CN101144790A - All-solid reference electrode for monitoring steel bar corrosion of concrete and its preparation method - Google Patents

Abstract

The invention provides a full-solid-state reference electrode used for reinforcing steel rust monitoring in concrete and the preparation method. The reference electrode adopts an Ag/AgCl/KClsat system, and consists of an Ag and AgCl layer with 99.99 percent purity, a ter-component porous layer and a cement slurry layer in sequence from the axle center of the reference electrode to the outside. The invention makes a full consideration to the particularity that the rebar corrosion monitoring in concrete requires a reference electrode with a long life and a stable electric potential, and adopts the inexpensive Ag/AgCl/KClsat system to prepare a novel full-solid-state long life reference electrode (ASSRE), and the disadvantages that the service life of the common liquid state reference electrode is short, and the intensity is low are overcome by adopting the ter-component porous structure; simultaneously because the cement slurry with a similar characteristic with the concrete is adopted to be as the outermost layer, the liquid-junction potential between the liquid state reference electrode used commonly and the concrete medium is eliminated, and the accuracy of the electrochemistry measurement is ensured.

Description

Rust of Rebar in Concrete all-solid reference electrode for monitoring and preparation method thereof

(1) technical field

What the present invention relates to is the Rust of Rebar in Concrete all-solid reference electrode for monitoring.Be the core component-all-solid-state reference electrode (ASSRE) that adopts in the designed sensor of electrochemical method monitoring steel bar corrosion concretely.

(2) background technology

The steel bar corrosion that studies show that in past is one of reason that causes steel and concrete structure damage and initial failure, the whole world has dropped into a large amount of expenses to the maintenance and repair and the replacing member of corrosion structure, and the monitoring of steel bar corrosion is the important component part of monitoring structural health conditions and life-cycle design in civil engineering work.

Under the concrete environment, because concrete poriness, moisture and oxygen can be along hole and crackle migrations, and this is the necessary condition of corrosions of steel such as mild carbon steel and high strength alloy steel just.It is in these holes because the hydration process of cement has formed the oxyhydroxide of calcium, sodium and the potassium of high concentration that reason for corrosion does not take place under most of situations, thereby kept pH value between 12-13, this high basicity environment is the steel passivation, forms the quick corrosion that fine and close γ type iron oxide has prevented steel.Yet work as Cl ^-(can from deicer salts or seawater) assembles or because CO at rebar surface through concrete surface ₂The effect of (from atmosphere, also being one of key factor that causes global warming) makes under the situation of hole solution pH value reduction, and passivating film is destroyed, and concrete lost efficacy to the protective effect of reinforcing bar, at O ₂And H ₂Under the situation of O abundance reinforcing steel area reduce or occur the erosion point.

Most metal erosion processes belongs to electrochemical reaction process (except that high-temperature oxidation process) in the civil engineering work in essence.So electrochemical method becomes the most essential method of steel corrosion in the monitoring of structures.Researcher both domestic and external in the last few years adopts electrochemical method under laboratory conditions the corrosion science problem to be carried out a large amount of research, research by stable state and transient state electrochemical method, not only can obtain such as corrosion electric current density, the such basic parameter of corrosion rate, can also learn the more detailed information that discloses the corrosion electrochemistry process, as generating process of polarization resistance, electric double layer capacitance, diffusion process, spot corrosion or the like.The measurement of these parameters can provide foundation more reliably for corrosion monitoring.

Electrochemical method is the most essential method that discloses the corrosion science problem, yet adopt the electrochemical method research etching problem overwhelming majority to be in the past to carry out under the laboratory conditions, how electrochemical method being applied to actual engineering became in recent years the focus of research both at home and abroad.Undoubtedly the galvanochemistry granting is ripe and reliably in principle, and at concrete engineering how framework sensor and acquisition system, building application platform for electrochemical method is the concrete technical matters that actual engineering will solve.

The electrochemical process that the Applied Electrochemistry method takes place above-mentioned reinforcement corrosion carries out long term monitoring needs the stable contrast electrode of current potential, for corrosion monitoring contrast electrode must possess stable, to the chemical reaction of xoncrete structure and temperature-insensitive, can be under less polarization by faint electric current, have characteristics such as smaller hysteresis effect, long-life, environmental protection.Prepared contrast electrode in a large amount of research of past because serviceable life is limited, effects limit such as cost an arm and a leg its in actual application in engineering.Since the liquid contrast electrode of Ag/AgCl in the past considerable time inherent electrochemical field obtained using widely, its stability and price all are better than other contrast electrode, so this paper to studying based on the contrast electrode of Ag/AgCl system, has prepared new all-solid-state reference electrode (ASSRE).

Advantages such as designed all-solid-state reference electrode service life is long, cheap will make in its corrosion that can be widely used in reinforcing bar in the electrochemical method monitoring concrete, provide powerful guarantee for solving the design of monitoring structural health conditions and life-cycle.

(3) summary of the invention

The object of the present invention is to provide a kind of have long-life, stable performance and cheap Rust of Rebar in Concrete all-solid reference electrode for monitoring and preparation method thereof.

Product structure of the present invention is: adopt the Ag/AgCl/KClsat system, outwards being followed successively by purity by the axle center from contrast electrode is that 99.99% Ag, AgCl layer, three component porous layers and grout layer constitute.

Product of the present invention also has some technical characterictics like this:

1, wherein three component porous layers are that mass ratio is KCI: Al ₂O ₃: PTFE=1: O.5～2: porous structure O.5～2.

The preparation method of product of the present invention is: at first adopt the direct chlorination method to form the AgCl layer on Ag silk surface; With the surface is that the Ag silk of AgCl layer is put into mould, and the mass ratio that adds premix in mould is KCI: Al ₂O ₃: PTFE=1: O.5～2: Al2O3 O.5～2, KCl and PTFE three components, extrusion forming; Ag/AgCl/ three component layers of forming are put into other mould, in mould, add cement paste, place the demoulding after 24 hours; Last welding lead adopts epoxy sealing.

The preparation method of product of the present invention can also comprise some technical characterictics like this:

1, adopt the direct chlorination method on the Ag silk, to prepare AgCl;

2, the AgCl powder of adding and KCl equal quality in three components.

According to the Nemst equation as can be known,

$E=E_{\mathrm{AgCllAg}}^0\frac{2.303\mathrm{RT}}{\mathrm{nF}}-\lg \left[{\mathrm{Cl}}^{-}\right]$

Here

It is equilibrium potential; N is a quantivalency; F is the Faraday constant; T is a temperature; [Cf ^-] be cl ^-Concentration.When T is 25 ℃,

E=0.224-0.0592lg[c ^-]

Work as Cl ^-When reaching capacity, it is stable that electrode potential E keeps.As seen work as cl ^-Behind the porous structure by ASSRE, reach capacity on the Ag/AgCl surface, the ASSRE current potential reaches stable.

The solubleness of AgCl is very little, but absolute insoluble material is non-existent, and the design period of building structure is very long, the life-span of ASSRE can not be shorter than the serviceable life of structure like this, thereby can realize life-cycle monitoring, in the long like this time, though the lip-deep AgCl solubleness of Ag/AgCl is very little to steel bar corrosion in the structure, but in the total military service phase, because excessive Cl ^-The appearance that causes Complex effect, thereby AgCl dissolving is quickened, further have influence on the stability of ASSRE.Excessive Cl ^-Influence to AgCl solubleness sees Table 1.According to table as can be known, as excessive Cl ^-When concentration was not more than 3.9E-3mol/L, common-ion effcet reduced the solubleness of AgCl, thereby prolonged the serviceable life of ASSRE; As excessive Cl ^-When concentration surpassed 3.9E-3mol/L, Complex effect worked, Ag ⁺Form

Deng complex ion, thereby the solubleness of AgCl is increased, further make bad stability even the inefficacy of ASSRE.But the Cl in the concrete environment ^-Can't artificially control, it is decided by corrosion environment, therefore for the service life that increases ASSRE must increase the AgCl powder in the component that constitutes, makes its balance Cl ^-Complex effect, thereby prolong serviceable life of ASSRE.

The excessive Cl of table 1 ^-The time AgCl changes in solubility

The present invention is to provide all solid state ginseng long-life contrast electrode (ASSRE) of Applied Electrochemistry method monitoring Rust of Rebar in Concrete institute palpus.This contrast electrode adopts the Ag/AgCl/KClsat system, outwards is followed successively by purity from the axle center of contrast electrode and is 99.99% AG, AgCl layer, three component porous layers and grout layer and constitute, and wherein three component porous layers are that mass ratio is KCl: Al ₂O ₃: PTFE=1: O.5～2: porous structure O.5～2.The present invention takes into full account Rust of Rebar in Concrete and monitors singularity such as required contrast electrode long-life, current potential be stable, adopt cheap Ag/AgCl/KClsat system to prepare a kind of novel all solid state long-life contrast electrode (ASSRE), adopt three component porous structures to overcome the shortcoming that the ordinary liquid contrast electrode life-span is short, intensity is low; Simultaneously owing to adopt grout with the concrete feature similarity, thereby eliminated the liquid junction potential between liquid contrast electrode of common usefulness and the concrete medium, for the accuracy of electrochemical measurement provides assurance as outermost layer.All-solid-state reference electrode is that electrochemical method has set up bridge in the Rust of Rebar in Concrete Application in Monitoring, has broad application prospects.

(4) description of drawings

Fig. 1 is the structural representation of embodiment of the present invention;

Fig. 2 is preparation flow figure of the present invention.

(5) embodiment

For example the present invention is done more detailed description below in conjunction with accompanying drawing:

In conjunction with Fig. 1, present embodiment Rust of Rebar in Concrete all-solid reference electrode for monitoring adopts the Ag/AgCl/KClsat system, and outwards being followed successively by purity by the axle center from contrast electrode is that 99.99% Ag silk, AgCl layer, three component porous layers 3 and grout layer 4 constitute.

In conjunction with Fig. 2, the preparation method is:

1. be that 1mm, purity are that direct chlorination prepares the AgCl layer on 99.99% the Ag silk at diameter, forming the surface is the Ag silk 2 of AgCl layer.Concrete preparation method and flow process are as follows:

(1) gets the Ag silk of lmm diameter, remove surface masses, meter area with No. 600 abrasive paper for metallograph;

(2) clean the Ag silk with acetone soln, remove surface and oil contaminant;

(3) after water cleans, the Ag silk is put into 5%HNO ₃Remove oxide on surface in the solution about 1min;

(4) adopt ultrasonic cleaning after, with the Ag silk as anode, graphite as negative electrode in the HCl of 0.1mol/L solution with anodic current density DA=0.1A/dm ²Carry out electrolysis, time 60min makes AgCl electrode (surface is lavender).Distilled water cleans, and is placed in the 0.1mol/LKCl solution and soaks, and is stand-by.

2.ASSRE the preparation of core three component conductive layers

With KCl:Al ₂O ₃: PTFE=1: it is premix 1h. wherein KCl, Al in the premix machine of 120rad/min that the compound of 1: 0.5 (mass ratio) is placed on rotating speed ₂O ₃It is pure to be analysis.With the mould of packing into of the powder behind the premix, wherein prepared surface is the axis part that the Ag silk of AgCl layer is placed on mould in the step 1, by pressing machine with premix compacting (resulting pressure is 5MPa).At last the ASSRE core for preparing is taken out standby (if think further to prolong the serviceable life of contrast electrode, can add the AgCl powder with the KCl equal quality).

3. the preparation of cement paste layer

Adopt and identical this layer of cement production of institute's used concrete of monitoring of structures.Cement wherein: water=1: 0.6 (mass ratio).Adopt mortar mixer stirring at low speed cement paste 10min.The cement paste for preparing is injected in the mould earlier, then the ASSRE core for preparing in the step 2 is inserted into gently in the cement paste in the mould, and then in mould, inject an amount of cement paste, and suitably vibration, thereby make and be full of grout in the mould, lid with die tip compresses at last, and putting into humidity is 100%, and temperature is form removal behind 25 ℃ the fog room maintenance 24h.It must be noted that and guarantee the smooth of mould therefor inwall in step 2 and the step 3, otherwise can cause demoulding difficulty.

4. the welding of lead and epoxy sealing thereof

To reveal the Ag silk through the ASSRE termination of step 3 preparation adopts sand papering to light.Adopt the scolding tin welding lead then.ASSRE is inserted 10mm in the sealing mould therefor (thermoplastic tube of internal diameter 10mm, height 20mm) gently with 5 one sections in lead, in mould, inject thermoplastic epoxy 1 at last.Place 3d.

After tested, the prepared current potential of all-solid-state reference electrode ASSRE in concrete is-20mv (vs.SCE).Stable, long-lived, cheap all-solid-state reference electrode is that electrochemical method has set up bridge in the Rust of Rebar in Concrete Application in Monitoring, has broad application prospects.

Claims (5)

1. Rust of Rebar in Concrete all-solid reference electrode for monitoring, it is characterized in that: adopt the Ag/AgCl/KClsat system, outwards being followed successively by purity by the axle center from contrast electrode is that 99.99% Ag, AgCl layer, three component porous layers and grout layer constitute.

2. Rust of Rebar in Concrete all-solid reference electrode for monitoring according to claim 1 is characterized in that: wherein three component porous layers are that mass ratio is KCl: Al ₂O ₃: PTFE=1: 0.5～2: 0.5～2 porous structure.

3. the preparation method of a Rust of Rebar in Concrete all-solid reference electrode for monitoring is characterized in that: at first form the AgCl layer on Ag silk surface; With the surface is that the Ag silk of AgCl layer is put into mould, and the mass ratio that adds premix in mould is KCl: Al ₂O ₃: PTFE=1: 0.5～2: 0.5～2 Al ₂O ₃, KCl and PTFE three components, extrusion forming; Ag/AgCl/ three component layers of forming are put into other mould, in mould, add cement paste, place the demoulding after 24 hours; Last welding lead adopts epoxy sealing.

4. the preparation method of Rust of Rebar in Concrete all-solid reference electrode for monitoring according to claim 3 is characterized in that: adopt the direct chlorination method to prepare AgCl on the Ag silk.

5. according to the preparation method of claim 3 or 4 described Rust of Rebar in Concrete all-solid reference electrode for monitoring, it is characterized in that: in three components, add AgCl powder with the KCl equal quality.

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