CN1011545B - Measuring method of differential polarization resistance and measuring apparatus - Google Patents
Measuring method of differential polarization resistance and measuring apparatusInfo
- Publication number
- CN1011545B CN1011545B CN 86105493 CN86105493A CN1011545B CN 1011545 B CN1011545 B CN 1011545B CN 86105493 CN86105493 CN 86105493 CN 86105493 A CN86105493 A CN 86105493A CN 1011545 B CN1011545 B CN 1011545B
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- China
- Prior art keywords
- circuit
- differential
- polarization resistance
- polarization
- electrode
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Abstract
The present invention provides a method for measuring the polarization resistance of a corrosion system, which is characterized in that small amplitude value linear polarization scanning is carried out to electrodes, and the polarization resistance is obtained through the measurement of current differential value at corrosion potential positions. The present invention also provides a differential polarization resistance measurement instrument for realizing the measurement method, which is composed of a linear potential scanning signal circuit, a constant-potential circuit, a differential circuit, a filtering amplification circuit, a differential electric current sample holding circuit and a corrosion potential track holding circuit. The method for measuring the differential polarization resistance and the measurement instrument provided by the present invention overcomes the defects of the existing linear polarization measurement technique, and can enhance measurement speed.
Description
The invention belongs to the decay resistance of test material and determine the technical field of corrosion speed or analysis of material corrosion resisting property by the polarization resistance of test corrosion system.A kind of method and instrument of measuring the polarization resistance monitoring corrosion speed of metal erosion system promptly is provided.
The polarization resistance technology all has a wide range of applications in corrosion research and commercial production, by measurement to the polarization resistance of metal erosion system, and the corrosion speed of analysis of metallic materials in medium quantitatively, the corrosion situation of the monitoring equipment of industrial product.Usually popular employing square-wave potential method is measured near corrosion electrification certainly " Linear Polarization Resistance " (being designated hereinafter simply as linear polarization technique) as polarization resistance in corrosion electrochemistry.Can prove, not only theoretical error is unconquerable to measure polarization resistance with above-mentioned linear polarization technique, and consider from measuring technology enforcement aspect, also can run into some problems, the size of measuring the theoretical error comprised as (1) linear polarization depends on the polarization property of polarised direction and measured system.Yet concerning a practical systems to be measured, remove non-exhaustive its polarization behavior of inquiring into, otherwise can't determine the theoretical error size that measurement result comprises; (2) though in measuring polarization value △ E littler, theoretical error is also little, △ E reduces to make because corrosion potential (to call Ecorr in the following text) changes the reading error that causes increases; (3) speed of linear polarization survey measurements and frequency are selected all can influence measurement result, because reading is too fast, it is stable that electrode does not reach, and reading is slow excessively, and above-mentioned Ecorr changes the error that is caused and then can increase in measurement.
Purpose of the present invention is exactly the aging method that will give up with linear polarization technique, proposes a kind of new method of differential Polarization technique, fundamentally overcomes above-mentioned shortcoming.Polarization resistance measuring method provided by the present invention is characterized in that electrode is carried out the polarization of small magnitude linear potential, tries to achieve polarization resistance by the current differential value of measuring the corrosion potential place.Adopt the differential Polarization technique to measure polarization resistance, owing to be based on the slope of measuring polarization curve Ecorr place, rather than, polarization curve obtains polarization resistance by being treated to straight line, so not only can eliminate theoretical error, in addition, owing to utilize the differential method to eliminate the influence of double-deck charging current, can also improve measuring speed.
The proposition of differential polarization resistance measuring method of the present invention, based on following theoretical analysis: for a corrosion system to be measured, if contrast electrode can be ignored to the solution resistance Rs between the research electrode, or is compensated, then the equivalent electrical circuit of this system can be represented with Fig. 1.(Cd is used for simulated dual-layer electric capacity among Fig. 1, and Zf is used for the faraday impedance of simulation electrode)
Now to the research electrode polarization, electrode polarization is changed by linear rule, even polarization of electrode signal E(t)=Kt(wherein K be the sweep velocity constant, t is a time variable), then polarization current I=Inf+If(wherein Inf be double-deck charging current, be non-faraday electric current, If is an electrode reaction current, i.e. the faraday electric current).
If the potential change scope is little during polarization (be generally ± 10mv), can think that the double-layer capacitance Cd of electrode is constant, thereby have:
Inf＝Cd·dE/dt （1）
When electrode potential changed, total polarization current was:
I＝Cd·dE/dt+If （2）
Since dE/dt=K, so formula (2) can be write as:
I＝K·Cd+If （3）
To time t differential, and the current differential value when only reading E=Ecorr can be got by formula (3) with formula (3):
（dI/dt）Ecorr＝（dIf/dE·dE/dt）Ecorr
＝ (K)/(Rp) （4）
Rp polarization resistance just wherein, it is directly represented at the slope at corrosion potential place by polarization curve, because the sweep velocity of current potential is given, so polarization resistance can be obtained at the differential value of corrosion potential place electric current by measurement.
This shows that differential polarization measurement method of the present invention has following advantage:
(1) adopts the differential polarization resistance to measure, can eliminate the theoretical error that causes owing to linear-apporximation;
(2) because measurement is the differential current value of getting the Ecorr place, therefore can near Ecorr, select a fixing polarization scan scope;
(3) utilize differential can eliminate of the influence of double-deck charging current, improve measuring speed measurement result.
The present invention also provides a kind of differential polarization resistance tester that is used to implement differential polarization resistance measuring method, and its structural principle as shown in Figure 2.
As seen from Figure 2, analyze from structural principle, differential polarization resistance tester provided by the present invention comprises following a few part: (I) linear polarization scanning signal generating circuit; (II) potentiostatic circuit; (III) differentiating circuit; (IV) filter amplification circuit; (V) differential current sampling hold circuit; (VI) corrosion potential track and hold circuit.
In Fig. 2, WE is that auxiliary electrode, RE are contrast electrode for research electrode, CE.The research polarization of electrode is controlled by potentiostatic circuit, the polarization scan signal is given by linear polarization scanning generation circuit, when the research electrode polarization, the electric current that flows through electrode is voltage signal output through the current-voltage transitions, amplify through filtering and make signal be increased to certain amplitude to deliver to differentiator introduction end, the parameter of the feedback resistance that differential signal output amplitude and sweep velocity, current-voltage are changed, filtering enlargement factor, differentiator and the character of system are all relevant.
The grab sampling of differential current is by controlling of sampling pulse control, and when linear polarization scanning signal zero passage, promptly polarization of electrode is at the Ecorr place, and the controlling of sampling pulsing circuit provides a sampling pulse, and digital watch is sampled to the differential current of differentiator output.
In the differential polarization resistance was measured, corrosion potential was given by the corrosion potential track and hold circuit, helps improving the accuracy and the measuring speed of measurement like this.
When actual corrosion system was measured, as described in principle, the solution Ohmage can have influence on measurement result.The compensation of solution Ohmage is adopted the method for voltage positive feedback, promptly on the output terminal of potentiostatic circuit, get a dividing potential drop and feed back to the potentiostatic circuit amplifier input terminal, it is suitable with the solution ohm voltage drop to regulate partial pressure value, just can compensate the influence of solution Ohmage.
By differential polarization resistance tester embodiment provided by the present invention shown in Fig. 3～9.Wherein Fig. 3 is differential polarization resistance tester machine line figure, and its six included main circuit is: the linear polarization scanning generation circuit that Fig. 4 provides; The potentiostatic circuit that Fig. 5 provides; The differentiating circuit that Fig. 6 provides; The filter amplification circuit that Fig. 7 provides; The differential current sampling hold circuit that Fig. 8 provides; The corrosion potential track and hold circuit that Fig. 9 provides.In the present embodiment, adopted some integrated operational amplifiers for making line construction compactness and miniaturization, and these integrated operational amplifiers are fully feasible as replacing with discrete component.
Each main circuit of just forming this differential polarization resistance tester below respectively is illustrated:
(I) linear polarization scanning signal circuit, it is by integrator (A
6), comparer (A
7), tracker (A
8) and comparer trigger circuit formation.
When starting K
3Trigger switch makes comparer (A
7) upset, integrator (A
6) begin the electric current that flows through integrating resistor is carried out integration, make its output terminal produce a linear rising signals, through B
3Dividing potential drop is by follower (A
8) output.This circuit function is for producing the linear polarization scanning signal that is used for electrode polarization.B
1Be trigger network.
(II) potentiostatic circuit, to the current potential between the research electrode (WE), potentiostatic circuit adopts anti-phase amplification constant potential principle in this tester in order to constant contrast electrode (RE), and it is by main amplifier (A
1), current-voltage converter (A
3) and voltage follower (A
2) and follower (A
5) constitute.(A wherein
1), (A
2), (A
3) constituting basic anti-phase amplifying type potentiostatic circuit, the electric current by the research electrode is directly through current-voltage converter A
3Be transformed into voltage signal.Compensation for the solution Ohmage is by (A
3) output terminal on setting-positive feedback bleeder circuit B
2Realize that the feedback signal of this circuit is by follower (A
5) feed back to main amplifier (A
1) input bring in.
(III) differentiating circuit, it is used for the current signal of electrode is carried out the differential processing.It is by operational amplifier (A
9) and resistance, capacitance network constitute, and be connected on the output terminal of filter amplification circuit, in order to suppress of the influence of Experiment in Erosive Electrochemistry high-frequency noises, at differential capacitance C differentiating circuit
0Small resistor R of preceding serial connection
1, and in backfeed loop adjunction C
1With R
0Parallel connection makes R
0C
1=R
1C
0Can carry out phase compensation.
(IV) filter amplification circuit in order further to reduce the influence of noise to differential, also can be set up a filter amplification circuit at the differentiating circuit front end, and it is a two wires quadravalence filtering circuit and inverting amplifier (A
15) constitute.Amplification is promptly by amplifier A
15Carry out, the current-voltage converter output terminal of its input end and potentiostat joins, output termination differentiating circuit.
(V) differential current sampling hold circuit, it is by comparer (A
14), field effect transistor 3DJ and digital voltmeter constitute, two control ends of the triggering sampling of digital voltmeter are connected with bushing (the D utmost point), the source electrode (the S utmost point) of field effect transistor respectively, the grid of field effect transistor (the G utmost point) then with comparer (A
14) output terminal joins.When corrosion potential is E=Ecorr, i.e. during linear signal scanning zero passage, the signal that the sampling maintenance of differential current is gathered has utilized the sampling of digital watch to keep function.Its principle of work as shown in Figure 8, sampling retentive control pulse is by comparer (A
14) produce (A in its input and the linear sweep signal circuit
6) output join, when the sweep signal zero passage, comparer (A
14) produce positive pulse, make field effect transistor 3DJ conducting, so digital watch is once sampled to differential current.
(VI) corrosion potential track and hold circuit in order to follow the tracks of corrosion potential automatically before measurement, keeps corrosion potential in measurement and imposes on the research electrode.Be provided with the corrosion potential track and hold circuit in instrument, as shown in Figure 9, it is by phase inverter (A
12), follower (A
4), follower (A
13) and the relay J formation.Its input end is contrast electrode (RE), output terminal and potentiostatic circuit amplifier (A
1) input end link to each other.By follower (A
4) output terminal obtains is corrosion potential, through phase inverter (A
12) anti-phase, through relay J again through holding circuit (A
13) be input to potentiostatic circuit to amplifier (A
1) input end, because relay J is in closure before measurement, in measurement, be in off-state, therefore can realize keeping of corrosion potential from motion tracking.
Differential polarization resistance tester component-assembled provided by the present invention and surface structure are shown in Figure 10,11.
In Figure 10, Figure 11, (1) potentiostatic circuit is prepared, working selecting switch; (2) digital watch is continuous, triggers the sampling selector switch; (3) linear polarization scanning signal enabling switch; (4) the linear polarization scanning signal is swept fast selector switch; (5) linear polarization scanning signal amplitude selector switch; (6) power light; (7) solution Ohmage compensation divider resistance; (8) power switch; (9) measure current potential, electric current, differential current selector switch; (10) current range selector switch; (11) digital watch; (12) the potentiostatic circuit master is put zeroing; (13) differential output zeroing; (14) potentiostatic circuit current-voltage conversion zeroing; (15) fuse; (16) attaching plug; (17) external research electrode WE, auxiliary electrode CE, contrast electrode RE plug.
When adopting differential polarization resistance tester provided by the present invention to carry out the polarization resistance measurement, elder generation's starting switch (1) makes the potentiostatic circuit duty, make switch (12) be in the single-point sampling location again, and make switch (10) be in measurement differential current position, press trigger switch (3) at last, so the linear polarization scanning circuit produces sweep signal and is applied on the research electrode WE by potentiostatic circuit, the electric current that flows through research electrode WE amplifies through filtering, arrive the digital voltmeter input end through differential, when the sweep signal zero passage, the differential current sampling keeps pulse to produce sampling pulse, and this moment, digital watch was carried out once sampling to differential current.So the i.e. value of (dI/dt) Ecorr is according to (4) formula Rp=K/(dI/dt) Ecorr just can draw the polarization resistance of the corrosion system of studying.
Claims (8)
1, a kind of method of measuring the corrosion system polarization resistance is characterized in that electrode is carried out small magnitude linear potential polarization scan, tries to achieve polarization resistance by measuring in the current differential value at corrosion potential place.
2, a kind of differential polarization resistance tester of implementing the described method of claim 1 that is exclusively used in is characterized in that it is by (I) linear polarization scanning signal circuit; (II) potentiostatic circuit; (III) differentiating circuit; (IV) filter amplification circuit; (V) differential current sampling hold circuit; (VI) corrosion potential follow the tracks of to keep current potential to form, and wherein potentiostatic circuit (II) is exported to filter amplification circuit (IV) and corrosion potential track and hold circuit (VI) simultaneously directly and study electrode WE, and auxiliary electrode CE is connected with contrast electrode RE; Linear polarization scanning signal generating circuit (I) and corrosion potential track and hold circuit (VI) are exported to potentiostatic circuit respectively.
3, by the described differential polarization resistance of claim 2 tester, it is characterized in that said linear polarization scanning signal circuit is by integrator (A
6), comparer (A
7), follower (A
8) and comparer trigger circuit formation.
4, by the described differential polarization resistance of claim 2 tester, it is characterized in that said potentiostatic circuit is by main amplifier (A
1), voltage follower (A
2), current-voltage converter (A
3) and follower (A
5) constitute.And at (A
3) output terminal establishes-positive feedback bleeder circuit (B
2), the feedback signal of this circuit is through follower (A
5) feed back to (A
1) input end.
5,, it is characterized in that said differentiating circuit is by amplifier (A by the described differential polarization resistance of claim 2 tester
9) and resistance, capacitance network constitute, its input end is connected on the filter amplification circuit output terminal.
6, by the described differential polarization resistance of claim 2 tester, it is characterized in that said filter amplification circuit is by a secondary 4 rank filtering circuits and inverting amplifier (A
15) constitute, the output terminal of the current-to-voltage convertor of its input end and potentiostatic circuit joins, output termination differentiating circuit input end.
7, by the described differential polarization resistance of claim 2 tester, it is characterized in that said differential current sampling hold circuit is by comparer (A
14), field effect transistor 3DJ and digital voltmeter constitute, two control ends of the triggering sampling of digital voltmeter are connected grid (the G utmost point) and comparer (A respectively with drain electrode (the D utmost point), the source electrode (the S utmost point) of field effect transistor 3DJ
14) output terminal joins.
8,, it is characterized in that said corrosion potential tracking, holding circuit are by inverting amplifier (A by the described differential polarization resistance of claim 2 tester
12), follower (A
4), follower (A
13) and the relay J formation, its input end is contrast electrode (BE), output terminal and potentiostatic circuit amplifier (A
1) input end links to each other.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 86105493 CN1011545B (en) | 1986-08-20 | 1986-08-20 | Measuring method of differential polarization resistance and measuring apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 86105493 CN1011545B (en) | 1986-08-20 | 1986-08-20 | Measuring method of differential polarization resistance and measuring apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN86105493A CN86105493A (en) | 1988-03-02 |
| CN1011545B true CN1011545B (en) | 1991-02-06 |
Family
ID=4802862
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 86105493 Expired CN1011545B (en) | 1986-08-20 | 1986-08-20 | Measuring method of differential polarization resistance and measuring apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1011545B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1037920C (en) * | 1992-01-30 | 1998-04-01 | 北京科技大学 | Corrosion monitor and monitoring method based on digital integration |
| CN100437085C (en) * | 2006-07-23 | 2008-11-26 | 中国船舶重工集团公司第七二五研究所 | Detector for steel bar corrosion in concrete |
| CN104535487A (en) * | 2015-01-13 | 2015-04-22 | 南京钢铁股份有限公司 | Electrochemical experiment method for continuously measuring polarization resistance of material |
| CN107918428B (en) * | 2017-11-02 | 2019-08-06 | 宁波大学 | A kind of quick scanning circuit for eliminating function with background current |
-
1986
- 1986-08-20 CN CN 86105493 patent/CN1011545B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| CN86105493A (en) | 1988-03-02 |
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