CN116990216A - Device and method for measuring capacitance time constant of metal interface under dynamic direct current interference - Google Patents
Device and method for measuring capacitance time constant of metal interface under dynamic direct current interference Download PDFInfo
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 7
- 238000001453 impedance spectrum Methods 0.000 abstract description 7
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- 238000000157 electrochemical-induced impedance spectroscopy Methods 0.000 description 3
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
- G01N17/006—Investigating resistance of materials to the weather, to corrosion, or to light of metals
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
- G01N17/02—Electrochemical measuring systems for weathering, corrosion or corrosion-protection measurement
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/226—Construction of measuring vessels; Electrodes therefor
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/301—Reference electrodes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/02—General constructional details
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- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
Abstract
The inventionThe device and the method for measuring the capacitance time constant of the metal interface under the dynamic direct current interference are provided. The device comprises: the device comprises a metal sample, a reference electrode, an auxiliary electrode, a dynamic direct current power supply, a circuit breaker and a data recorder, wherein the metal sample, the reference electrode and the auxiliary electrode are buried in a soil simulation medium. The dynamic direct current power supply is used for providing experimental current flowing into and out of the metal sample; the data recorder is used for collecting the energizing potential and the de-energizing potential E of the metal sample in real time when the circuit breaker is switched on and off off The method comprises the steps of carrying out a first treatment on the surface of the By integrating E of multiple dynamic DC power supply interference periods in a measurement period off Obtaining E in a dynamic DC power supply interference period off And calculating a metal interface capacitance time constant based on the curve. The invention solves the problems that the charge-discharge capacitance effect of the electric double layer of the metal interface is researched by measuring the electrochemical impedance spectrum of the metal in a laboratory in the prior art, the corrosion behavior of the metal sample in the positive and negative current alternating process cannot be reflected in real time, and the like.
Description
Technical Field
The invention belongs to the technical field of measurement and calculation of corrosion of buried metal pipelines, and particularly relates to a device and a method for measuring a capacitance time constant of a metal interface under dynamic direct current interference.
Background
Due to the complexity and unpredictability of the stray current leakage path in the urban rail transit system, prediction and protection of dynamic direct current stray current interference corrosion also become the difficult problem of ensuring safe operation of buried steel pipelines in recent years. The direct current stray current generated by the rail transit system has dynamic fluctuation characteristics because the position of the train on the rail is continuously changed during running. For buried pipelines, stray current flows in and out at the same position of the pipeline at different moments, and alternate cathode and anode polarization is caused on the exposed metal surface at the defect of the coating, and is reflected on the measurement result of the ground potential or the test piece current, and the measurement result shows dynamic positive and negative fluctuation of the potential or the current. While another type of stray current interference, alternating current interference, experienced by buried steel pipes also has alternating positive and negative fluctuation characteristics. In the research of the influence of frequency on corrosion under the condition of alternating current interference, basically, the corrosion rate gradually decreases with the increase of alternating current frequency, and the majority of alternating current is non-Faraday current and is used for charging and discharging an interface double layer, and only a small part of alternating current is related to metal dissolution (Faraday current). For the interference of dynamic direct current stray current, the interface electric double layer has the same fluctuation characteristic of positive and negative alternation, and the charge-discharge capacitance effect of the interface electric double layer can play an important role in inhibiting metal corrosion.
In the prior art, electrochemical Impedance Spectroscopy (EIS) of metal is generally measured in a laboratory, impedance spectrum fitting software is utilized, and a proper equivalent circuit is selected to fit data, so that parameters of elements such as resistance, capacitance, inductance and the like in the equivalent circuit are obtained, and the charge-discharge capacitance effect of an electric double layer of a metal interface is studied. However, because the alternating current impedance spectrum EIS is scanned under the condition that the corrosion system reaches a stable open-circuit potential, the alternating current impedance spectrum can be scanned after waiting for 30 minutes approximately after the experiment is finished, and the corrosion behavior of the metal sample in the alternating current and the positive current can not be reflected in real time. In addition, the structure of the metal/electrolyte interfacial double layer is related to the arrangement of charges on both sides of the interface, and the specific arrangement structure of charged particles or dipoles on the interface is greatly affected by the electrode potential and pH value. In the alternating process of positive and negative currents, the polarization potential and the near-surface pH value have fluctuation, and the size of the capacitor can also change, which is electrochemical information that the simulation result of the alternating current impedance spectrum cannot reflect.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a device and a method for measuring the capacitance time constant of a metal interface under dynamic direct current interference.
In order to achieve the above object, the present invention adopts the following technical scheme.
In a first aspect, the present invention provides a device for measuring a capacitance time constant of a metal interface under dynamic direct current interference, including: the device comprises a metal sample, a reference electrode, an auxiliary electrode, a dynamic direct current power supply, a circuit breaker and a data recorder, wherein the metal sample, the reference electrode and the auxiliary electrode are buried in a soil simulation medium; one output end of the dynamic DC power supply is electrically connected with the metal sample through a breaker, and the other output end is electrically connected with the metal sample through a breakerAn output end is electrically connected with the auxiliary electrode and is used for providing experimental current flowing into and out of the metal sample by outputting a voltage signal with a positive-negative voltage width ratio of 1:1 and an interference period of T; the on-off ratio of the breaker is a 1, and the on-off period is T 1 The method comprises the steps of carrying out a first treatment on the surface of the The data recorder is connected in parallel between the metal sample and the reference electrode for a period T 2 Collecting the energizing potential E of a metal sample in real time when a circuit breaker is switched on and off on And a power-off potential E off The method comprises the steps of carrying out a first treatment on the surface of the By integrating E of multiple dynamic DC power supply interference periods in a measurement period off Obtaining E in a dynamic DC power supply interference period off Calculating a capacitance time constant of the metal interface based on the curve which changes with time; wherein T is 2 <T 1 /(a+1)，T 1 <T/2，a>1。
Further, E in a dynamic DC power supply interference period is obtained off The method for the time-varying curve comprises the following steps:
e for acquiring N dynamic DC power supply interference periods for integration in measurement period off Wherein, the method comprises the steps of, wherein,
N＝[T,T 1 ]/T
wherein [ T, T ] 1 ]Representing T and T 1 Least common multiple of [ T, T ] 1 ]≠T；
Only the last 1E is reserved in the on-off period of the circuit breaker off The j E of the i-th dynamic DC power supply interference period off Denoted as E off (t i +(i-1)T+(j-1)T 1 ) Wherein t is i For the first E off Acquisition time, t i ＝T 1 -mod((i-1)T,T 1 ) Mod (a, b) represents the remainder of a divided by b;
e of the i-th dynamic DC power supply interference period off Shift (i-1) T, jth E leftwards in the time axis off Becomes E off (t i +(j-1)T 1 )，0≤t i +(j-1)T 1 ≤T；E off (t i +(j-1)T 1 ) I.e. E in the integrated dynamic DC power supply interference period off A time-dependent curve of 2 adjacent E off Is of the time interval ofT 1 N; where i=1, 2, …, N, j=1, 2, …, int (T/T 1 ) Int () is a rounding function.
Further, 2E are collected in each breaker on-off period off Shielding the first E in each breaker on-off period off Reserve the second E off 。
Further, the metal interface capacitance time constant τ is equal to the time constant τ calculated in the positive half period and the negative half period of the dynamic DC power supply interference period based on the curve + And τ - A kind of electronic device.
Further, τ + The calculation method of (1) comprises the following steps:
calculating E in the positive half period off Maximum value E of (2) max+ ；
Calculating E from the positive half period off Initial value E of (2) 0+ Change to E 1 The required time to obtain tau + The method comprises the steps of carrying out a first treatment on the surface of the Wherein E is 1 ＝E 0+ +0.63(E max+ -E 0+ )。
Further, τ - The calculation method of (1) comprises the following steps:
calculating E in the negative half period off Minimum value E of (2) min- ；
Calculating E from within the negative half period off Initial value E of (2) 0- Change to E 2 The required time to obtain tau - The method comprises the steps of carrying out a first treatment on the surface of the Wherein E is 2 ＝E min- +0.37(E 0- -E min- )。
Further, the method for analyzing corrosion risk according to the relative magnitudes of the dynamic DC power supply interference period T and the metal interface capacitance time constant tau comprises the following steps:
when T is less than or equal to tau, most of the current is charged and discharged through the metal interface capacitor, and the current is non-Faraday current; only a small part of current flows through the reaction resistor to cause corrosion, so that the corrosion risk is small;
when T > τ, most of the current flows through the interface reaction resistance, which is Faraday current, with a greater risk of corrosion.
Further toThe duration of the measurement period is 13h, t=1h, t 1 ＝130s，T 2 ＝1s，a＝64。
Further, the metal sample adopts an X70 pipeline steel pipe, is processed into a cylindrical shape with the diameter of 11.3mm and the length of 5mm, and has the working surface with the area of 1cm 2 The back surface of the metal plate is electrically connected with a copper wire, and the density of current flowing out of the surface of the metal sample is 10mA/cm 2 。
In a second aspect, the present invention provides a method for measuring a metal interface capacitance time constant by using the device, comprising the following steps:
the dynamic direct current power supply outputs interference signals according to a set interference period and a set positive-negative voltage width ratio, and experimental current flowing into and out of a metal sample is provided; the circuit breaker works according to the set on-off period and the on-off ratio;
in the measuring period, the data recorder collects the energizing potential E of the metal sample when the breaker is switched on and off in real time according to a set period on And a power-off potential E off ；
E for a plurality of dynamic DC power supply interference periods in a measurement period off Integrating to obtain E in a dynamic DC power supply interference period off And calculating a metal interface capacitance time constant based on the curve.
Compared with the prior art, the invention has the following beneficial effects.
The invention is characterized in that a metal sample, a reference electrode and an auxiliary electrode buried in a soil simulation medium are arranged, a dynamic direct current power supply, a circuit breaker and a data recorder are arranged, wherein the dynamic direct current power supply is used for providing experimental current flowing into and flowing out of the metal sample, the circuit breaker works with a set on-off period and on-off ratio, the data recorder is used for collecting the electrifying potential and the outage potential of the metal sample when the circuit breaker is switched on and off, and E of a plurality of dynamic direct current power supply interference periods in a measurement period is integrated off And obtaining a curve of the power-off potential change along with time in a dynamic direct-current power supply interference period, and calculating the capacitance time constant of the metal interface based on the curve. The invention is based on real timeThe method comprises the steps of monitoring the outage potential of a metal sample to measure the capacitance time constant of a metal interface, and evaluating the corrosion behavior caused by dynamic direct current stray interference in real time based on the time constant, so that the problems that the equivalent resistance, capacitance, inductance and other parameters are obtained by measuring the electrochemical impedance spectrum of the metal in a laboratory, the charge-discharge capacitance effect of an electric double layer of the metal interface is researched, the corrosion behavior of the metal sample in the positive-negative current alternating process cannot be reflected in real time and the like are solved.
Drawings
Fig. 1 is a block diagram of a measuring device for a metal interface capacitance time constant under dynamic direct current interference according to an embodiment of the invention. In the figure, 1-metal sample, 2-reference electrode, 3-soil simulation medium, 4-auxiliary electrode, 5-data recorder, 6-dynamic DC power supply and 7-circuit breaker.
FIG. 2 is a graph of E real-time monitoring during multiple periods of dynamic DC power supply interference on 、E off Schematic waveform diagram.
FIG. 3 shows E in a dynamic DC power supply interference period off A time-dependent curve.
Fig. 4 is a schematic diagram of a time constant calculation principle.
FIG. 5 is a flowchart of a method for measuring a capacitance time constant of a metal interface using the device according to an embodiment of the present invention.
Detailed Description
The present invention will be further described with reference to the drawings and the detailed description below, in order to make the objects, technical solutions and advantages of the present invention more apparent. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Fig. 1 is a block diagram of a device for measuring a capacitance time constant of a metal interface under dynamic direct current interference according to an embodiment of the present invention, including: the device comprises a metal sample 1, a reference electrode 2, an auxiliary electrode 4, a dynamic direct current power supply 6, a circuit breaker 7 and a data recorder 5 which are buried in a soil simulation medium 3; dynamic stateOne output end of the direct current power supply 6 is electrically connected with the metal sample 1 through a breaker 7, and the other output end is electrically connected with the auxiliary electrode 4 and is used for providing experimental current flowing into and out of the metal sample 1 by outputting voltage signals with positive-negative voltage width ratio of 1:1 and interference period of T; the on-off ratio of the breaker 7 is a 1, and the on-off period is T 1 The method comprises the steps of carrying out a first treatment on the surface of the A data recorder 5 connected in parallel between the metal sample 1 and the reference electrode 2 for a period T 2 Collecting in real time the energizing potential E of the metal sample 1 when the circuit breaker 7 is on and off on And a power-off potential E off The method comprises the steps of carrying out a first treatment on the surface of the By integrating E of multiple dynamic DC power supply interference periods in a measurement period off Obtaining E in a dynamic DC power supply interference period off Calculating a capacitance time constant of the metal interface based on the curve which changes with time; wherein T is 2 <T 1 /(a+1)，T 1 <T/2，a>1。
In this embodiment, the device mainly comprises a metal sample 1, a reference electrode 2, an auxiliary electrode 4, a dynamic direct current power supply 6, a circuit breaker 7 and a data recorder 5, wherein the metal sample is buried in a soil simulation medium 3, and the connection relation of the parts is shown in fig. 1. The metal sample 1, the reference electrode 2 and the auxiliary electrode 4 are all buried in the soil simulating medium 3. The soil simulation medium 3 is used for simulating the soil environment of the buried pipeline, and can prepare a soil simulation solution by deionized water and a chemical pure reagent according to experimental requirements, and meanwhile, quartz sand after cleaning and drying is prepared for later use, and the corrosion medium is quartz sand and the soil simulation solution. The metal sample 1 is used for simulating a buried pipeline to be tested, and is made into a cylindrical shape with a certain surface area (working surface). The non-buried end of the metal sample 1 is connected with one end of a data recorder 5, the other end of the data recorder 5 is connected with a reference electrode 2, the reference electrode 2 is used as a reference comparison electrode for measuring the potential of the metal sample 1, and the data recorder 5 is used for collecting the potential of the metal sample 1 in real time. The non-buried end of the metal sample 1 is also connected to one output end of the dynamic direct current power supply 6 through a breaker 7, and the other output end of the dynamic direct current power supply 6 is connected to the auxiliary electrode 4. The dynamic dc power supply 6 is used for simulating dynamic dc stray interference current, and supplies an inflow and outflow current (denseDegree). The dynamic dc power supply 6 outputs an interference voltage signal having a positive-negative voltage width ratio of 1:1 and a period T, and the interference period T is generally about 1 hour. The circuit breaker 7 also works in the on-off state of the period, the on-off ratio is a 1, and the on-off period is T 1 。T 1 Is obviously smaller than T/2, i.e. each half interference period T contains a plurality of on-off periods T 1 . T in on-off period 1 The longer power-on time and the shorter power-off time, namely the larger value of a, can avoid the excessive disturbance of the surface state of the metal sample 1 caused by the interruption of the loop current. To improve the measurement accuracy, the data acquisition period T of the data logger 5 2 Should be as small as possible to ensure that the power-off state of the circuit breaker 7 can also collect a plurality of potential data, i.e. T 2 <T 1 /(a+1). The potential acquired when the circuit breaker 7 is turned on is called the energizing potential E on The potential collected during disconnection is called the power-off potential E off . In this embodiment, the measurement period is selected as a plurality of dynamic dc power supply interference periods (the duration is several days), and the power-off potential E acquired by integrating the plurality of dynamic dc power supply interference periods is used off Obtaining E in a dynamic DC power supply interference period off And calculating the capacitance time constant of the metal interface according to the definition of the time constant based on the obtained power-off potential-time curve in one period T.
According to the embodiment, the time constant of the capacitance of the metal interface is measured based on the real-time monitoring of the outage potential of the metal sample 1, the corrosion behavior caused by the dynamic direct current stray interference can be evaluated in real time based on the time constant, and the problems that in the prior art, parameters such as equivalent resistance, capacitance and inductance can only be obtained by measuring the electrochemical impedance spectrum of metal in a laboratory, the charge-discharge capacitance effect of an electric double layer of the metal interface is researched, the corrosion behavior of the metal sample 1 in the positive and negative current alternating process cannot be reflected in real time and the like are solved.
As an alternative embodiment, E is obtained in a dynamic DC power supply interference period off The method for the time-varying curve comprises the following steps:
e for acquiring N dynamic DC power supply interference periods for integration in measurement period off Wherein, the method comprises the steps of, wherein,
N＝[T,T 1 ]/T
wherein [ T, T ] 1 ]Representing T and T 1 Least common multiple of [ T, T ] 1 ]≠T；
Only the last 1E is reserved in the on-off period of the circuit breaker off The j E of the i-th dynamic DC power supply interference period off Denoted as E off (t i +(i-1)T+(j-1)T 1 ) Wherein t is i For the first E off Acquisition time, t i ＝T 1 -mod((i-1)T,T 1 ) Mod (a, b) represents the remainder of a divided by b;
e of the i-th dynamic DC power supply interference period off Shift (i-1) T, jth E leftwards in the time axis off Becomes E off (t i +(j-1)T 1 )，0≤t i +(j-1)T 1 ≤T；E off (t i +(j-1)T 1 ) I.e. E in the integrated dynamic DC power supply interference period off A time-dependent curve of 2 adjacent E off Is of time interval T 1 N; where i=1, 2, …, N, j=1, 2, …, int (T/T 1 ) Int () is a rounding function.
The embodiment shows that E is obtained in a dynamic DC power supply interference period through integration off A technical scheme of a curve changing with time. E for real-time monitoring in multiple dynamic DC power supply interference periods on 、E off The waveform diagram is shown in FIG. 2, in which the waveform with larger amplitude is E on The waveform with smaller amplitude is E off The method comprises the steps of carrying out a first treatment on the surface of the E in one period off The waveform is shown in fig. 3.
In this embodiment, E of N dynamic DC power supply interference periods for integration is obtained first off . In this embodiment, the duration T of the dynamic dc power supply interference period is not the duration T of the breaker on-off period 1 Integer multiples of [ T, T ] 1 ]Not equal to T, therefore, take n= [ T, T 1 ]After T, N dynamic DC power supply interference periods T, E off The law of variation of the first N periods T is repeated. To simplify the scheme, only the last 1E is reserved in one breaker on-off period off That is, each E off The collection time of the circuit breaker is the last time of the on-off period of each circuit breaker. Thus, the kth E of N dynamic DC power supply interference periods off Denoted as E off (kT 1 )，kT 1 Is the acquisition time. Then, starting from the 2 nd dynamic DC power supply interference period, E off (kT 1 ) To shift left along the time axis, shift 1T in the 2 nd period, shift 2T in the 3 rd period, and so on, shift N-1T in the N th period, thus E in N periods can be obtained off (kT 1 ) Are translated to 0 to T, and E in one period can be obtained off The time-dependent curve is shown. Because of [ T, T ] 1 ]Not equal to T, so each period E off Initial acquisition time t i Are all different, of course each period E off Are not coincident, and 2 adjacent E are integrated off Is of time interval T 1 /N。
As an alternative embodiment, 2E are collected in each breaker on-off period off Shielding the first E in each breaker on-off period off Reserve the second E off 。
The embodiment acquires E in the on-off period of each circuit breaker off Is limited in number. Since the operations of the data recorder 5 and the circuit breaker 7 are not synchronously controlled by the synchronous clock, the respective clocks may not be synchronous, and the first power-off potential data of each circuit breaker on-off period may be collected by the data recorder 5 during the execution of the opening action of the circuit breaker 7, so that the first power-off data may be inaccurate. For this reason, the present embodiment masks (clears) the first power-off potential value in each breaker on-off period, and retains the power-off potential after the first.
As an alternative embodiment, the metal interface capacitance time constant τ is equal to the time constant τ calculated based on the curve in the positive half-cycle and the negative half-cycle of the dynamic DC power supply disturbance period, respectively + And τ - A kind of electronic device.
The embodiment provides a technical scheme for calculating the capacitance time constant of the metal interface. This practice isThe embodiment divides the time constant τ into two parts: a portion of the curve E is based on the positive half period of the dynamic DC power supply disturbance period off (j) Calculated time constant τ + The method comprises the steps of carrying out a first treatment on the surface of the Another part is based on curve E in the negative half cycle off (j) Calculated time constant τ - . The time constant τ is equal to the sum of the two time constants, i.e. τ=τ + +τ - . As shown in fig. 4. The present embodiment calculates τ from the definition of the time constant + And τ - . In an electronic circuit, when a capacitor is charged with a constant voltage through a resistor, the time required for the terminal voltage of the capacitor to reach 1-1/e (about equal to 0.63) of the maximum value is the time constant; and when the circuit is open, the time constant is the time required for the terminal voltage of the capacitor to reach 1/e (approximately equal to 0.37) of the maximum value.
As an alternative embodiment, τ + The calculation method of (1) comprises the following steps:
calculating E in the positive half period off Maximum value E of (2) max+ ；
Calculating E from the positive half period off Initial value E of (2) 0+ Change to E 1 The required time to obtain tau + The method comprises the steps of carrying out a first treatment on the surface of the Wherein E is 1 ＝E 0+ +0.63(E max+ -E 0+ )。
The present embodiment gives τ + Is a calculation method of (a). As shown in FIG. 4, the present embodiment uses a curve E of positive half cycles (0-30 min) off (j) Calculating τ from the definition of the time constant + Specific methods and related formulas are not repeated. It is worth noting that a certain E is calculated based on the curve off Value (e.g. E 1 ) At the corresponding time, if the data point of the curve does not exist the E off Can be based on and the E off Interpolation is used to calculate the E for two adjacent data points off Corresponding time values.
As an alternative embodiment, τ - The calculation method of (1) comprises the following steps:
calculating E in the negative half period off Minimum value E of (2) min- ；
Calculating E from within the negative half period off Initial value E of (2) 0- Change to E 2 The required time to obtain tau - The method comprises the steps of carrying out a first treatment on the surface of the Wherein E is 2 ＝E min- +0.37(E 0- -E min- )。
The present embodiment gives τ - Is a calculation method of (a). As shown in FIG. 4, the present embodiment utilizes a curve E of the negative half period (30-60 min) off (j) Calculating τ from the definition of the time constant - Specific methods and related formulas are not repeated.
As an alternative embodiment, the method for analyzing corrosion risk according to the relative magnitudes of the dynamic dc power supply interference period T and the metal interface capacitance time constant τ includes:
when T is less than or equal to tau, most of the current is charged and discharged through the metal interface capacitor, and the current is non-Faraday current; only a small part of current flows through the reaction resistor to cause corrosion, so that the corrosion risk is small;
when T > τ, most of the current flows through the interface reaction resistance, which is Faraday current, with a greater risk of corrosion.
The embodiment provides a method for analyzing corrosion risk according to the relative sizes of a dynamic direct current power supply interference period T and a metal interface capacitance time constant tau. When the dynamic direct current interference period is smaller than the time constant, the fact that most of current is charged and discharged through the interface double-layer capacitor is shown, the current is non-Faraday current, and only a small part of current flows through the reaction resistor to cause corrosion, so that the corrosion risk is small; when the period of disturbance is greater than its time constant, it is indicated that the capacitance effect of the interfacial double layer is reduced, and most of the current will flow through the interfacial reaction resistance as faraday current, which will lead to increased corrosion.
As an alternative embodiment, the duration of the measurement period is 13h, t=1h, t 1 ＝130s，T 2 ＝1s，a＝64。
The present example gives a specific set of experimental parameters. In this embodiment, the duration of the measurement period is 72h, i.e. 3 days; the dynamic direct current power supply interference period T=1h=3600s, and the positive half period and the negative half period are both 30min; the measuring period comprises a dynamic DC power supply interference period number N= [ T, T ] 1 ]/T＝[3600,130]V3600=13; on-off period T of circuit breaker 7 1 130s, the on-off ratio is 64:1, and the on-off time is 128s and 2s respectively; acquisition period T of data recorder 5 2 ＝1s。
Time constant calculations were performed based on the above parameters, and the calculation results are shown in table 1.
TABLE 1 time constant calculation results
As an alternative embodiment, the metal sample 1 is an X70 pipeline steel pipe, is processed into a cylindrical shape with the diameter of 11.3mm and the length of 5mm, and has the working surface with the area of 1cm 2 The back surface of the metal plate is electrically connected with a copper wire, and the density of current flowing into the surface of the metal sample 1 is 10mA/cm 2 。
This example shows a specific structural parameter of the metal sample 1. It should be noted that this example shows a preferred embodiment, and does not negate or exclude other possible embodiments, such as metal samples 1 made of different sizes and materials.
FIG. 5 is a flowchart of a method for measuring a capacitance time constant of a metal interface by using the device according to an embodiment of the invention, which comprises the following steps:
step 101, the dynamic direct current power supply 6 outputs interference signals according to a set interference period and positive-negative voltage width ratio, and provides experimental current flowing into and out of the metal sample 1; the circuit breaker 7 works according to the set on-off period and the on-off ratio;
step 102, the data recorder 5 collects the energizing potential E of the metal sample 1 when the breaker 7 is turned on and off in real time according to the set period during the measurement period on And a power-off potential E off ；
Step 103, E for a plurality of dynamic DC power supply interference periods in the measurement period off Integrating to obtain E in a dynamic DC power supply interference period off And calculating a metal interface capacitance time constant based on the curve.
Compared with the technical scheme of the embodiment of the apparatus shown in fig. 1, the method of the embodiment has similar implementation principle and technical effect, and is not repeated here.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present invention should be included in the present invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (10)
1. The utility model provides a measuring device of metal interface electric capacity time constant under dynamic direct current interference which characterized in that includes: the device comprises a metal sample, a reference electrode, an auxiliary electrode, a dynamic direct current power supply, a circuit breaker and a data recorder, wherein the metal sample, the reference electrode and the auxiliary electrode are buried in a soil simulation medium; one output end of the dynamic direct current power supply is electrically connected with the metal sample through a circuit breaker, and the other output end of the dynamic direct current power supply is electrically connected with the auxiliary electrode and is used for providing experimental current flowing into and out of the metal sample by outputting voltage signals with positive and negative voltage width ratio of 1:1 and interference period of T; the on-off ratio of the breaker is a 1, and the on-off period is T 1 The method comprises the steps of carrying out a first treatment on the surface of the The data recorder is connected in parallel between the metal sample and the reference electrode for a period T 2 Collecting the energizing potential E of a metal sample in real time when a circuit breaker is switched on and off on And a power-off potential E off The method comprises the steps of carrying out a first treatment on the surface of the By integrating E of multiple dynamic DC power supply interference periods in a measurement period off Obtaining E in a dynamic DC power supply interference period off Calculating a capacitance time constant of the metal interface based on the curve which changes with time; wherein T is 2 <T 1 /(a+1)，T 1 <T/2，a>1。
2. The device for measuring the capacitance time constant of a metal interface under dynamic DC interference as set forth in claim 1, wherein E is obtained during a period of dynamic DC power supply interference off The method for the time-varying curve comprises the following steps:
acquiring measurementsE for N dynamic DC power supply interference periods integrated in time period off Wherein, the method comprises the steps of, wherein,
N＝[T,T 1 ]/T
wherein [ T, T ] 1 ]Representing T and T 1 Least common multiple of [ T, T ] 1 ]≠T；
Only the last 1E is reserved in the on-off period of the circuit breaker off The j E of the i-th dynamic DC power supply interference period off Denoted as E off (t i +(i-1)T+(j-1)T 1 ) Wherein t is i For the first E off Acquisition time, t i ＝T 1 -mod((i-1)T,T 1 ) Mod (a, b) represents the remainder of a divided by b;
e of the i-th dynamic DC power supply interference period off Shift (i-1) T, jth E leftwards in the time axis off Becomes E off (t i +(j-1)T 1 )，0≤t i +(j-1)T 1 ≤T；E off (t i +(j-1)T 1 ) I.e. E in the integrated dynamic DC power supply interference period off A time-dependent curve of 2 adjacent E off Is of time interval T 1 N; where i=1, 2, …, N, j=1, 2, …, int (T/T 1 ) Int () is a rounding function.
3. The device for measuring the capacitance time constant of a metal interface under dynamic direct current interference according to claim 2, wherein 2E are collected in each breaker on-off period off Shielding the first E in each breaker on-off period off Reserve the second E off 。
4. The device for measuring a metal interface capacitance time constant under dynamic DC interference according to claim 1, wherein the metal interface capacitance time constant τ is equal to a time constant τ calculated based on the curve in a positive half-cycle and a negative half-cycle of a dynamic DC power supply interference period, respectively + And τ - A kind of electronic device.
5. The device for measuring a capacitance time constant of a metal interface under dynamic DC interference as defined in claim 4, wherein τ + The calculation method of (1) comprises the following steps:
calculating E in the positive half period off Maximum value E of (2) max+ ；
Calculating E from the positive half period off Initial value E of (2) 0+ Change to E 1 The required time to obtain tau + The method comprises the steps of carrying out a first treatment on the surface of the Wherein E is 1 ＝E 0+ +0.63(E max+ -E 0+ )。
6. The device for measuring a capacitance time constant of a metal interface under dynamic DC interference as defined in claim 4, wherein τ - The calculation method of (1) comprises the following steps:
calculating E in the negative half period off Minimum value E of (2) min- ；
Calculating E from within the negative half period off Initial value E of (2) 0- Change to E 2 The required time to obtain tau - The method comprises the steps of carrying out a first treatment on the surface of the Wherein E is 2 ＝E min- +0.37(E 0- -E min- )。
7. The device for measuring a metal interface capacitance time constant under dynamic direct current interference according to claim 1, wherein the method for analyzing corrosion risk according to the relative magnitudes of the dynamic direct current power supply interference period T and the metal interface capacitance time constant τ comprises:
when T is less than or equal to tau, most of the current is charged and discharged through the metal interface capacitor, and the current is non-Faraday current; only a small part of current flows through the reaction resistor to cause corrosion, so that the corrosion risk is small;
when T > τ, most of the current flows through the interface reaction resistance, which is Faraday current, with a greater risk of corrosion.
8. The device for measuring a metal interface capacitance time constant under dynamic direct current interference according to claim 1, wherein the measurement period has a duration of 13h, t=1h, t 1 ＝130s，T 2 ＝1s，a＝64。
9. The device for measuring the capacitance time constant of a metal interface under dynamic direct current interference according to claim 1, wherein the metal sample is a cylindrical shape with a diameter of 11.3mm and a length of 5mm and is processed by an X70 pipeline steel pipe, and the working surface is 1cm in area 2 The back surface of the metal plate is electrically connected with a copper wire, and the density of current flowing out of the surface of the metal sample is 10mA/cm 2 。
10. A method of measuring a metal interface capacitance time constant using the apparatus of claim 1, comprising the steps of:
the dynamic direct current power supply outputs interference signals according to a set interference period and a set positive-negative voltage width ratio, and experimental current flowing into and out of a metal sample is provided; the circuit breaker works according to the set on-off period and the on-off ratio;
in the measuring period, the data recorder collects the energizing potential E of the metal sample when the breaker is switched on and off in real time according to a set period on And a power-off potential E off ；
E for a plurality of dynamic DC power supply interference periods in a measurement period off Integrating to obtain E in a dynamic DC power supply interference period off And calculating a metal interface capacitance time constant based on the curve.
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