CN112179833A - Preparation method of metal matrix with corrosion scale layer on surface and under-scale corrosion test thereof - Google Patents
Preparation method of metal matrix with corrosion scale layer on surface and under-scale corrosion test thereof Download PDFInfo
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical group O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 13
- 238000007654 immersion Methods 0.000 claims description 13
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- 229910002027 silica gel Inorganic materials 0.000 claims description 13
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
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Abstract
The invention provides a preparation method of a metal matrix with a corrosive scale layer on the surface and a corrosion test under the scale, which comprises the following steps: step 1, reserving a prefabricated corrosion scale layer area on the surface of a metal matrix, and sealing the surfaces of other smooth samples except the prefabricated corrosion scale layer area; step 2, connecting the metal matrix treated in the step 1 with the positive electrode of a direct current power supply through a lead, connecting the negative electrode of the direct current power supply with an auxiliary electrode, and placing the metal matrix and the auxiliary electrode in a simulation solution; step 3, carrying out an impressed current accelerated corrosion experiment on the metal matrix in the simulated solution, and corroding the prefabricated corrosion scale layer area to form a corrosion scale layer to obtain the metal matrix with the corrosion scale layer on the surface; the preparation method has simple process and convenient operation, and effectively forms a corrosion scale layer on the surface of the metal matrix without clearance.
Description
Technical Field
The invention relates to the technical field of corrosion experiments, in particular to a preparation method of a metal matrix with a corrosion scale layer on the surface and an under-scale corrosion test thereof.
Background
With the continuous deep exploration and development of oil and gas resources, the corrosion and leakage of an oil and gas pipeline network system are frequent due to complex and harsh oil and gas operation and production environment. According to field failure analysis statistics of certain oil fields in the west, 90% of corrosion failures of the ground pipeline are internal corrosion perforations, and perforations caused by underlining corrosion at the bottom of the pipeline are the main failure reasons. The corrosion resistance evaluation in the ground pipeline material selection design is mainly carried out by adopting a uniform corrosion soaking test method, the method mainly evaluates the uniform corrosion rate (mainly aiming at low-carbon steel materials) and the pitting corrosion rate (mainly aiming at stainless steel and corrosion-resistant materials) of the materials, and does not consider the adverse effect caused by the accumulation of corrosion products at the bottom of the pipeline to form a scale layer. However, during use, more and more failure cases show that the under-scale corrosion rate of the bottom of the pipeline is far higher than the uniform corrosion rate of the material, so that the pipeline is locally corroded and perforated before the service life is reached, and leakage accidents are caused. Therefore, the research on the scale corrosion of the ground pipeline is of great significance.
At present, there is no unified method for the under-scale corrosion test, the research is mainly carried out by adopting a three-electrode system electrochemical testing method at home and abroad, and the combination of the metal matrix and the scale layer is usually formed by artificially placing the scale layer on the surface of the sample. Patent CN 102680382A designs a dirt corrosion experiment support under, reserves the working electrode hole, places the sample in the working electrode hole after, adds the dirt layer in the electrode hole and forms the dirt and corrodes the structure under. Patent CN 103792182A designs a two electrolytic cell that corrode under simulation dirt, fills the dirt layer in two electrolytic cell UNICOM organic glass channels department, carries out the electrochemistry test of dirt layer both sides, as the inside and outside electrochemical analysis of dirt layer, and the dirt layer is not direct contact with the metal substrate surface, but exists the certain distance. Patent CN 105181569 a designed an electrochemical device for corrosion test under elemental sulfur scale, which simulates elemental sulfur deposition by coating elemental sulfur on the working electrode. Patent CN 105181569A discloses an ammonium salt under-deposit corrosion experimental device and method, which are provided with a scale salt pool, and a sample is placed in the scale salt pool filled with scale salt to carry out under-deposit corrosion research. Patent CN 103884639 a discloses an experimental method and device for dynamically simulating under-deposit corrosion, which is to place deposit layers of different thicknesses on the surface of a fan-shaped test piece to form a combination of a sample and the deposit layers. In the experimental method, the combination of the scale layer and the metal matrix is in a non-tight state and has no binding force, and the difference from the actual working condition exists.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a preparation method of a metal matrix with a corrosive scale layer on the surface and an under-scale corrosion test thereof.
The invention is realized by the following technical scheme:
a preparation method of a metal matrix with a corrosion scale layer on the surface comprises the following steps:
and 3, carrying out an impressed current accelerated corrosion experiment on the metal matrix in the simulated solution, and corroding the prefabricated corrosion scale layer area to form a corrosion scale layer to obtain the metal matrix with the corrosion scale layer on the surface.
Preferably, in step 1, the sealing treatment is performed by silica gel sealing.
Preferably, in the step 2, the electrifying time of the metal matrix in the simulated solution is 1-4 hours, and the ion composition in the simulated solution comprises 191-956 mg/L of HCO3 -69600-123000 mg/L Cl-125-1216.2 mg/L SO4 2-5170.2-11900 mg/L of Ca2+193.9-552 Mg/L Mg2+And 49170-66500 mg/L of Na+。
Preferably, in step 2, the auxiliary electrode is a platinum mesh auxiliary electrode.
Preferably, the applied current density is in the range of 10mA/cm2～70mA/cm2。
The metal matrix with the corrosion scale layer on the surface is obtained by the preparation method of the metal matrix with the corrosion scale layer on the surface.
A scale-down corrosion test comprises the following steps,
step S1, bisecting the metal matrix with the corrosion scale layer on the surface to form a first metal matrix sample and a second metal matrix sample with the corrosion scale layer on the surface;
step S2, after the first metal matrix sample is sealed and removed, a simulated operation working condition immersion corrosion test is carried out without welding a lead, the hardness of a corrosion product scale layer is measured by adopting nano indentation, and the change of the mechanical property of the corrosion scale layer existing on the surface of the first metal matrix sample before and after the test is compared to obtain a simulated operation working condition immersion corrosion test result;
and step S3, removing the seal of the second metal matrix sample, sealing the section, and performing electrochemical test on the welding wire to obtain an electrochemical test result.
Preferably, in step S2, the immersion corrosion test method is as follows,
and placing the first metal matrix sample in a high-temperature high-pressure kettle to perform a soaking corrosion test simulating the operation conditions, wherein the operation conditions comprise temperature, pressure and medium.
Preferably, in step S3, the electrochemical test method is as follows,
and removing the seal from the surface of the second metal matrix sample, sealing the section of the second metal matrix sample, placing the second metal matrix sample in an electrochemical testing device, and connecting the second metal matrix sample with an electrochemical workstation through a lead to perform electrochemical testing.
Further, the electrochemical testing device comprises a bottom plate with holes, a reference electrode, an annular container, a cover plate with holes and a graphite auxiliary electrode;
the annular container is fixed on the bottom plate with holes, and the top of the annular container is provided with a cover plate with holes; the perforated bottom plate and the perforated cover plate are respectively provided with an annular groove which is in sealed splicing fit with the annular container; the bottom plate with the hole is provided with a wire guide hole, and the inner side and the outer side of the wire guide hole are respectively and correspondingly provided with an inner sealing ring and an outer sealing ring;
the copper wire connected with the metal base body sequentially passes through the inner sealing ring, the rubber pad and the outer sealing ring in a sealing manner to be connected with the electrochemical workstation;
four openings are arranged on the cover plate with the holes, and a rubber plug is arranged on each opening and is respectively used for ventilating and exhausting air and fixing the reference electrode and the graphite auxiliary electrode.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention provides a preparation method of a metal matrix with a corrosion scale layer on the surface, which is characterized in that a prefabricated corrosion scale layer area is reserved on the surface of the metal matrix, the other surfaces of the metal matrix are sealed, effective conditions are provided for the formation of the corrosion scale layer on the surface of the metal matrix, the metal matrix is placed in a simulation solution for a corrosion test of impressed current, a preparation environment is provided for forming a gapless corrosion scale layer on the metal matrix through the concentration ratio of different ion contents in the simulation solution, the preparation efficiency is improved, and the corrosion scale layer is effectively formed on the surface of the metal matrix without gaps through the control of the impressed current and the electrifying time.
Furthermore, silica gel sealing treatment is carried out on the surfaces of other smooth samples except the prefabricated corrosion scale layer area, the surface sealing performance of other smooth samples is improved, and the prefabricated corrosion scale layer area and the surfaces of other smooth samples are effectively distinguished.
Furthermore, the electrifying time and the impressed current density of the metal matrix in the simulated solution effectively control the thickness and the compactness of the corrosion scale layer generated on the surface of the metal matrix.
A metal matrix with a corrosion scale layer on the surface is provided, and a gapless corrosion scale layer is obtained on the surface of the metal matrix through a preparation method of the metal matrix with the corrosion scale layer on the surface, so that the bonding property of the surface of the metal matrix and the corrosion scale layer is effectively increased.
A corrosion test under scale, carry on immersion corrosion test and electrochemical test separately the metal base, the immersion corrosion test compares the change of the corrosion scale layer mechanical property that exists on the surface of metal base and first metal base sample before and after the test effectively; the electrochemical test effectively obtains a test result which is different from a test result that the working electrode is a sample with only a dirt layer.
Furthermore, by setting the temperature and the pressure of the high-temperature high-pressure kettle and the soaking time, an effective testing environment is provided for the soaking corrosion test, and the accuracy of the testing result is improved.
Furthermore, a second metal matrix sample is connected with the electrochemical workstation through a lead, and electrochemical test is carried out in the electrochemical test device, so that the real working condition that the on-site scale layer is connected with the metal matrix is reduced, and the result is closer to the actual working condition.
Furthermore, the electrochemical detection device provides an environment for electrochemical detection, and improves the accuracy of a test result.
Drawings
FIG. 1 is a schematic view of an impressed current accelerated corrosion test apparatus according to the present invention;
FIG. 2 is a schematic view of a preformed corrosion product scale sample of the present invention;
FIG. 3 is a schematic diagram of the hardness test point of the corrosion product scale layer in this embodiment;
FIG. 4 is a schematic view of the structure of the under-scale etching electrochemical test in this embodiment.
In the figure: 1 is an experimental container; 2 is a simulated solution; 3 is a metal matrix; 4 is an auxiliary electrode; 5 is a direct current power supply; 6 is a prefabricated corrosion scale layer area; 7 is a smooth sample surface; 8 is a base with holes; 9 is an outer sealing ring; 10 is a bottom plate with holes; 11 is a rubber pad; 12 is an inner sealing ring; reference electrode 13; 14 is a ring-shaped container; 15 is a cover plate with holes; 16 is a rubber plug; 17 is an electrochemical workstation; and 18 is a graphite auxiliary electrode.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
The invention provides a preparation method of a metal matrix with a corrosion scale layer on the surface, which adopts an impressed current accelerated corrosion experimental device shown in figure 1, wherein a metal matrix 3 with a prefabricated corrosion scale layer area 6 is connected with the anode of a direct current power supply 5 through a copper wire, an auxiliary electrode 4 is connected with the cathode of the direct current power supply 5, the metal matrix 3 is placed in a simulation solution 2 of an experimental container 1, the ion composition (mg/L) of the oil field simulation solution is shown in table 1, and a corrosion product of the scale layer on the surface of the metal matrix is obtained in different impressed current densities and electrifying times through impressed current input by the direct current power supply 5.
TABLE 1 ion composition (mg/L) of oilfield simulation solution
The invention provides a preparation method of a metal matrix with a corrosion scale layer on the surface, which comprises the following steps:
in the invention, macroscopic observation, SEM scanning electron microscope microscopic observation and EDS energy spectrum analysis of corrosion products are carried out on the corrosion scale layer formed on the surface of the metal matrix 3 after the accelerated corrosion experiment, so as to ensure the gapless state of the corrosion scale layer on the surface of the metal matrix, as shown in figure 2; and then, splitting the metal matrix 3 into two pieces, measuring and recording the depth of the scale layer, and forming a first metal matrix sample and a second metal matrix sample which have corrosion scale layers on the surfaces, namely subsequent under-scale corrosion test samples.
Based on the scale layer preparation method, a plurality of continuous or discontinuous scale layer areas can be prepared on a sample with larger size, and a plurality of under-scale corrosion points are simultaneously subjected to experimental research.
Carrying out silica gel sealing treatment on other smooth sample surfaces 7 except the prefabricated corrosion scale layer area 6 in the metal matrix 3, wherein the electrifying time of the metal matrix 3 in the simulated solution 2 is 1-4 hours, and the ion composition in the simulated solution 2 comprises 191-956 mg/L HCO3 -69600-123000 mg/L Cl-125-1216.2 mg/L SO4 2-5170.2-11900 mg/L of Ca2+193.9-552 Mg/L Mg2+And 49170-66500 mg/L of Na+(ii) a The auxiliary electrode 4 connected with the negative electrode of the direct current power supply adopts a platinum mesh auxiliary electrode, impressed current accelerated corrosion is carried out on the metal matrix 3 in the simulated solution 2, and the impressed current density range is 10mA/cm2～70mA/cm2。
The preparation method of the metal matrix with the corrosive scale layer on the surface can obtain the metal matrix 3 with the corrosive scale layer on the surface.
A corrosion test under scale was carried out by the preparation method of the present invention, comprising the steps of:
step S1, the metallic matrix 3 with the erosion scale layer on the surface is cut through to form a first metallic matrix sample and a second metallic matrix sample with the erosion scale layer on the surface;
step S2, after the first metal matrix sample is sealed and removed, a simulated operation working condition immersion corrosion test is carried out without welding a lead, the hardness of a corrosion product scale layer is measured by adopting nano indentation, and the change of the mechanical property of the corrosion scale layer existing on the surface of the first metal matrix sample before and after the test is compared to obtain a simulated operation working condition immersion corrosion test result;
and step S3, removing the seal of the second metal matrix sample, sealing the section, and performing electrochemical test on the welding wire to obtain an electrochemical test result.
In step S2, the immersion corrosion test method includes:
placing a first metal matrix sample in a high-temperature high-pressure kettle to perform a soaking corrosion test for simulating operation conditions, wherein the operation conditions comprise temperature, pressure and medium;
and (4) carrying out microscopic morphology analysis on the scale layer of the section corrosion product by adopting an SEM scanning electron microscope. Then, removing the silica gel on the surface of the first metal matrix test sample by slightly polishing the local area, and recording the thickness t of the sample0Thickness t of scale layerdMinimum metal matrix thickness t corresponding to under scale layer1. Secondly, the hardness of the corrosion product scale layer is measured by adopting nano indentation, 3-5 points are measured at equal intervals along the depth direction, 3-5 points are measured at equal intervals along the width direction, and the reference measurement point position is shown in figure 3. And finally, sealing the section by using silica gel, and placing the prefabricated corrosion product scale layer of the first metal matrix sample with one side facing upwards in a test container or a high-temperature high-pressure kettle for a soaking corrosion test for simulating operating conditions such as temperature, pressure, medium and the like. After the test, cleaning and drying the first metal matrix sample, removing the silica gel on 5 non-observation surfaces of the first metal matrix sample, and then measuring the thickness t of the tested first metal matrix sample0', thickness of scale layer td' minimum Metal matrix thickness t corresponding to under Scale layer1' measurement and recording are performed. And analyzing the micro-morphology of the scale layer of the first metal matrix sample after the simulated immersion corrosion test by adopting an SEM (scanning Electron microscope). Subsequently, the hardness of the corrosion product scale was measured again using nanoindentation and comparedChange of mechanical properties of corrosion product scale.
In step S3, the electrochemical test method is as follows:
removing the seal of the surface of the second metal matrix sample, sealing the opposite section of the second metal matrix sample, placing the second metal matrix sample in an electrochemical testing device, and connecting the second metal matrix sample with an electrochemical workstation through a lead to carry out electrochemical testing;
and removing silica gel on one side of the scale layer prefabricated of the second metal matrix sample with the lead, sealing the section with the silica gel, enabling the scale layer prefabricated to face upwards, and placing the second metal matrix sample in an electrochemical test container for electrochemical test. The test surface of the second metal matrix sample consists of a scale layer area with a smaller area and a metal matrix area with a larger area, and is closer to the actual corrosion working condition of the bottom of the pipeline. The electrochemical test container is made of organic glass, and the structural schematic diagram of an electrochemical test experiment is shown in figure 4, and comprises a bottom plate 10 with holes, a reference electrode 13, an annular container 14, a cover plate 15 with holes and a graphite auxiliary electrode 18;
the annular container 14 is fixed on the perforated bottom plate 10, and the perforated cover plate 15 is arranged at the top of the annular container; the perforated bottom plate 10 and the perforated cover plate 15 are respectively provided with an annular groove which is in sealed splicing fit with the annular container 14; the bottom plate 10 with the hole is provided with a wire guide hole, and the inner side and the outer side of the wire guide hole are respectively and correspondingly provided with an inner sealing ring 12 and an outer sealing ring 9;
the copper wire connected with the metal base body 3 sequentially passes through the inner sealing ring 12, the rubber pad 11 and the outer sealing ring 9 in a sealing manner to be connected with the electrochemical workstation 17;
four openings are arranged on the perforated cover plate 1, and each opening is provided with a rubber plug 16 which is respectively used for ventilation and air exhaust and is used for fixing the reference electrode 13 and the graphite auxiliary electrode 18.
Example 1
Taking scale corrosion of a certain 20# steel gathering pipeline as an example:
1) preparation of Scale layer samples
Cutting 3 rectangular plate-shaped samples of 30 × 30 × 8mm, polishing with sand paper to 1200# sand paper, cleaning with alcohol, blow-drying, welding copper wire at the width position of bottom 1/4, and adhering the middle part of the other surface with an area of 1cm2The paper of (a) was then sealed to all surfaces of the sample with silica gel, and after drying for 24 hours, the paper was removed and the dimensions of the area of the 3 preformed corrosion scale layers 6 were recorded and the preformed corrosion product scale layer started.
Pouring the oilfield on-site retrieval solution into the container, connecting the metal substrate 3 with the prefabricated corrosion scale layer area 6 with a direct current power supply anode, connecting a platinum mesh auxiliary electrode with a direct current power supply cathode, and using 10mA/cm2Applying an external current for 1 hour to obtain a thickness t of the scale layerdPrepared pre-fabricated corrosion product scale samples of 30 μm, longitudinal scale hardness of 3.86GPa, 3.48GPa and 3.14GPa, and transverse scale hardness of 3.32GPa, 3.78GPa and 3.48GPa, measured from the bottom of the pit.
Example 2
Pouring the oilfield on-site retrieval solution into the container, connecting the metal substrate 3 with the prefabricated corrosion scale layer area 6 with a direct current power supply anode, connecting a platinum mesh auxiliary electrode with a direct current power supply cathode, and using 25mA/cm2Applying an external current for 2 hours to obtain the thickness t of the scale layerdPrepared pre-fabricated corrosion product scale samples of 79 μm, longitudinal scale hardness of 2.84GPa, 2.35GPa and 2.28GPa, and transverse scale hardness of 2.48GPa, 2.35GPa and 2.76GPa, measured from the bottom of the pit.
Example 3
Pouring the oilfield on-site retrieval solution into the container, connecting the metal substrate 3 with the prefabricated corrosion scale layer area 6 with a direct current power supply anode, connecting a platinum mesh auxiliary electrode with a direct current power supply cathode, and using 50mA/cm2Applying an external current for 3 hours to obtain the thickness t of the scale layerdPrepared pre-fabricated corrosion product scale samples of 127 μm, longitudinal scale hardness of 2.52GPa, 2.14GPa and 1.92GPa, and transverse scale hardness of 2.38GPa, 2.14GPa and 2.62GPa, measured from the bottom of the pit.
After the sample is prepared, macro and micro analysis is carried out on the surface of the sample, and the analysis shows that the scale layers under different current densities have different densities and thicknesses, as shown in table 2;
TABLE 2 Scale layer thickness prepared at different applied Current Density
The longitudinal scale hardness is a number of hardness values measured from the pit bottom.
After bisection, the thickness t of the sample is measured under a body microscope0Thickness t of scale layerdMinimum metal matrix thickness t corresponding to under scale layer1And obtaining the relation between the thickness of the corrosion product scale layer and the current density. And then, measuring the hardness of the scale layer by adopting nano indentation to obtain the hardness values of the scale layer at different positions, wherein the inner layer is a denser scale layer, the outer layer is a loose scale layer, and the SEM appearance of the cross section of the scale layer also reflects the characteristic.
2) Under-deposit corrosion test
After the first metal matrix sample pair section is sealed by silica gel, one surface of a prefabricated corrosion product scale layer of the first metal matrix sample is upward, and the first metal matrix sample pair section is placed in a high-temperature high-pressure kettle to be subjected to a soaking corrosion test in a field water sample at 60 ℃ and 2MPa for 168 hours. After the test, the thickness t of the first metal matrix sample is measured0', thickness of scale layer td' minimum Metal matrix thickness t corresponding to under Scale layer1And analyzing the microscopic morphology of the scale layer of the first metal matrix sample after the simulated immersion corrosion test. And then, measuring the hardness of the corrosion product scale layer by adopting the nano indentation again, and changing the mechanical property of the corrosion product scale layer.
Polishing and removing silica gel on one side of a prefabricated scale layer of a second metal matrix sample with a wire, polishing the surface with 1200# abrasive paper to be smooth, paying attention to avoid damaging the prefabricated scale layer, and cleaning and drying with alcohol. Subsequently, the cut-out section was sealed with silica gel and dried in a drying cabinet for 12 hours. After taking out, one side of the scale preparation layer faces upwards, a lower lead is connected with an inner sealing ring 12 and a rubber pad 11, the inner sealing ring and the rubber pad penetrate through the lower cover with the hole and are arranged in an electrochemical test container, and the lead penetrates out of the bottom plate and is connected with an outer sealing ring 9, and finally is connected with a working electrode lead of an electrochemical workstation 17 through a base 8 with the hole. The Ag/AgCl reference electrode and the graphite auxiliary electrode 18 are fixed at proper positions through open holes on the upper cover with holes and rubber plugs, and are connected with an electrochemical workstation 17 through leads to carry out electrochemical test in a field water sample. Through the upper coverIntroducing N into the opening2And removing oxygen. Because the sample is tightly corroded, the periphery of the scale layer is surrounded by the metal matrix, the real working condition that the on-site scale layer is connected with the metal matrix is well reduced during testing, a test result different from a test result that the working electrode is a pure scale layer sample is obtained, and the working condition is closer to the actual working condition.
The device and the method are used for developing the under-scale corrosion experiment of the oil field ground pipeline, promoting the research and control of the under-scale corrosion problem of the ground pipeline, and can also be used for the under-scale corrosion experiment research of other metal pipeline and device materials.
Claims (10)
1. A preparation method of a metal matrix with a corrosion scale layer on the surface is characterized by comprising the following steps:
step 1, reserving a prefabricated corrosion scale layer area (6) on the surface of a metal matrix (3), and sealing other smooth sample surfaces (7) except the prefabricated corrosion scale layer area (6);
step 2, connecting the metal matrix (3) treated in the step 1 with the positive electrode of a direct current power supply through a lead, connecting the negative electrode of the direct current power supply with an auxiliary electrode (4), and placing the metal matrix (3) and the auxiliary electrode in the simulated solution (2);
and 3, carrying out an impressed current accelerated corrosion experiment on the metal matrix (3) in the simulated solution (2), and corroding in the prefabricated corrosion scale layer area (6) to form a corrosion scale layer to obtain the metal matrix with the corrosion scale layer on the surface.
2. The method for preparing a metal matrix with a corrosion scale layer on the surface according to claim 1, wherein in step 1, the sealing treatment is silica gel sealing.
3. The method for preparing a metal matrix with a corrosion scale layer on the surface according to claim 1, wherein in step 2, the energization time of the metal matrix (3) in the simulated solution (2) is 1-4 hours, and the ionic composition in the simulated solution (2) comprises 191-956 mg/L of HCO3 -69600-123000 mg/L Cl-125-1216.2 mg/L SO4 2-5170.2-11900 mg/L of Ca2+193.9-552 Mg/L Mg2+And 49170-66500 mg/L of Na+。
4. The method for preparing a metal matrix with a corrosion scale layer on the surface according to claim 1, wherein in the step 2, a platinum mesh auxiliary electrode is adopted as the auxiliary electrode.
5. The process for preparing a metal substrate having a layer of erosion scale on the surface according to claim 1, wherein the applied current density is in the range of 10mA/cm2～70mA/cm2。
6. A metal substrate having an erosion layer on the surface thereof, which is obtained by the method for producing a metal substrate having an erosion layer on the surface thereof according to any one of claims 1 to 5.
7. A scale corrosion test is characterized by comprising the following steps,
step S1, the metallic matrix (3) with the erosion scale layer on the surface is cut into two pieces to form a first metallic matrix sample and a second metallic matrix sample with the erosion scale layer on the surface;
step S2, after the first metal matrix sample is sealed and removed, a simulated operation working condition immersion corrosion test is carried out without welding a lead, the hardness of a corrosion product scale layer is measured by adopting nano indentation, and the change of the mechanical property of the corrosion scale layer existing on the surface of the first metal matrix sample before and after the test is compared to obtain a simulated operation working condition immersion corrosion test result;
and step S3, removing the seal of the second metal matrix sample, sealing the section, and performing electrochemical test on the welding wire to obtain an electrochemical test result.
8. A sub-scale corrosion test according to claim 7, characterized in that: in step S2, the immersion corrosion test method is as follows,
and placing the first metal matrix sample in a high-temperature high-pressure kettle to perform a soaking corrosion test simulating the operation conditions, wherein the operation conditions comprise temperature, pressure and medium.
9. A sub-scale corrosion test according to claim 7, characterized in that: in step S3, the electrochemical test method is as follows,
and removing the seal from the surface of the second metal matrix sample, sealing the section of the second metal matrix sample, placing the second metal matrix sample in an electrochemical testing device, and connecting the second metal matrix sample with an electrochemical workstation through a lead to perform electrochemical testing.
10. A sub-scale corrosion test according to claim 9, characterized in that: the electrochemical testing device comprises a bottom plate (10) with holes, a reference electrode (13), an annular container (14), a cover plate (15) with holes and a graphite auxiliary electrode (18);
the annular container (14) is fixed on the bottom plate (10) with holes, and the top of the annular container is provided with a cover plate (15) with holes; the perforated bottom plate (10) and the perforated cover plate (15) are respectively provided with an annular groove which is in sealed splicing fit with the annular container (14); the perforated bottom plate (10) is provided with a wire guide hole, and the inner side and the outer side of the wire guide hole are respectively and correspondingly provided with an inner sealing ring (12) and an outer sealing ring (9);
a copper wire connected with the metal base body (3) sequentially passes through the inner sealing ring (12), the rubber pad (11) and the outer sealing ring (9) in a sealing manner and is connected with the electrochemical workstation (17);
four openings are arranged on the cover plate (15) with the holes, and a rubber plug (16) is arranged on each opening and is respectively used for ventilation and air exhaust, and a reference electrode (13) and a graphite auxiliary electrode (18) are fixed.
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