Hot-dip Al-Zn-In-Sn-Si alloy coating as well as preparation method and application of hot-dip Al-Zn-In-Sn-Si alloy coating

Abstract

The invention relates to the technical field of hot dipping, in particular to a hot dipping Al-Zn-In-Sn-Si alloy coating and a preparation method and application thereof.The hot dipping Al-Zn-In-Sn-Si alloy coating comprises, by mass, 4%-5% of Zn, 0.01%-0.05% of In, 0.05%-0.06% of Sn, 0.1%-0.5% of Si and the balance Al and inevitable impurities; wherein the hot dipping Al-Zn-In-Sn-Si alloy plating layer is obtained by carrying out hot dipping on steel in an Al-Zn-In-Sn-Si alloy melt solution, the hot dipping temperature is 550-560 DEG C, the hot dipping time is 3-5 minutes, and the prepared hot dipping Al-Zn-In-Sn-Si alloy plating layer is high in uniformity and high in corrosion resistance.

Description

Technical Field

[0001] The invention relates to the technical field of hot-dip plating, and in particular to a hot-dip Al-Zn-In-Sn-Si alloy coating and a preparation method and application thereof. Background Art

[0002] In modern industry, steel, as one of the main structural materials of modern industry, has deeply and widely penetrated into many pillar industries such as construction, chemical industry, and transportation. In the field of construction, from high-rise building frames to bridge bodies, steel bears the heavy responsibility of supporting huge weights and resisting complex external forces; in the field of chemical industry, various reaction vessels and pipeline facilities cannot do without steel's ability to withstand high temperatures, high pressures and chemical corrosion; in the field of transportation, rails and car frames rely on the strength of steel to ensure safe operation.

[0003] However, the high chemical activity of steel makes it face many challenges during its service. When it is in continuous contact with oxygen and water vapor in the atmosphere, or when it is attacked by corrosive media, the electrons on the surface of the steel quickly become active and corrosion reactions easily occur. In the marine environment, the high concentration of chloride ions in seawater is extremely aggressive and will strongly destroy the passivation film on the surface of the steel, forming pits; in the industrial acid-base environment, strong acids and strong alkalis will accelerate the destruction of the metal lattice, causing the strength, hardness and other mechanical properties of the steel to be greatly reduced.

[0004] Traditional steel anti-corrosion treatment methods include hot-dip aluminum and hot-dip galvanizing. However, aluminum and zinc coatings provide limited anti-corrosion effects in harsh service environments, especially in high-salt environments. Conventional coatings often cannot prevent further corrosion of steel in harsh environments due to the lack of effective cathodic protection. In recent years, researchers have begun to develop technologies to add other alloying elements to the plating solution to improve corrosion resistance, such as adding Bi, Mg, Ti and other elements. There are many elements to choose from for hot-dip plating, but in the process of multi-element alloying hot-dip steel plates, the element ratio is not selected reasonably, which can easily lead to problems such as uneven coating and poor corrosion resistance, affecting the application of steel in various fields. Summary of the invention

[0005] Aiming at the technical problem that the coating prepared by hot-dip plating in the prior art has insufficient corrosion resistance, especially easy corrosion in a high chloride ion environment, the present invention provides a hot-dip Al-Zn-In-Sn-Si alloy coating and its preparation method and application. By adding zinc, indium, tin and silicon in a suitable ratio to molten aluminum liquid, the corrosion resistance of steel materials is improved, and the preparation method is simple in process and low in cost, and is suitable for industrial large-scale production and application.

[0006] In a first aspect, the present invention provides a hot-dip Al-Zn-In-Sn-Si alloy coating, wherein the mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coating are: Zn 4%-5%, In 0.01%-0.05%, Sn 0.05%-0.06%, Si0.1%-0.5%, and the balance is Al and unavoidable impurities; The hot-dip Al-Zn-In-Sn-Si alloy coating is obtained by hot-dip plating the steel in a molten Al-Zn-In-Sn-Si alloy solution, the hot-dip plating temperature is 550-560° C., and the hot-dip plating time is 3-5 minutes.

[0007] Zn (zinc): provides the function of sacrificial anode and cathodic protection for steel. The Zn content affects the corrosion behavior and protection life of hot-dip Al-Zn-In-Sn-Si alloy coating. When the Zn content in the alloy coating is greater than 5%, Zn will precipitate along the grain boundaries to form a large amount of segregation phase, increasing the tendency of intergranular corrosion. Moreover, since Zn can promote the solid solution of other alloy elements such as In and Sn, the composition ratio of Zn, In, and Sn is related and cannot be adjusted separately.

[0008] Al (Aluminum): As a base metal, aluminum in the coating mainly provides the function of improving oxidation resistance and enhancing corrosion resistance by forming a dense oxide film.

[0009] In (Indium): It can reduce the passivation range of aluminum anodes. A small amount of In can activate the anode surface and make the corrosion products loose and easy to fall off, improving the anode dissolution performance. The solubility of In in aluminum is extremely small, and its added content is controlled at 0.01%-0.05%. When the In content is in this range, the potential becomes negative as the In content increases, the current efficiency increases rapidly, and the anode performance is significantly improved; when the content is lower than 0.01%, In has almost no effect on the anode performance; when it is higher than 0.05%, the anode cannot be fully activated, the current efficiency is low, and indium segregates in the form of a new phase, accelerating the self-corrosion of aluminum, resulting in a decrease in the current efficiency of the aluminum anode.

[0010] Sn (tin): Sn dissolved in the aluminum matrix as Sn 2+ Sn 4+ Sn enters the oxide film on the surface of the alloy in the form of ions, destroying the compactness of the oxide film, thereby activating the aluminum anode, and the addition of Sn also promotes the preferential dissolution of the grain boundaries of the aluminum anode. When the Sn content is less than 0.05%, the effect of activating the aluminum anode is not obvious; when the Sn content is greater than 0.06%, it has an inhibitory effect on the growth of the oxide film, and the Sn that is not dissolved in the matrix is ​​prone to segregation at the grain boundaries.

[0011] Adding a certain proportion of In can form a more stable passivation film and slow down the corrosion process of the alloy coating. Adding a certain proportion of Sn can optimize the hardness of the coating and reduce the occurrence of cracks. The passivation protection of In combined with the enhanced mechanical properties of Sn can provide comprehensive protection in more severe environments.

[0012] Si (Silicon): Inhibits excessive growth of the alloy layer, enhances the adhesion and uniformity of the coating, and forms intermetallic compounds in the coating to increase mechanical properties. The Si content is selected to be 0.1%-0.5%, which can balance the thickness of the alloy layer and the strength of the coating.

[0013] Furthermore, the mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coating are: Zn 5%, In 0.02%, Sn 0.06%, Si 0.1%, and the remainder is Al and unavoidable impurities.

[0014] Furthermore, the hot-dip coating temperature is 550°C.

[0015] Furthermore, the difference in thickness between any two locations of the hot-dip Al-Zn-In-Sn-Si alloy coating does not exceed 1.0 μm.

[0016] In a second aspect, the present invention provides a method for preparing the above-mentioned hot-dip Al-Zn-In-Sn-Si alloy coating, comprising the following steps: (1) Add Zn, In, Sn and Si to the Al melt, stir evenly at 1180-1220°C to obtain Al-Zn-In-Sn-Si alloy melt for standby use; (2) Grinding the steel surface twice with sandpaper, rinsing with deionized water after grinding, and drying to obtain the steel to be hot-dip plated; (3) The steel to be hot-dip plated is immersed in a 550-560°C Al-Zn-In-Sn-Si alloy melt for hot-dip plating, and is kept still for 3-5 minutes. After cooling, a hot-dip Al-Zn-In-Sn-Si alloy coating is formed on the surface of the steel.

[0017] Furthermore, the Al melt in step (1) is obtained by melting Al in a furnace heated to 1200°C.

[0018] Furthermore, in step (2), the first grinding is to use 80-grit sandpaper to roughly grind the steel surface; and the second grinding is to use 120-grit sandpaper to finely grind the steel surface until the surface is smooth.

[0019] In a third aspect, the present invention provides application of the above-mentioned hot-dip Al-Zn-In-Sn-Si alloy coating in steel corrosion protection.

[0020] Furthermore, the service conditions of the steel include seawater.

[0021] The beneficial effects of the present invention are: The present invention provides a hot-dip Al-Zn-In-Sn-Si alloy coating. By adjusting the addition ratio of each component and strictly controlling the hot-dip coating temperature, the corrosion resistance of the hot-dip Al-Zn-In-Sn-Si alloy coating can be enhanced, so that it can provide cathodic protection in a corrosive medium containing high chloride ions, and significantly extend the service life of steel materials. In addition, the operation is simple and no complex equipment is required. The formed hot-dip Al-Zn-In-Sn-Si alloy coating has good adhesion and uniformity on the surface of steel, is suitable for surface protection of various steels, and has a wide range of applications. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. 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 should fall within the scope of protection of the present invention.

[0023] Example 1 A hot-dip Al-Zn-In-Sn-Si alloy coating, wherein the mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coating are: 5% Zn, 0.02% In, 0.06% Sn, 0.1% Si, and the balance is Al and unavoidable impurities.

[0024] A method for preparing a hot-dip Al-Zn-In-Sn-Si alloy coating comprises the following steps: (1) Preparation of Al-Zn-In-Sn-Si alloy melt: Heat Al to 1200°C in a furnace, add Zn, In, Sn and Si in sequence after complete melting, and stir thoroughly to ensure uniform and stable composition; the temperature is always maintained at 1180-1220°C during stirring to avoid decomposition or loss of alloy elements; (2) Preparation of steel to be hot-dip plated: Use 80-grit sandpaper to roughly grind the steel surface to remove surface oxides and impurities, then use 120-grit sandpaper to finely grind until the surface is smooth (no unevenness visible to the naked eye), rinse the polished steel with deionized water to remove dust and debris, and dry it for later use; (3) Preparation of hot-dip Al-Zn-In-Sn-Si alloy coating: Use a fixture to immerse the steel to be hot-dip plated into a 550°C Al-Zn-In-Sn-Si alloy melt for hot-dip plating, keep it still for 3 minutes, and then take it out. After natural cooling, a hot-dip Al-Zn-In-Sn-Si alloy coating is formed on the surface of the steel.

[0025] Example 2 A hot-dip Al-Zn-In-Sn-Si alloy coating, wherein the mass percentage of each component in the hot-dip Al-Zn-In-Sn-Si alloy coating is the same as that in Example 1.

[0026] A method for preparing a hot-dip Al-Zn-In-Sn-Si alloy coating comprises the following steps: (1) Preparation of Al-Zn-In-Sn-Si alloy melt: Heat Al to 1200°C in a furnace, add Zn, In, Sn and Si in sequence after it is completely melted, and stir thoroughly to ensure uniform and stable composition; The melting temperature is always maintained within the temperature range of 1180-1220° C. to avoid decomposition or loss of alloy elements; the mass percentage of each component in the Al-Zn-In-Sn-Si alloy melt is the same as that in Example 1; (2) Preparation of steel to be hot-dip plated: Use 80-grit sandpaper to roughly grind the steel surface to remove surface oxides and impurities, then use 120-grit sandpaper to finely grind until the surface is smooth (no unevenness visible to the naked eye), rinse the polished steel with deionized water to remove dust and debris, and dry it for later use; (3) Preparation of hot-dip Al-Zn-In-Sn-Si alloy coating: Use a fixture to immerse the steel to be hot-dip plated into a 550°C Al-Zn-In-Sn-Si alloy melt for hot-dip plating, keep it still for 5 minutes, and then take it out. After natural cooling, a hot-dip Al-Zn-In-Sn-Si alloy coating is formed on the surface of the steel.

[0027] Comparative Examples 1-4 The preparation methods of the hot-dip Al-Zn-In-Sn-Si alloy coatings of Comparative Examples 1-4 are the same as those of Example 1. The mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coatings of Example 1 and Comparative Examples 1-4 are shown in Table 1.

[0028] Table 1 Mass percentage of each component in hot-dip Al-Zn-In-Sn-Si alloy coating (%)

[0029] Comparative Example 5-Comparative Example 8 The mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coating of Comparative Example 5 are the same as those in Example 1, and the preparation method is the same as that in Example 1, except that the hot-dip plating temperature in step (3) is 500°C.

[0030] The mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coating of Comparative Example 6 are the same as those in Example 1, and the preparation method is the same as that in Example 1, except that the hot-dip plating temperature in step (3) is 600°C.

[0031] The mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coating of Comparative Example 7 are the same as those in Comparative Example 4, and the preparation method is the same as that of Example 1, except that the hot-dip plating temperature in step (3) is 500°C.

[0032] The mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coating of Comparative Example 8 are the same as those in Comparative Example 4, and the preparation method is the same as that of Example 1, except that the hot-dip plating temperature in step (3) is 600°C.

[0033] Experimental Example 1 Thickness Detection The hot-dip Al-Zn-In-Sn-Si alloy coating obtained in Example 1 was non-destructively measured for thickness using an eddy current thickness gauge. Ten test points were randomly selected and data were statistically analyzed after the measurement. The same thickness test was performed on Example 2 and Comparative Examples 1 to 8, and the thickness values ​​are shown in Table 2.

[0034] Table 2 Thickness of hot-dip Al-Zn-In-Sn-Si alloy coating (μm)

[0035] From the comparison of the thickness data of Example 1, Comparative Example 5 and Comparative Example 6 in Table 2, it can be seen that when the composition ratio of the Al-Zn-In-Sn-Si alloy melt is the same, the higher the hot-dip plating temperature, the higher the average thickness, but when the hot-dip plating temperature is 550°C, the uniformity of the hot-dip Al-Zn-In-Sn-Si alloy coating is good. Similarly, the same conclusion can be drawn by comparing the thickness data of Comparative Example 4, Comparative Example 7 and Comparative Example 8.

[0036] By comparing the thickness data of Example 1 and Comparative Examples 1-4, it can be seen that in addition to the hot-dip plating temperature, the composition ratio of the Al-Zn-In-Sn-Si alloy melt will also affect the uniformity of the hot-dip plating Al-Zn-In-Sn-Si alloy coating. The hot-dip plating Al-Zn-In-Sn-Si alloy coating of Example 1 has good uniformity.

[0037] By comparing the thickness data of Example 1 and Example 2, it can be seen that the longer the hot-dip plating time is, the thicker the hot-dip Al-Zn-In-Sn-Si alloy coating is.

[0038] Experimental Example 2 Microstructure Analysis The hot-dip Al-Zn-In-Sn-Si alloy coatings obtained in Example 1 and Comparative Examples 4 to 8 were subjected to microstructural analysis. The hot-dip Al-Zn-In-Sn-Si alloy coatings in Example 1 had a dense structure and a uniform distribution of Zn-Al solid solution. The hot-dip Al-Zn-In-Sn-Si alloy coatings in Comparative Example 5 had a dense structure and a small amount of needle-shaped FeAl3. The hot-dip Al-Zn-In-Sn-Si alloy coatings in Comparative Example 6 exhibited a layered structure with excessive Zn-rich phases. It can be seen that the hot-dip temperature has a great influence on the microstructural morphology. When the hot-dip temperature is 550°C, the hot-dip Al-Zn-In-Sn-Si alloy coating exhibits a good microstructural morphology.

[0039] The hot-dip Al-Zn-In-Sn-Si alloy coating of Comparative Example 4 has a dense structure, but contains a small amount of needle-shaped FeAl3 and Zn-rich phase. The hot-dip Al-Zn-In-Sn-Si alloy coating of Comparative Example 7 has uneven Zn enrichment and a thin alloy layer. The hot-dip Al-Zn-In-Sn-Si alloy coating of Comparative Example 8 has more holes and severe Zn-Al segregation. It can be seen that the same results can be obtained in Comparative Examples 4, 7 and 8.

[0040] Experimental Example 3 Performance Testing The hot-dip Al-Zn-In-Sn-Si alloy coatings of Example 1 and Comparative Examples 1 to 8 were subjected to full immersion corrosion test, salt spray corrosion test and adhesion test. The test results are shown in Table 3.

[0041] The hot-dip-plated steel prepared in Example 1 was cut to prepare samples. The size of the hot-dip Al-Zn-In-Sn-Si alloy coating on each sample was 100 mm × 100 mm. A total of 4 samples were prepared, which were marked as Example 1-a, Example 1-b, Example 1-c and Example 1-d respectively. The samples of Comparative Examples 1 to 8 were prepared in the same way.

[0042] (1) Full immersion corrosion test Example 1-a was immersed in 100 mL of 3.5% sodium chloride solution (simulating the sodium chloride content in seawater) for 30 days, taken out every 7 days, cleaned the corrosion products and immersed again, until the corrosion products were cleaned on the 30th day, the mass loss was measured and the corrosion rate was calculated. Comparative Examples 1-a to Comparative Examples 8-a were compared and tested under the same conditions.

[0043] The corrosion rate calculation formula is as follows: v=

[0044] Where, v: corrosion rate (g / m 2 ·h); ΔW: mass loss (g); A: sample surface area (m 2 ); t: corrosion time (h).

[0045] (2) Salt spray corrosion test The salt spray corrosion test was carried out according to ASTM B117. The test environment temperature was 35°C, the spray solution was 5% sodium chloride solution, the spray pH range was 6.5-7.2, and the surface corrosion state of Example 1-b was observed every 100 hours, and the exposure time was 500 hours. Comparative Examples 1-b to Comparative Examples 8-b were subjected to comparative tests under the same conditions.

[0046] (3) Adhesion test A criss-cross grid was scratched on Example 1-c, and the 3M tape was used to adhere and then torn off. The percentage of the detached area of ​​the hot-dip Al-Zn-In-Sn-Si alloy coating to the total area (100mm×100mm) was calculated. Comparative tests were carried out on Comparative Examples 1-c to 8-c under the same conditions.

[0047] According to ASTM D4541 standard, the adhesion strength of the hot-dip Al-Zn-In-Sn-Si alloy coating of Example 1-d was measured by a puller. Comparative Examples 1-d to 8-d were subjected to comparative tests under the same conditions.

[0048] Table 3 Performance test results

[0049] The composition ratio of the Al-Zn-In-Sn-Si alloy melt in Example 1 is different from that in Comparative Examples 1 to 4, and their corrosion effects, detachment areas, and adhesion strengths will show obvious differences. In comparison, the performance test results of Example 1 are the best, and the performance test results of Comparative Example 4 are the worst. The reason for this may be that the proportion of Zn in the alloy coating of Comparative Example 4 is too high, and the ratio with In and Sn is not in the appropriate range, resulting in performance changes. The hot-dip plating temperature of Example 1 is different from that of Comparative Examples 5 and 6, and their corrosion effects, detachment areas, and adhesion strengths will show obvious differences. In comparison, the performance test results of Example 1 are the best. The composition ratio and hot-dip plating temperature of the Al-Zn-In-Sn-Si alloy melt in Example 1 are different from those of Comparative Examples 7 and 8, and their corrosion effects, detachment areas, and adhesion strengths will show more obvious differences. Similarly, the performance test results of Example 1 are the best.

[0050] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily conceive of changes or substitutions within the technical scope disclosed by the present invention, and such changes or substitutions shall be within the scope of protection of the present invention.

Claims

1. A hot-dip Al-Zn-In-Sn-Si alloy coating, characterized in that: The mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coating are: Zn 4%-5%, In 0.01%-0.05%, Sn 0.05%-0.06%, Si 0.1%-0.5%, and the balance is Al and unavoidable impurities; The hot-dip Al-Zn-In-Sn-Si alloy coating is obtained by hot-dip plating the steel in a molten Al-Zn-In-Sn-Si alloy solution, the hot-dip plating temperature is 550-560° C., and the hot-dip plating time is 3-5 minutes.

2. The hot-dip Al-Zn-In-Sn-Si alloy coating according to claim 1, characterized in that: The mass percentages of the components in the hot-dip Al-Zn-In-Sn-Si alloy coating are: Zn 5%, In 0.02%, Sn 0.06%, Si 0.1%, and the balance is Al and unavoidable impurities.

3. The hot-dip Al-Zn-In-Sn-Si alloy coating according to claim 1, characterized in that: The hot-dip galvanizing temperature is 550°C.

4. The hot-dip Al-Zn-In-Sn-Si alloy coating according to claim 1, characterized in that: The difference in thickness between any two locations of the hot-dip Al-Zn-In-Sn-Si alloy coating does not exceed 1.0 μm.

5. A method for preparing a hot-dip Al-Zn-In-Sn-Si alloy coating as claimed in claim 1, characterized in that: The steps include: (1) Add Zn, In, Sn and Si to the Al melt, stir evenly at 1180-1220°C to obtain Al-Zn-In-Sn-Si alloy melt for standby use; (2) Grinding the steel surface twice with sandpaper, rinsing with deionized water after grinding, and drying to obtain the steel to be hot-dip plated; (3) The steel to be hot-dip plated is immersed in a 550-560°C Al-Zn-In-Sn-Si alloy melt for hot-dip plating, and is kept still for 3-5 minutes. After cooling, a hot-dip Al-Zn-In-Sn-Si alloy coating is formed on the surface of the steel.

6. The method for preparing the hot-dip Al-Zn-In-Sn-Si alloy coating according to claim 5, characterized in that: The Al melt in step (1) is obtained by melting Al in a furnace heated to 1200°C.

7. The method for preparing the hot-dip Al-Zn-In-Sn-Si alloy coating according to claim 5, characterized in that: The first grinding in step (2) is to use 80-grit sandpaper to roughly grind the steel surface; the second grinding is to use 120-grit sandpaper to finely grind the steel surface until the surface is smooth.

8. Use of the hot-dip Al-Zn-In-Sn-Si alloy coating as claimed in claim 1 in steel corrosion protection.

9. The use according to claim 8, characterized in that The service conditions of the steel include sea water.

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