CN117686418A - Coupling probe, method and system for detecting instant and accumulated corrosion rate - Google Patents
Coupling probe, method and system for detecting instant and accumulated corrosion rate Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 38
- 238000010168 coupling process Methods 0.000 title claims abstract description 21
- 230000008878 coupling Effects 0.000 title claims abstract description 20
- 238000005859 coupling reaction Methods 0.000 title claims abstract description 20
- 238000001514 detection method Methods 0.000 claims abstract description 61
- 230000001186 cumulative effect Effects 0.000 claims abstract description 50
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 7
- 238000010521 absorption reaction Methods 0.000 claims description 7
- 229910002804 graphite Inorganic materials 0.000 claims description 7
- 239000010439 graphite Substances 0.000 claims description 7
- 239000012670 alkaline solution Substances 0.000 claims description 6
- 238000004090 dissolution Methods 0.000 claims description 6
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims description 6
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- 230000027756 respiratory electron transport chain Effects 0.000 claims 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 26
- 230000008859 change Effects 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 9
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- 238000010438 heat treatment Methods 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 238000009833 condensation Methods 0.000 description 3
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- 230000001360 synchronised effect Effects 0.000 description 3
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
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- 229910000041 hydrogen chloride Inorganic materials 0.000 description 2
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 2
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- G01N17/04—Corrosion probes
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- 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
- 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
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
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Abstract
The invention relates to a coupling probe, a method and a system for detecting instant and accumulated corrosion rates, and relates to the technical field of corrosion detection, wherein the coupling probe for detecting the instant and accumulated corrosion rates comprises a shell, a first electrode, a second electrode, a third electrode, a film resistor and a zero-resistance ammeter; the method for detecting the instant and the accumulated corrosion rates comprises the steps of detecting the instant corrosion rate and detecting the accumulated corrosion rate; the system for detecting the instantaneous and cumulative corrosion rates comprises a detection device, a temperature sensor, a pH sensor and a central processing unit. The invention can accurately detect the corrosion rate.
Description
Technical Field
The invention relates to the technical field of corrosion detection, in particular to a coupling probe, a coupling method and a coupling system for detecting instant and cumulative corrosion rates.
Background
When the vapor phase steam generated in the petrochemical device is lower than the dew point temperature, the steam condenses on the metal surface to form liquid water, and absorbs the acid gas in the environment to form an acid electrolyte film, so that the corrosion to the metal material is called dew point corrosion. The hydrochloric acid dew point corrosion is a dynamic change process, when the dew point continuously occurs, a condensed liquid film on the surface of the metal continuously forms and diffuses, the instant corrosion rate of the metal is increased, and as the condensed liquid film further forms acid droplets, and when the condensed liquid film drops under the influence of gravity, the instant corrosion rate of the metal is reduced. Meanwhile, because the hydrochloric acid dew point corrosion environment in the condensation pipeline is continuously changed (such as temperature change, corrosion medium change, flow state change and the like), the accumulated corrosion rate of the pipeline in a period of time also dynamically changes along with the change of the environment. The instant corrosion rate reflects the dynamic change process of dew point corrosion, and the speed of accumulated corrosion rate reflects the service life of the petrochemical device, so that the synchronous measurement of the instant corrosion rate and the accumulated corrosion rate is realized by adopting different methods, and the method has very important engineering significance for researching corrosion mechanism.
The traditional methods for measuring the hydrochloric acid dew point corrosion are mainly an in-situ weightlessness method and an ex-situ electrochemical method. In-situ weightlessness is a method of exposing a sample to the inside of a petrochemical apparatus, measuring its weight loss and estimating an average corrosion rate, which cannot obtain electrochemical parameters related to an instantaneous corrosion rate, and calculating the obtained average corrosion rate to deviate from an actual corrosion rate. The ectopic electrochemical method adopts hydrochloric acid solution to simulate the hydrochloric acid dew point environment, so that various traditional electrochemical measurements are realized, but single measurement time is long, the adsorption and the falling off of acid drops on the surface of the metal cannot be accurately reflected, and the dynamic dew point corrosion principle of the metal under the electrolyte film is not met.
Currently, detection probes based on electrochemical impedance principles and galvanic principles have been widely used to monitor corrosion of metals. When the electrochemical impedance probe is used for detecting the dew point corrosion process of hydrochloric acid, according to an electrochemical impedance principle, the impedance probe in a corrosion environment is in contact with a working electrode to generate electrochemical reaction, when the working electrode is subjected to tiny potential disturbance, the current density flowing through the working electrode is correspondingly changed, a Nyquist spectrogram is obtained by measuring the periodic change of the current caused by the potential disturbance and impedance data, a proper model is selected to fit the spectrogram, the polarization resistance is obtained by calculation, and then the instant corrosion rate is obtained by calculation through a Stern-Geary formula. The galvanic probe is usually formed by using two materials with different potentials as electrodes and coupling the electrodes through a Zero Resistance Ammeter (ZRA), when the galvanic probe is in a corrosion environment, the whole galvanic system and the corrosion environment form a complete current loop, the galvanic current between the two electrodes can be displayed through the zero resistance ammeter, and the galvanic current can be quantitatively converted into the corrosion rate of an anode, namely the accumulated corrosion rate through Faraday law.
According to the technical scheme, when the electrochemical impedance probe is used for detecting the corrosion rate, a spectrogram is required to be fitted by manually selecting a proper model, so that the polarization resistance and the instant corrosion rate are obtained through calculation, the measurement result is easy to deviate from the actual result, and the detection accuracy is low.
Disclosure of Invention
In order to be able to accurately detect corrosion rates, the present invention provides a coupled probe, method and system for detecting instantaneous and cumulative corrosion rates.
In a first aspect, the present invention provides a coupling probe for detecting instantaneous and cumulative corrosion rates, using the following technical scheme:
the utility model provides a detect coupling probe of instant and cumulative corrosion rate, includes casing, first electrode, second electrode, third electrode, sheet resistance, zero resistance ammeter, first switch and second switch, the one end of first electrode, second electrode and third electrode all sets up inside the casing, and the other end all exposes outside the casing, the material and the structure of first electrode and second electrode are the same, the electrode potential of third electrode is higher than the electrode potential of second electrode, when detecting instant corrosion rate, first electrode, first switch, sheet resistance, second electrode establish ties in proper order, when detecting cumulative corrosion rate, second electrode, zero resistance ammeter, second switch, third electrode establish ties in proper order.
By adopting the technical scheme, when the instant corrosion rate is detected, the first switch is closed, the second switch is opened, the first electrode, the film resistor and the second electrode in the probe and the acid liquid film on the surface of the probe form a circuit, the two electrodes are connected with each other through the acid liquid film and are provided with current to flow through, tiny sine alternating current disturbance is applied to the circuit, impedance values at high frequency and low frequency are measured respectively at angular frequency, the film resistor can be regarded as the resistance of the electrode because the resistance of the electrode and the resistance of a wire are negligible, and the charge transfer resistance and the interface capacitance of the two electrodes are the same because the materials and the structures of the two electrodes are the same, the equivalent circuit model is simplified, the impedance value calculation formulas corresponding to the high frequency and the low frequency are calculated respectively, and then the instant corrosion rate is calculated, the polarization resistance value is only related to the film resistance value, the high frequency impedance value and the low frequency impedance value, and the instant corrosion rate are calculated and obtained through direct calculation, therefore the instant corrosion rate can be accurately detected, compared with the electrochemical impedance probe used in the traditional test method, the electrochemical corrosion rate detection method has the advantages that the accuracy is improved by only through the high frequency and the low frequency impedance value, and the correlation error is not needed to be calculated, and the artificial error is calculated; when the accumulated corrosion rate is detected, the first switch is opened, the second switch is closed, a circuit is formed by the second electrode, the zero-resistance ammeter and the third electrode in the probe and the acid liquid film on the surface of the probe, continuous couple current is generated by the circuit, the second electrode is used as an anode to generate couple corrosion, and the mass of a substance dissolved on the second electrode is calculated, so that the accumulated corrosion rate is calculated.
Optionally, the first electrode, the second electrode and the third electrode are spaced within 2 mm of each other.
By adopting the technical scheme, when the distance between the electrodes is increased, the solution resistance between the electrodes is increased, the couple current density and the accumulated charge amount obtained by measurement are correspondingly reduced, the distance between the electrodes in the traditional detection probe is 3 mm, the accumulated corrosion rate obtained by measurement is about 0.5 times that of the hanging piece method, and the deviation is obvious, so that the distance between the electrodes is controlled within 2 mm by artificial preparation, the measurement error can be further reduced, and the detection accuracy is improved.
Optionally, the third electrode is a graphite electrode.
Through adopting above-mentioned technical scheme, galvanic probe wide application in monitoring atmospheric corrosion, generally select copper, silver as the cathode material, these two kinds of materials easily take place to oxidize, if it is used for measuring hydrochloric acid dew point corrosion, its self corrosion will increase, and the oxide layer that produces after the corrosion can keep apart electrode and corrosion environment, and then lead to the probe to become invalid, graphite electrode is because difficult corrosion in hydrochloric acid environment, and the cost is lower, can satisfy the long-time use of detecting probe, has improved the degree of accuracy of detection.
Optionally, the first electrode and the second electrode are carbon steel electrodes.
By adopting the technical scheme, the carbon steel material is a common material in the petrochemical device, the electrode is made of the carbon steel material, the hydrochloric acid dew point corrosion process can be more accurately monitored, further the electrochemical parameters related to corrosion are calculated, the detection result is close to the real result, the detection accuracy and reliability are improved, the graphite electrode and the carbon steel electrode form a galvanic couple pair, the cathode-anode reaction of the galvanic couple pair is closer to the actual corrosion condition of the carbon steel material, the potential difference between the two electrodes has an acceleration effect on the corrosion of the carbon steel electrode, the corrosion dynamics of the carbon steel electrode is met, and the detection accuracy is improved.
In a second aspect, the present invention provides a method for detecting instantaneous and cumulative corrosion rates, using the following technical scheme:
a method of detecting instantaneous and cumulative corrosion rates using a coupled probe for detecting instantaneous and cumulative corrosion rates as described in the first aspect, comprising the steps of detecting instantaneous corrosion rates and detecting cumulative corrosion rates:
detecting the instantaneous corrosion rate: the method comprises the steps of obtaining an impedance value, calculating polarization resistance and calculating an instant corrosion rate;
Obtaining an impedance value: the first electrode, the film resistor, the second electrode and the acidic liquid film on the surface of the probe form a first circuit, sinusoidal alternating current excitation potential is applied to the first circuit at a certain sampling frequency, and an impedance value is obtainedWhen the angular frequency of the excitation potential is at a high frequency, the recorded impedance value is +.>When the angular frequency of the excitation potential is at a low frequency, the recorded impedance value is +.>；
Calculating polarization resistance: according to the impedance value calculation formula of the first circuit
Calculating the polarization resistance, inFor the series connection of the thin film resistor in the probe, +.>For the solution resistance between the two electrodes, +.>For the charge transfer resistance at the interface between the two electrodes and the solution, < >>Is the imaginary unit of impedance +.>For the angular frequency of the excitation potential, +.>Interface capacitance for two electrode surfaces, +.>Is the capacitance of rust layer->For the resistance of the rust layer, when the angular frequency of the excitation potential is at high frequency, the +.>Approaching ++ ->Calculating to obtain->When the angular frequency of the excitation potential is at a low frequency,approaching zero->According to->And->Calculated->Polarization resistance is +.>；
Calculating the instantaneous corrosion rate: calculating the instant corrosion rate ofThe unit is->In the formula->For the average atomic mass of the second electrode material (+) >），/>For the number of electron transfer->Is a Stern constant->For Farad Li Changshu ()>），/>For the density of the electrode material (+)>）；
Detecting the cumulative corrosion rate: comprises a step of calculating dissolution quality and a step of calculating accumulated corrosion rate;
calculating the dissolution mass: the second electrode, the zero-resistance ammeter, the third electrode and the acidic liquid film on the surface of the probe form a second circuit, and the second circuit generates continuous couple currentThe mass of the dissolved substances in the process of galvanic corrosion of the second electrode isIn the formula->For the molar mass of the second electrode material (+)>），/>Is the valence number of the second electrode material, < ->Is Faraday constant (+)>），/>For galvanic current (")>），/>For detecting time (+)>）；
Calculating the cumulative corrosion rate: calculating an accumulated corrosion rate ofThe unit is->In the formula->Surface area for exposing the second electrode to the acidic solution (++>），/>For the density of the second electrode material (+)>）。
By adopting the technical scheme, the method can detectWhen the corrosion rate is high, the first electrode, the film resistor, the second electrode and the acid liquid film on the surface of the probe form a first circuit, the two electrodes are connected with each other through the acid liquid film, and current flows through the two electrodes, and a tiny sinusoidal alternating current disturbance is applied to the first circuit, so that the film resistor is caused by the negligible resistance of the electrodes and the negligible resistance of the wires The resistance of the electrodes can be considered as the resistance of the electrodes, and the materials and the structures of the two electrodes are the same, so that the charge transfer resistance and the interface capacitance of the two electrodes are the same, the equivalent circuit model is simplified, and the impedance value of the equivalent circuit is obtainedCalculation formula for measuring impedance value +.>And impedance value at low frequency +.>And calculating an impedance value calculation formula corresponding to the high frequency and the low frequency by formula +.>Calculating to obtain solution resistance->Will->Substituted +.>Is calculated byPolarization resistance for calculating corrosion rate of metal surface according to electrochemical impedance principle>Equivalent to->Therefore, the polarization resistance is +.>Further, by the corrosion rate calculation formula +.A.A. by the Stern-Geary formula>Calculating to obtain the instantaneous corrosion rate, setting the polarization resistance value to be equal to +>、/>And->Related to the value of (2) due to->And->The value of (2) can be directly measured and obtained, so that the polarization resistance value and the instant corrosion rate are directly calculated through a formula, the instant corrosion rate can be accurately detected, a model is not needed to be manually selected to fit a spectrogram, and the accuracy and the reliability of detection are improved; when the cumulative corrosion rate is detected, a second electrode, a zero-resistance ammeter, a third electrode and an acid liquid film on the surface of the probe form a second circuit, the second circuit generates continuous couple current, the second electrode is subjected to couple corrosion, and the cumulative corrosion rate is calculated by calculating the mass of a substance dissolved on the second electrode.
Optionally, the step of calculating the cumulative corrosion rate is further followed by the step of calculating the corrosion acceleration rate and the step of judging;
calculating the corrosion acceleration ratio: the average current density of the second circuit isThe unit is->Wherein->For detection time +.>The self-etching current density of the second electrode is +.>The unit is->The galvanic corrosion acceleration ratio is +.>；
Judging: if it isJudging that the second electrode is in normal corrosion state, if +.>And judging that the corrosion state of the second electrode is abnormal, and outputting a judging result.
By adopting the technical scheme, the second electrode and the third electrode form a pair of galvanic couple pairs, and the potential difference between the two electrodes plays a certain corrosion acceleration role on the second electrode, so that the corrosion condition of the anode, namely the second electrode, in the galvanic couple pairs needs to be evaluated, the ratio of the average current density generated between the second electrode and the third electrode to the self-corrosion current density of the second electrode is defined as the galvanic couple corrosion acceleration ratio, and when the galvanic couple corrosion acceleration ratio is less than or equal to 10%, namely the acceleration effect of the galvanic couple pair relative to the self-corrosion is less than or equal to 10%, the corrosion condition of the anode in the galvanic couple pairs and the natural corrosion condition of the anode can be considered to be basically the same, namely the measured galvanic couple current can reflect the actual corrosion condition of the second electrode in the environment, and the second electrode or the third electrode can be replaced in time as required, thereby being beneficial to improving the accuracy and reliability of detection.
Optionally, the sampling frequency in the step of obtaining the impedance value is 100KHz-1.0Hz.
By adopting the technical scheme, the electrode system in the traditional electrochemical impedance testing method has the time constant of the product of the interface capacitance and the charge transfer resistance, the value of the time constant is larger, the single corrosion rate test needs to be carried out within the frequency range of 100KHz-0.01Hz, the time required for the test is longer, usually tens of minutes, and compared with the traditional testing method, the calculation formula of the impedance value in the method can be converted into
Let->Then->As is known from the electrochemical impedance principle, the impedance model of the circuit corresponds to a time constant of +.>Due to->Therefore, the value of the time constant is relatively small, and the lower the value of the time constant is, the higher the low-frequency test frequency can be correspondingly increased, namely +.>Therefore, the method uses the sampling frequency of 100KHz-1.0Hz to test the single corrosion rate, so that the test result can be quickly obtained, the test time of the single corrosion rate can be shortened to tens of seconds, the detection speed is improved, the detection error is reduced, the instant corrosion rate can be accurately and quickly detected, and the detection accuracy is further improved Degree and reliability.
In a third aspect, the present invention provides a system for detecting instantaneous and cumulative corrosion rates, using the following technical scheme:
a system for detecting instantaneous and cumulative corrosion rates comprising a coupling probe for detecting instantaneous and cumulative corrosion rates as described in the first aspect, further comprising a test tank, a heater and an electrochemical workstation, wherein the test tank is disposed on the heater, an acidic medium is contained in the test tank, the housing is inserted into the test tank and is in sealed connection with the test tank, one end of the housing, which is close to the interior of the test tank, is positioned above the acidic medium, an auxiliary/reference electrode (CE/RE) end of the electrochemical workstation is connected between a first switch and a film resistor when detecting the instantaneous corrosion rates, a first research electrode (WE 1) end of the electrochemical workstation is connected between the film resistor and a second electrode, a first research electrode (WE 1) end of the electrochemical workstation is connected between the second electrode and a zero-resistance ammeter, and a second research electrode (WE 2) end of the electrochemical workstation is connected between the zero-resistance ammeter and a third electrode when detecting the cumulative corrosion rates.
By adopting the technical scheme, the probe shell is inserted above the test box, the lower ends of the electrodes are exposed above the acid medium, the probe shell is in sealing connection with the test box, when the instant corrosion rate is detected, the auxiliary/reference electrode (CE/RE) end of the electrochemical workstation is connected between the first switch and the film resistor, the first research electrode (WE 1) end of the electrochemical workstation is connected between the film resistor and the second electrode, the first switch is closed, the second switch is opened, the temperature of the acid medium in the test box is controlled through the heater, water and acid substances in the acid medium volatilize, so that the acid liquid film is formed on the surface of the probe by condensation, the electrode in the probe and the acid liquid film on the surface of the probe form a circuit, the electrochemical workstation applies tiny sinusoidal alternating current disturbance to the circuit, the impedance values at high frequency and low frequency are measured through the electrochemical workstation, and then the polarization resistance value and the instant corrosion rate are calculated, the electrochemical parameters related to corrosion can be accurately calculated through the impedance values at high frequency and low frequency, the model is not needed to be manually fitted any more, and the corrosion rate can be detected accurately and reliably; when the accumulated corrosion rate is detected, a first research electrode (WE 1) end of an electrochemical workstation is connected between a second electrode and a zero-resistance ammeter, a second research electrode (WE 2) end of the electrochemical workstation is connected between the zero-resistance ammeter and a third electrode, the first switch is opened, the second switch is closed, the second electrode, the third electrode, the zero-resistance ammeter and an acid liquid film on the surface of a probe form a circuit, the circuit generates continuous couple current, the second electrode is subjected to couple corrosion, the mass of a substance dissolved by the second electrode is calculated, and the accumulated corrosion rate is calculated.
Optionally, the device further comprises an exhaust gas absorption assembly for absorbing acid gas, the exhaust gas absorption assembly comprises an exhaust gas pipe and an exhaust gas bottle, alkaline solution is filled in the exhaust gas bottle, one end of the exhaust gas pipe is communicated with the inside of the test box, and the other end of the exhaust gas pipe stretches into the position below the liquid level of the alkaline solution in the exhaust gas bottle.
Through adopting above-mentioned technical scheme, at the in-process that the heater heated acidic medium, water and acid substance in the acidic medium volatilize in a large number, form acid gas, acid gas gets into in the gas cylinder through the exhaust pipe, neutralizes with alkaline solution, has reduced the influence of the excessive accumulation of acid gas to testing result accuracy, has reduced harm to the tester simultaneously, has improved security and the reliability of using.
Optionally, the device further comprises a temperature sensor, a pH sensor and a central processing unit, wherein the temperature sensor and the pH sensor are arranged at the upper end of the test box and are positioned above the acidic medium, and the heater, the electrochemical workstation, the temperature sensor and the pH sensor are all in electrical signal connection with the central processing unit.
By adopting the technical scheme, the central processing unit sets the detected parameters such as the total detection duration, the detection temperature and the like, and after the setting is completed, the central processing unit transmits signals to the electrochemical workstation and the heater so as to detect under the condition of the corresponding parameters; in the detection process, acid steam is formed above the test box, the pH sensor detects the pH of the acid steam and transmits signals to the central processing unit, and the central processing unit records the pH change during detection in real time, so that a tester can conveniently adjust the detection progress in time according to the current pH; the temperature sensor detects the temperature of acid steam, and when temperature sensor detected that the temperature was too low or too high, temperature sensor gave central processing unit with signal transmission, and central processing unit gives the heater with signal transmission, and control heater heats or stops heating, so sets up, can accurately detect instant corrosion rate, has improved the degree of automation of detection.
In summary, the present invention includes at least one of the following beneficial technical effects:
1. by detecting the setting of the coupling probe of the instant and cumulative corrosion rate, the electrochemical parameters related to corrosion can be accurately calculated only through the impedance values of two points in the high-frequency area and the low-frequency area, and the fitting of a model to a spectrogram is not needed to be selected manually, so that the accuracy and the reliability of detection are improved; the probe can switch the detection state according to the need, is convenient for synchronously detecting the instant corrosion rate and the accumulated corrosion rate, does not need to be provided with a plurality of probes or a plurality of sets of detection devices for detection, and improves the rapidness and convenience of detection.
2. By setting the method for detecting the instantaneous and cumulative corrosion rate, the polarization resistance value is only equal to that of、/>And->Related to the value of (2) due to->And->The value of (2) can be directly measured and obtained, so that the polarization resistance value and the instant corrosion rate can be directly calculated through a formula, the instant corrosion rate can be accurately detected, a model is not needed to be manually selected to fit a spectrogram, and the accuracy and the reliability of detection are improved.
3. Setting up a system for detecting the instant and cumulative corrosion rate, setting up detected parameters such as total detection duration, detection temperature and the like through a central processing unit, and transmitting signals to an electrochemical workstation and a heater by the central processing unit after the setting is completed, so as to detect under the condition of corresponding parameters; the pH sensor detects the pH value of the acid steam and transmits signals to the central processing unit, the temperature sensor detects the temperature of the acid steam and transmits signals to the central processing unit, and the central processing unit controls the heater to heat or stop heating, so that the device can accurately detect the instant corrosion rate, and the automatic degree of detection is improved.
Drawings
FIG. 1 is a schematic view showing the overall structure of embodiment 1 of the present invention;
FIG. 2 is a schematic diagram of the internal circuit structure of embodiment 1 of the present invention;
FIG. 3 is a flow chart of embodiment 2 of the present invention;
fig. 4 is an equivalent circuit diagram of embodiment 2 of the present invention;
FIG. 5 is a schematic view showing the structure of embodiment 3 of the present invention;
FIG. 6 is a schematic diagram showing the connection of the probe body to the electrochemical workstation according to embodiment 3 of the present invention.
Reference numerals: 1. a probe body; 11. a housing; 12. a first electrode; 13. a second electrode; 14. a third electrode; 15. a thin film resistor; 16. zero resistance ammeter; 17. a first switch; 18. a second switch; 2. a system body; 21. a test box; 22. a heater; 23. an electrochemical workstation; 24. an exhaust gas absorption assembly; 241. an exhaust pipe; 242. a waste gas bottle; 25. a temperature sensor; 26. a pH sensor; 27. and a central processing unit.
Detailed Description
The present invention is described in further detail below in conjunction with fig. 1-6.
Example 1: the embodiment discloses a coupling probe for detecting an instant corrosion rate and an accumulated corrosion rate, referring to fig. 1-2, the coupling probe comprises a shell 11, a first electrode 12, a second electrode 13, a third electrode 14, a film resistor 15, a zero-resistance ammeter 16, a first switch 17 and a second switch 18, one ends of the first electrode 12, the second electrode 13 and the third electrode 14 are all connected inside the shell 11 in a sealing manner, the other ends of the first electrode 12, the second electrode 13 and the third electrode 14 are all exposed outside the shell 11, the distance between the first electrode 12, the second electrode 13 and the third electrode 14 is 1 millimeter, the materials and structures of the first electrode 12 and the second electrode 13 are the same, the electrode potential of the third electrode 14 is higher than the electrode potential of the second electrode 13, and when the instant corrosion rate is detected, the first electrode 12, the first switch 17, the film resistor 15 and the second electrode 13 are sequentially connected in series, and when the accumulated corrosion rate is detected, the second electrode 13, the zero-resistance ammeter 16, the second switch 18 and the third electrode 14 are sequentially connected in series.
In this embodiment, the first electrode 12 and the second electrode 13 are carbon steel electrodes, the third electrode 14 is a graphite electrode, in other embodiments, the first electrode 12 and the second electrode 13 may be copper electrodes and nickel electrodes, and the third electrode 14 may be a titanium electrode and a gold foil electrode.
The implementation principle of the coupling probe for detecting the instantaneous and cumulative corrosion rates in the embodiment is as follows:
when the instant corrosion rate is detected, the first switch 17 is closed, the second switch 18 is opened, the first electrode 12, the film resistor 15 and the second electrode 13 in the probe and the acid liquid film on the surface of the probe form a circuit, sinusoidal alternating current disturbance is applied to the circuit, impedance values at high frequency and low frequency are respectively measured, the resistance of the electrode and the resistance of the lead are negligible, so the film resistor 15 can be regarded as the resistance of the electrode, the charge transfer resistance and the interface capacitance of the two electrodes are the same because the materials and the structures of the two electrodes are the same, the impedance value calculation formulas corresponding to the high frequency and the low frequency in the equivalent circuit are respectively calculated, the instant corrosion rate is further calculated, the polarization resistance value is only related to the film resistor 15 value, the high frequency impedance value and the low frequency impedance value, the polarization resistance value is further calculated, and the instant corrosion rate is further obtained, therefore, the instant corrosion rate can be accurately detected, the manual selection model is not needed for carrying out spectrogram detection, the accuracy and the reliability are improved, and the detection error is reduced;
When the accumulated corrosion rate is detected, the first switch 17 is opened, the second switch 18 is closed, the second electrode 13, the zero-resistance ammeter 16 and the third electrode 14 in the probe and the acid liquid film on the surface of the probe form a circuit, the circuit generates continuous couple current, the second electrode 13 is subjected to couple corrosion, the mass of the dissolved substance of the second electrode 13 is calculated, and then the accumulated corrosion rate is calculated, so that the detection state can be switched according to the requirement, the synchronous detection of the instant corrosion rate and the accumulated corrosion rate is convenient, a plurality of probes or a plurality of detection systems are not required to be installed for detection, and the rapidity and the convenience of detection are improved;
when the distance between the electrodes is increased, the solution resistance between the electrodes is increased, the couple current density and the accumulated charge amount obtained by measurement are correspondingly reduced, and the measurement error can be further reduced by controlling the distance between the electrodes to be 1 millimeter through artificial preparation;
copper and silver are usually selected as cathode materials for the galvanic probe, oxidation is easy to occur, if the galvanic probe is used for measuring the dew point corrosion of hydrochloric acid, the corrosion of the galvanic probe is increased, an oxide layer generated after the corrosion can isolate an electrode from a corrosion environment, so that the probe is invalid, and the graphite electrode is not easy to corrode in the hydrochloric acid environment, has lower cost and can meet the long-time use requirement of the detection probe;
The carbon steel material is a common material in petrochemical devices, and the electrode is made of the carbon steel material, so that the hydrochloric acid dew point corrosion process can be more accurately monitored, further, electrochemical parameters related to corrosion are calculated, the detection result is close to the real result, the accuracy and reliability of detection are improved, the graphite electrode and the carbon steel electrode form a galvanic couple pair, the cathode-anode reaction of the galvanic couple pair is closer to the actual corrosion condition of the carbon steel material, and the corrosion dynamics of the carbon steel is met.
Example 2: the embodiment discloses a method for detecting the instantaneous and cumulative corrosion rates, which is to apply the coupling probe for detecting the instantaneous and cumulative corrosion rates described in the embodiment 1, referring to fig. 3-4, and comprises a step S1 for detecting the instantaneous corrosion rate and a step S2 for detecting the cumulative corrosion rate;
s1: detecting the instantaneous corrosion rate: the method comprises a step S11 of obtaining an impedance value, a step S12 of calculating polarization resistance and a step S13 of calculating an instantaneous corrosion rate;
s11: obtaining an impedance value: the first electrode, the film resistor, the second electrode and the acidic liquid film on the surface of the probe form a first circuit, sinusoidal alternating current excitation potential is applied to the first circuit at a certain sampling frequency, and an impedance value is obtainedWhen the angular frequency of the excitation potential is at a high frequency, the recorded impedance value is +. >When the angular frequency of the excitation potential is at a low frequency, the recorded impedance value isThe sampling frequency in this embodiment is 100KHz-1.0Hz;
s12: calculating polarization resistance: according to the impedance value calculation formula of the first circuit
Calculating the polarization resistance, inFor the series connection of the thin film resistor in the probe, +.>Is the resistance of the solution between the two electrodes,for the charge transfer resistance at the interface between the two electrodes and the solution, < >>Is the imaginary unit of impedance +.>For the angular frequency of the excitation potential, +.>Interface capacitance for two electrode surfaces, +.>Is the capacitance of rust layer->For the resistance of the rust layer, when the angular frequency of the excitation potential is at high frequency, the +.>Approaching ++ ->Calculating to obtain->When the angular frequency of the excitation potential is at a low frequency, and (2)>Approaching zero->According to->And->Calculated->Polarization resistance is +.>；
S13: calculating the instantaneous corrosion rate: to instant corrosionCalculating the speed, namely, the instant corrosion speed isThe unit is->In the formula->For the average atomic mass of the second electrode material (+)>），/>For the number of electron transfer->Is a Stern constant->For Farad Li Changshu ()>），/>For the density of the electrode material (+)>）；
S2: detecting the cumulative corrosion rate: comprises a dissolution quality calculating step S21, a cumulative corrosion rate calculating step S22, a corrosion acceleration rate calculating step S23 and a judging step S24;
S21: calculating the dissolution mass: the second electrode, the zero-resistance ammeter, the third electrode and the acidic liquid film on the surface of the probe form a second circuit, and the second circuit generates continuous couple currentThe mass of the dissolved substances in the galvanic corrosion of the second electrode is +.>In the formula->For the molar mass of the second electrode material (+)>），/>Is the valence number of the second electrode material, < ->Is Faraday constant (+)>），/>For galvanic current (")>），/>For detecting time (+)>）；
S22: calculating the cumulative corrosion rate: calculating an accumulated corrosion rate ofThe unit is->In the formula->Surface area for exposing the second electrode above the acidic medium (+.>），For the density of the second electrode material (+)>）。
S23: calculating the corrosion acceleration ratio: the average current density of the second circuit isThe unit is->Wherein->For detection time +.>The self-etching current density of the second electrode is +.>In units ofThe galvanic corrosion acceleration ratio is +.>；
S24: judging: if it isJudging that the second electrode is in normal corrosion state, if +.>And judging that the corrosion state of the second electrode is abnormal, and outputting a judging result.
The implementation principle of the method for detecting the instantaneous and cumulative corrosion rate in the embodiment is as follows:
When the instant corrosion rate is detected, a first circuit is formed by a first electrode, a film resistor, a second electrode and an acid liquid film on the surface of the probe, and the acid liquid film passes through the two electrodesA current is connected to flow through the first circuit, and a tiny sinusoidal alternating current disturbance is applied to the first circuit, so that the resistance of the electrode and the resistance of the lead wire are negligible, and the film resistance is thereforeThe resistance of the electrodes can be considered as the resistance of the electrodes, and the materials and the structures of the two electrodes are the same, so that the charge transfer resistance and the interface capacitance of the two electrodes are the same, the equivalent circuit model is simplified, and the impedance value of the equivalent circuit is obtained>Calculation formula for measuring impedance value +.>And impedance value at low frequency +.>And calculating an impedance value calculation formula corresponding to the high frequency and the low frequency by formula +.>Calculating to obtain solution resistance->Will->Substituted +.>Calculated in (1)>Polarization resistance for calculating corrosion rate of metal surface according to electrochemical impedance principle>Equivalent to->Therefore, the polarization resistance isFurther, the corrosion rate calculation formula obtained by the Stern-Geary formulaCalculating to obtain the instantaneous corrosion rate, setting the polarization resistance value to be equal to +>、/>And->Related to the value of (2) due to- >And->The value of (2) can be directly measured and obtained, so that the polarization resistance value and the instant corrosion rate are directly calculated through a formula, the instant corrosion rate can be accurately detected, a model is not needed to be manually selected to fit a spectrogram, and the accuracy and the reliability of detection are improved;
when the accumulated corrosion rate is detected, a second electrode, a zero-resistance ammeter, a third electrode and an acid liquid film on the surface of the probe form a second circuit, the second circuit generates continuous couple current, the second electrode is subjected to couple corrosion, the mass of a substance dissolved by the second electrode is calculated, and then the accumulated corrosion rate is calculated, so that the probe can switch the detection state according to the requirement, synchronous detection of the instant corrosion rate and the accumulated corrosion rate is facilitated, a plurality of probes or a plurality of detection systems are not required to be installed for detection, and the rapidness and convenience of detection are improved;
the second electrode and the third electrode form a pair of galvanic couple pairs, and the potential difference between the two electrodes plays a certain corrosion acceleration role on the second electrode, so that the corrosion condition of the anode, namely the second electrode, in the galvanic couple pairs needs to be evaluated, the ratio of the average current density generated between the second electrode and the third electrode to the self-corrosion current density of the second electrode is defined as the galvanic couple corrosion acceleration ratio, when the galvanic couple corrosion acceleration ratio is less than or equal to 10%, namely the acceleration effect of the galvanic couple pair relative to the self-corrosion is less than or equal to 10%, the corrosion condition of the anode in the galvanic couple pairs and the natural corrosion condition of the anode can be considered to be basically the same, namely the measured galvanic couple current can reflect the actual corrosion condition of the second electrode in the environment, and the second electrode or the third electrode can be replaced in time as required;
The electrode system in the traditional electrochemical impedance test method has the advantages that the time constant is the product of interface capacitance and charge transfer resistance, the value of the time constant is larger, the test of single corrosion rate is required to be carried out within the frequency range of 100KHz-0.01Hz, the test time is longer, usually more than ten minutes, and compared with the traditional test method, the calculation formula of the impedance value in the method can be converted intoLet->Then->As is known from the electrochemical impedance principle, the impedance model of the circuit corresponds to a time constant of +.>Due to->Therefore, the value of the time constant is relatively small, and the lower the value of the time constant is, the higher the low-frequency test frequency can be correspondingly increased, namely +.>Therefore, the method uses the sampling frequency of 100KHz-1.0Hz to test the single corrosion rate, so that the test result can be quickly obtained, the test time of the single corrosion rate can be shortened to tens of seconds, the detection speed is improved, the detection error is reduced, and the instant corrosion can be accurately and quickly detectedEtch rate.
Example 3: the embodiment discloses a system for detecting the instantaneous and cumulative corrosion rate, referring to fig. 5-6, comprising a coupling probe for detecting the instantaneous and cumulative corrosion rate according to embodiment 1, a test box 21, a heater 22, an electrochemical workstation 23, an exhaust gas absorption assembly 24, a temperature sensor 25, a pH sensor 26 and a central processing unit 27, wherein the test box 21 is arranged on the heater 22, an acidic medium is filled in the test box 21, the shell 11 is inserted into the test box 21 and is in sealing connection with the test box 21, one end of the shell 11 near the inside of the test box 21 is positioned above the acidic medium, an auxiliary/reference electrode (CE/RE) end of the electrochemical workstation 23 is connected between the first switch 17 and the membrane resistor 15 when detecting the instantaneous corrosion rate, a first research electrode (WE 1) end of the electrochemical workstation 23 is connected between the membrane resistor 15 and the second electrode 13, a first research electrode (WE 1) end of the electrochemical workstation 23 is connected between the second electrode 13 and the zero resistance ammeter 16, a second research electrode (WE 1) end of the electrochemical workstation 23 is connected between the second electrode 23 and the waste gas cylinder 24 and the waste gas sensor 12, an alkaline sensor end 242 is connected between the temperature sensor 22 and the waste gas sensor 22, the waste gas sensor 2 is connected between the waste gas sensor 2 and the waste gas sensor 24 and the waste gas sensor end 242, the waste gas sensor end of the electrochemical workstation 23 is connected between the waste gas sensor 22 and the waste gas sensor 22, and the waste gas sensor end 242 is connected between the waste gas sensor end 242 and the waste gas sensor end of the electrochemical workstation 23, and the waste gas sensor end is positioned in the vacuum sensor 22, and the waste gas sensor end is connected between the waste gas sensor end of the waste gas sensor 22 and the waste gas sensor 22, and the waste gas sensor end is in the vacuum sensor 11, and the waste gas sensor end is in the vacuum tank, and the vacuum, the temperature sensor 25 and the pH sensor 26 are electrically connected with the CPU 27.
The implementation principle of the system for detecting the instantaneous and cumulative corrosion rates of the embodiment is as follows:
setting detected parameters such as total detection duration, detection temperature and the like by the central processing unit 27, and after the setting is completed, transmitting signals to the electrochemical workstation 23 and the heater 22 by the central processing unit 27 so as to detect the parameters;
when the instant corrosion rate is detected, the shell 11 of the probe is inserted above the test box 21, the lower ends of the electrodes are exposed above an acid medium, the shell 11 is in sealed connection with the test box 21, an auxiliary/reference electrode (CE/RE) end of the electrochemical workstation 23 is connected between the first switch 17 and the thin film resistor 15, a first research electrode (WE 1) end of the electrochemical workstation 23 is connected between the thin film resistor 15 and the second electrode 13, the first switch 17 is closed, the second switch 18 is opened, the temperature of the acid medium in the test box 21 is controlled through the heater 22, water and hydrogen chloride in the acid medium volatilize, so that an acid liquid film is formed on the surface of the probe by condensation, the electrodes in the probe and the acid liquid film on the surface of the probe form a circuit, the electrochemical workstation 23 applies tiny sinusoidal alternating current disturbance to the circuit, and the impedance values at high frequency and low frequency are measured through the electrochemical workstation 23, the polarization resistance values and the instant corrosion rate are calculated, the parameters related to corrosion can be accurately calculated through the impedance values at the high frequency and the low frequency, the artificial corrosion rate can be detected, and the accuracy of the detection can be improved, and the accuracy of a spectrogram can be accurately fitted;
When the cumulative corrosion rate is detected, the first research electrode (WE 1) end of the electrochemical workstation 23 is connected between the second electrode 13 and the zero-resistance ammeter 16, the second research electrode (WE 2) end of the electrochemical workstation 23 is connected between the zero-resistance ammeter 16 and the third electrode 14, the first switch 17 is opened, the second switch 18 is closed, a circuit is formed by the second electrode 13, the third electrode 14, the zero-resistance ammeter 16 and an acid liquid film on the surface of a probe, the circuit generates continuous couple current, the second electrode 13 is subjected to couple corrosion, and the cumulative corrosion rate is calculated by calculating the mass of a substance dissolved by the second electrode 13;
in the process of heating the acid medium by the heater 22, a large amount of water and hydrogen chloride in the acid medium volatilize to form acid gas, the acid gas enters the waste gas bottle 242 through the waste gas pipe 241 and is neutralized with alkaline solution, so that the influence of excessive accumulation of the acid gas on the accuracy of a detection result is reduced, meanwhile, the harm to a tester is reduced, and the use safety and reliability are improved;
In the detection process, acid steam is formed above the test box 21, the pH sensor 26 detects the pH of the acid steam and transmits signals to the central processing unit 27, and the central processing unit 27 records the pH change during detection in real time, so that a tester can conveniently adjust the detection progress in time according to the current pH;
the temperature sensor 25 detects the temperature of acid steam, and when the temperature sensor 25 detects that the temperature is too low or too high, the temperature sensor 25 transmits signals to the central processing unit 27, the central processing unit 27 transmits signals to the heater 22, and the heater 22 is controlled to heat or stop heating.
The above embodiments are not intended to limit the scope of the present invention, so: all equivalent changes in structure, shape and principle of the invention should be covered in the scope of protection of the invention.
Claims (10)
1. A coupled probe for detecting instantaneous and cumulative corrosion rates, comprising: including casing (11), first electrode (12), second electrode (13), third electrode (14), sheet resistance (15), zero resistance ammeter (16), first switch (17) and second switch (18), the one end of first electrode (12), second electrode (13) and third electrode (14) all sets up inside casing (11), and the other end all exposes in casing (11) outside, the material and the structure of first electrode (12) and second electrode (13) are the same, the electrode potential of third electrode (14) is higher than the electrode potential of second electrode (13), when detecting instant corrosion rate, first electrode (12), first switch (17), sheet resistance (15), second electrode (13) establish ties in proper order, when detecting cumulative corrosion rate, second electrode (13), zero resistance ammeter (16), second switch (18), third electrode (14) establish ties in proper order.
2. A coupling probe for detecting instantaneous and cumulative corrosion rates according to claim 1, wherein: the first electrode (12), the second electrode (13) and the third electrode (14) are spaced within 2 mm.
3. A coupling probe for detecting instantaneous and cumulative corrosion rates according to claim 1, wherein: the third electrode (14) is a graphite electrode.
4. A coupling probe for detecting instantaneous and cumulative corrosion rates according to claim 1, wherein: the first electrode (12) and the second electrode (13) are carbon steel electrodes.
5. A method of detecting instantaneous and cumulative corrosion rates using a coupled probe for detecting corrosion rates according to any one of claims 1 to 4, comprising the steps of:
detecting the instantaneous corrosion rate: the method comprises the steps of obtaining an impedance value, calculating polarization resistance and calculating an instant corrosion rate;
obtaining an impedance value: the first electrode, the film resistor, the second electrode and the acidic liquid film on the surface of the probe form a first circuit, sinusoidal alternating current excitation potential is applied to the first circuit at a certain sampling frequency, and an impedance value is obtained When the angular frequency of the excitation potential is at a high frequency, the recorded impedance value is +.>When the angular frequency of the excitation potential is at a low frequency, the recorded impedance value is +.>；
Calculating polarization resistance: according to the impedance value calculation formula of the first circuit
Calculating polarization resistance, wherein->For the series connection of the thin film resistor in the probe, +.>For the solution resistance between the two electrodes, +.>For the charge transfer resistance at the interface between the two electrodes and the solution, < >>Is the imaginary unit of impedance +.>For the angular frequency of the excitation potential, +.>Interface capacitance for two electrode surfaces, +.>Is the capacitance of rust layer->For the resistance of the rust layer, when the angular frequency of the excitation potential is at a high frequency,approaching ++ ->Calculating to obtain->When the angular frequency of the excitation potential is at a low frequency,approaching zero->According to->And->Calculated->Polarization resistance is +.>；
Calculating the instantaneous corrosion rate: calculating the instant corrosion rate ofThe unit is->In the formula->For the average atomic mass of the second electrode material (+)>），/>In order to obtain the number of electron transfer,is a Stern constant->For Farad Li Changshu ()>），/>For the density of the electrode material (+)>）；
Detecting the cumulative corrosion rate: comprises a step of calculating dissolution quality and a step of calculating accumulated corrosion rate;
Calculating the dissolution mass: the second electrode, the zero-resistance ammeter, the third electrode and the acidic liquid film on the surface of the probe form a second circuit, and the second circuit generates continuous couple currentThe mass of the dissolved substances in the process of galvanic corrosion of the second electrode isIn the formula->For the molar mass of the second electrode material (+)>），/>Is the valence number of the second electrode material, < ->Is Faraday constant (+)>），/>For galvanic current (")>），/>For detecting time (+)>）；
Calculating the cumulative corrosion rate: calculating an accumulated corrosion rate ofThe unit is->In the formula->Surface area for exposing the second electrode above the acidic medium (+.>），/>For the density of the second electrode material (+)>）。
6. A method of detecting instantaneous and cumulative corrosion rates according to claim 5, wherein: the step of calculating the accumulated corrosion rate is further provided with a step of calculating the corrosion acceleration rate and a step of judging;
calculating the corrosion acceleration ratio: the average current density of the second circuit isThe unit is->Wherein->For detection time +.>The self-etching current density of the second electrode is +.>The unit is->The galvanic corrosion acceleration ratio is +.>；
Judging: if it isJudging that the second electrode is in normal corrosion state, if +. >And judging that the corrosion state of the second electrode is abnormal, and outputting a judging result.
7. A method of detecting instantaneous and cumulative corrosion rates according to claim 5, wherein: the sampling frequency in the step of obtaining the impedance value is 100KHz-1.0Hz.
8. A system for detecting instantaneous and cumulative corrosion rates, characterized by: a coupling probe comprising an immediate and cumulative corrosion rate detection as claimed in any one of claims 1 to 4, further comprising a test tank (21), a heater (22) and an electrochemical workstation (23), said test tank (21) being arranged on the heater (22), said test tank (21) being internally filled with an acidic medium, said housing (11) being inserted into the test tank (21) and being in sealing connection with the test tank (21), said housing (11) being located above the acidic medium at an end near the interior of the test tank (21), an auxiliary/reference electrode (CE/RE) end of the electrochemical workstation (23) being connected between the first switch (17) and the membrane resistor (15) when the immediate corrosion rate is detected, a first research electrode (WE 1) end of the electrochemical workstation (23) being connected between the membrane resistor (15) and the second electrode (13), a first research electrode (WE 1) end of the electrochemical workstation (23) being connected between the second electrode (13) and the zero-resistance ammeter (16), and a second research electrode (WE 1) end of the electrochemical workstation (23) being connected between the second electrode (2) and the zero-resistance ammeter (WE) when the cumulative corrosion rate is detected.
9. A system for detecting instantaneous and cumulative corrosion rates according to claim 8, wherein: the waste gas absorption device is characterized by further comprising a waste gas absorption assembly (24) for absorbing acid gas, wherein the waste gas absorption assembly (24) comprises a waste gas pipe (241) and a waste gas bottle (242), alkaline solution is filled in the waste gas bottle (242), one end of the waste gas pipe (241) is communicated with the inside of the test box (21), and the other end of the waste gas pipe extends into the position below the liquid level of the alkaline solution in the waste gas bottle (242).
10. A system for detecting instantaneous and cumulative corrosion rates according to claim 8, wherein: still include temperature sensor (25), pH sensor (26) and central processing unit (27), temperature sensor (25) and pH sensor (26) all set up in the upper end of test box (21), and are located acid medium top, heater (22), electrochemical workstation (23), temperature sensor (25) and pH sensor (26) all are connected with central processing unit (27) electrical signal.
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