zinc, aluminum, magnesium or a base metal thereof. The cathodic protection method according to claim 1, which is selected from respective alloys. 3. The cathodic protection method according to claim 1, wherein the surface of the auxiliary cathode is coated with an ion-selective substance. 4. The auxiliary cathode is a filler electrode in which a granular carbonaceous material is filled around an insoluble central electrode, and the filler electrode is wholly immersed in the environment or partially exposed to the atmosphere. The cathodic protection method according to claim 1. 5. The cathodic protection method according to claim 1, wherein the body to be protected is a reinforcing bar in reinforced concrete. 6. The DC / DC converter includes a voltage conversion unit and a power supply constituent unit, and has a secondary battery for operating a driving unit of a switching transistor in both units, and an input DC voltage is provided in the power supply constituent unit. After converting to AC, boost,
By rectifying and charging the secondary battery, the voltage conversion unit is stably operated continuously, and an input DC voltage lower than the secondary battery voltage is converted into AC by the voltage conversion unit and then boosted or reduced in pressure. Switching method for voltage conversion D, which is an arbitrary value and is continuously output as a DC voltage which is insulated from the input circuit or connected to the input circuit
C / DC converter.