A method for detecting preferential corrosion phase in high-aluminum zinc-aluminum-magnesium coating

Abstract

The application provides a method for detecting preferential corrosion phases in high-aluminum zinc-aluminum-magnesium plating, and belongs to the technical field of plating detection and analysis. i The method comprises the following steps: performing first microscopic scanning on the high-aluminum zinc-aluminum-magnesium plating to be detected to obtain a curve L of the content of different characteristic elements i in the high-aluminum zinc-aluminum-magnesium plating to be detected varying with depth ’ i The method comprises the following steps: performing first microscopic scanning on the high-aluminum zinc-aluminum-magnesium plating to be detected to obtain a curve L of the content of different characteristic elements i in the high-aluminum zinc-aluminum-magnesium plating to be detected varying with depth i The method comprises the following steps: performing first microscopic scanning on the high-aluminum zinc-aluminum-magnesium plating to be detected to obtain a curve L of the content of different characteristic elements i in the high-aluminum zinc-aluminum-magnesium plating to be detected varying with depth ’ i The method has the advantages of high precision and good repeatability, shows wide application prospects, and effectively solves the technical problem that traditional corrosion observation methods cannot determine the preferential corrosion phases in high-aluminum zinc-aluminum-magnesium plating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coating detection and analysis, and particularly relates to a method for detecting preferentially corroded phases in a high-aluminum zinc-aluminum-magnesium coating. BACKGROUND

[0002] The zinc-aluminum-magnesium coating is a ternary alloy coating formed by adding a small amount of aluminum and magnesium elements on the basis of a pure zinc coating. Compared with the traditional pure zinc coating, the zinc-aluminum-magnesium coating exhibits more excellent corrosion resistance.

[0003] At present, for the corrosion resistance evaluation of the coating material, an accelerated corrosion test is usually performed, and a chemical rust removal method is used to calculate the corrosion weight loss rate. The disadvantages of this method are as follows: (1) During the corrosion test, the corrosion rate of the base body at the cutout of the coating steel plate is much greater than that of the coating. In order to avoid the influence of the cutout corrosion, the edges around the cutout are usually treated. This will bring a large error in the weight loss measurement before and after the corrosion and the calculation of the corrosion rate, especially when there is little corrosion product in the early stage of corrosion, which will cause a large deviation in the corrosion rate. (2) This method can only calculate the average corrosion rate of the coating material, and is suitable for products with a uniform coating surface and uniform corrosion of the coating. However, for the high-aluminum zinc-aluminum-magnesium coating, the surface is composed of aluminum-rich phases, zinc-rich phases and MgZn2 phases. Since the corrosion potentials of different phases are different, the corrosion rates of different phases are different in different corrosion tests, and the corrosion is not uniform. Therefore, the traditional corrosion weight loss method cannot determine the relative corrosion order between different phases, and the local corrosion has a greater impact on the durability of the coating material. SUMMARY

[0004] The embodiments of the present application provide a method for detecting preferentially corroded phases in a high-aluminum zinc-aluminum-magnesium coating, so as to solve the technical problem that the conventional corrosion observation method cannot determine the preferentially corroded phases in the high-aluminum zinc-aluminum-magnesium coating.

[0005] In a first aspect, the embodiments of the present application provide a method for detecting preferentially corroded phases in a high-aluminum zinc-aluminum-magnesium coating, and the method comprises the following steps.

[0006] Firstly, a first microscan is performed on the high-aluminum zinc-aluminum-magnesium coating to be detected, so as to obtain a curve L of the content of different characteristic elements i in the high-aluminum zinc-aluminum-magnesium coating to be detected varying with the depth i ;

[0007] Secondly, the high-aluminum zinc-aluminum-magnesium coating to be detected after the first microscan is corroded to obtain a corroded coating.

[0008] Thirdly, a second microscan is performed on the corroded coating to obtain a curve L' of the content of different characteristic elements i in the corroded coating varying with the depth i ;

[0009] According to the curve L i and the curve L' i , the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is obtained.

[0010] wherein the different characteristic elements i are Al elements, Zn elements or Mg elements.

[0011] Further, the content of the zinc element in the high-aluminum zinc-aluminum-magnesium coating to be detected is 38-48 wt.%, the content of the aluminum element is 50-60 wt.%, and the content of the magnesium element is <2 wt.%.

[0012] Further, the high-aluminum zinc-aluminum-magnesium coating to be detected is subjected to first micro-scan to obtain a curve L i , specifically comprising:

[0013] The surface of the high-aluminum zinc-aluminum-magnesium coating to be detected is subjected to first cleaning to obtain the high-aluminum zinc-aluminum-magnesium coating to be detected after first cleaning.

[0014] The high-aluminum zinc-aluminum-magnesium coating to be detected after first cleaning is subjected to first drying to obtain the high-aluminum zinc-aluminum-magnesium coating to be detected after first drying.

[0015] The surface of the high-aluminum zinc-aluminum-magnesium coating to be detected after first drying is subjected to progressive first micro-scan along the radial depth by using a glow discharge spectrometer to obtain a curve L i .

[0016] Further, the size of the high-aluminum zinc-aluminum-magnesium coating to be detected is greater than or equal to 2 cm, the surface roughness Ra value is less than or equal to 3, and the sputtering depth is greater than the coating thickness.

[0017] Further, the high-aluminum zinc-aluminum-magnesium coating to be detected after first micro-scan is subjected to corrosion to obtain a corroded coating; specifically comprising:

[0018] The high-aluminum zinc-aluminum-magnesium coating to be detected after first micro-scan is subjected to corrosion and then subjected to second cleaning to obtain the corroded coating after second cleaning.

[0019] The corroded coating after second cleaning is subjected to second drying to obtain the corroded coating.

[0020] wherein the second cleaning comprises: soaking and cleaning the corroded surface by using a rust remover, and then rinsing the corroded surface by using deionized water.

[0021] Further, the rust remover comprises at least one of aminoacetic acid, ammonium chloride, chromium trioxide, hydriodic acid and ammonium persulfate.

[0022] Further, the corrosion mode comprises at least one of the following: cyclic immersion corrosion, full immersion corrosion and erosion corrosion.

[0023] Further, the corrosion coating is subjected to a second micro-scan to obtain a curve L' of content of different characteristic elements i in the corrosion coating varying with depth. i , and specifically comprises:

[0024] The surface of the corrosion coating is subjected to a second micro-scan by a glow discharge optical emission spectrometer along the radial depth to obtain a curve L' of content of different characteristic elements i in the corrosion coating varying with depth. i .

[0025] Further, the curve L i and the curve L' i are used to obtain the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected, and specifically comprises:

[0026] The curve L i is used to obtain an integral area S i of the curve L i .

[0027] The curve L' i is used to obtain an integral area S' i of the curve L' i .

[0028] The integral area S i and the integral area S' i are used to obtain an integral area reduction rate H i of different characteristic elements i before and after corrosion by formula (I),

[0029] The formula (I) is:

[0030] H i = (S i -S' i ) / S i ×100%; wherein H i represents the integral area reduction rate of different characteristic elements i, and i is Al, Zn or Mg;

[0031] The integral area reduction rate H i of different characteristic elements i is used to obtain the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected.

[0032] Further, the integral area reduction rate H i of different characteristic elements i is used to obtain the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected, and specifically comprises:

[0033] According to the integral area reduction rate H of the different characteristic elements i i , the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is obtained by judging formula (II);

[0034] The judging formula (II) is:

[0035] If H Mg >H Zn >H Al , the order of the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is: MgZn2 phase > zinc-rich phase > aluminum-rich phase;

[0036] If H Mg >H Al >H Zn , the order of the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is: MgZn2 phase > aluminum-rich phase > zinc-rich phase;

[0037] If H Zn >H Mg >H Al , the order of the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is: zinc-rich phase > MgZn2 phase > aluminum-rich phase;

[0038] If H Zn >H Al >H Mg , the order of the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is: zinc-rich phase > aluminum > MgZn2 phase;

[0039] If H Al >H Mg >H Zn , the order of the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is: aluminum-rich phase > MgZn2 phase > zinc-rich phase;

[0040] If H Al >H Zn >H Mg , the order of the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is: aluminum-rich phase > zinc-rich phase > MgZn2 phase.

[0041] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0042] The embodiments of the present application provide a method for detecting preferentially corroded phases in a high-aluminum zinc-aluminum-magnesium coating, through micro-scan detection, the content of different characteristic elements i (Al element, Zn element or Mg element) in the high-aluminum zinc-aluminum-magnesium coating before and after corrosion is obtained as a curve L i and a curve L' iThus, the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is obtained, and the technical problem that the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating is difficult to determine by using a traditional corrosion observation method is effectively solved. The method has the advantages of high accuracy and good repeatability, and shows a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0043] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, those skilled in the art can obtain other drawings from these drawings without any creative effort.

[0045] Figure 1 A flowchart of a method for detecting a preferentially corroded phase in a high-aluminum zinc-aluminum-magnesium coating according to an embodiment of the present application is shown in the figure.

[0046] Figure 2 A graph showing the content of different characteristic elements in the high-aluminum zinc-aluminum-magnesium coating before and after corrosion changing with depth according to Example 1 of the present application is shown in the figure. The curve at 0h corresponds to the content before corrosion, and the curve at 168h corresponds to the content after corrosion.

[0047] Figure 3 A graph showing the content of different characteristic elements in the high-aluminum zinc-aluminum-magnesium coating before and after corrosion changing with depth according to Example 2 of the present application is shown in the figure. The curve at 0h corresponds to the content before corrosion, and the curve at 240h corresponds to the content after corrosion. DETAILED DESCRIPTION

[0048] The advantages and various effects of the present application will be more clearly presented by the following specific embodiments and examples. Those skilled in the art should understand that these specific embodiments and examples are used to illustrate the present application, rather than limit the present application.

[0049] Throughout the specification, unless otherwise specifically indicated, the terms used herein are to be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as generally understood by those skilled in the art to which the present application belongs. If there is a conflict, the present specification takes precedence.

[0050] Unless otherwise specifically indicated, the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0051] Zinc-aluminum-magnesium coating is a ternary alloy coating formed by adding a small amount of aluminum and magnesium elements on the basis of pure zinc coating. Compared with the traditional pure zinc coating, the zinc-aluminum-magnesium coating exhibits more excellent corrosion resistance.

[0052] At present, for the corrosion resistance evaluation of the coating material, the accelerated corrosion test and the method of calculating the corrosion weight loss rate by using chemical rust removal are usually used. The disadvantages of this method are as follows: (1) during the corrosion test, the corrosion rate of the base at the cutout of the coated steel sheet is much greater than that of the coating. In order to avoid the influence of the cutout corrosion, the edge of the cutout is usually treated. This will bring a large error in the weight loss measurement before and after the corrosion and the calculation of the corrosion rate, especially in the initial stage of corrosion when there is little corrosion product, which will cause a large deviation of the corrosion rate. (2) this method can only calculate the average corrosion rate of the coating material, and is suitable for products with uniform surface coating and uniform coating corrosion. However, for high-aluminum zinc-aluminum-magnesium coating, the surface is composed of aluminum-rich phase, zinc-rich phase and MgZn2 phase. Because the corrosion potentials of different phases are different, the corrosion rates of different phases are different in different corrosion tests, and it is not uniform corrosion. Therefore, the traditional corrosion weight loss method cannot determine the relative corrosion order of different phases, and the local corrosion has a greater impact on the durability of the coating material.

[0053] The technical scheme provided by the embodiment of the present application solves the above technical problems, and the general idea is as follows:

[0054] In a first aspect, the embodiment of the present application provides a method for detecting preferentially corroded phases in a high-aluminum zinc-aluminum-magnesium coating, as shown in Figure 1 The method comprises the following steps:

[0055] First microscopically scanning the high-aluminum zinc-aluminum-magnesium coating to be detected to obtain a curve L i representing the content of different characteristic elements i in the high-aluminum zinc-aluminum-magnesium coating to be detected varying with depth;

[0056] Corroding the high-aluminum zinc-aluminum-magnesium coating to be detected after the first microscopical scanning to obtain a corroded coating;

[0057] Second microscopically scanning the corroded coating to obtain a curve L' i representing the content of different characteristic elements i in the corroded coating varying with depth;

[0058] According to the curve L i and the curve L' i , the preferentially corroded phases in the high-aluminum zinc-aluminum-magnesium coating to be detected are obtained;

[0059] In the method, the different characteristic elements i are Al element, Zn element or Mg element.

[0060] The embodiment of the present application provides a method for detecting preferentially corroded phases in high-aluminum zinc-aluminum-magnesium plating, through micro scanning detection, the content of different characteristic elements i (Al element, Zn element or Mg element) in the high-aluminum zinc-aluminum-magnesium plating before and after corrosion is obtained respectively, and the curve L i and the curve L' i of the content of the different characteristic elements i in the high-aluminum zinc-aluminum-magnesium plating to be detected varying with depth is obtained, so that the preferentially corroded phases in the high-aluminum zinc-aluminum-magnesium plating to be detected are obtained, and the technical problem that the traditional corrosion observation method is difficult to determine the preferentially corroded phases in the high-aluminum zinc-aluminum-magnesium plating is effectively solved. The method has the advantages of high accuracy and good repeatability, and shows wide application prospect.

[0061] As an embodiment of the present application, the content of the zinc element in the high-aluminum zinc-aluminum-magnesium plating to be detected is 38-48 wt.%, the content of the aluminum element is 50-60 wt.%, and the content of the magnesium element is <2 wt.%.

[0062] In the present application, the zinc-aluminum-magnesium plating is a high-aluminum zinc-aluminum-magnesium plating, the content of the zinc element in the high-aluminum zinc-aluminum-magnesium plating to be detected is 38-48 wt.%, the content of the aluminum element is 50-60 wt.%, and the content of the magnesium element is <2 wt.%. In the high-aluminum zinc-aluminum-magnesium plating, because the content of the MgZn2 phase in the high-aluminum zinc-aluminum-magnesium is small, the reduction rate of the content of the zinc element can be approximately the reduction rate of the content of the zinc-rich phase.

[0063] As an embodiment of the present application, the high-aluminum zinc-aluminum-magnesium plating to be detected is subjected to first micro scanning, and the curve L i of the content of the different characteristic elements i in the high-aluminum zinc-aluminum-magnesium plating to be detected varying with depth is obtained, specifically including:

[0064] The surface of the high-aluminum zinc-aluminum-magnesium plating to be detected is subjected to first cleaning, and the high-aluminum zinc-aluminum-magnesium plating to be detected after first cleaning is obtained;

[0065] The high-aluminum zinc-aluminum-magnesium plating to be detected after first cleaning is subjected to first drying, and the high-aluminum zinc-aluminum-magnesium plating to be detected after first drying is obtained;

[0066] The surface of the high-aluminum zinc-aluminum-magnesium plating to be detected after first drying is subjected to progressive first micro scanning along the radial depth by using a glow discharge optical emission spectrometer, and the curve L i of the content of the different characteristic elements i in the high-aluminum zinc-aluminum-magnesium plating to be detected varying with depth is obtained.

[0067] In some specific embodiments in the present application, the specific process of the first cleaning can be ultrasonic cleaning by using ethanol, and the purpose is to remove oil stains and impurities on the surface of the plating; and the specific process of the first drying can be cold air blowing.

[0068] As an embodiment of the present application, the size diameter of the high-aluminum zinc-aluminum magnesium coating to be detected is greater than or equal to 2 cm, the surface roughness Ra value is less than or equal to 3, and the sputtering depth is greater than the coating thickness.

[0069] In the present application, the sputtering depth specifically refers to the element detection depth of the glow discharge spectrometer, and needs to be greater than the coating thickness because the integral is the integral of the whole coating, which facilitates the calculation of the area reduction rate.

[0070] In the present application, the purpose of controlling the size diameter of the high-aluminum zinc-aluminum magnesium coating to be detected to be greater than or equal to 2 cm is to facilitate the detection of the glow discharge spectrometer with a diameter of 0.1-0.8 cm, which is too small to be detected.

[0071] As an embodiment of the present application, the high-aluminum zinc-aluminum magnesium coating to be detected after the first microscopic scanning is corroded to obtain a corroded coating, specifically including:

[0072] The high-aluminum zinc-aluminum magnesium coating to be detected after the first microscopic scanning is corroded and then subjected to a second cleaning to obtain a second cleaned corroded coating;

[0073] The second cleaned corroded coating is subjected to a second drying to obtain a corroded coating;

[0074] The second cleaning includes: soaking and cleaning the corroded surface with a rust remover, and then rinsing the corroded surface with deionized water.

[0075] In the present application, the corroded surface is soaked and cleaned with a rust remover, and then rinsed with deionized water, which is beneficial to the subsequent second microscopic scanning of the corroded coating and improves the measurement accuracy.

[0076] As an embodiment of the present application, the rust remover includes at least one of aminoacetic acid, ammonium chloride, chromium trioxide, hydriodic acid, and ammonium persulfate.

[0077] As an embodiment of the present application, the corrosion method includes at least one of circumferential immersion corrosion, full immersion corrosion, and scouring corrosion.

[0078] In the present application, the circumferential immersion corrosion can be performed according to the periodic immersion corrosion test method described in standard HB 5194-1981.

[0079] In the present application, the full immersion corrosion is also called full immersion zone corrosion, and specifically refers to corrosion occurring at the full immersion part of a metal component. The full immersion corrosion can be performed according to the uniform corrosion full immersion test method for metal materials in the laboratory described in standard GB 10124-1988.

[0080] In this application, erosion corrosion refers to metal damage caused by high-speed relative motion between the metal surface and the corrosive fluid. Typically, corrosion is not severe in static or low-speed flowing corrosive media. However, when the corrosive fluid moves at high speed, it destroys the protective surface film or corrosion product film on the metal surface. The thinning or removal of the surface film accelerates the corrosion process. Therefore, erosion corrosion is the result of the synergistic effect of fluid scouring and corrosion. The main methods include: rotational erosion, pipe flow erosion, impact jet erosion, and high-speed scouring.

[0081] As one embodiment of this application, the etched coating is subjected to a second microscopic scan to obtain a curve L' showing the change in the content of different characteristic elements i in the etched coating with depth. i Specifically, it includes:

[0082] A progressive second microscopic scan of the surface of the etched coating along radial depth was performed using a glow discharge spectrometer to obtain curves L' showing the variation of the content of different characteristic elements i in the etched coating with depth. i .

[0083] As one embodiment of this application, the step of proceeding according to the curve L i and the curve L' i The preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested were obtained, specifically including:

[0084] According to the curve L i The curve L is obtained. i The integral area S i ;

[0085] According to the curve L' i The curve L' is obtained. i The integral area S' i ;

[0086] According to the integral area S i and the integral area S' i Equation (I) is used to obtain the reduction rate H of the integral area of ​​different characteristic elements i before and after corrosion. i ,

[0087] Equation (I):

[0088] H i =(S i -S' i ) / S i ×100%; where H i The integral area reduction rate represents different characteristic elements i, where i is Al, Zn, or Mg.

[0089] According to the integral area reduction rate H of the different characteristic elements i i The preferentially corroded phase in the high-aluminum-zinc-aluminum-magnesium coating to be tested was obtained.

[0090] In this application, according to the curve L i The curve L is obtained. i The integral area S i The specific process can be achieved by directly analyzing curve L on the glow discharge spectrometer. i Integrating, we obtain the integral area S. i Alternatively, by using the curve L in Origin plotting software... i The area S obtained by integration i "According to the curve L'" i The curve L is obtained. i The integral area S' i The process of "according to the curve L" is similar to "the process of "according to the curve L". i The curve L is obtained. i The integral area S i The process is the same.

[0091] As one embodiment of this application, the integral area reduction rate H based on the different feature elements i is... i The preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested were obtained, specifically including:

[0092] According to the integral area reduction rate H of the different characteristic elements i i By using the judgment formula (II), the preferential corrosion phase in the high-aluminum zinc-aluminum-magnesium coating to be tested is obtained;

[0093] The judgment formula (II):

[0094] If H Mg >H Zn >H Al The order of preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested is: MgZn2 phase > zinc-rich phase > aluminum-rich phase;

[0095] If H Mg >H Al >H Zn The order of preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested is: MgZn2 phase > aluminum-rich phase > zinc-rich phase;

[0096] If H Zn >H Mg >H Al The order of preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested is: zinc-rich phase > MgZn2 phase > aluminum-rich phase;

[0097] If H Zn >HAl >H Mg Therefore, the order of the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is: zinc-rich phase > aluminum-rich phase > MgZn2 phase;

[0098] If H Al >H Mg >H Zn Therefore, the order of the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is: aluminum-rich phase > MgZn2 phase > zinc-rich phase;

[0099] If H Al >H Zn >H Mg Therefore, the order of the preferentially corroded phase in the high-aluminum zinc-aluminum-magnesium coating to be detected is: aluminum-rich phase > zinc-rich phase > MgZn2 phase.

[0100] The application will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and are not used to limit the scope of the application. The experimental methods not specified in the following examples are generally determined according to national standards. If there is no corresponding national standard, the general international standard, conventional conditions, or the conditions suggested by the manufacturer are used.

[0101] Example 1

[0102] This example provides a method for detecting the preferentially corroded phase in a high-aluminum zinc-aluminum-magnesium coating, specifically comprising the following steps:

[0103] Treatment object: high-aluminum zinc-aluminum coating material subjected to 168 h immersion test (sodium bisulfite system); wherein the zinc element content in the high-aluminum zinc-aluminum-magnesium coating to be detected is 38-48 wt.%, the aluminum element content is 50-60 wt.%, and the magnesium element content is <2 wt.%.

[0104] 1. First, the high-aluminum zinc-aluminum-magnesium coated steel plate is subjected to ethanol ultrasonic cleaning to remove surface dirt and impurities, and then the zinc-aluminum-magnesium coated steel plate is subjected to progressive scanning from the surface along the radial depth using a glow discharge spectrometer to obtain the curves of the changes of the contents of Zn, Al, and Mg elements with depth, as shown in FIG. 1 (specifically, the curve at 0 h), and the curves are integrated, wherein the integral area of the Zn element curve is 325.9, the integral area of the Al element curve is 234.3, and the integral area of the Mg element curve is 11.5. Figure 2

[0105] ​2. The sample is subjected to a circumferential immersion accelerated corrosion test according to GB / T 19746-2005 "Salt Solution Circumferential Immersion Test for Corrosion of Metals and Alloys", and after 168 h, the sample is taken for rust removal, the corrosion products are immersed and cleaned with ammonium acetate cleaning solution (mass ratio of ammonium acetate to deionized water is 1:4), the residual cleaning solution is washed with deionized water, and the cold air is blown dry.

[0106] 3. The depth distribution scanning of Zn, Al and Mg elements of the plated steel sheet after rust removal is performed using a glow discharge optical emission spectrometer, as shown in Figure 2 , and the curves are integrated respectively, and the integral area of the Zn element curve is 195.9, the integral area of the Al element curve is 158.3, and the integral area of the Mg element curve is 1.2.

[0107] 4. The Zn element content reduction rate is calculated according to the integral result: (325.9-195.9) / 325.9x100%=39.9%

[0108] The Al element content reduction rate is: (234.3-158.3) / 234.3x100%=32.4%

[0109] The Mg element content reduction rate is: (11.5-1.2) / 11.5x100%=89.6%

[0110] 5. Since Mg element mainly exists in the form of MgZn2, it can be obtained that MgZn2 preferentially corrodes, and since the content of high-aluminum zinc-aluminum-magnesium eutectic phase is small, the Zn element content reduction rate can be approximately equal to the rich zinc phase content reduction rate, and therefore the corrosion rate is MgZn2>rich zinc phase>rich aluminum phase; that is, the preferential corrosion phase order is MgZn2>rich zinc phase>rich aluminum phase.

[0111] Example 2

[0112] The example provides a method for detecting preferential corrosion phase in high-aluminum zinc-aluminum-magnesium coating, which specifically comprises the following steps:

[0113] The treatment object: high-aluminum zinc-aluminum coating material is subjected to 240 h circumferential immersion test (sodium bisulfite system); wherein, the zinc element content in the high-aluminum zinc-aluminum-magnesium coating to be detected is 38-48 wt.%, the aluminum element content is 50-60 wt.%, and the magnesium element content is <2 wt.%.

[0114] 1. First, the zinc-aluminum-magnesium plated steel sheet is subjected to ethanol ultrasonic cleaning to remove surface oil stains and impurities, and then the zinc-aluminum-magnesium plated steel sheet is subjected to progressive scanning from the surface along the radial depth using a glow discharge optical emission spectrometer, to obtain the curves of the changes of the Zn, Al and Mg element contents with depth, and the results are shown in Figure 3The curves are shown in FIG. 1 (specifically, the curves shown at 0h), and the curves are integrated, respectively, wherein the integral area of the Zn element curve is 325.9, the integral area of the Al element curve is 234.3, and the integral area of the Mg element curve is 11.5.

[0115] 2. The sample is subjected to a circular immersion accelerated corrosion test according to GB / T 19746-2005 "Metal and alloy corrosion salt solution immersion test" standard, and after 240h, the sample is taken for rust removal, the corrosion products are immersed and cleaned with ammonium acetate cleaning solution (mass ratio of ammonium acetate to deionized water is 1:4), and the residual cleaning solution is washed with deionized water and dried with cold air.

[0116] 3. The Zn, Al and Mg elements of the plated steel sheet after rust removal are subjected to depth distribution scanning using a glow discharge optical emission spectrometer, as shown in FIG. 2 (specifically, the curves shown at 240h), and the curves are integrated, respectively, to obtain the integral area of the Zn element curve as 91.3, the integral area of the Al element curve as 121.1, and the integral area of the Mg element curve as 0.78. Figure 3

[0117] 4. The Zn element content reduction rate is calculated according to the integral result: (325.9-91.3) / 325.9x100%=72.0%

[0118] The Al element content reduction rate is: (234.3-121.1) / 234.3x100%=48.3%

[0119] The Mg element content reduction rate is: (11.5-0.78) / 11.5x100%=93.2%

[0120] 5. Since the Mg element mainly exists in the form of MgZn2, it can be concluded that MgZn2 is preferentially corroded, and since the content of high-aluminum zinc-aluminum-magnesium eutectic phase is small, the reduction rate of Zn element content can be approximately equal to the reduction rate of zinc-rich phase content, and therefore the corrosion rate is MgZn2> zinc-rich phase> aluminum-rich phase; that is, the preferential corrosion phase order is MgZn2> zinc-rich phase> aluminum-rich phase.

[0121] Comparative Example 1

[0122] This example provides a method for detecting preferential corrosion phase in high-aluminum zinc-aluminum-magnesium coating using a traditional method, which specifically comprises:

[0123] Treatment object: high-aluminum zinc-aluminum-magnesium material after 240h of circular immersion test (sodium bisulfite system); wherein, in the high-aluminum zinc-aluminum-magnesium coating to be detected, the content of zinc element is 38-48wt.%, the content of aluminum element is 50-60wt.%, and the content of magnesium element is <2wt.%.

[0124] ​1. The high-aluminum zinc-aluminum-magnesium plated steel sheet is subjected to ethanol ultrasonic cleaning to remove the surface oil and impurities, the sample size is measured, and the corrosion area is calculated as 4 cm x 10 cm = 40 cm 2 The original plate weight m0 before the corrosion test is weighed as 20.3356 g.

[0125] 2. The accelerated corrosion test is performed by using GB / T 19746-2005 "Metal and alloy corrosion salt solution immersion test", and the sample is taken after 240 h for rust removal. The corrosion product is subjected to immersion cleaning by using ammonium acetate cleaning solution (mass ratio of ammonium acetate: deionized water is 1:4), and the residual cleaning solution is washed by using deionized water, and cold air is used for drying;

[0126] 3. The sample weight m1 after rust removal is weighed as 19.8586 g by using an electronic balance, and the corrosion rate calculation formula is (20.3356-19.8586) / (40x240x2) g cm -2 h -1 = 2.48x10 -5 g cm -2 h -1 = 0.25 g m -2 h -1 . The calculated corrosion rate is the average corrosion rate of the entire steel sheet, and it is impossible to determine the preferential corrosion phase.

[0127] It should be understood that the endpoints of the ranges and any values disclosed herein are not limited to the precise values, and that the ranges or values should be construed to be roughly about the ranges or values. For ranges, the endpoints are included in the ranges, and the ranges are inclusive of the single points. New ranges can be created from the endpoints of the ranges and the single points by combining the endpoints and single points with each other. These new ranges are to be considered disclosed herein.

[0128] It should be noted that, in the present text, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual such relationship or order between or among the entities or actions. Also, the terms "comprises", "comprising", or any other variant thereof are intended to cover non-exclusive inclusions, so that a process, method, article, or apparatus that comprises a list of elements does not only include those elements, but also includes other elements not expressly listed or inherent to such process, method, article, or apparatus. In addition, the term "and / or" appearing in the present text only describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases of A alone, A and B together, and B alone.

[0129] The foregoing is considered as illustrative only of the principles of the application. Numerous modifications and changes will readily occur to those skilled in the art, and it is intended to embrace all such modifications and changes that fall within the scope of the application. Accordingly, the application is not to be restricted in scope to the specific embodiments disclosed herein but is to be accorded the full scope that the principles and novel features request appropriately granted.

Claims

1. A method for detecting preferentially corroded phases in high-aluminum zinc-aluminum-magnesium coatings, characterized in that, The method includes: The high-aluminum-zinc-aluminum-magnesium coating to be tested was subjected to a first microscopic scan, and the curves L showing the changes in the content of different characteristic elements i with depth in the high-aluminum-zinc-aluminum-magnesium coating to be tested were obtained. i ; The high-aluminum-zinc-aluminum-magnesium coating to be tested after the first microscopic scan is etched, and then a second cleaning is performed to obtain the etched coating after the second cleaning. A second microscopic scan was performed on the etched coating to obtain curves L showing the variation of the content of different characteristic elements i in the etched coating with depth. ’ i ; According to the curve L i and the curve L ’ i The preferentially corroded phase in the high-aluminum-zinc-aluminum-magnesium coating to be tested was obtained; Wherein, the different characteristic element i is Al, Zn or Mg; By mass fraction, the zinc content in the tested high-aluminum-zinc-aluminum-magnesium coating is 38-48 wt.%, the aluminum content is 50-60 wt.%, and the magnesium content is <2 wt.%. The diameter of the high-aluminum zinc-aluminum magnesium coating to be tested is ≥2 cm, the surface roughness Ra value is ≤3, and the sputtering depth is greater than the coating thickness. The second cleaning process includes: soaking the corroded surface in a rust remover and then rinsing it with deionized water; According to the curve L i and the curve L ’ i The preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested were obtained, specifically including: According to the curve L i The curve L is obtained. i The integral area S i ; According to the curve L ’ i The curve L is obtained. ’ i The integral area S ’ i ; According to the integral area S i and the integral area S ’ i Equation (I) is used to obtain the integral area reduction rate H of different characteristic elements i before and after corrosion. i , Equation (I): H i = (S) i -S ’ i ) / S i ×100%; where H i The integral area reduction rate represents different characteristic elements i, where i is Al, Zn, or Mg. According to the integral area reduction rate H of the different characteristic elements i i The preferentially corroded phase in the high-aluminum-zinc-aluminum-magnesium coating to be tested was obtained; The integral area reduction rate H based on the different feature elements i i The preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested were obtained, specifically including: According to the integral area reduction rate H of the different characteristic elements i i By using the judgment formula (II), the preferential corrosion phase in the high-aluminum zinc-aluminum magnesium coating to be tested is obtained; The judgment formula (II): If H Mg H Zn H Al The order of preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested is: MgZn2 phase > zinc-rich phase > aluminum-rich phase; If H Mg H Al H Zn The order of preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested is: MgZn2 phase > aluminum-rich phase > zinc-rich phase; If H Zn H Mg H Al The order of preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested is: zinc-rich phase > MgZn2 phase > aluminum-rich phase; If H Zn H Al H Mg The order of preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested is: zinc-rich phase > aluminum-rich phase > MgZn2 phase; If H Al H Mg H Zn The order of preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested is: aluminum-rich phase > MgZn2 phase > zinc-rich phase; If H Al H Zn H Mg The order of preferentially corroded phases in the high-aluminum-zinc-aluminum-magnesium coating to be tested is: aluminum-rich phase > zinc-rich phase > MgZn2 phase.

2. The method for detecting preferentially corroded phases in high-aluminum zinc-aluminum-magnesium coatings according to claim 1, characterized in that, The high-aluminum-zinc-aluminum-magnesium coating to be tested was subjected to a first microscopic scan, and the curves L showing the changes in the content of different characteristic elements i with depth in the high-aluminum-zinc-aluminum-magnesium coating to be tested were obtained. i Specifically, it includes: The surface of the high-aluminum-zinc-aluminum-magnesium coating to be tested is first cleaned to obtain the high-aluminum-zinc-aluminum-magnesium coating to be tested after the first cleaning. The high-aluminum-zinc-aluminum-magnesium coating to be tested after the first cleaning is first dried to obtain the first dried high-aluminum-zinc-aluminum-magnesium coating to be tested. A glow discharge spectrometer was used to perform a progressive first microscopic scan along the radial depth of the surface of the high-aluminum-zinc-aluminum-magnesium coating to be tested after the first drying, and the curves L showing the changes in the content of different characteristic elements i in the high-aluminum-zinc-aluminum-magnesium coating to be tested with depth were obtained. i .

3. The method for detecting preferentially corroded phases in high-aluminum zinc-aluminum-magnesium coatings according to claim 1, characterized in that, The etched coating after the second cleaning is then subjected to a second drying process to obtain the etched coating.

4. The method for detecting preferentially corroded phases in high-aluminum zinc-aluminum-magnesium coatings according to claim 3, characterized in that, The rust remover includes at least one of glycine, ammonium chloride, chromium trioxide, hydroiodic acid, and ammonium persulfate.

5. The method for detecting preferentially corroded phases in high-aluminum zinc-aluminum-magnesium coatings according to claim 1, characterized in that, The corrosion mode includes at least one of peripheral immersion corrosion, total immersion corrosion, and erosion corrosion.

6. The method for detecting preferentially corroded phases in high-aluminum zinc-aluminum-magnesium coatings according to claim 1, characterized in that, A second microscopic scan was performed on the etched coating to obtain curves L showing the variation of the content of different characteristic elements i in the etched coating with depth. ’ i Specifically, it includes: A progressive second microscopic scan of the surface of the etched coating along radial depth was performed using a glow discharge spectrometer to obtain curves L showing the variation of the content of different characteristic elements i in the etched coating with depth. ’ i .

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