CN100570348C - The comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics - Google Patents

Abstract

The present invention relates to a kind of comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics, at first adopt the mCRR transmission line model to fit within and satisfy the electrochemical impedance spectroscopy of measuring under causality, stability and the linear conditions, wherein m is a positive integer, and C and R represent pure electric capacity and pure resistance respectively; Then according to formula f ^*=1/ (2 π C _iR _i) obtain each C respectively _iAnd R _iThe characteristic frequency f of parallel branch ^*, and be made in discrete parameter C under the different series of studies conditions _iAnd R _iLogarithmic graph and R with the characteristic frequency change profile _oFigure with the study condition variation; At last, determine the difference of metal material surface characteristics according to the feature of figure.The present invention has utilized the rich of the sensitivity of electrochemical impedance spectroscopy and information, and objectivity of mCRR transmission line model, versatility etc., thereby objective, differentiated the difference between the metal material surface character under the different condition delicately.

Description

The comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics

[technical field]

The present invention relates to the comprehensive analysis method of electrochemical impedance spectrum of a kind of analysis metal material surface characteristics under the influence of different factors, thereby differentiate the difference of metal sample surface state, these different affecting factors comprise pretreatment condition, corrosion potential, dielectric concentration and composition, system temperature and sample soak time, and the difference of properties of sample comprises the dielectric properties of cleanliness, wetting state, corrosion activity, surface film oxide or pre-service film, the complete and compactness of film.

[background technology]

The surface property that needs the metal material of method synthesis evaluation easily and efficiently in many cases, for example change into each link of paper tinsel production procedure, the monitoring of metal material surface pretreating effect and quality and control in coating, welding or the electroplating industry, in the battery industry surface property of conductive plate and and active material between cohesive force, the screening of silane pretreatment metal optimum process condition and evaluation etc., and other research and development field relevant with metal material.

Do not lack at present the method for estimating metal material surface characteristics.Relevant macro approach has, and estimates surface wettability and can adopt wetting angle, estimates corrosion activity and can adopt polarization curve and surface observation etc.Relevant microscopic approach has: the distribution of microelectrode dynamic scan surface measurements current potential, ellipsometry (Ellipsometry) surface measurements film thickness, scanning electron microscope, Auger electron spectroscopy (Auger electronspectroscopy, AES) and atomic force microscope etc. can characterize microscopic appearance and variation thereof, utilize x-ray photoelectron spectroscopy (X-ray photoelectron spectroscopy, XPS), the chemical constitution and the variation thereof of method characterization of membrane such as fourier infrared conversion and reflection-absorption-infrared spectrum, or the like.

Though above-mentioned all multi-methods can provide the information of metal material surface characteristics from different perspectives, the defective that also exists some to remedy, the one, some large-scale instrument price is high-leveled and difficult to popularize; The 2nd, the preparation process complexity of some detection method sample, time-consuming, have destructiveness, be not easy to on-the-spot continuous monitoring surface property over time; The 3rd, a kind of method only can characterize a kind of performance usually, can not carry out the comprehensive evaluation of many performances; The 4th, the most important thing is electrochemical properties in the metal material surface characteristics, so the electrochemical Characterization method is the most basic characterizing method, can not replace with other method; The 5th, in electrochemical method, polarization curve etc. have destructiveness to sample, and the disturbing signal form is single, are difficult to separate diffusion influence, thereby the information that can provide is limited, and are not suitable for estimating metal surface film, wetting state etc.

Electrochemical impedance spectroscopy can be in corrosion system the variation of continuously monitoring metal material surface state, measuring condition is simple, be easy to get, do not have destructive, and can estimate the key property of macro surface such as wetting state (passing through interface capacitance), corrosion resistance simultaneously, provide the abundant information of relevant change mechanism, in characterizing metal material surface performance important potential advantages being arranged, is the important means of a very promising exosyndrome material surface property, receives the many concerns of domestic and international researcher.The most frequently used spectrum elucidation method is to adopt the equivalent-circuit model of fixed sturcture at present, and generally acknowledge the electrochemical reaction resistance that to use equivalent resistance element characterizing metal material surface, with the equivalent capacity element characterize related properties such as its surface electric double layer or surface film thickness, voidage, specific inductive capacity and, can adopt the definition of plate condenser to describe this equivalent electric capacity: $C={\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_r\frac{A}{d}$ , ε wherein ₀Be permittivity of vacuum, ε _rBe relative dielectric constant, A is an electrode area, and d is the distance between the capacity plate antenna model pole plate.

Although can use equivalence element characterizing metal material surface performance, yet the method for determining these equivalence elements is not apparent, and spectral line can corresponding a plurality of equivalent-circuit models, obviously adopt different equivalent-circuit models to obtain different analysis results.In addition, multiple factors such as wettability of the surface, electrochemical activity, corrosion product are to the difference that influences of impedance component, cause the impedance spectrum pattern changeable, and one of foundation of setting up the fixed sturcture equivalent-circuit model is the impedance spectrum pattern, promptly according to the feature of concrete impedance spectrum, the physical significance of articulated system is determined suitable equivalent circuit structure and number of parameters, in the hope of satisfied fitting result can be arranged when physical significance is clearer and more definite.In the method, give each equivalence element certain physical meaning, and according to the variation appraisement system performance and the Changing Pattern thereof of component parameters.Because the impedance spectrum to different characteristic need be used the equivalent-circuit model match of different structure, thereby can not explain well that the system corresponding with the circuit structure sudden change changes pilot process.In addition, even if, also have quite a few impedance spectrum to be difficult to match according to the characteristic change equivalent circuit structure of impedance spectrum.Especially it is to be noted the CPE element that extensively adopts in equivalent-circuit model at present, though can obviously improve fitting precision, it is the element of a presentation after all, is a mathematics formula of setting up for the trial curve that coincide, its two parameter Y ₀More ambiguous with the n meaning, so far still among inquiring into, they are non-pure capacitive character, also non-pure resistance, it changes the numerical value directly influence other resistance and capacity cell in the equivalent-circuit model, obscure and covered the basic reason and the regularity of they variations to a certain extent, causing the gained parameter is the coefficient result of multiple influence factor, is not the actual conditions that can be studied system as desirable objective, the accurate reflection of analyst.Owing to can not fundamentally find and separate of the influence of various different factors to the impedance spectrum pattern, so the model of setting up is of all kinds, objectivity, regularity and the comparability of analysis result have directly been influenced, so that the relation between analytic parameter under the considerable situation and system performance is also indeterminate, cause the analytic parameter variation intersected with each other of different time, different systems, usually need 10 times difference just can compare, the gained result mostly is qualitative, in addition with the system performance tradeoff.The disadvantage of above fixed sturcture equivalent-circuit model has been covered electrochemical impedance spectroscopy abundant information, sensitive advantage on sizable degree, seriously hindered electrochemical impedance spectroscopy is applied to scientific research and commercial production reality as a kind of independently analytical technology.

In view of above reason, at present in changing into the commercial production relevant such as paper tinsel, battery, plating, metal pretreatment with metal material, lack in the on-the-spot technology that metal material surface characteristics changes that detects of following the tracks of of each process procedure, usually only can infer the whether suitable of process conditions according to the finished product after certain operation or half-finished quality, some crucial production links are lacked suitable adjustment foundation, have sizable blindness.And in the research and development process of relevant product,, also hindered the efficient and the definition of research and development owing to provide reliable details to suitable, objective, the sensitive evaluation means of variation shortage of metal surface wetting state and chemical property.

[summary of the invention]

In order to address the above problem, the present invention has set up a kind of comprehensive analysis method of electrochemical impedance spectrum that characterizes golden metal material surface characteristics, the present invention has utilized the rich of the sensitivity of electrochemical impedance spectroscopy and information, and the match of mCRR transmission line model, analyze objectivity, the versatility of impedance spectrum, thereby can be objective, consistent, the difference between the comprehensive characterization metal material surface character delicately, and be used for instructing produce actual; Can also be by changing measuring condition, amplify the difference between the electrochemical impedance spectroscopy of different samples, the sensitivity that improves analysis result.

The technical scheme that technical solution problem of the present invention is adopted is: a kind of comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics, at first adopt the mCRR transmission line model to fit within and satisfy the electrochemical impedance spectroscopy of measuring under causality, stability and the linear conditions, wherein m is a positive integer, and C and R represent pure electric capacity and pure resistance respectively; Then according to formula f ^*=1/ (2 π C _iR _i) obtain each C respectively _iAnd R _iThe characteristic frequency f of parallel branch ^*, and be made in discrete parameter C under the different series of studies conditions _iAnd R _iLogarithmic graph and R with the characteristic frequency change profile _oFigure with the study condition variation; At last, determine the difference of metal material surface characteristics according to the feature of figure.

Can determine to determine respectively the best m value of its transmission line model according to the relative error of match variance and element for the impedance spectrum of the metal material sample under the different condition.

For different samples, different time measured impedance spectrum, satisfying under the little situation of match variance and element relative error, best m value can be different.

Element R in the mCRR model of determining best m value _oNumerical value and each metal material sample surfaces corrosion resistance big or small consistent.

Make the discrete parameter C of mCRR transmission line model under the best m value condition _iAnd R _iWith characteristic frequency $f_i^{*}(f^{*}=1/\left(2\mathrm{\π}{C}_i{R}_i\right))$ The logarithmic curve that changes is according to the feature of logarithmic curve and variation characteristic characterizing metal surface state thereof.

For some specific system, after having determined best m value, compare the discrete parameter C of the transmission line model of m, m+1, the pairing different length of m-1 _iAnd R _iWith characteristic frequency f _i ^*The logarithmic curve that changes can find that corrosion system has not the certain characteristics discrete value that the length with transmission line model changes.

The number of this feature discrete value seldom even does not have in battery system, has reflected the difference of system internal characteristics.

The variation characteristic of described logarithmic curve comprises: (1) discrete elements value with the distribution value of characteristic frequency over time, (2) the discrete elements value is with the speed of characteristic frequency variation, (3) discrete elements is with the Changing Pattern of the extreme value of characteristic frequency distribution, the Changing Pattern of (4) discrete elements extreme value characteristic of correspondence frequency.

By the computer software that matches, can be according to the mCRR transmission line model is definite automatically and the best m value of the mCRR transmission line model that the impedance spectrum of different samples is corresponding, and automatically processing, match, analysis impedance spectrum data, provide the analysis result of metal material surface characteristics difference at last.

Theoretical foundation one of the present invention is: transmission line model is suitable for describing the transmission course of material, and mass transport process is prevalent in all electrochemical systems, thereby this model has universality to different electrochemical systems, can separate the influence of diffusion process under the various conditions, influence the factor difference of diffusion process in the announcement system simultaneously, for example the block of surface film and with relative size of electrochemical reaction resistance etc.

Theoretical foundation two of the present invention is: it is charge transfer resistance and the opposite result of diffusional resistance two polyphones process influence factor effect that extreme value appears in discrete elements, be charge transfer resistance more little (electrochemical reaction speed is big more), the importance of diffusional resistance is obvious more, thereby the characteristic frequency that the discrete elements extreme value occurs is high more, and vice versa.Thereby the discrete elements extreme value can reflect the relevant system critical nature of feature therewith with the characteristic of correspondence frequency

Theoretical foundation three of the present invention is: owing to only comprise univocal resistance of physics and capacity cell in the model, thereby the relation between the variation of its discrete parameter numerical value and the metal surface performance difference is clear and definite.

Theoretical foundation four of the present invention is: because the influence of roughness, the real surface of metal is long-pending to be an amount that is difficult to accurately measure and control, the difference of roughness can directly influence the numerical value of electric capacity and resistive component between the series of samples, but do not influence the product of resistance and electric capacity, thereby effect characteristics frequency not.So can not be subjected to the interference of roughness during with the characteristic frequency representation system, improve the definition and the regularity of analysis result.

Good effect of the present invention is: utilize the rich of the sensitivity of electrochemical impedance spectroscopy and information, and the match of mCRR transmission line model, analyze objectivity, the versatility of impedance spectrum, thereby difference objective, consistent, that exist between the comprehensive characterization metal material surface character delicately, and be used for instructing production actual, with regard to research impedance spectrum analytic method, also has important significance for theories simultaneously.

Before and after the important procedure in the metal material processing process, measure the variation of electrochemical impedance spectroscopy under its different condition, and according to mCRR transmission line model Fitting Analysis impedance spectrum data, best m value is determined in variation according to error of fitting (comprising total error and equivalence element relative error), and make all equivalence element numerical value in the mCRR transmission line model, make discrete parameter C _iAnd R _iWith characteristic frequency f ^*The logarithmic curve that changes, and R ₀Curve with the test condition variation.According to the variation characteristic of curvilinear motion characteristic evaluating metal material surface characteristics, as features relevant of wetting situation, clean-up performance and the surface film of metal material surface etc.; According to R ₀Estimate the corrosion activity of metal material surface etc.Can also resolve the also Changing Pattern between the analytical parameters with the computing machine Automatic Program, provide the authentic communication of measured metal material surface state, thereby play the effect of prediction, monitoring and evaluation technological process, for rationally adjusting process condition, control product quality provide reliable basis.

The present invention is applied in and changes into paper tinsel technology when beginning, to immerse in the suitable electrolyte solution through the pretreated foil samples of suitable surface earlier, under different condition, measure the variation of its impedance spectrum, the analysis-by-synthesis difference is criticized the differences between the metal material surface states then, for determining that the subsequent technique condition provides authentic communication.

Because impedance spectrum does not have destructiveness to sample, so can be used in the production line relevant the variation of monitoring metal material surface state with raw material metal.

The present invention is used for plating production process, can monitor and analyze the reason of quality problems such as plated item generation coating foaming.

The present invention is used for the R﹠D and production process of secondary cell, electrochemical activity that can the comprehensive evaluation battery grid, with the bonding state of surface reactive material, reactivity etc.

The present invention can also be used for the testing product quality, estimates, screens the top condition of metal material pretreating process process.

[accompanying drawing and description of drawings]

Fig. 1 is a mCRR transmission line model synoptic diagram of the present invention;

Fig. 2 is A ₃Steel sample soaks the impedance spectrum fitting result figure after 3 hours in 3% NaCl solution;

Fig. 3 and 4 is that electrochemical impedance spectroscopy comprehensive evaluation acetone of the present invention and water clean A ₃The instance graph of steel surface property influence;

Fig. 5 and 6 is that electrochemical impedance spectroscopy comprehensive evaluation silane aging temp of the present invention and time are to A ₃The instance graph of the influence of steel surface property;

Fig. 7 is silane hydrolyzate time effects pre-service A of the present invention ₃The instance graph of the discrete parameter extreme value institute character pair frequency of steel;

Fig. 8 is silane pretreatment A of the present invention ₃Steel influences the instance graph that discrete parameter extreme value characteristic of correspondence frequency changes with soak time;

Fig. 9 is silane pretreatment A of the present invention ₃Steel influences the instance graph that the discrete resistance minimum value changes with the sample soak time;

Figure 10 is the instance graph that density of corrosion inhibitor of the present invention influences mCRR transmission line model discrete resistance component minimum value and character pair frequency thereof;

Figure 11 is that concentration of electrolyte solutions of the present invention influences the instance graph (numerical value is electrolyte concentration in the legend, and unit is a mol) that mCRR transmission line model resistive component distributes;

Figure 12 is the instance graph (physical quantity in the legend is represented different overpotentials) that overpotential of the present invention influences mCRR transmission line model resistive component;

Figure 13-Figure 16 is of the present invention at different potential regions, with the difference of the electrode process that sample surfaces took place, the discrete electric capacity of CR transmission line model has the instance graph of diverse feature (being positioned at different characteristic frequency intervals simultaneously) with the variation of characteristic frequency.The pairing potential region feature of 4 width of cloth figure is respectively: the corresponding electrostatic double layer potential region of Figure 13, the film formed potential region of the corresponding oxidation of Figure 14, the potential region that the potential region of the corresponding oxide growth of Figure 15, the corresponding oxygen of Figure 16 are separated out.

Figure 17-Figure 20 is of the present invention at different potential regions, and with the difference of the electrode process that sample surfaces took place, the discrete resistance of CR transmission line model has diverse feature with the variation of characteristic frequency, is positioned at different characteristic frequency intervals simultaneously.The pairing potential region feature of 4 width of cloth figure is respectively: the corresponding electrostatic double layer potential region of Figure 17, the film formed potential region of the corresponding oxidation of Figure 18, the potential region that the potential region of the corresponding oxide growth of Figure 19, the corresponding oxygen of Figure 20 are separated out.

[embodiment]

The invention will be further described below in conjunction with example and accompanying drawing.

Fig. 1 is the equivalent-circuit model of match metal material electrochemical impedance spectroscopy of the present invention, and wherein C and R represent pure electric capacity and pure resistance respectively.With the discrete equivalence element in the different circuit branch among the subscript i difference figure, the polyphone branch of total m C and R.

Example 1, the present invention can be used for estimating the influence to metal surface wetting state and electrochemical activity of the medium that adopted on the clean metal surface and process conditions.For example, be stained with A after acetone is cleaned the sand paper rust cleaning with absorbent cotton ₃Steel, and in baking oven after different temperatures heats certain hour respectively, in exsiccator, be cooled to room temperature.Be immersed in then in the 3%NaCl aqueous solution, under open circuit potential, measure the impedance spectrum of different soak times immediately.Concrete measuring condition is: use Solartron 1280Z type galvanochemistry instrument, the disturbance amplitude is got 5mV, and frequency range is got 0.1Hz～10kHz, adopts stainless steel substrates as auxiliary electrode, uses saturated calomel electrode as contrast electrode, the about 12cm of apparent survey area ², with mCRR transmission line model fitting data.Fig. 2 is discrete parameter C _iWith characteristic frequency f ^*The legend that changes, as can be seen, near best m value, the length of transmission line does not influence C _iThe regularity of distribution, and at f ^*Low frequency range between, C _iStationary value is arranged (with C ^*Represent), and relevant with the wetting state of metal surface.The different heating temperature and time is to C ^*And R ₀Square root (t with soak time ^0.5) rule that changes sees Fig. 3 and Fig. 4, for relatively, gives sand paper rust cleaning back among the figure directly with the A that measures immediately behind tap water and the deionized water rinsing ₃The result of steel sample.

As shown in Figure 3, the C of all samples ^*Increase with soak time, and widely different between the different sample.Sample capacitance C after water directly washes ^*Maximum, scope is 1.5 * 10 ^-4～3 * 10 ^-4F.cm ^-2(pentagram).Acetone cleans the C of back sample ^*Minimum value about 5 * 10 ^-5F.cm ^-2, and increase (square) with the increase of heating-up temperature and time.Pass through again after if acetone cleans long period, higher temperature processing (as 160 ℃, 1h), its C ^*Numerical value illustrates that still less than (the following triangle) of water flushing sample acetone is difficult to eliminate to the influence of surface wettability.In addition, the C of all samples ^*All obviously increase with soak time, especially at the immersion initial stage, reason is that effects such as corrosion have reduced the acetone of surface attachment, and has increased the water wettability or the roughness of metal surface, causes C ^*Increase.Surface observation can see that also the color and luster of corrosion product appears in the part substrate surface, and open circuit potential is low more, and it is big more to present the area that corrodes color and luster.

Fig. 4 illustrates that the method for acetone cleaning is to A ₃Steel corrosion resistance (R ₀) influence not quite all samples R ₀Numerical value and variation tendency more concentrated, and all increase with soak time, this is the feature that the metallic substrates of no any protective effect is corroded.

Though the present invention to the sample analysis result value comparison under the different condition near (differing 5 times of less thaies each other), but the difference of the surface state that is reflected and the regularity of variation are very clear and definite, have reflected the influence of different cleaning methods to metal material surface wetting state and corrosion resistance.The sensitivity of the method is better than the equivalent-circuit model of other fixed sturcture, its simple micro-analysis method that then is better than large-scale instrument.

It is very big that example 2, the effect of silane pretreatment metal surface are influenced by process conditions, and wherein, accurately definite suitable aging temp and time has great importance, and now illustrates this method application in this regard.With the A after the acetone cleaning ₃Steel takes out the back room temperature and dries with the alcohol solution dipping 30～60 seconds that contains 1%KH-550, put into then baking oven under different condition, carry out timeliness (140 ℃, 0.5h, pentagram; 140 ℃, 1h, last triangle; 160 ℃, 1h, filled circles), in exsiccator, be cooled to room temperature at last.The measuring condition of impedance spectrum and data analysing method be with example 1,4 parallel sample of each conditioned measurement, and analysis result is seen Fig. 5 and Fig. 6.As seen the C of parallel sample ^*And R ₀It is more concentrated that parameter value distributes, different sample difference are obvious, illustrated that aging condition is obviously different to the influence of the wetting state of metal surface and corrosion resistance.This example explanation this method can be differentiated the influence of the less process conditions of difference to the metal surface state, and the result has higher sensitivity and reappearance, thereby has important use be worth in relevant product development and commercial production.

Example 3, the hydrolysising condition of silane is very big to the influence of metal material pretreating effect, the top condition that this example explanation this method can be used for estimating and screening silane hydrolyzate.Under identical pretreatment condition, act on A after getting the aqueous hydrolysis different time that contains 0.6%KH-550 ₃Variation (2.5% the Na of its impedance spectrum with soak time measured on the surface of steel ₂SO ₄Aqueous solution is a corrosive medium, room temperature, the impedance spectrum measuring condition is with example 2), resolve with this method then.Different hydrolysis times are to discrete elements extreme value character pair frequency (f ^* _Min) influence see Fig. 7 (soak 4 minutes then measure) in corrosive medium, dotted line represents not have the sample of silane treatment among the figure.As seen, the formed silane film of pretreating process has obviously influenced f ^* _MinNumerical value, and the explanation silane-water solution can stablize nearly 8 days.f ^* _MinFig. 8 is seen in variation with soak time, prolongs with soak time, and silane film is destroyed gradually, so f ^* _MinValue descends and gradually near result's (filled squares) of blank sample.The minimum value R of discrete resistance _{I, min}The decline (see figure 9) with the prolongation of soak time, this is the ruined important symbol of film, and does not have the R of pre-service blank sample (filled squares) _{I, min}Then be increase trend with the soak time prolongation, this is the key character that the metal material substrate is corroded.When the silane film (for example film forming in lean solution) of pre-service gained approaches (principle that silane pretreatment increases metal/coating interface cohesive force requires film), impedance spectrum pattern and blank sample are similar on complex plane, and increase the variation tendency unanimity with soak time, be that single arc on the complex plane and the mould value on the Bode figure all increase with soak time, illustrate that the corrosive attack of substrate covered the variation of film properties.And analyze with this method, influence that then can sepatation etching discloses the changing features of metal material surface silane film.

Example 4, this method can also be studied the mechanism of the corrosion inhibiter increase material surface corrosion resistance in the corrosive medium.For the mild carbon steel sample of 5%HCl corrosive medium, the variation of tannic acid concentration is to f ^* _MinAnd R _{I, min}Influence see Figure 10, as can be seen from the figure, f ^* _MinIncrease with tannic acid (as corrosion inhibiter) concentration is linear increase, and the mechanism of action that corrosion inhibiter is described is to have reduced the corrosion activity area, has increased the resistance of diffusion, thereby the influence of diffusional resistance just occurred at higher characteristic frequency region.Figure 10 also shows R _{I, min}Numerical value fluctuate with the increase of tannic acid concentration, the mechanism of action that corrosion inhibiter is described mainly is by the absorption increase corrosion resistance of tannic acid at material surface, and the stability of adsorption film is obviously not as reaction produced film (as the silane film of the formation of pre-service in example 3).

Example 5, this method can also be used to study the influence of electrolyte concentration.Under the room temperature, at different N a ₂SO ₄The partial results of the impedance spectrum analysis of Cu-65Ni alloy system is seen Figure 11 (numeral Na in the legend in the aqueous solution of concentration ₂SO ₄Concentration, unit is mol/L), wherein provided discrete resistance R _iVariation with characteristic frequency.As can be seen from the figure, increase with electrolyte concentration, with R _{I, min}The characteristic of correspondence frequency moves to high frequency direction, and mainly influences the R of HFS _i, and to the R of low frequency part _iNot influence.

Example 6, this method also can be used for studying the influence of bias potential to the metal material system.In the KOH of 6mol/L solution under the different bias potentials impedance spectrum analysis result of Co electrode system see Figure 12 (provided corresponding biased electrical place value in the legend, with respect to Hg/HgO, OH ^-1Contrast electrode), wherein provided discrete resistance R _iVariation with characteristic frequency.As can be seen from the figure, bias potential mainly influences the R of low frequency part _i, and to the R of HFS _iNot influence.And increase R with bias potential _{I, min}Increase gradually, its characteristic of correspondence frequency moves to high frequency direction simultaneously, and the increase with bias potential is described, the reactivity of Co electrode increases, the resistance of electrochemical reaction descends, and the resistance of mass transport process strengthens gradually, and its influence appears at more and more higher frequency range.

Example 7, this method also can be used for studying the bias potential interval different, the various process that metal material surface took place.Figure 13-Figure 20 has provided under different bias potentials, at pH 10, contains the H of 0.1mol/L ₃BO ₃The impedance spectrum analysis result of the In electrode system the in+NaOH solution.-1.25～-electrostatic double layer potential region C between the 1.20V _iAnd R _iFigure 13 and 17 are seen in distribution with characteristic frequency respectively;-1.15～-oxide film between the 0.90V forms potential region, C _iAnd R _iFigure 14 and 18 are seen in distribution with characteristic frequency respectively; Oxide growth potential region between-0.85～1.10V, C _iAnd R _iFigure 15 and 19 are seen in distribution with characteristic frequency respectively; Oxygen deposition potential interval between 1.20～1.60V, C _iAnd R _iFigure 16 and 20 are seen in distribution with characteristic frequency respectively.As can be seen, when the process of electrode surface not simultaneously, discrete elements C _iAnd R _iDistribution with characteristic frequency has diverse feature, thereby can infer that metal material shows the process of generation, and then infer its surface characteristics according to these features.

Above example explanation the present invention has multiple use, can be widely used in the multiple production field relevant with metal material.For example can fill up the blank that lacks suitable, sensitive method characterizing metal material surface feature in the production fields such as changing into paper tinsel, plating, battery; Can form active different metal of identical surface electrochemistry and the definite more suitably on-line monitoring of process choice standard, technological process combination and production run quality of alloy thereof in batches for difference, reduce the blindness of production run, under the condition that satisfies the certain specification product index, reduce production cost to greatest extent, enhance productivity.In addition, the method can also be used to estimate the metal material surface effects of pretreatment, screening and optimization pre-service prescription and technology.

In the process of implementing concrete technical scheme, following problem deserving of attention is arranged.

1, for different samples, different time measured impedance spectrum,, allow best m value to differ from one another satisfying under the comprehensive less situation of total error and element relative error.

Though 2 best m value differences can cause circuit discrete parameter number difference, also can't determine the one-to-one relationship between all discrete parameters and the certain electric chemical process at present, discrete parameter is with f ^*The rule that changes is simply clear and definite, and and the system surface property between clear and definite correlativity is arranged.

3, the present invention is owing to adopt the mCRR transmission line model match of structure unanimity to resolve relevant impedance spectrum data, thereby the subjectivity when having avoided determining that for the impedance spectrum of different characteristic the difficulty of different structure equivalent-circuit model and analyst set up model is disturbed, and has increased substantially the objectivity of analysis result.

4, can form and measuring condition by changing corrosive medium, amplify the difference between the metal material surface characteristics, to improve the sensitivity of analysis result.

5, can pass through supporting computer software, automatically processing, match, analysis impedance spectrum data, and provide the analysis result of metal material surface characteristics difference.

Claims (7)

1, a kind of comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics is characterized in that:

Analysis is under the influence of the factor that comprises pretreatment condition, corrosion potential, dielectric concentration and composition, system temperature and sample soak time, the comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics, thereby differentiate the difference of metal sample surface state, and the difference of properties of sample comprises the dielectric properties of cleanliness, wetting state, corrosion activity, surface film oxide or pre-service film, the complete and compactness of film;

At first adopt the mCRR transmission line model to fit within and satisfy the electrochemical impedance spectroscopy of measuring under causality, stability and the linear conditions, wherein m is a positive integer, and C and R represent pure electric capacity and pure resistance respectively; Then according to formula f*=1/ (2 π C _iR _i) obtain each C respectively _iAnd R _iThe characteristic frequency f* of parallel branch, and be made in discrete parameter C under the different series of studies conditions _iAnd R _iThe figure that changes with study condition with the logarithmic graph of characteristic frequency change profile and Ro; Make the discrete parameter C of mCRR transmission line model under the best m value condition _iAnd R _iWith characteristic frequency f _i* (f _i*=1/ (2 π C _iR _i)) logarithmic curve that changes, come the feature of characterizing metal surface state according to logarithmic curve and variation characteristics thereof; The variation characteristic of described logarithmic curve comprises: (1) discrete elements value with the distribution value of characteristic frequency over time, (2) the discrete elements value is with the speed of characteristic frequency variation, (3) discrete elements is with the Changing Pattern of characteristic frequency distribution value, the Changing Pattern of (4) discrete elements extreme value characteristic of correspondence frequency size; At last, determine the difference of metal material surface characteristics according to the feature of figure; Utilize the rich of the sensitivity of electrochemical impedance spectroscopy and information, and the match of mCRR transmission line model, analyze objectivity, the versatility of impedance spectrum, thereby difference objective, consistent, that exist between the comprehensive characterization metal material surface character delicately, and be applied to comprise and change into paper tinsel, battery, plating and the metal pretreatment production technology relevant with metal material.

2, the comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics as claimed in claim 1, it is characterized in that:, determine the best m value of its transmission line model respectively according to the relative error of match variance and element for the impedance spectrum of the metal material sample under the different condition.

3, the comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics as claimed in claim 1 or 2, it is characterized in that: for different samples, different time measured impedance spectrum, satisfying under the little situation of match variance and element relative error, best m value can be different.

4, the comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics as claimed in claim 1 or 2 is characterized in that: the numerical value of the element Ro in the mCRR model of determining best m value is big or small consistent with each metal material sample surfaces corrosion resistance.

5, the comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics as claimed in claim 1 or 2, it is characterized in that: for some specific system, after having determined best m value, compare the discrete parameter C of the transmission line model of m, m+1, the pairing different length of m-1 _iAnd R _iWith characteristic frequency f _i ^*The logarithmic curve that changes can find that corrosion system has not the certain characteristics discrete value that the length with transmission line model changes.

6, the comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics as claimed in claim 1 is characterized in that: the number of this feature discrete value seldom even does not have in battery system, has reflected the difference of system internal characteristics.

7, the comprehensive analysis method of electrochemical impedance spectrum of metal material surface characteristics as claimed in claim 1 or 2, it is characterized in that: by the computer software that matches, according to the mCRR transmission line model is definite automatically and the m value of the mCRR transmission line model that the impedance spectrum of different samples is corresponding, and automatically processing, match, analysis impedance spectrum data, provide the analysis result of metal material surface characteristics difference at last.

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