Ferritic stainless steel metallographic corrosive agent and preparation method and corrosion method thereof

Abstract

The invention discloses a ferritic stainless steel metallographic corrosive as well as a preparation method and a corrosion method thereof, and belongs to the technical field of metal material detection. Dissolving picric acid in deionized water until the picric acid is saturated to obtain a saturated picric acid solution; uniformly mixing ferric chloride, hydrochloric acid and a solvent to obtain a ferric chloride hydrochloric acid solution; and uniformly mixing the saturated picric acid solution and the ferric chloride hydrochloric acid solution, adding the hand sanitizer containing the surfactant, and uniformly mixing to obtain the ferritic stainless steel metallographic corrosive. After the ferritic stainless steel is corroded, the metallographic structure of the ferritic stainless steel is clear, the dendritic crystal and the size of the ferritic stainless steel can be accurately distinguished, then the metallographic structure, the grain size and other data of the ferritic stainless steel can be accurately obtained, accordingly, the welding process can be adjusted in time, and the method is extremely important for improving the performance of the ferritic stainless steel.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material detection, and in particular relates to a ferrite stainless steel metallographic corrosive agent and a preparation method and a corrosive method thereof. Background Art

[0002] Ferritic stainless steel is a special steel with low carbon and high alloy content. It has excellent corrosion resistance and oxidation resistance and is often used for important parts. In the production process of ferritic stainless steel, due to differences in material composition, hot rolling and heat treatment processes, different metallographic structures are often obtained, and the performance of ferritic stainless steel is also different. In order to obtain ferritic stainless steel with the required performance, it is usually corroded with a metallographic corrosive agent and then the metallographic structure is observed. Combined with the performance test data, the alloy composition, rolling process and heat treatment process are adjusted in time.

[0003] The patent application with the publication number CN 110530701 A discloses a metallographic etchant for stainless steel, its preparation method and corrosion method, specifically for ferritic stainless steel welded with austenitic welding wire containing cerium and titanium, and the welded joint is a mixture of austenite and ferrite that has undergone multiple thermal cycles. The metallographic etchant is composed of the following components in terms of mass and concentration: 2 mL of aqueous solution, 0.4-0.6 g of solid FeCl3 with the molecular formula of FeCl3·6H2O, and 6 mL of nitric acid solution with a concentration of 60%-65%. The metallographic etchant for stainless steel, its preparation method and corrosion method, can solve the problem that stainless steel with a mixture of austenite and ferrite at the welded joint is difficult to corrode, and claims that the welded joint after multiple thermal cycles can be corroded and the initial corrosion effect can be achieved simply by changing the length of the corrosion time.

[0004] However, it is difficult for common metallographic corrosive agents to obtain good corrosion effects when corroding ferritic steel samples. Specifically, the grain boundaries of ferritic stainless steel structures will be unclear, or only a small amount of grain boundaries can be corroded, which will have an adverse effect on the observation of metallographic structures and the determination of grain size, thereby affecting product development and improvement.

[0005] In view of this, it is necessary to develop a ferritic stainless steel metallographic corrosive agent and a corrosion method thereof to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a ferritic stainless steel metallographic etchant and a preparation method and a corrosion method thereof, to develop an etchant that can clearly display the grain boundaries of the metallographic structure, to improve the corrosion effect of the metallographic etchant on ferritic stainless steel, and to improve the performance of ferritic stainless steel.

[0007] The first object of the present invention is to provide a ferritic stainless steel metallographic etching agent.

[0008] A ferritic stainless steel metallographic etching agent comprises a picric acid solution, a ferric chloride hydrochloric acid solution and a hand washing liquid containing a surfactant.

[0009] Furthermore, the usage ratio of the picric acid aqueous solution, the ferric chloride hydrochloric acid solution and the hand sanitizer containing a surfactant is (80-120) mL: (80-120) mL: (10-30) g.

[0010] Furthermore, the picric acid solution is prepared by dissolving picric acid in deionized water until a saturated picric acid solution is obtained.

[0011] Furthermore, the hand sanitizer containing a surfactant is a hand sanitizer containing a surfactant APG.

[0012] Furthermore, the dosage ratio of ferric chloride, hydrochloric acid and solvent in the ferric chloride hydrochloric acid solution is (4-6) g: (8-12) mL: (80-100) mL.

[0013] Furthermore, the solvent is deionized water or anhydrous ethanol.

[0014] The second object of the present invention is to provide a method for preparing a ferritic stainless steel metallographic corrosive agent.

[0015] A method for preparing a ferritic stainless steel metallographic corrosive agent comprises the following steps:

[0016] The picric acid is dissolved in deionized water until saturated to obtain a saturated picric acid solution; ferric chloride, hydrochloric acid and a solvent are mixed to obtain a ferric chloride hydrochloric acid solution; the saturated picric acid solution and the ferric chloride hydrochloric acid solution are mixed to add a hand soap containing a surfactant, and the mixture is mixed to obtain a ferritic stainless steel metallographic etching agent.

[0017] The third object of the present invention is to provide a method for metallographic corrosion of ferritic stainless steel.

[0018] A method for metallographic corrosion of ferritic stainless steel comprises the following steps:

[0019] Performing metallographic sample preparation and cleaning on the surface of the ferritic stainless steel to obtain the ferritic stainless steel to be corroded;

[0020] The ferritic stainless steel to be corroded is immersed in the ferritic stainless steel metallographic corroding agent to obtain the corroded ferritic stainless steel.

[0021] Furthermore, the soaking time is 50s to 170s.

[0022] Furthermore, a method for metallographic corrosion of ferritic stainless steel comprises the following steps:

[0023] Performing metallographic sample preparation and cleaning on the surface of the ferritic stainless steel to obtain the ferritic stainless steel to be corroded;

[0024] The surface of the ferritic stainless steel to be corroded is wiped with a liquid-absorbing cloth dipped in the ferritic stainless steel metallographic corroding agent described in the first invention to obtain the corroded ferritic stainless steel.

[0025] Furthermore, the wiping times is 20-100 times.

[0026] Furthermore, the corroded ferritic stainless steel is cleaned and dried.

[0027] Furthermore, the cleaning includes ultrasonic cleaning and alcohol rinsing.

[0028] Furthermore, the ultrasonic cleaning time is 1 min to 10 min, and the alcohol rinsing time is 5 s to 20 s.

[0029] Furthermore, the drying is drying by oven drying, blow drying with a hair dryer or natural air drying.

[0030] Beneficial effects of the present invention:

[0031] (1) The present invention provides a ferritic stainless steel metallographic etchant and a preparation method and a corrosion method thereof. After the ferritic stainless steel is metallographically etched by a mixed etchant of picric acid, hydrochloric acid and nitric acid, the metallographic structure is clear, and the dendrites and their sizes of the ferritic stainless steel can be accurately distinguished, thereby accurately obtaining data such as the metallographic structure and grain size of the ferritic stainless steel, and the welding process can be adjusted in time based on the data, which is extremely important for improving the performance of the ferritic stainless steel.

[0032] (2) The surfactant APG used in the present invention can reduce surface tension, improve wettability and emulsification ability due to its amphiphilic structure. In addition, after being compounded with picric acid and ferric chloride hydrochloric acid solution, it can neutralize part of the charge and reduce the electrostatic repulsion between molecules, making it easier for molecules to arrange and adsorb on the interface. At the same time, APG enhances the interfacial activity, thereby improving the corrosion effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the accompanying drawings.

[0034] Figure 1 This is the metallographic structure of the corroded ferritic stainless steel obtained in Example 1 of the present invention under a microscope;

[0035] Figure 2 This is the metallographic structure of the corroded ferritic stainless steel obtained in Example 2 of the present invention under a microscope;

[0036] Figure 3This is the metallographic structure of the corroded ferritic stainless steel obtained in Example 3 of the present invention under a microscope. DETAILED DESCRIPTION

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] This embodiment provides a ferritic stainless steel metallographic etching agent and a preparation method and an etching method thereof, and the specific steps are as follows:

[0040] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid solution; mix 5 g of ferric chloride, 10 mL of hydrochloric acid and 90 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid solution and 100 mL of the ferric chloride hydrochloric acid solution, add 20 g of hand sanitizer containing a surfactant APG, and mix well to obtain a ferritic stainless steel metallographic etchant;

[0041] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 60 seconds to obtain a corroded austenitic stainless steel weld joint, and observe the corroded ferritic stainless steel under a microscope;

[0042] S3. The corroded ferritic stainless steel is cleaned and dried, wherein the cleaning includes ultrasonic cleaning and alcohol rinsing, the ultrasonic cleaning time is 5 minutes, the alcohol rinsing time is 10 seconds, and the drying is oven drying.

[0043] Observe the metallographic structure under a microscope. Figure 1 shown.

[0044] Example 2

[0045] Compared with Example 1, the difference between this embodiment and Example 1 is that the "100 mL saturated picric acid solution and 100 mL ferric chloride hydrochloric acid solution, 20 g of hand sanitizer containing surfactant APG" in S1 is changed to "80 mL saturated picric acid solution and 120 mL ferric chloride hydrochloric acid solution, 30 g of hand sanitizer containing surfactant APG", and the specific implementation steps are:

[0046] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid solution; mix 5 g of ferric chloride, 10 mL of hydrochloric acid and 90 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 80 mL of the saturated picric acid solution and 120 mL of the ferric chloride hydrochloric acid solution, add 30 g of hand sanitizer containing surfactant APG, and mix well to obtain a ferritic stainless steel metallographic etching agent.

[0047] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 60 seconds to obtain a corroded austenitic stainless steel weld joint, and observe the corroded ferritic stainless steel under a microscope;

[0048] S3. The corroded ferritic stainless steel is cleaned and dried, wherein the cleaning includes ultrasonic cleaning and alcohol rinsing, the ultrasonic cleaning time is 5 minutes, the alcohol rinsing time is 10 seconds, and the drying is oven drying.

[0049] Observe the metallographic structure under a microscope. Figure 2 shown.

[0050] The remaining raw materials and preparation process remain the same as in Example 1.

[0051] Example 3

[0052] Compared with Example 1, the difference between this embodiment and Example 1 is that the "100 mL saturated picric acid solution and 100 mL ferric chloride hydrochloric acid solution, 20 g of hand sanitizer containing surfactant APG" in S1 is changed to "120 mL saturated picric acid solution and 80 mL ferric chloride hydrochloric acid solution, 10 g of hand sanitizer containing surfactant APG", and the specific implementation steps are:

[0053] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid solution; mix 5 g of ferric chloride, 10 mL of hydrochloric acid and 90 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 120 mL of the saturated picric acid solution and 80 mL of the ferric chloride hydrochloric acid solution, add 10 g of hand sanitizer containing a surfactant APG, and mix well to obtain a ferritic stainless steel metallographic etching agent.

[0054] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 60 seconds to obtain a corroded austenitic stainless steel weld joint, and observe the corroded ferritic stainless steel under a microscope;

[0055] S3. The corroded ferritic stainless steel is cleaned and dried, wherein the cleaning includes ultrasonic cleaning and alcohol rinsing, the ultrasonic cleaning time is 5 minutes, the alcohol rinsing time is 10 seconds, and the drying is oven drying.

[0056] Observe the metallographic structure under a microscope. Figure 3 shown.

[0057] The remaining raw materials and preparation process remain the same as in Example 1.

[0058] Example 4

[0059] Compared with Example 1, the difference between this embodiment and Example 1 is that the "5 g of ferric chloride, 10 mL of hydrochloric acid and 90 mL of anhydrous ethanol are mixed to obtain a ferric chloride hydrochloric acid solution" in S1 is changed to "4 g of ferric chloride, 12 mL of hydrochloric acid and 100 mL of anhydrous ethanol are mixed to obtain a ferric chloride hydrochloric acid solution", and the specific implementation steps are:

[0060] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid solution; mix 4 g of ferric chloride, 12 mL of hydrochloric acid and 100 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid solution and 100 mL of the ferric chloride hydrochloric acid solution, add 20 g of hand sanitizer containing surfactant APG, and mix well to obtain a ferritic stainless steel metallographic etching agent.

[0061] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 60 seconds to obtain a corroded austenitic stainless steel weld joint, and observe the corroded ferritic stainless steel under a microscope;

[0062] S3. The corroded ferritic stainless steel is cleaned and dried, wherein the cleaning includes ultrasonic cleaning and alcohol rinsing, the ultrasonic cleaning time is 5 minutes, the alcohol rinsing time is 10 seconds, and the drying is oven drying.

[0063] The remaining raw materials and preparation process remain the same as in Example 1.

[0064] Example 5

[0065] Compared with Example 1, the difference between this embodiment and Example 1 is that the "5g ferric chloride, 10mL hydrochloric acid and 90mL anhydrous ethanol are mixed to obtain a ferric chloride hydrochloric acid solution" in S1 is changed to "6g ferric chloride, 8mL hydrochloric acid and 80mL anhydrous ethanol are mixed to obtain a ferric chloride hydrochloric acid solution", and the specific implementation steps are:

[0066] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid solution; mix 6 g of ferric chloride, 8 mL of hydrochloric acid and 80 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid solution and 100 mL of the ferric chloride hydrochloric acid solution, add 20 g of hand sanitizer containing surfactant APG, and mix well to obtain a ferritic stainless steel metallographic etching agent.

[0067] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 60 seconds to obtain a corroded austenitic stainless steel weld joint, and observe the corroded ferritic stainless steel under a microscope;

[0068] S3. The corroded ferritic stainless steel is cleaned and dried, wherein the cleaning includes ultrasonic cleaning and alcohol rinsing, the ultrasonic cleaning time is 5 minutes, the alcohol rinsing time is 10 seconds, and the drying is oven drying.

[0069] The remaining raw materials and preparation process remain the same as in Example 1.

[0070] Example 6

[0071] Compared with Example 1, this embodiment differs in that the treatment method "immersing" in S2 is changed to "wiping", and the specific implementation steps are as follows:

[0072] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid solution; mix 5 g of ferric chloride, 10 mL of hydrochloric acid and 90 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid solution and 100 mL of the ferric chloride hydrochloric acid solution, add 20 g of hand sanitizer containing the surfactant APG, and mix well to obtain a ferritic stainless steel metallographic etching agent.

[0073] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; wipe the surface of the ferritic stainless steel to be corroded 80 times with an absorbent cloth dipped in the ferritic stainless steel metallographic corrosive agent described in Example 1 or Example 2 to obtain corroded ferritic stainless steel. During the wiping process, observe the metallographic structure through a microscope every 10 wiping times to determine whether a clear grain size and grain boundary of the metallographic structure are obtained, until the wiping is qualified. The number of wiping times can be flexibly adjusted according to actual conditions and experience;

[0074] S3. The corroded ferritic stainless steel is cleaned and dried, wherein the cleaning includes ultrasonic cleaning and alcohol rinsing, the ultrasonic cleaning time is 7 minutes, the alcohol rinsing time is 15 seconds, and the drying is oven drying.

[0075] The remaining raw materials and preparation process remain the same as in Example 1.

[0076] Comparative Example 1

[0077] Compared with Example 1, this comparative example is different in that no ferric chloride is added, and the specific implementation steps are as follows:

[0078] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid solution; mix 10 mL of hydrochloric acid and 90 mL of anhydrous ethanol to obtain a hydrochloric acid solution; mix 100 mL of the saturated picric acid solution and 100 mL of the hydrochloric acid solution, add 20 g of hand sanitizer containing surfactant APG, and mix well to obtain a ferritic stainless steel metallographic etchant;

[0079] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 60 seconds to obtain a corroded austenitic stainless steel weld joint, and observe the corroded ferritic stainless steel under a microscope;

[0080] S3. The corroded ferritic stainless steel is cleaned and dried, wherein the cleaning includes ultrasonic cleaning and alcohol rinsing, the ultrasonic cleaning time is 5 minutes, the alcohol rinsing time is 10 seconds, and the drying is oven drying.

[0081] The remaining raw materials and preparation process remain the same as in Example 1.

[0082] Comparative Example 2

[0083] Compared with Example 1, this comparative example differs in that the hand sanitizer containing the surfactant APG is not added, and the specific implementation steps are as follows:

[0084] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid solution; mix 5 g of ferric chloride, 10 mL of hydrochloric acid and 90 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid solution and 100 mL of the ferric chloride hydrochloric acid solution to obtain a ferritic stainless steel metallographic etchant;

[0085] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 60 seconds to obtain a corroded austenitic stainless steel weld joint, and observe the corroded ferritic stainless steel under a microscope;

[0086] S3. The corroded ferritic stainless steel is cleaned and dried, wherein the cleaning includes ultrasonic cleaning and alcohol rinsing, the ultrasonic cleaning time is 5 minutes, the alcohol rinsing time is 10 seconds, and the drying is oven drying.

[0087] The remaining raw materials and preparation process remain the same as in Example 1.

[0088] Comparative Example 3

[0089] Compared with Example 1, the difference between this comparative example is that ferric chloride and hand sanitizer containing surfactant APG are not added at the same time, and the specific implementation steps are as follows:

[0090] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid solution; mix 10 mL of hydrochloric acid and 90 mL of anhydrous ethanol to obtain a hydrochloric acid solution; mix 100 mL of the saturated picric acid solution and 100 mL of the hydrochloric acid solution to obtain a ferritic stainless steel metallographic etchant;

[0091] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 60 seconds to obtain a corroded austenitic stainless steel weld joint, and observe the corroded ferritic stainless steel under a microscope;

[0092] S3. The corroded ferritic stainless steel is cleaned and dried, wherein the cleaning includes ultrasonic cleaning and alcohol rinsing, the ultrasonic cleaning time is 5 minutes, the alcohol rinsing time is 10 seconds, and the drying is oven drying.

[0093] Performance Test:

[0094] The corroded ferritic stainless steel obtained from Examples 1 to 6 and Comparative Examples 1 to 3 was observed under a microscope. Figure 1 The metallographic structure of the corroded ferritic stainless steel obtained in Example 1 under a microscope; Figure 2 The metallographic structure of the corroded ferritic stainless steel obtained in Example 2 under a microscope; Figure 3 The metallographic structure of the corroded ferritic stainless steel obtained in Example 3 under a microscope;

[0095] It can be seen from the embodiments and comparative examples that after the ferritic stainless steel is corroded by a mixed corrosive agent prepared by picric acid, ferric chloride + hydrochloric acid, and a surfactant, the metallographic structure is clear, the dendrites of the ferritic stainless steel and their sizes can be accurately distinguished, and the metallographic structure, grain size and other data of the ferritic stainless steel can be accurately obtained, and the welding process can be adjusted in time, which is extremely important for improving the performance of ferritic stainless steel.

[0096] It should be noted that, in this article, relational terms such as first and second, etc. 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 thereof 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.

[0097] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A metallographic etching agent for ferritic stainless steel, characterized in that: These include picric acid solution, ferric chloride hydrochloric acid solution, and hand sanitizer containing surfactants; The dosage ratio of the picric acid aqueous solution, the ferric chloride hydrochloric acid solution and the hand washing liquid containing a surfactant is (80-120) mL: (80-120) mL: (10-30) g.

2. The metallographic etching agent for ferritic stainless steel according to claim 1, characterized in that: The picric acid solution is prepared by dissolving picric acid in deionized water until a saturated picric acid solution is obtained.

3. The metallographic etching agent for ferritic stainless steel according to claim 1, characterized in that: The hand washing liquid containing a surfactant is a hand washing liquid containing a surfactant APG.

4. The metallographic etching agent for ferritic stainless steel according to claim 1, characterized in that: The dosage ratio of ferric chloride, hydrochloric acid and solvent in the ferric chloride hydrochloric acid solution is (4-6) g: (8-12) mL: (80-100) mL.

5. The metallographic etching agent for ferritic stainless steel according to claim 4, characterized in that: The solvent is deionized water or anhydrous ethanol.

6. A method for preparing a ferritic stainless steel metallographic etching agent according to any one of claims 1 to 5, characterized in that: The following steps are involved: The picric acid is dissolved in deionized water until saturated to obtain a saturated picric acid solution; ferric chloride, hydrochloric acid and a solvent are mixed to obtain a ferric chloride hydrochloric acid solution; the saturated picric acid solution and the ferric chloride hydrochloric acid solution are mixed to add a hand soap containing a surfactant, and the mixture is mixed to obtain a ferritic stainless steel metallographic etching agent.

7. A method for metallographic corrosion of ferritic stainless steel according to any one of claims 1 to 6, characterized in that: The following steps are involved: Performing metallographic sample preparation and cleaning on the surface of the ferritic stainless steel to obtain the ferritic stainless steel to be corroded; The ferritic stainless steel to be corroded is treated with the ferritic stainless steel metallographic corrosive agent to obtain the corroded ferritic stainless steel.

8. The method for metallographic corrosion of ferritic stainless steel according to claim 7, characterized in that: The treatment is one of soaking and wiping; the soaking time is 50s to 170s; and the wiping times are 20-100 times.

9. The method for metallographic corrosion of ferritic stainless steel according to claim 7, characterized in that: The corroded ferritic stainless steel is cleaned and dried; the cleaning includes ultrasonic cleaning and alcohol rinsing; the drying includes drying, blowing with a hair dryer or air drying.

10. The method for metallographic corrosion of ferritic stainless steel according to claim 9, characterized in that: The ultrasonic cleaning time is 1 min to 10 min, and the alcohol flushing time is 5 s to 20 s.

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