A method for preparing a rust layer cross-section specimen

Abstract

The present invention provides a method for preparing a rust layer cross-section sample, which belongs to the field of characterization and detection of rust layers on steel plate surfaces. The preparation method comprises: microscopically observing the pretreated rust layer sample to obtain different phase micromorphological regions of the rust layer sample; and using a FIB-SEM dual-beam system to in-situ cut the different phase micromorphological regions to obtain a rust layer cross-section sample. The preparation method uses a FIB-SEM dual-beam system to in-situ cut the different phase micromorphological regions, and uses a special sample preparation method of a focused ion beam. During the entire sample preparation process, the stress on the sample is very small, so the prepared rust layer cross section also has good integrity, and almost non-destructive preparation of the rust layer in-situ cross section is achieved, and the state of the rust layer itself is restored to the greatest extent, effectively solving the problem that the true morphology of the rust layer cannot be completely restored due to damage in the existing rust layer cross-section sample preparation process.

Description

Technical Field

[0001] The present application relates to the field of characterization and detection of rust layers on steel plate surfaces, and in particular to a method for preparing a rust layer cross-section specimen. Background Art

[0002] Steel corrosion is a common and serious problem, which has caused huge losses to the national economy. Therefore, the research on the corrosion resistance of steel has always been the focus of material researchers. The research on the corrosion resistance of steel materials focuses on the analysis and research of the corrosion product of steel materials - rust layer, in order to understand the corrosion mechanism of steel materials.

[0003] The conventional method for preparing rust layer samples for SEM or electron probe observation is as follows: (1) Use a cutting machine to cut the steel material after the corrosion test into small pieces of samples that are easy to embed; (2) Use embedding equipment to hot embed or cold embed the cross-section of the sample with rust layer; (3) Perform different levels of sandpaper grinding and polishing on the embedded sample until a mirror surface sample is formed; (4) Place it in a SEM or electron probe for observation and analysis.

[0004] At present, the existing rust layer cross-section sample preparation process has the problem that the true morphology of the rust layer cannot be completely restored due to damage such as mechanical cutting. Summary of the invention

[0005] The embodiment of the present application provides a method for preparing a rust layer cross-section sample to solve the technical problem that the true morphology of the rust layer cannot be completely restored due to damage in the existing rust layer cross-section sample preparation process.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a rust layer cross-section specimen, the preparation method comprising:

[0007] The pretreated rust layer sample is microscopically observed to obtain different phase micromorphological regions of the rust layer sample;

[0008] The FIB-SEM dual-beam system is used to perform in-situ cutting of the different phase micromorphology regions to obtain rust layer cross-section samples.

[0009] Furthermore, the cross section of the rust layer cross section specimen includes at least one of a rust layer cross section and a rust layer longitudinal section.

[0010] Furthermore, the different phase micromorphology regions include at least one of a Fe3O4 phase micromorphology region, a Fe2O3 phase micromorphology region, an α-FeOOH phase micromorphology region, a β-FeOOH phase micromorphology region and a γ-FeOOH phase micromorphology region.

[0011] Furthermore, before microscopically observing the pretreated rust layer sample to obtain different phase microscopic morphology regions of the rust layer sample, the method further includes:

[0012] The rust layer specimen is macroscopically observed and then mechanically cut to obtain a rust layer specimen of a preset size;

[0013] The surface pollutants of the rust layer sample of the preset size are removed, and then the surface of the rust layer sample is plated to obtain the pretreated rust layer sample.

[0014] Furthermore, the coating process includes: spraying carbon or gold on the surface of the sample with rust layer; the working parameters of the carbon spraying and the gold spraying are: sputtering current: 20-40mA, sputtering time: 3-5 minutes.

[0015] Furthermore, the preset size includes 15mm×15mm.

[0016] Furthermore, the FIB-SEM dual beam system is used to perform in-situ cutting of the different phase micromorphology regions to obtain rust layer cross-section samples, specifically including:

[0017] The pretreated rust layer sample is placed in the sample chamber of the FIB-SEM dual beam system, and the rust layer sample is adjusted to the common focus point of the SEM electron beam and the FIB ion beam, and then the different phase microscopic morphology areas of the rust layer sample are cut in situ to obtain a rust layer cross-section sample;

[0018] Wherein, the in-situ cutting includes rough cutting and fine polishing;

[0019] The working parameters of the rough cutting include: FIB acceleration voltage: 20-30 kV; beam current: >15 nA; the direction of the FIB is perpendicular to the surface of the rust layer sample;

[0020] The working parameters of the fine polishing include: FIB acceleration voltage: 20-30 kV; beam current: 1 nA-4 nA; the direction of the FIB is inclined 2o-4o to the vertical surface of the rust layer sample.

[0021] Furthermore, the working parameters of the rough cutting include: FIB acceleration voltage: 30 kV; beam current: 16 nA.

[0022] Furthermore, the working parameters of the fine polishing include: FIB acceleration voltage: 30 kV; beam current: 2 nA; the direction of the FIB is inclined 2 degrees to the vertical surface of the rust layer sample.

[0023] Furthermore, the in-situ cutting has a cutting area width of 50 to 200 microns and a depth of 50 to 100 microns.

[0024] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0025] An embodiment of the present application provides a method for preparing a rust layer cross-section sample. The preparation method adopts a FIB-SEM dual-beam system to perform in-situ cutting of the different phase micromorphology areas, and utilizes a special sample preparation method of a focused ion beam (FIB). During the entire sample preparation process, the stress on the sample is very small, so the prepared rust layer cross section also has good integrity, and almost non-destructive preparation of the in-situ cross section of the rust layer is achieved, and the state of the rust layer itself is restored to the greatest extent, effectively solving the problem that the true morphology of the rust layer cannot be completely restored due to damage in the existing preparation process of the rust layer cross-section sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1 A schematic flow chart of a method for preparing a rust layer cross-section specimen provided in an embodiment of the present application;

[0029] Figure 2 Microscopic morphology of the rust layer cross-section sample prepared in the embodiment of this application Figure 1 ;

[0030] Figure 3 Microscopic morphology of the rust layer cross-section sample prepared in the embodiment of this application Figure 2 ;

[0031] Figure 4 This is a microscopic morphology of a cross-section sample of a rust layer prepared using the prior art in this application. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below in conjunction with specific implementations and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementations and examples are for illustrating the present invention, rather than limiting the present invention.

[0033] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0034] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0035] Steel corrosion is a common and serious problem, which has caused huge losses to the national economy. Therefore, the research on the corrosion resistance of steel has always been the focus of material researchers. The research on the corrosion resistance of steel materials focuses on the analysis and research of the corrosion product of steel materials - rust layer, in order to understand the corrosion mechanism of steel materials.

[0036] At present, the conventional method for preparing rust layer samples for SEM or electron probe observation is as follows:

[0037] (1) Use a cutting machine to cut the steel material after the corrosion test into small pieces for easy embedding;

[0038] (2) Using mounting equipment to hot mount or cold mount the cross section of the sample with rust layer;

[0039] (3) Grinding and polishing the mounted specimen with sandpaper in different passes until a mirror surface is formed;

[0040] (4) Place in a scanning electron microscope or electron probe for observation and analysis.

[0041] Conventionally prepared rust layer samples have the following disadvantages when used for SEM observation:

[0042] 1) Since the rust layer is the product of corrosion of steel materials, it is loose, not tightly connected to the steel base, and easy to peel off. Therefore, in the general sample preparation process, each link such as cutting the sample by the cutting machine, extrusion of the rust layer by the high-temperature molten resin in the hot mounting, grinding and polishing of the mounted sample, etc., will cause certain mechanical damage to the cross section of the rust layer, and it is impossible to completely restore the true morphology of the rust layer.

[0043] 2) When observing with a scanning electron microscope, since the resin used for mounting is not conductive, it needs to be attached to the aluminum sample holder with conductive glue. Long-term observation will cause charge accumulation, discharge or image drift due to long electron beam irradiation time, thus affecting observation and analysis.

[0044] Therefore, the technical problems that need to be solved urgently are as follows:

[0045] 1) The influence of mechanical cutting specimens on the rust layer;

[0046] 2) The effect of high temperature on the rust layer when mounting the specimen;

[0047] 3) The influence of mechanical stress on the rust layer during grinding and polishing of samples;

[0048] 4) The impact of non-conductive mounting materials on the image quality of scanning electron microscope.

[0049] In summary, the existing process of preparing rust layer cross-section samples has the problem that the true morphology of the rust layer cannot be completely restored due to damage such as mechanical cutting.

[0050] The technical solution provided by the embodiment of the present invention is to solve the above technical problems, and the overall idea is as follows:

[0051] In the first aspect, the present application provides a method for preparing a rust layer cross-section specimen, such as Figure 1 As shown, the preparation method comprises:

[0052] The pretreated rust layer sample is microscopically observed to obtain different phase micromorphological regions of the rust layer sample;

[0053] The FIB-SEM dual-beam system is used to perform in-situ cutting of the different phase micromorphology regions to obtain rust layer cross-section samples.

[0054] An embodiment of the present application provides a method for preparing a rust layer cross-section sample. The preparation method adopts a FIB-SEM dual-beam system to perform in-situ cutting of the different phase micromorphology areas, and utilizes a special sample preparation method of a focused ion beam (FIB). During the entire sample preparation process, the stress on the sample is very small, so the prepared rust layer cross section also has good integrity, and almost non-destructive preparation of the in-situ cross section of the rust layer is achieved, and the state of the rust layer itself is restored to the greatest extent, effectively solving the problem that the true morphology of the rust layer cannot be completely restored due to damage in the existing preparation process of the rust layer cross-section sample.

[0055] In this application, the FIB-SEM dual beam system refers to a system that has both the functions of a focused ion beam (FIB) and a scanning electron microscope (SEM). It can realize the function of real-time observation of the FIB micromachining process by SEM, combining the advantages of high spatial resolution of electron beam and fine processing of ion beam.

[0056] As an implementation of an embodiment of the present application, the cross section of the rust layer cross section specimen includes at least one of a rust layer cross section and a rust layer longitudinal section.

[0057] In the present application, the cross section of the rust layer cross section specimen includes a cross section of the rust layer and a longitudinal section of the rust layer, which can reflect the typical morphology of the entire rust layer.

[0058] As an implementation manner of an embodiment of the present application, the different phase micromorphology regions include at least one of the Fe3O4 phase micromorphology region, the Fe2O3 phase micromorphology region, the α-FeOOH phase micromorphology region, the β-FeOOH phase micromorphology region and the γ-FeOOH phase micromorphology region.

[0059] In the present application, the corrosion products of the rust layer include different phases such as Fe3O4, Fe2O3, α-FeOOH, β-FeOOH, and γ-FeOOH, and the microscopic morphology of each phase is different. The different phases existing on the surface of the rust layer can be first observed microscopically using a scanning electron microscope to determine the typical microscopic morphology area of ​​the rust layer surface that needs to be cut. In-situ cross-section cutting is performed in the typical microscopic morphology area of ​​the surface, that is, the area of ​​different phases, so that the typical morphology of the entire rust layer can be reflected.

[0060] As an implementation method of the present application, before microscopically observing the pretreated rust layer sample to obtain different phase microscopic morphology regions of the rust layer sample, the method further includes:

[0061] The rust layer specimen is macroscopically observed and then mechanically cut to obtain a rust layer specimen of a preset size;

[0062] The surface pollutants of the rust layer sample of the preset size are removed, and then the surface of the rust layer sample is plated to obtain the pretreated rust layer sample.

[0063] As an implementation method of an embodiment of the present application, the coating process includes: spraying carbon or gold on the surface of a sample with a rust layer; the working parameters of the carbon spraying and the gold spraying are: sputtering current: 20-40 mA, sputtering time: 3-5 minutes.

[0064] In the present application, during the pretreatment of the sample with rust layer: first, the sample with rust layer is macroscopically observed to judge and analyze whether the rust layer on the surface of the sample with rust layer is relatively loose (excluded) and firm (selected), and then the relatively firm area on the surface of the sample is mechanically cut at a low speed using precision cutting to a size that can be placed in a scanning electron microscope for observation (preset size), but unlike conventional sample preparation, the mechanically cut surface is not the rust layer observation surface; then an ultrasonic cleaner is used to remove contaminants on the surface of the sample; finally, a vacuum coating machine is used to spray carbon or gold on the surface of the sample, with a sputtering current of 20 to 40 mA and a sputtering time of 3 to 5 minutes.

[0065] In the present application, the purpose of pretreating the rust layer sample is mainly to obtain a rust layer sample that can be used for subsequent microscopic observation using a scanning electron microscope, and to prevent the powder of the rust layer (the rust layer is loose and easily peeled off) from falling off and affecting the vacuum degree of the scanning electron microscope.

[0066] As an implementation of the embodiment of the present application, the preset size includes 15mm×15mm.

[0067] In the present application, the rust layer sample is mechanically cut into sizes such as 15 mm × 15 mm so that it can be placed in a scanning electron microscope for observation, which is convenient for subsequent operations.

[0068] As an implementation method of the present application, a FIB-SEM dual-beam system is used to in-situ cut the different phase micromorphology areas to obtain a rust layer cross-section sample, which specifically includes:

[0069] The pretreated rust layer sample is placed in the sample chamber of the FIB-SEM dual beam system, and the rust layer sample is adjusted to the common focus point of the SEM electron beam and the FIB ion beam, and then the different phase microscopic morphology areas of the rust layer sample are cut in situ to obtain a rust layer cross-section sample;

[0070] Wherein, the in-situ cutting includes rough cutting and fine polishing;

[0071] The working parameters of the rough cutting include: FIB acceleration voltage: 20-30 kV; beam current: >15 nA; the direction of the FIB is perpendicular to the surface of the rust layer sample;

[0072] The working parameters of the fine polishing include: FIB acceleration voltage: 20-30 kV; beam current: 1 nA-4 nA; the direction of the FIB is inclined by 2°-4° to the vertical surface of the rust layer sample.

[0073] In this application, in some specific embodiments, the above process may be:

[0074] Step 1: Adjust the confocal point

[0075] a) Load the pretreated sample into the sample chamber of a dual beam system (SEM-FIB) with a focused ion beam, and place the defective part of the sample as close to the edge of the sample stage as possible.

[0076] b) The accelerating voltage of the ion beam and the electron beam is increased to a suitable working voltage, the accelerating voltage of the electron beam is 5 to 15 kV, and the accelerating voltage of the ion beam is 25 to 30 kV.

[0077] c) Adjust the sample surface to the common focus of the electron beam and ion beam. Tilt the sample stage to 54° to 56°, make the ion beam perpendicular to the sample surface, and set the working distance (WD) to 5.0 to 5.2 mm. The analysis area is located at the center of the electron beam and ion beam observation areas at the same time (i.e., the position of the analysis area remains basically unchanged when switching between the two particle beam observations).

[0078] Step 2: Section cutting

[0079] d) Cutting size setting: According to the area size of the rust layer, the width of the cutting area is the width of the rust layer that needs to be observed, and the depth is mainly to show the thickness of the complete rust layer. The width of the cutting area is 50-200μm, and the depth is 50-100μm. The increase in cutting depth and width will lead to a significant increase in cutting time. Therefore, the cutting area is selected according to the typical surface morphology.

[0080] e) Ion beam setting: Cutting generally includes rough cutting and fine polishing. Rough cutting: Acceleration voltage: 20-30kV, beam current: >15nA, ion beam perpendicular to the sample surface. Fine polishing: According to the preliminary observation results of the rust layer, fine polishing is performed on the area of ​​interest, acceleration voltage: 20-30kV, beam current: 1nA-4nA, ion beam is inclined 2°-4° to the vertical surface of the sample. Determine the fine polishing current according to the actual situation. The lower the beam current, the finer the cutting surface and the smaller the cutting damage, but the cutting time will increase significantly.

[0081] f) After setting the cutting parameters, cut the rust layer area. During the cutting process, the process needs to be monitored in real time, and a large aperture and high beam mode are used for observation. The cutting is completed based on the display of the complete rust layer.

[0082] In this application, the specific ion beam parameter settings in cutting are found through a large number of experiments and studies: the larger the ion beam current, the faster the cutting, but the rougher the cross-sectional morphology; the smaller the ion beam current, the slower the cutting, but the smoother the cross-sectional morphology. Therefore, first a large beam current is used for fast cutting, then a small beam current is used for fine polishing, and finally the cross-sectional smoothing sample is prepared. That is, the preparation of a sample with a smooth cross-sectional rust layer is achieved through the combined effects of rough cutting and fine polishing as well as parameter settings.

[0083] As an implementation method of an embodiment of the present application, the rough cutting working parameters include: FIB acceleration voltage: 30 kV; beam current: 16 nA.

[0084] As an implementation method of an embodiment of the present application, the working parameters of the fine polishing include: FIB acceleration voltage: 30kV; beam current: 2nA; the direction of the FIB is inclined by 2° to the vertical surface of the rust layer sample.

[0085] As an implementation manner of an embodiment of the present application, the width of the cutting area of ​​the in-situ cutting is 50 to 200 microns, and the depth is 50 to 100 microns.

[0086] In this application, according to the regional size of the rust layer, the width of the cutting area is the width of the rust layer that needs to be observed, and the depth is mainly to show the thickness of the complete rust layer. The width of the cutting area is 50 to 200 microns, and the depth is 50 to 100 microns. The increase in cutting depth and width will lead to a significant increase in cutting time. Therefore, the cutting area is selected according to the typical surface morphology.

[0087] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually measured according to national standards. If there is no corresponding national standard, then proceed according to general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0088] Example 1

[0089] This example provides a method for preparing a rust layer cross-section specimen, which specifically includes:

[0090] The sample used in the example is an accelerated corrosion sample of HG785 high-strength steel. The FIB sample was used for analysis, and the analysis process is as follows:

[0091] 1) Sample pretreatment

[0092] a) Use a precision cutting machine to cut the sample into 15×15 mm at low speed.

[0093] b) Use an ultrasonic cleaner to remove contaminants on the sample surface.

[0094] c) Use a vacuum coating machine to spray carbon or gold on the surface of the sample, with a sputtering current of 40 mA and a sputtering time of 5 minutes.

[0095] 2) In situ cutting observation

[0096] a) Load the pretreated sample into the sample chamber of a dual beam system (SEM-FIB) with a focused ion beam, with the rust layer of the sample as close to the edge of the sample stage as possible.

[0097] b) Set the electron beam accelerating voltage to 5 kV and the ion beam accelerating voltage to 30 kV.

[0098] c) Use electron beam to observe the different phases and typical morphologies on the surface of the rust layer and select the cutting area.

[0099] d) Adjust the sample to the confocal point, tilt the sample stage to 52°, make the ion beam perpendicular to the sample surface, and the working distance WD is 5.2 mm.

[0100] f) Rough cutting: The width of the cutting area is a trapezoidal frame, the upper edge of the trapezoidal frame is the termination line, the width is 50 microns, the depth is 50 microns, the voltage is 30kV, and the beam current is 16nA. Fine polishing: The width of the cutting area is a trapezoidal frame, the ion beam is inclined 2° to the vertical surface of the sample, the voltage is 30kV, and the beam current is 2nA.

[0101] In this example, the microscopic morphology and analysis of the rust layer cross-section specimen obtained above were performed. Figure 2 and Figure 3As shown in the figure, there are cracks on the surface of some areas, and the cross section extends to the steel base. In some areas, the rust layer is intact and there is no crack on the cross section. Compared with the rust layer cross section (as shown in the figure) prepared by conventional sample preparation (prepared by the conventional method for rust layer specimens observed by scanning electron microscope or electron probe as described in the background technology) Figure 4 As shown in the figure, there are basically cracks in all samples, so it is judged that conventional sample preparation will cause many cracks in the rust layer, while this method basically achieves non-destructive sample preparation.

[0102] Example 2

[0103] This example provides a method for preparing a rust layer cross-section sample, which differs from Example 1 only in that: the working parameters of the rough cutting include: FIB acceleration voltage: 25 kV; beam current: 17 nA; the direction of the FIB is perpendicular to the surface of the rust layer sample; the working parameters of the fine polishing include: FIB acceleration voltage 25 kV; beam current: 4 nA; the direction of the FIB is inclined 4° to the vertical surface of the rust layer sample; the remaining steps and parameters are the same.

[0104] The rust layer cross-section samples obtained in this example were subjected to microscopic morphology and analytical judgment. The produced rust layer cross-section had good integrity, achieving almost non-destructive preparation of the in-situ cross-section of the rust layer.

[0105] It should be understood that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0106] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In addition, the term "and / or" appearing in this article is only a kind of association relationship describing associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone.

[0107] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a rust layer cross-section sample, characterized in that: The preparation method comprises: The rust layer sample is macroscopically observed and then mechanically cut to obtain a rust layer sample of a preset size, wherein the mechanically cut cutting surface is a non-rust layer observation surface; The surface contaminants of the rust layer sample with a preset size are removed, and then the surface of the rust layer sample is plated to obtain a pretreated rust layer sample; The pretreated rust layer sample is microscopically observed to obtain different phase micromorphological regions of the rust layer sample; The FIB-SEM dual beam system is used to in-situ cut the different phase micromorphology regions to obtain the rust layer cross-section sample; The coating process includes: spraying carbon or gold on the surface of the sample with rust layer; the working parameters of the carbon spraying and the gold spraying are: sputtering current: 20-40mA, sputtering time: 3-5 minutes; The FIB-SEM dual beam system is used to in-situ cut the different phase micromorphology areas to obtain the rust layer cross-section sample, which specifically includes: The pretreated rust layer sample is placed in the sample chamber of the FIB-SEM dual beam system, the rust layer sample is adjusted to the common focus of the SEM electron beam and the FIB ion beam, and then the different phase micromorphology areas of the rust layer sample are cut in situ to obtain the rust layer cross-section sample, the electron beam acceleration voltage is 5-15 kV, the ion beam acceleration voltage is 25-30 kV, the sample stage is tilted to 54°-56°, the ion beam is perpendicular to the sample surface, the working distance is 5.0-5.2 mm, and the analysis area is located at the center of the electron beam and ion beam observation areas at the same time; Wherein, the in-situ cutting includes rough cutting and fine polishing; The working parameters of the rough cutting include: FIB acceleration voltage: 20-30 kV; beam current: >15 nA; the direction of the FIB is perpendicular to the surface of the rust layer sample; The working parameters of the fine polishing include: FIB acceleration voltage: 20-30 kV; beam current: 1 nA-4 nA; the direction of the FIB is inclined 2°-4° to the vertical surface of the rust layer sample; The working parameters of the rough cutting include: FIB acceleration voltage: 30kV; beam current: 16nA; The working parameters of the fine polishing include: FIB acceleration voltage: 30kV; beam current: 2nA; the direction of the FIB is inclined 2° to the vertical surface of the rust layer sample; The in-situ cutting has a cutting area width of 50 to 200 microns and a depth of 50 to 100 microns.

2. The method for preparing a rust layer cross-section specimen according to claim 1, characterized in that: The cross section of the rust layer cross section specimen includes at least one of a rust layer cross section and a rust layer longitudinal section.

3. The method for preparing a rust layer cross-section specimen according to claim 1, characterized in that: The different phase micromorphology regions include at least one of a Fe3O4 phase micromorphology region, a Fe2O3 phase micromorphology region, an α-FeOOH phase micromorphology region, a β-FeOOH phase micromorphology region and a γ-FeOOH phase micromorphology region.

4. The method for preparing a rust layer cross-section specimen according to claim 1, characterized in that: The preset size includes 15 mm×15 mm.

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