CN-121992328-A - Preparation and analysis method of hot dip Zn.Al.Mg alloy plating layer

Abstract

The invention provides a preparation and analysis method of a hot dip Zn-Al-Mg alloy plating layer, belonging to the technical field of metal surface coating. The invention also provides a matched coating analysis method, which comprises the steps of carrying out phase analysis by adopting an X-ray diffractometer and quantitatively characterizing the microstructure of the coating by adopting a scanning electron microscope and image analysis software. According to the invention, the corrosion resistance of the coating is obviously improved by improving the content of Al and cooperatively adding Mg and Si, and the microstructure characteristics of the coating are revealed through analysis, so that a theoretical basis is provided for component optimization and process control, and the coating has industrial application prospects.

Inventors

• QIAO DEGAO
• XU MINGWEN
• WANG JIN
• PENG PENG
• ZHANG GUOTANG
• XU YUANLI
• CHEN CUI
• WANG LIANWEN
• ZHAO YONGKE
• ZHANG XUDONG
• SHI JUNFENG

Assignees

• 酒钢集团甘肃宏兴宏宇新材料有限责任公司

Dates

Publication Date

20260508

Application Date

20260305

Claims (7)

1. 1. A preparation and analysis method of a hot dip Zn-Al-Mg alloy plating layer is characterized in that: the preparation method comprises the following steps: Steel strip pretreatment, namely degreasing, washing and annealing the steel strip; Hot dip coating, namely immersing the pretreated steel strip into molten alloy plating solution, and carrying out hot dip coating to form an alloy plating layer on the surface of the steel strip; Carrying out post-plating treatment, namely cooling, solidifying and passivating the steel strip subjected to hot dip plating to obtain a plate with a Zn-Al-Mg alloy plating layer on the surface; The analysis method comprises the following steps: Preparing a sample, namely cutting the sample from the plating plate, and cleaning and drying the sample; testing the sample by adopting an X-ray diffractometer, and determining the type of the phase in the coating by analysis software; And (3) observing and analyzing the microstructure, namely observing the surface and section microstructure of the plating layer by adopting a scanning electron microscope, and acquiring microstructure characteristic information by using image analysis software.
2. 2. The method according to claim 1, wherein the degreasing treatment in the first step adopts alkaline cleaning liquid, and the technological parameters are that the temperature is 50-70 ℃, the alkali liquor concentration is 10-40g/L, and the treatment time is 30-120s; The annealing treatment is carried out in a protective atmosphere consisting of N 2 and H 2 , and the volume fraction of H 2 is 3-10%; the annealing temperature curve is that the steel strip is heated to 720-780 ℃ rapidly and kept for 30-120s, then the cooling speed is controlled, and the steel strip enters the second step after the temperature of the steel strip is reduced to 460-480 ℃.
3. 3. The method according to claim 1, wherein the hot dip coating temperature in the step two is 420 ℃ to 500 ℃ and the dip coating time is 4 to 25 seconds, and the thickness of the formed alloy coating is 10 to 40 μm.
4. 4. The method according to claim 1, wherein the cooling solidification in the third step is performed by adopting an air cooling or an air cooling assisted by an atomization water cooling mode, the cooling rate is 10-50 ℃ per second, and the surface temperature of the coating is reduced to 60-120 ℃; The passivation film concentration adopted in the passivation treatment corresponds to the effective metal ion concentration of 0.5-2.0g/L, the pH value of 1.5-5.0, the contact time of 1-5s, the drying temperature after passivation of 80-120 ℃ and the drying time of 30-90s.
5. 5. The method according to claim 1, wherein in the sample preparation step, the cut sample has a size of 10-11cm long, 9-11cm wide and 1.0-1.2mm thick, and the cleaning process comprises the steps of ultrasonic cleaning in absolute ethyl alcohol for 600s, wiping the surface of the coating with a dust-free cloth dipped with acetone for 1-2min, washing with deionized water, and drying at 60 ℃ for 30min.
6. 6. The method according to claim 1, wherein the measuring parameters of the X-ray diffractometer in the phase analysis step are a measuring range of 10-90 degrees, the ray source is Cu-K alpha rays, and the scanning speed is 5-10 degrees/min.
7. 7. The method according to claim 1, wherein in the microscopic observation and analysis step, the observation parameters of the scanning electron microscope are acceleration voltage of 30kV and current of 0.4nA, and a back scattering electron imaging mode is adopted.

Description

Preparation and analysis method of hot dip Zn.Al.Mg alloy plating layer Technical Field The invention relates to the technical field of surface treatment of metal materials, in particular to a preparation and analysis method of a hot dip Zn-Al-Mg alloy plating layer. Background The steel is widely applied to the fields of building structures, transportation, energy facilities, household appliance manufacturing and the like due to the excellent mechanical properties, processability and economy, however, the steel is extremely easy to generate electrochemical corrosion in service environments, especially under the conditions of atmosphere, high humidity, high salt mist or industrial pollution, and the corrosion and mechanical properties are reduced, so that the service life of the steel is obviously shortened. In order to improve the corrosion resistance of steel, the hot dip galvanizing technology is one of the most widely applied protection means at present, namely, a metal zinc coating is formed on the surface of the steel, and the corrosion of a matrix is delayed by utilizing the cathodic protection effect and the physical shielding effect of zinc, however, the corrosion resistance of the traditional pure zinc coating is still obviously insufficient under a severe corrosion environment, and the protection requirement of long-term service is difficult to meet. In recent years, a Zn-Al-Mg alloy plating layer formed by adding aluminum and magnesium elements into a zinc bath becomes a research hot spot, a compact and stable composite corrosion product film (such as ZnO, al 2O3, mgO and hydroxide or basic salt thereof) can be formed in the corrosion process by adding the aluminum and the magnesium, the corrosion resistance of the plating layer is obviously improved, and even a certain self-healing capacity is given to the plating layer, but in the prior art, the aluminum content in the Zn-Al-Mg plating layer (such as a typical ZAM plating layer) is relatively low, and the compactness and long-term stability of the corrosion product film still have room for improvement under extreme environments. Researches show that the aluminum content in the coating is properly improved, so that more dense oxidation phases rich in aluminum can be generated, and the corrosion resistance and high-temperature oxidation resistance of the coating are further improved. At present, the research on Zn-Al-Mg alloy plating layers with high aluminum content in the prior art is not perfect, and particularly the phase composition, microstructure evolution rule and structure-activity relation with corrosion resistance of the plating layers under a high aluminum component system lack of deep analysis, which results in lack of reliable theoretical basis in component optimization and production process control (such as hot dip plating temperature, cooling rate and the like), so that the industrialized application and full play of performance potential of the Zn-Al-Mg alloy plating layers with high aluminum content are limited. Therefore, the Zn-Al-Mg series hot dip coating with reasonable component design, controllable structure and excellent corrosion resistance and high aluminum content is developed, microstructure characteristics of the Zn-Al-Mg series hot dip coating are clear, and the Zn-Al-Mg series hot dip coating has important practical significance for improving the protection level of steel. Disclosure of Invention The invention aims to solve the problems existing in the prior art, provides a preparation and analysis method of a hot dip Zn-Al-Mg alloy plating layer, and solves the problems that the aluminum content in the existing Zn-Al-Mg alloy plating layer is relatively low, and the structure-activity relationship between the phase composition, microstructure evolution rule and corrosion resistance of the plating layer under a high aluminum component system is lack of systematic analysis. Therefore, the invention adopts the following technical scheme: The hot dip Zn-Al-Mg alloy plating layer is applied to the surface of a steel substrate, and comprises, by mass, 8.0% -30.0% of Al, 1.0% -7.0% of Mg, 0.01% -0.8% of Si, and the balance of Zn and unavoidable impurities. The invention provides a method for preparing the alloy coating, which comprises the following steps: S1, steel strip pretreatment, namely degreasing, washing and annealing the steel strip to obtain a clean surface structure suitable for hot dip plating; Specifically, the degreasing treatment adopts alkaline cleaning liquid, the technological parameters are that the temperature is 50-70 ℃, the alkali liquor concentration is 10-40g/L, and the treatment time is 30-120s; the alkali liquor comprises NaOH/Na 2CO3 and a surfactant; The annealing treatment is carried out in a protective atmosphere consisting of N 2 and H 2, and the volume fraction of H 2 is 3-10%; The annealing temperature curve is that the steel strip is heated to 720-780 ℃ rapidly and kept for 30-120s, th