A process for corrosion-resistant zinc infiltration on the surface of a pin shaft for coal mines

Abstract

The application discloses a kind of coal mine with pin shaft surface corrosion-resistant zinc infiltration process, belong to zinc infiltration process technical field.The present application process includes: the pin shaft is carried out shot blasting, ultrasonic cleaning pretreatment;Pretreated pin shaft is loaded into rotary zinc infiltration jar with zinc infiltration agent, is heated to 370-380 DEG C and keeps warm 2.5-3h, during alternately positive and negative rotation;After zinc infiltration is completed, it is immersed into closed liquid and is closed aftertreatment.The zinc infiltration agent includes zinc powder, copper nickel tin alloy powder, nano yttrium oxide powder, multi-walled carbon nanotube, ternary composite activator, potassium iodide and alumina powder.The present application forms quinary alloy infiltration layer by introducing copper nickel tin alloy powder, effectively blocks hydrogen sulfide and chloride ion penetration;Nano yttrium oxide blocks corrosion channel and catalyzes zinc diffusion;Carbon nanotube forms three-dimensional network bridging structure and blocks micropore;Ternary composite activator synergistic effect reduces zinc infiltration temperature and energy consumption.The present application's infiltration layer has excellent corrosion resistance, and is especially suitable for the pin shaft surface protection under the harsh working conditions of coal mine.

Description

Technical Field

[0001] This invention belongs to the field of zinc diffusion process technology, specifically, it relates to a corrosion-resistant zinc diffusion process for the surface of pins used in coal mines. Background Technology

[0002] In coal mining operations, machinery and equipment are constantly exposed to harsh environments characterized by high humidity, high dust levels, and strong corrosion. Taking key equipment such as hydraulic supports, scraper conveyors, and tunneling machines as examples, the pins widely used in their connecting components not only bear enormous mechanical loads and frequent impacts and friction, but are also directly exposed to mine water, coal slurry, and humid air containing high concentrations of corrosive ions such as sulfur and chloride. As a core component of structural connections, corrosion of the pins can lead to increased equipment clearances, loose connections, operational failures, and even serious safety accidents such as breakage.

[0003] Currently, the surface protection treatment of pins used in coal mines mainly adopts processes such as electro-galvanizing, hot-dip galvanizing, Dacromet coating, and conventional zinc diffusion. While electro-galvanizing provides some corrosion resistance, the coating is relatively thin (usually only 5-15 μm) and carries the risk of hydrogen embrittlement. It is prone to peeling under underground impact loads, making it difficult to meet long-term corrosion protection requirements. Although hot-dip galvanizing forms a thicker zinc-iron alloy layer, the coating is hard and brittle. When the pin is subjected to bending or shear stress during assembly or operation, the coating is prone to cracking, allowing corrosive media to penetrate the substrate along the cracks and accelerate localized corrosion. While Dacromet coating offers good corrosion resistance, its high curing temperature and energy consumption, coupled with the presence of toxic substances such as hexavalent chromium, do not meet the requirements of green manufacturing and environmental protection policies. Furthermore, the coating is prone to wear and failure under the high-wear conditions of coal mines.

[0004] Conventional zinc diffusion processes form a zinc-iron alloy diffusion layer on the pin surface through powder zinc diffusion, offering advantages such as strong adhesion, high hardness, and no hydrogen embrittlement. However, existing conventional zinc diffusion processes result in a zinc-diffused layer with high surface porosity, allowing corrosive media to penetrate into the substrate through micropores, forming pitting corrosion that rapidly expands and leads to premature pin breakage. Furthermore, current zinc diffusion processes also suffer from long diffusion times and excessively high temperatures (high energy consumption). Therefore, there is an urgent need to develop a novel zinc diffusion process that can address these issues. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a corrosion-resistant zinc diffusion process for the surface of pins used in coal mines.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A corrosion-resistant zinc-diffusion process for the surface of pins used in coal mines includes the following steps: Step 1: Shot blasting (mechanical rust removal) is performed on the pin shaft, followed by ultrasonic cleaning in a solvent to remove residual grease and dust, and then drying to obtain the pre-treated pin shaft; Step 2: Load the pretreated pin and zinc diffusion agent into the rotary zinc diffusion tank, fill it tightly, seal the lid, heat it up, and keep it at that temperature for 2.5-3 hours. During the heat preservation period, the zinc diffusion tank is rotated in both directions (every 30 minutes) to ensure a uniform diffusion layer. Step 3: After zinc diffusion is completed, stop heating, continue rotating the tank until it is below 200°C, then allow it to cool naturally to room temperature. Remove the pin, use a vibrating screen to remove any residual zinc diffusion agent, and finally seal the tank for post-treatment to complete the zinc diffusion process.

[0008] As a preferred embodiment of the present invention, the shot blasting treatment time is 15-20 minutes.

[0009] As a preferred embodiment of the present invention, the ultrasonic cleaning time is 10-20 minutes.

[0010] As a preferred embodiment of the present invention, the solvent is a mixture of acetone and ethanol in a volume ratio of 1:1.

[0011] As a preferred embodiment of the present invention, the heating conditions are as follows: heating to 370-380℃ at a rate of 10-12℃ / min.

[0012] As a preferred embodiment of the present invention, the volume ratio of the pin to the zinc diffusion agent is 1:3.

[0013] As a preferred embodiment of the present invention, the post-sealing processing steps are as follows: Immerse the pin in the sealing liquid and soak it at 80℃ for 1-2 minutes. Then heat it to 120℃ and cure it for 20-25 minutes to form an ultra-thin hydrophobic film. Then perform post-treatment.

[0014] As a preferred embodiment of the present invention, the sealing liquid is 5 wt% silane coupling agent KH-560 and 0.5 wt% sodium molybdate.

[0015] As a preferred embodiment of the present invention, the zinc infiltration agent comprises the following raw materials in weight percentages: 65-70% zinc powder, 6-8% copper-nickel-tin alloy powder, 1.5-2.5% nano-yttrium oxide powder, 0.8-1.2% multi-walled carbon nanotubes, 3.5-4.5% ternary composite activator, 1.2-1.8% potassium iodide, and 15-18% alumina powder.

[0016] As a preferred embodiment of the present invention, the ternary composite activator comprises potassium fluoroborate, sodium fluoride and ammonium chloride, with a mass ratio of 2:1:1.

[0017] The addition of copper-nickel-tin alloy powder to the raw material introduces a ternary alloying element, forming a pentagonal alloy diffusion layer of Fe-Zn-Cu-Ni-Sn. Nickel and tin react with hydrogen sulfide to generate stable nickel sulfide and tin sulfide corrosion products. These sulfides have high melting points and dense structures, effectively blocking further penetration by hydrogen sulfide and chloride ions. Furthermore, a ternary composite activator is used; the three activators work synergistically to generate a sufficient concentration of active zinc atoms at a lower temperature, reducing the energy consumption required for the process. In addition, nano-yttrium oxide in the raw material is partially reduced at the diffusion temperature, releasing active rare earth ions that preferentially occupy grain boundaries and pores, blocking corrosion channels. Simultaneously, it catalyzes zinc atom diffusion, further reducing the zinc diffusion temperature. Multi-walled carbon nanotubes in the raw material have a high aspect ratio, forming a three-dimensional network bridging structure in the diffusion layer, physically sealing micropores. Their excellent conductivity homogenizes the surface potential, inhibiting localized galvanic corrosion. Finally, potassium iodide in the raw material provides I... - Ions can interact with Zn 2+ It forms a complex, increases the rate of zinc vapor generation, and shortens the zinc penetration time.

[0018] As a preferred embodiment of the present invention, the zinc diffusion agent is prepared through the following steps: S1. First, add nano-yttrium oxide powder and multi-walled carbon nanotubes to the solvent, and then disperse them by ultrasonication to form a stable suspension; S2. Then add zinc powder and copper-nickel-tin alloy powder to the suspension, stir to form a paste, and vacuum dry to remove the solvent to obtain the intermediate. S3. Add the intermediate obtained in step S2, ternary composite activator, potassium iodide and alumina powder into a mixer, mix for 30-45 minutes, and sieve to obtain zinc diffusion agent.

[0019] In a preferred embodiment of the present invention, the solvent is anhydrous ethanol.

[0020] As a preferred embodiment of the present invention, the temperature of the vacuum drying is 60-80℃.

[0021] Wet pre-dispersion is first used to ensure that yttrium oxide nanoparticles and multi-walled carbon nanotubes are uniformly coated on the zinc powder surface, avoiding agglomeration.

[0022] The beneficial effects of this invention are: 1. This invention introduces copper-nickel-tin alloy powder to form a pentagonal alloy diffusion layer of Fe-Zn-Cu-Ni-Sn, which can effectively block the penetration of high concentrations of sulfur and chloride ions in the mining environment and greatly improve corrosion resistance. 2. By employing a ternary composite activator with synergistic effect and adding nano-yttrium oxide, zinc atom diffusion is catalyzed, reducing the zinc diffusion temperature and significantly lowering energy consumption compared to conventional zinc diffusion processes; 3. By utilizing nano-yttrium oxide to preferentially occupy grain boundaries and micropores, multi-walled carbon nanotubes form a three-dimensional network bridging structure, which physically seals the pores of the penetration layer, prevents corrosive media from penetrating the matrix, and avoids pitting corrosion and early fracture. 4. Using potassium iodide to provide I - Ions and Zn 2+ It forms a complex, accelerates the generation of zinc vapor, and, in conjunction with the forward and reverse zinc diffusion tanks, achieves a uniform diffusion layer and shortens the process cycle; 5. A thin hydrophobic film is formed on the surface of the zinc-impregnated layer using silane coupling agent and sodium molybdate, which further improves the moisture resistance and resistance to adhesion of corrosive media. In summary, the process of this invention has made significant progress in terms of improving corrosion resistance, reducing energy consumption, shortening time, and adapting to the harsh working conditions of coal mines. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example Preparation of zinc penetration agent: S1. Weigh the raw materials of Examples 1-5 according to the raw material ratio in Table 1, add nano-yttrium oxide powder and multi-walled carbon nanotubes to anhydrous ethanol, and ultrasonically disperse (power 200W, frequency 40kHz) for 30min to form a stable suspension. S2. Then add zinc powder and copper-nickel-tin alloy powder (containing 80% copper, 15% nickel and 5% tin) to the suspension, stir to form a paste, and vacuum dry at 80°C for 5 hours to remove the solvent to obtain the intermediate. S3. Add the intermediate obtained in step S2, ternary composite activator, potassium iodide and alumina powder into a mixer, mix for 45 minutes, and pass through an 80-mesh sieve to obtain zinc diffusion agent.

[0025] A corrosion-resistant zinc-diffusion process for the surface of pins used in coal mines includes the following steps: Step 1: Shot blast the pin (mechanical rust removal) for 20 minutes, then place it in a solvent (a mixture of acetone and ethanol, with a volume ratio of 1:1) for ultrasonic cleaning for 20 minutes to remove residual grease and dust, and dry it to obtain the pre-treated pin. Step 2: Put the pretreated pin and zinc diffusion agent into a rotating zinc diffusion tank at a volume ratio of 1:3. After filling and sealing, heat the tank to 370℃ at a rate of 10℃ / min and keep it at that temperature for 3 hours. During the heat preservation period, the zinc diffusion tank is rotated in both directions (every 30 minutes) to ensure a uniform diffusion layer. Step 3: After zinc diffusion is completed, stop heating and continue rotating the tank until it is below 200°C. Then, allow it to cool naturally to room temperature. Remove the pin and use a vibrating screen to remove any residual zinc diffusion agent. Immerse the pin in a sealing solution (5 wt% silane coupling agent KH-560 and 0.5 wt% sodium molybdate) at 80°C for 2 minutes. Then, raise the temperature to 120°C and cure for 25 minutes to form an ultra-thin hydrophobic film, thus completing the zinc diffusion process.

[0026] Table 1 Comparative Example The only difference from the example is that the comparative raw materials are weighed according to the raw material ratio in Table 2 to complete the zinc diffusion process.

[0027] Table 2 The performance of the membranes in the above embodiments and comparative examples was measured, and the results are shown in Table 3. Table 3 As shown in Table 3, the measured data of the embodiments all exceeded 1100 hours in the salt spray test, far superior to the comparative examples, indicating that the synergistic effect of the pentagonal alloy layer, nano-yttrium oxide, and carbon nanotubes significantly improved the corrosion resistance. Comparative Example 1 (without copper-nickel-tin alloy) showed the greatest weight loss in H2S corrosion, indicating that the lack of nickel and tin elements prevented the formation of a dense sulfide barrier layer. Comparative Examples 2 and 3 (without nano-yttrium oxide or without carbon nanotubes) showed significantly increased porosity, indicating a decrease in micropore sealing ability. In summary, the membrane performance of the embodiments of the present invention is excellent, and the corrosion resistance is significantly better than that of the comparative examples, possessing important application value in the field of zinc diffusion process technology.

[0028] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A zinc-diffusion process for corrosion-resistant surfaces of pins used in coal mines, characterized in that, Includes the following steps: Step 1: Shot blast the pin, then ultrasonically clean it in a solvent and dry it to obtain a pre-treated pin. Step 2: Load the pre-treated pin and zinc diffusion agent into a rotary zinc diffusion tank, fill it tightly, seal the lid, heat it, and keep it at that temperature for 2.5-3 hours, alternating between forward and reverse rotation during the heat treatment. Step 3: After zinc diffusion is completed, stop heating, continue rotating the tank until it reaches below 200°C, then cool it to room temperature, remove the pin, remove any residual zinc diffusion agent using a vibrating screen, and finally seal it for post-treatment to complete the zinc diffusion process.

2. The corrosion-resistant zinc diffusion process for the surface of a pin used in coal mines according to claim 1, characterized in that, The heating conditions are as follows: heating to 370-380℃ at a rate of 10-12℃ / min.

3. The corrosion-resistant zinc diffusion process for the surface of a pin used in coal mines according to claim 1, characterized in that, The volume ratio of the pin to the zinc plating agent is 1:

3.

4. The corrosion-resistant zinc diffusion process for the surface of a pin used in coal mines according to claim 1, characterized in that, The post-sealing treatment steps are as follows: Immerse the pin in the sealing liquid, soak it at 80°C for 1-2 minutes, then heat it to 120°C and cure it for 20-25 minutes to form an ultra-thin hydrophobic film, and then perform post-treatment.

5. The corrosion-resistant zinc diffusion process for the surface of a pin used in coal mines according to claim 4, characterized in that, The sealing liquid consists of 5 wt% silane coupling agent KH-560 and 0.5 wt% sodium molybdate.

6. The corrosion-resistant zinc diffusion process for the surface of a pin used in coal mines according to claim 1, characterized in that, The zinc diffusion agent comprises the following raw materials in weight percentages: 65-70% zinc powder, 6-8% copper-nickel-tin alloy powder, 1.5-2.5% nano yttrium oxide powder, 0.8-1.2% multi-walled carbon nanotubes, 3.5-4.5% ternary composite activator, 1.2-1.8% potassium iodide, and 15-18% alumina powder.

7. The corrosion-resistant zinc diffusion process for the surface of a pin used in coal mines according to claim 6, characterized in that, The ternary composite activator comprises potassium fluoroborate, sodium fluoride, and ammonium chloride, with a mass ratio of 2:1:

1.

8. The corrosion-resistant zinc diffusion process for the surface of a pin used in coal mines according to claim 6, characterized in that, The zinc diffusion agent is prepared by the following steps: S1, first, add nano-yttrium oxide powder and multi-walled carbon nanotubes to a solvent, disperse them by ultrasonication to form a suspension; S2, then add zinc powder and copper-nickel-tin alloy powder to the suspension, stir to form a paste, and vacuum dry to obtain an intermediate; S3, put the intermediate obtained in step S2 into a mixer with a ternary composite activator, potassium iodide and alumina powder, mix, and sieve to obtain the zinc diffusion agent.

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