CN114062006A - On-site sampling and electrochemical corrosion test method for concrete surface anticorrosive material - Google Patents

Abstract

The invention provides a field sampling and electrochemical corrosion test method of a concrete surface anticorrosive material, which comprises the following steps: 1. selecting a sampling point: a. taking the side wall and the top of the sewage pool which is seriously corroded as a sampling position to be tested, and sampling the wall surface or the top of the side wall of the sewage pool; b. the surface of the sampling part is in an attached state and is flat without obvious holes and cracks; c. the sampling points are coated with a thickness of at least 500 μm; 2. cutting the surface coating and ensuring the complete surface structure of the coating sample; 3. polishing the back of the cut surface coating, removing the attached concrete and leaving a complete coating slice; adhering the coating slice to a metal back plate to prepare a tested electrode sample; 4. test solution was prepared as the test environment: 5. and carrying out electrochemical corrosion tests on the sample in different test solutions by using an electrochemical test platform, wherein the electrochemical corrosion tests at least comprise an open-circuit potential test, an alternating current impedance test, a potentiodynamic test and potentiodynamic cyclic polarization.

Description

On-site sampling and electrochemical corrosion test method for concrete surface anticorrosive material

Technical Field

The invention relates to a field sampling and electrochemical corrosion test method for a concrete surface anticorrosive paint.

Background

With the advance of urbanization, in order to meet the increasing sewage treatment demand, a new large-scale sewage treatment facility becomes a necessary choice. Compared with the prior art, the novel large-scale sewage treatment plant has higher sewage flow rate, and the organic matter concentration and the pollutant complexity in the sewage are relatively higher, so that the concrete structure is quickly corroded. However, the new large-scale sewage treatment plant enters a full-load or overload running state after being built, and the time for stopping production, maintenance and overhaul is difficult to adjust.

Therefore, it is the most common practice to extend the service life of concrete by applying an anticorrosive paint to the surface of the concrete. However, due to the harsh use environment, most of the anticorrosion paint for the concrete surface is damaged and fails before the expected service life is reached in the actual use process. Therefore, in the early development and model selection of the anticorrosive paint, the corrosion resistance of the anticorrosive paint is evaluated, and the method has important significance for the development of related products.

In the traditional evaluation means of the anti-corrosion coating, a salt spray test and an impressed current accelerated corrosion method are mainly adopted, the two methods are required to be carried out by coating anti-corrosion coating on a metal substrate for test, the method has deviation compared with the actual service environment, and most of the anti-corrosion coating which has good performance in the electrochemical corrosion test has the phenomena of bubbling, powdering, water seepage, falling off and the like before the service life in the actual service environment is reached. Therefore, in the selection and development of the anticorrosive paint, it is necessary to perform an anticorrosive test on a concrete substrate. In the case of performing an anticorrosion test with a concrete substrate, evaluation is generally performed by means of surface roughness, water absorption, color difference, mass loss, and the like, but there is a difference in characteristics between different materials, and it is difficult to perform quantitative evaluation by the above items.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the problems in the prior art, and provide a field sampling and electrochemical corrosion test method of an organic anticorrosive coating for concrete, which can accurately know the change of the corrosion resistance of the material in the actual service environment.

The technical problem to be solved can be implemented by the following means.

A field sampling and electrochemical corrosion test method for a concrete surface anticorrosive material is characterized by comprising the following steps:

(1) carrying out on-site investigation and selecting sampling points by combining with the actual service environment, wherein the selection rule is as follows:

1) selecting a part with serious corrosion in actual service as a sampling position to be tested, and at least comprising a group of side wall surfaces or tops of the sewage pool as the sampling position to be tested;

2) under the normal condition, the corrosion damage amplitude of the side wall of the sewage pool is distributed longitudinally, and point positions with different heights from a waterline can be selected for carrying out grouping sampling and measurement;

3) the method is suitable for organic inert coatings (epoxy, polyurea and the like) and is not suitable for permeable crystallization coatings and concrete modified admixtures; the surface of the sample keeps an adhesion state, is approximately flat and has no obvious holes and cracks;

4) the test method has certain requirements on the thickness, and the sampling points are required to be coated with a film with the thickness of 500 mu m at least;

(2) cutting the surface coating by using a cutting tool, wherein the method comprises the following steps:

1) cutting the outline on the surface of the sampling coating by using a conventional cutter at the point position with relatively low adhesive force, scraping the sample and sampling; sampling the point positions with relatively strong adhesive force by using a handheld cutting machine;

2) the integrity of the surface structure of the coating sample is ensured as much as possible when sampling, at least the area of 10mm x 10mm is ensured.

(3) Polishing the back of the cut coating, removing a concrete structure attached to the back of the coating, only leaving a complete coating slice, and adhering the coating slice to a metal back plate to prepare a tested electrode sample;

(4) preparing at least one group of salt solutions, one group of acid solutions, one group of alkali solutions and one group of strengthened sewage solutions as test environments for carrying out subsequent electrochemical tests;

(5) testing by using an electrochemical test platform, and using a coating slice adhered metal back plate as a working electrode, a saturated calomel electrode/saturated KCl electrode as a reference electrode and a platinum electrode as an auxiliary electrode to build a three-electrode system;

(6) and carrying out electrochemical corrosion tests on the sample in different test solutions, wherein the tests comprise an open circuit potential test (OPC), an alternating current impedance test (EIS), a potentiodynamic Test (TAF), potentiodynamic cyclic polarization and the like.

In the step (1), in the field sampling, the selected point position is corroded and damaged to a certain degree and can be kept completely attached, and for the coating which is obviously peeled off and has obvious damage, the anticorrosive material is considered to be invalid, and the conditions of sampling and electrochemical detection are not met.

Preferably, in the field sampling in the step (1), the sampling in the same sewage pool at least comprises a group of side wall surfaces or top parts of the sewage pool, and the sampling area of a single sewage pool is not less than 3. When the side wall is sampled, at least 3 groups are longitudinally distributed, and at least one group covers the waterline change area.

As a further improvement of the technology, in the sample preparation of the sampled coating in the step (3), the back surface of the coating needs to be polished, so that the surface of the coating has no visible concrete adhesion to avoid the influence of the concrete on the test, the thickness of the coating part is ensured to be uniform as much as possible in the polishing process, and the obtained sample wafer is not less than 10mm multiplied by 10 mm.

When grinding is carried out, wet grinding is carried out by using equipment as much as possible so as to avoid the influence of high temperature generated in the grinding process on the material performance.

After a sample of the coated sheet was taken, the sheet was adhered to a stainless steel metal sheet of the same size using conductive adhesive and edge sealed with an inert material to serve as the working electrode in a three electrode system.

As a further improvement of the technology, the test solution prepared in the step (4) should be at least one type of salt solution, and an acid solution, an alkali solution and a strengthened sewage solution test can be additionally selected according to requirements.

Wherein, according to the mass percentage concentration, at least one type of salt solution is 3% NaCl solution; at least one type of acidic solution is H with the mass percentage concentration of 2%₂SO₄A solution; at least one type of alkaline solution should be 0.1% NaOH + saturated Ca (OH)₂The alkaline solution of (1).

As a further improvement of the technology, the strengthened sewage solution in the step (4) is an organic sewage solution, municipal sewage in a local sewage treatment system is used, and a certain amount of organic substances are added for culture, wherein the COD value of the strengthened sewage solution is not lower than 1000 mg/L.

As a further improvement of the technology, the electrochemical corrosion test should be adjusted according to the actual experiment requirements, the test should at least comprise a group of experiment environments with the temperature of 23 +/-5 ℃, and the test can be carried out at other temperatures to further evaluate the material performance.

As a further improvement of the technology, the experimental parameter selection should be adjusted according to the situation, wherein the open circuit potential testing time is not less than 10min, the recommended range of the alternating current impedance frequency is 100 kHz-10 mHz, the amplitude is 10mV, the electrokinetic potential/Tafel recommended initial voltage is-1V, the termination voltage is 2V, and the scanning rate is 0.01V/S.

By adopting the technical scheme, the field sampling and electrochemical corrosion test method for the concrete surface anticorrosive material can more accurately obtain the change condition of the corrosion resistance of the organic inert coating under the actual service condition, is beneficial to the model selection and development of the concrete anticorrosive material in a sewage pool and similar working conditions, and can be used for early-stage research and field detection evaluation in a laboratory. Compared with the traditional three-electrode electrochemical experimental method, the performance of the anti-corrosion material in the actual service environment can be better achieved, and the experimental result has better accuracy.

Drawings

FIG. 1 is a Tafel plot of the results of an electrochemical experiment for a polyurea coating in an example of the invention;

FIG. 2 is a Tafel plot of the results of an electrochemical experiment of a solvent-free epoxy coating in an example of the present invention;

Detailed Description

The following provides a more detailed description of the embodiments of the present invention.

The invention provides a field sampling and electrochemical corrosion test method of a surface anticorrosive paint for concrete, which can be used for laboratory and field sampling to evaluate the change condition of the corrosion resistance of an organic inert anticorrosive paint in an actual service environment.

The invention relates to a field sampling and electrochemical experimental method of a concrete surface anticorrosive material (mainly suitable for organic inert paint), which mainly comprises the following steps:

1. the method for cutting the anticorrosive paint sample on site comprises the following steps: selecting positions of the side wall or the pool wall with a certain height from the water surface to cut samples, and taking the samples cut at the position with the same height as a group;

2. sampling point selection rule: selecting a position with a smooth surface and no obvious pores at the point position;

3. subsequent treatment of the anticorrosive material and preparation of the test electrode: 1) removing concrete attached to the back surface of the coating by using an angle grinder; 2) polishing the coating into a sheet with a certain thickness, adhering the sheet to a metal back plate, and sealing edges to prepare a test electrode;

4. selection of electrochemical experimental environment and parameters: and sewage in the actual service environment is adopted, or a test solution with similar components to the sewage is prepared, so that a more accurate result is obtained.

Specific examples are as follows.

The method is used for carrying out on-site sampling on the anticorrosive paint for the urban sewage pool concrete, and in combination with earlier-stage on-site investigation, the side wall of a biological reaction pool of a certain local sewage treatment plant is selected as a sampling part, epoxy paint is used for carrying out surface anticorrosive treatment on the sampling part, and the part has water level change and illumination effect simultaneously. Epoxy-based paint applied to the surface of the same type of concrete was used as a control.

Selecting a concrete test block which is used for acid resistance test in a laboratory and is coated with an anticorrosive paint for sampling, wherein the test block is 100 multiplied by 100mm, the surface of the test block is coated with a polyurea anticorrosive coating, and the content of the polyurea anticorrosive coating is 5 percent H₂SO₄Soaking in the solution for 120 days, and taking out. A test block immersed in water for 120 days in the same environment was selected as a control group.

When the sample, select lateral wall waterline change region, select for use the waterline to change regional intermediate position same horizontal plane height grouping and get the point, same horizontal plane gets 3 points and tests. The adhesive force of the coating at the sampling part is relatively poor, and the coating can be directly scraped off by a tool. During sampling, the surface of the coating has certain chalking and light loss phenomena, but the surface of the coating is kept complete and has no phenomena of leakage, damage, falling off and the like.

During sampling, a triangle crack is marked along the edge of the coating by using an art knife, then a strip knife is embedded between the coating and the concrete substrate, the coating is pried off in a whole piece, and the taken-off sample is sealed and stored by using a sealing bag and is taken back to a laboratory for later use.

For the coating with better adhesion condition, a triangular cone concrete test block with the coating is obliquely cut at 60 degrees by using a handheld cutting machine, a thin film can be adhered to the surface of a sample during cutting so as to ensure that the thin film is not brittle and cracked, and the surface is watered and cooled during cutting so as to avoid the performance change of the coating caused by high temperature.

Before testing the sample, the temperature is adjusted for at least 24h at 23 +/-5 ℃ and 50 +/-10% RH, so that the sample is ensured to be in a normal temperature state, and the influence on the experimental result is avoided. The coating slice is polished to ensure that concrete particles are not attached to the back surface of the coating slice, water spraying is kept while polishing, and the coating is not affected by heat generated in the polishing operation process. Meanwhile, the polished coating slice should be not less than 500 μm and have a uniform thickness.

To ensure as much as possible a uniform thickness of the coating, a hand-held angle grinder may be used for the grinding operation. And cutting the polished coating into sheets of 10 multiplied by 10mm, adhering the sheets to the surface of a stainless steel metal back plate by using conductive adhesive, sealing the edges by using epoxy paint, and adjusting the sample to be in a room temperature state after the sample preparation is finished.

Preparing 3% NaCl solution as the solution prepared in the electrochemical test, or selecting H with 2% mass percentage concentration according to the test requirement₂SO₄Solution, 0.1% NaOH + saturated Ca (OH)₂The COD value of the solution is not less than 1000mg/L, and the strengthened sewage solution is used as an experimental environment.

A coating slice is pasted with a metal back plate to serve as a working electrode, a saturated calomel electrode/saturated KCl electrode serves as a reference electrode, and a platinum electrode serves as an auxiliary electrode to build a three-electrode system.

The electrochemical experiment comprises an open circuit potential test (OPC), an alternating current impedance test (EIS) and a potentiodynamic Test (TAF), wherein the open circuit potential test time is not less than 10min, the alternating current impedance frequency recommended range is 100 kHz-10 mHz, the amplitude is 10mV, the potentiodynamic/Tafel recommended initial voltage is-1V, the termination voltage is 2V, and the scanning rate is 0.01V/S.

Compared with the solvent-free epoxy coating after corrosion soaking, the potential polarization curve moves to the upper right, and the corrosion current density Jcorr is increased by one order of magnitude, which shows that the high-molecular cross-linked structure is damaged after corrosion, and the corrosion resistance is reduced. Compared with a polyurea coating, the potential polarization curve has smaller change amplitude, and meanwhile, the polyurea coating has the minimum corrosion current density Jcorr and relatively better corrosion resistance.

Claims (13)

1. A field sampling and electrochemical corrosion test method for a concrete surface anticorrosive material is characterized by comprising the following steps:

(1) selecting sampling points, and requiring the following steps:

a. taking the side wall and the top of the sewage pool which is seriously corroded in actual service as a sampling position to be tested, wherein the sampling part at least comprises a group of sewage pool side wall surfaces or tops;

b. selecting the surface coated with the organic inert coating as a sampling part, wherein the selected surface is in an adhesion state, the surface is basically flat, and no obvious hole or crack exists;

c. the selected sampling points are at least coated with a 500-micron thick anticorrosive coating;

(2) cutting the surface coating by using a cutting tool, and ensuring the integrity of the surface structure of the coating sample during sampling; the cutting area of the single sheet is not less than 10mm multiplied by 10 mm;

(3) polishing the back of the cut surface coating, removing a concrete structure attached to the back of the coating, and only leaving a complete coating slice; adhering the coating slice to a metal back plate to prepare a tested electrode sample;

(4) and preparing a test solution as a test environment for carrying out subsequent electrochemical tests:

(5) and carrying out electrochemical corrosion tests on the sample in different test solutions by using an electrochemical test platform, wherein the electrochemical corrosion tests at least comprise an open circuit potential test (OPC), an alternating current impedance test (EIS), a potentiodynamic Test (TAF) and potentiodynamic cyclic polarization.

2. The method for on-site sampling and electrochemical corrosion testing of the corrosion protection material for concrete surfaces according to claim 1, wherein the testing solution is prepared to include at least one group of salt solutions; or alternatively, a set of salt solutions and optionally additionally a set of acid solutions, a set of base solutions and/or a set of enhanced sewage solutions.

3. The on-site sampling and electrochemical corrosion test method for the concrete surface anticorrosive material according to claim 1, characterized in that when an electrochemical test platform is used for testing, a metal back plate adhered with a coating slice is used as a working electrode, a saturated calomel electrode/saturated KCl electrode is selected as a reference electrode, and a platinum electrode is used as an auxiliary electrode to build a three-electrode system.

4. The method for on-site sampling and electrochemical corrosion testing of the concrete surface anticorrosive material according to claim 1, wherein when the sampling part is a side wall of a sewage pool, points with different heights from a waterline are selected for group sampling and measurement.

5. The on-site sampling and electrochemical corrosion test method for the anticorrosive material on the concrete surface according to claim 1, characterized in that, when cutting the surface coating, for the point with relatively low adhesive force, the profile is cut on the surface of the sampling coating by using a conventional cutter, and the sample is scraped for sampling; and for the point position with relatively strong adhesive force, a handheld cutting machine is used for sampling.

6. The method for on-site sampling and electrochemical corrosion testing of the concrete surface anticorrosive material according to claim 1, wherein the organic inert paint is an epoxy organic inert paint or a polyurea organic inert paint.

7. The method for on-site sampling and electrochemical corrosion test of the corrosion-resistant material for concrete surface according to claim 1,

in the field sampling in the step (1), when the same sewage pool is selected for sampling, at least one group of wall surfaces or tops of the side walls of the sewage pool is included, and the sampling area of a single sewage pool is not less than 3; when the side wall is selected for sampling, at least 3 groups of the side wall are longitudinally distributed, and at least one group of the side wall covers the waterline change area.

8. The method for on-site sampling and electrochemical corrosion testing of the corrosion-resistant material on the concrete surface according to claim 1, wherein when preparing the tested electrode sample, the coated thin sheet is adhered to a stainless steel metal sheet with the same size by using a conductive adhesive and sealed by using an inert material to be used as a working electrode in a three-electrode system.

9. The method for on-site sampling and electrochemical corrosion testing of the concrete surface anticorrosive material according to claim 2, wherein the salt solution is 3% NaCl solution; the acid solution is 2% H₂SO₄A solution; the alkali solution is 0.1% NaOH + saturated Ca (OH)₂And (3) alkaline solution.

10. The method for on-site sampling and electrochemical corrosion testing of corrosion-resistant materials on concrete surfaces according to claim 2, wherein the enhanced sewage solution is an organic sewage solution selected from municipal sewage in a local sewage treatment system, and is cultured by adding a certain amount of organic substances, and the COD value is not lower than 1000 mg/L.

11. The method for on-site sampling and electrochemical corrosion testing of the corrosion-resistant material on the concrete surface according to claim 1, wherein the back of the cut surface coating is ground by a wet grinding process.

12. The method for on-site sampling and electrochemical corrosion testing of corrosion-resistant materials on concrete surfaces according to claim 1, wherein the electrochemical corrosion test of step (5) comprises at least one set of corrosion tests in an experimental environment of 23 ± 5 ℃.

13. The on-site sampling and electrochemical corrosion testing method for the corrosion-resistant material on the concrete surface according to claim 1, wherein in the electrochemical corrosion test in the step (5), the test parameters are as follows: the open-circuit potential testing time is not less than 10min, the frequency range of the alternating current impedance is 100 kHz-10 mHz, the amplitude is 10mV, the dynamic potential/Tafel initial voltage is-1V, the final voltage is 2V, and the scanning speed is 0.01V/S.

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