Method for improving corrosion resistance of steel

Abstract

The invention discloses a method for improving corrosion resistance of steel, and belongs to the technical field of metal protection. The method for improving the corrosion resistance of the steel comprises the following procedures of acid pickling, rinsing, drying, reduction, hot dipping, passivation, drying and packaging. Replacing a plating assisting process in the hot dipping process with a thermal reduction process; and in the thermal reduction process, hydrogen with the volume content of 3-25% is adopted for thermal reduction. A plating assisting technology in a traditional hot dipping technology is replaced with a reduction technology, the steel obtained after acid pickling is dried and then fed into the atmosphere box, a small amount of iron oxide remaining on the surface of the steel is reduced into sponge iron in the hydrogen reduction atmosphere, the surface of the steel keeps active, and then a zinc-based or zinc alloy plating layer can be better plated; therefore, the corrosion resistance of the steel is greatly improved, and the service life is prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal protection, and particularly relates to a method for improving the corrosion resistance of steel. BACKGROUND

[0002] Steel is the skeleton material of modern industry, but it is prone to electrochemical corrosion in the atmosphere, seawater, acid rain and industrial pollution environment, among which the partial perforation and stress corrosion cracking of infrastructure and steel structure often result from the premature failure of the surface protective layer. Therefore, how to economically and efficiently prolong the service life of steel has become the focus of attention of the material and engineering fields.

[0003] Hot-dip plating technology is still the main way to increase the service life of steel at present due to its mature process, low cost, metallurgical bonding between the plating layer and the substrate and other advantages. The service life of steel materials is prolonged by sacrificing the anode plating layer to protect the steel substrate. The traditional hot-dip galvanizing process of steel is that the steel is sequentially subjected to pickling, rinsing, plating aid, drying, hot-dip plating, passivation, drying and packaging. The main role of the plating aid process is to coat a layer of salt film on the surface of the steel, so that the atmosphere is isolated from the surface of the steel, thereby maintaining the activity of the surface of the steel. However, improper control of the plating aid process can cause surface defects such as zinc explosion, zinc nodules and pitting; Fe 2+ Inclusions with zinc slag can form a cathode phase and physical barrier at the interface, causing star-shaped plating leakage and weakening the long-acting corrosion resistance of the hot-dip plating layer.

[0004] Therefore, how to further improve the plating layer quality, reduce plating leakage and improve the corrosion resistance of the plating layer without omitting the plating aid process has become a technical problem to be solved in the field. SUMMARY

[0005] To solve the above technical problems, the application provides a method for improving the corrosion resistance of steel.

[0006] To achieve the above object, the application provides the following technical scheme.

[0007] The application provides a method for improving the corrosion resistance of steel, which comprises the following processes: pickling, rinsing, drying, reduction, hot-dip plating, passivation, drying and packaging; the plating aid process in the hot-dip plating process is replaced by a hot reduction process; the hot reduction process uses hydrogen with a volume content of 3-25% for hot reduction.

[0008] Technical principles: The present application replaces the plating process in the traditional hot-dip process with a reduction process. After drying the pickled steel, it is sent to an atmosphere box, where the small amount of iron oxide remaining on the surface of the steel is reduced to iron under a hydrogen reduction atmosphere, keeping the surface of the steel active and enabling better plating of zinc-based or zinc alloy coatings, thereby greatly improving the corrosion resistance of the steel and extending its service life.

[0009] Further, the hot reduction process uses a mixture of nitrogen and hydrogen gas for hot reduction, and the volume content of hydrogen is 3-25%.

[0010] Further, the temperature of the hot reduction is 100-900℃.

[0011] Further, the hot-dip process uses zinc liquid for hot-dip plating.

[0012] Further, the zinc liquid is selected from aluminum-zinc-silicon liquid or zinc-aluminum-magnesium liquid.

[0013] Further, the aluminum content in the aluminum-zinc-silicon liquid is 0.01-55.0wt.%, and the silicon content is 0.02-0.3wt.%; the aluminum content in the zinc-aluminum-magnesium liquid is 0.01-55.0wt.%, and the magnesium content is 0.01-3.0wt.%.

[0014] Further, the equipment used in the reduction process includes an atmosphere box and a conveying mechanism.

[0015] The top of the atmosphere box is provided with a plurality of nitrogen-hydrogen mixed gas input ports.

[0016] The atmosphere box is provided with a steel inlet and a steel outlet.

[0017] The conveying mechanism is fixed to the bottom of the atmosphere box.

[0018] Further, the number of nitrogen-hydrogen mixed gas input ports is 6-10.

[0019] Further, the steel inlet and the steel outlet are both flat slits; the slit height of the steel inlet is adjusted by an inlet baffle; the slit height of the steel outlet is adjusted by an outlet baffle.

[0020] Further, the slit passage length of the steel outlet is 5-10 meters; 6-10 nitrogen charging inlets are uniformly distributed at the steel outlet to control the hydrogen content at the steel outlet to be below 4%.

[0021] Compared with the prior art, the present application has the following advantages and technical effects:

[0022] 1) The method provided by the present application can significantly improve the coating quality, reduce the plating leakage phenomenon, and improve the corrosion resistance of the coating.

[0023] 2) Compared with the prior method for improving the corrosion resistance of steel, the present application omits the plating aid process, avoiding the pollution of the environment by waste smoke and waste gas generated when the plating aid layer enters the high-temperature zinc liquid;

[0024] 3) The method provided by the present application can plate a zinc-based coating containing aluminum and magnesium on the surface of the steel, thereby greatly improving the corrosion resistance of the coating. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which form a part of the present application, are used to provide a further understanding of the present application, and the illustrative embodiments thereof, and are not intended for limiting the present application. In the drawings:

[0026] Figure 1 The structure of the equipment used in the reduction process and the hot-dip plating process in the method for improving the corrosion resistance of steel provided by the present application is shown in the figure, wherein 1 is an atmosphere box, 2 is a zinc liquid tank, 3 is a water cooling tank, 4 is a conveying mechanism, 5 is a nitrogen-hydrogen mixed gas input port, 6 is a nitrogen gas input port, 7 is a submerged roller, 8 is a rotating gear, 9 is a shifting shaft, 10 is a shifting gear, 11 is a first baffle, 12 is a second baffle, 13 is an inlet baffle, and 14 is an outlet baffle. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0028] In order to make the above-mentioned objects, features and advantages of the present application more apparent and comprehensible, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] The method for improving the corrosion resistance of steel provided by the embodiments of the present application comprises the following processes: pickling, rinsing, drying, reduction, hot-dip plating, passivation, drying, and packaging. The plating aid process in the hot-dip plating process is replaced by a hot reduction process. The hot reduction process uses hydrogen with a volume content of 3-25% for hot reduction.

[0030] The plating aid process in the traditional hot-dip plating process is replaced by the reduction process in the present application. After the steel is pickled and dried, it is sent into an atmosphere box, and a small amount of residual iron oxide on the surface of the steel is reduced to iron single element under a hydrogen reduction atmosphere, so that the surface of the steel remains active and can be better plated with a zinc-based or zinc alloy coating, thereby greatly improving the corrosion resistance of the steel and prolonging its service life.

[0031] In a preferred embodiment, the thermal reduction process uses a mixed gas of nitrogen and hydrogen for thermal reduction, and the volume content of the hydrogen is 3-25%.

[0032] In a preferred embodiment, the temperature of the thermal reduction is 100-900° C. The present invention can reduce a small amount of iron oxide remaining or generated on the surface of the steel after pickling to sponge iron through thermal reduction, thereby ensuring the adhesion of the zinc solution to the steel surface and avoiding defects such as plating leakage.

[0033] In a preferred embodiment, the equipment used in the reduction process includes an atmosphere box 1 and a conveying mechanism 4. The present invention ensures that the steel, after being dried, passes smoothly through the reduction atmosphere box and enters the zinc bath for hot dip coating by using equipment including the atmosphere box and the conveying mechanism.

[0034] In a preferred embodiment, the top of the atmosphere box 1 is provided with a plurality of nitrogen-hydrogen mixture inlets 5; the number of the nitrogen-hydrogen mixture inlets 5 is 6-10. The present invention ensures that the atmosphere box is at a slightly positive pressure by providing a plurality of nitrogen-hydrogen mixture inlets.

[0035] In a preferred embodiment, the volume content of hydrogen in the nitrogen-hydrogen mixture in the atmosphere box 1 is 3-25%.

[0036] In a preferred embodiment, the atmosphere box 1 is provided with a steel material inlet and a steel material outlet; both the steel material inlet and the steel material outlet are flat slits; the slit height of the steel material inlet is adjusted by an inlet baffle 13; and the slit height of the steel material outlet is adjusted by an outlet baffle 14. Adjusting the slit height in the present invention can minimize the leakage rate of the reducing atmosphere.

[0037] In a preferred embodiment, the length of the slit passage at the steel outlet is 5-10 meters; 6-10 nitrogen filling inlets are evenly distributed at the steel outlet to control the hydrogen content at the steel outlet to be below 4%.

[0038] In a preferred embodiment, the atmosphere box 1 is provided with a heating wire, a heating belt or a Kai-type heater inside to ensure that the temperature field inside the atmosphere box is stable within a desired range.

[0039] In a preferred embodiment, the conveying mechanism 4 is fixed to the bottom of the atmosphere box 1; the conveying mechanism 4 is a crawler-type transmission; the crawler-type transmission is achieved by supporting the crawler with two rows of bottom rollers arranged side by side. The conveying mechanism of the present invention is used to transport steel.

[0040] In a preferred embodiment, the hot-dip plating process uses a zinc solution for hot-dip plating; the zinc solution is selected from an aluminum-zinc-silicon solution or a zinc-aluminum-magnesium solution; the aluminum content of the aluminum-zinc-silicon solution is 0.01-55.0wt.%, and the silicon content is 0.02-0.3wt.%; the aluminum content of the zinc-aluminum-magnesium solution is 0.01-55.0wt.%, and the magnesium content is 0.01-3.0wt.%.

[0041] In a preferred embodiment, the steel outlet of the atmosphere box 1 is connected to the zinc liquid tank 2. After the steel is reduced in the atmosphere box, it enters the zinc liquid tank containing zinc liquid for subsequent hot dip coating process.

[0042] In a preferred embodiment, a rotating gear device is provided in the zinc liquid tank 2; the rotating gear device presses the steel material falling into the zinc liquid into the zinc liquid for hot dip plating. When the steel material leaves the zinc liquid, the zinc liquid refluxes for a short time, and then the plated steel material is shifted to the water cooling tank 3 for water cooling via a fork device.

[0043] In a preferred embodiment, the rotating gear device is composed of a sinking roller 7 and a driving gear 8 fixedly mounted on the sinking roller 7 .

[0044] In a preferred embodiment, the shift fork device consists of a shift shaft 9 and a shift gear 10 fixedly mounted on the shift shaft 9; the shift fork device is fixed to the wall panel through the shift shaft; the shift gear 10 and the wheel gear 8 are staggered and spaced apart and not in direct contact. The shift gear 10 rises from between the rotating gears 8 and shifts the plated parts that have arrived there to above the second baffle 12 on the right. After the plated parts are separated from the rotating gear 8, they fall onto the second baffle 12 by gravity and then fall into the water cooling tank 3 for cooling.

[0045] In a preferred embodiment, the water cooling tank 3 and the zinc liquid tank 2 are connected via a second baffle 12 .

[0046] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0047] Example 1

[0048] A method for improving the corrosion resistance of steel, comprising the following steps: pickling - rinsing - drying - reduction - hot dipping - passivation - drying - packaging;

[0049] The equipment used in the reduction process includes an atmosphere box 1 and a conveying mechanism 4, which ensure that the steel passes smoothly through the atmosphere box after drying and then enters the zinc liquid for hot dip plating;

[0050] The conveying mechanism 4 is fixed at the bottom of the atmosphere box 1. The conveying mechanism 4 is a crawler type transmission, with two rows of bottom rollers supporting the crawler and transporting steel;

[0051] Six nitrogen-hydrogen mixture inlets are evenly distributed on the top of the atmosphere box 1 to ensure a slightly positive pressure inside the atmosphere box 1; the volume content of hydrogen in the nitrogen-hydrogen mixture in the atmosphere box 1 is 8%;

[0052] The atmosphere box 1 is also provided with a heating wire to heat the temperature inside the atmosphere box to 460°C, and the steel is subjected to reduction treatment in an atmosphere of nitrogen-hydrogen mixed gas, so that a small amount of iron oxide remaining or generated on the surface of the steel after pickling is reduced to sponge iron;

[0053] The front end of the atmosphere box 1 is provided with a steel inlet, and the rear end of the atmosphere box 1 is provided with a steel outlet. Both the steel inlet and the steel outlet are flat slits. The slit height of the steel inlet is adjusted by the inlet baffle 13, and the slit height of the steel outlet is adjusted by the outlet baffle 14 to minimize the leakage rate of the reducing atmosphere. The slit aisle length of the steel outlet is 8 meters, and 6 nitrogen filling inlets are evenly distributed at the steel outlet to control the hydrogen content at the steel outlet to below 4%;

[0054] The steel outlet of the atmosphere box 1 is connected to the zinc liquid tank 2, which contains zinc-aluminum-magnesium liquid with an aluminum content of 16.0 wt.% and a magnesium content of 3.0 wt.%;

[0055] The zinc liquid tank 2 is also equipped with a rotating gear device, which consists of a sinking roller 7 and a rotating gear 8 fixedly installed on the sinking roller 7. The rotating gear device presses the steel falling into the zinc-aluminum-magnesium liquid into the zinc-aluminum-magnesium liquid, so that the steel and the zinc-aluminum-magnesium liquid are fully in contact and reacted. When the steel is separated from the zinc-aluminum-magnesium liquid through the rotating gear device and the zinc-aluminum-magnesium liquid refluxes for a short time, the plated steel is shifted to the right water-cooling tank 3 for water cooling via the fork device installed on the right side. The fork device consists of a shift shaft 9 and a shift gear 10 fixedly installed on the shift shaft 9. The shift gear 10 and the rotating gear 8 are arranged at an offset interval, and the fork device is fixed to the wall panel through the shift shaft.

[0056] The steel was taken out of the water cooling tank, and the thickness of the galvanized layer on the surface of the steel was visually inspected to be uniform and without any missing plating phenomenon; the neutral salt spray resistance of the galvanized layer was tested using the "GBT10125-2012 Artificial Atmosphere Corrosion Test Salt Spray Test" method. The results showed that its neutral salt spray resistance was about 1500h, which was about 7.5 times that of the traditional hot-dip pure zinc coating (Comparative Example 2).

[0057] Example 2

[0058] A method for improving the corrosion resistance of steel, comprising the following steps: pickling - rinsing - drying - reduction - hot dipping - passivation - drying - packaging;

[0059] The equipment used in the reduction process includes an atmosphere box 1 and a conveying mechanism 4, which ensure that the steel passes smoothly through the atmosphere box after drying and then enters the zinc liquid for hot dip plating;

[0060] The conveying mechanism 4 is fixed at the bottom of the atmosphere box 1. The conveying mechanism 4 is a crawler type transmission, with two rows of bottom rollers supporting the crawler and transporting steel;

[0061] Eight nitrogen-hydrogen mixture inlets are evenly distributed on the top of the atmosphere box 1 to ensure a slightly positive pressure inside the atmosphere box 1; the volume content of hydrogen in the nitrogen-hydrogen mixture in the atmosphere box 1 is 6%;

[0062] The atmosphere box 1 is also provided with a heating belt to heat the temperature inside the atmosphere box to 500°C, and the steel is subjected to reduction treatment in an atmosphere of nitrogen-hydrogen mixed gas, so that a small amount of iron oxide remaining or generated on the surface of the steel after pickling is reduced to sponge iron;

[0063] The front end of the atmosphere box 1 is provided with a steel inlet, and the rear end of the atmosphere box 1 is provided with a steel outlet. Both the steel inlet and the steel outlet are flat slits. The slit height of the steel inlet is adjusted by the inlet baffle 13, and the slit height of the steel outlet is adjusted by the outlet baffle 14 to minimize the leakage rate of the reducing atmosphere. The slit aisle length of the steel outlet is 8 meters, and 6 nitrogen filling inlets are evenly distributed at the steel outlet to control the hydrogen content at the steel outlet to below 4%;

[0064] The steel outlet of the atmosphere box 1 is connected to the zinc liquid tank 2, which contains zinc-aluminum-magnesium liquid with an aluminum content of 6.0 wt.% and a magnesium content of 2.0 wt.%;

[0065] The zinc liquid tank 2 is also equipped with a rotating gear device, which consists of a sinking roller 7 and a rotating gear 8 fixedly installed on the sinking roller 7. The rotating gear device presses the steel falling into the zinc-aluminum-magnesium liquid into the zinc-aluminum-magnesium liquid, so that the steel and the zinc-aluminum-magnesium liquid are fully in contact and reacted. When the steel is separated from the zinc-aluminum-magnesium liquid through the rotating gear device and the zinc-aluminum-magnesium liquid refluxes for a short time, the plated steel is shifted to the right water-cooling tank 3 for water cooling via the fork device installed on the right side. The fork device consists of a shift shaft 9 and a shift gear 10 fixedly installed on the shift shaft 9. The shift gear 10 and the rotating gear 8 are arranged at an offset interval, and the fork device is fixed to the wall panel through the shift shaft.

[0066] The steel was taken out of the water cooling tank, and the thickness of the galvanized layer on the surface of the steel was visually inspected to be uniform and without any missing plating phenomenon; the neutral salt spray resistance of the galvanized layer was tested using the "GBT10125-2012 Artificial Atmosphere Corrosion Test Salt Spray Test" method. The results showed that its neutral salt spray resistance was 1000h, which was 5 times that of the neutral salt spray resistance of the traditional hot-dip pure zinc coating (Comparative Example 2).

[0067] Example 3

[0068] A method for improving the corrosion resistance of steel, comprising the following steps: pickling - rinsing - drying - reduction - hot dipping - passivation - drying - packaging;

[0069] The equipment used in the reduction process includes an atmosphere box 1 and a conveying mechanism 4, which ensure that the steel passes smoothly through the atmosphere box after drying and then enters the zinc liquid for hot dip plating;

[0070] The conveying mechanism 4 is fixed at the bottom of the atmosphere box 1. The conveying mechanism 4 is a crawler type transmission, with two rows of bottom rollers supporting the crawler and transporting steel;

[0071] Six nitrogen-hydrogen mixture inlets are evenly distributed on the top of the atmosphere box 1 to ensure a slightly positive pressure inside the atmosphere box 1; the volume content of hydrogen in the nitrogen-hydrogen mixture in the atmosphere box 1 is 15%;

[0072] The atmosphere box 1 is also provided with a heating wire to heat the temperature inside the atmosphere box to 420°C, and the steel is subjected to reduction treatment in an atmosphere of nitrogen-hydrogen mixed gas, so that a small amount of iron oxide remaining or generated on the surface of the steel after pickling is reduced to sponge iron;

[0073] The front end of the atmosphere box 1 is provided with a steel inlet, and the rear end of the atmosphere box 1 is provided with a steel outlet. Both the steel inlet and the steel outlet are flat slits. The slit height of the steel inlet is adjusted by the inlet baffle 13, and the slit height of the steel outlet is adjusted by the outlet baffle 14 to minimize the leakage rate of the reducing atmosphere. The slit aisle length of the steel outlet is 10 meters, and 6 nitrogen filling inlets are evenly distributed at the steel outlet to control the hydrogen content at the steel outlet to below 4%;

[0074] The steel outlet of the atmosphere box 1 is connected to the zinc liquid tank 2, which contains aluminum-zinc-silicon liquid with an aluminum content of 55.0 wt.% and a silicon content of 0.3 wt.%;

[0075] The zinc liquid tank 2 is also equipped with a rotating gear device, which consists of a sinking roller 7 and a rotating gear 8 fixedly installed on the sinking roller 7. The rotating gear device presses the steel that falls into the aluminum-zinc-silicon liquid into the aluminum-zinc-silicon liquid, so that the steel and the aluminum-zinc-silicon liquid are fully in contact and react. When the steel is separated from the aluminum-zinc-silicon liquid through the rotating gear device, after a short period of aluminum-zinc-silicon liquid reflux, the plated steel is shifted to the right water-cooling tank 3 for water cooling via the fork device installed on the right. The fork device consists of a shift shaft 9 and a shift gear 10 fixedly installed on the shift shaft 9. The shift gear 10 and the rotating gear 8 are arranged at intervals, and the fork device is fixed to the wall panel through the shift shaft.

[0076] The steel was taken out of the water cooling tank, and the thickness of the galvanized layer on the surface of the steel was visually inspected to be uniform and without any missing plating phenomenon; the neutral salt spray resistance of the galvanized layer was tested using the "GBT10125-2012 Artificial Atmosphere Corrosion Test Salt Spray Test" method. The results showed that its neutral salt spray resistance was 600h, which was 3 times that of the traditional hot-dip pure zinc coating (Comparative Example 2).

[0077] Comparative Example 1

[0078] A method for improving the corrosion resistance of steel, comprising the following steps: pickling - rinsing - flux plating - drying - hot-dip plating - passivation - drying - packaging;

[0079] The flux solution is composed of zinc chloride and ammonium chloride, the solvent is water, and the pH value is 3.5; the total mass of zinc chloride and ammonium chloride is 260 g / L, and the mass content of zinc chloride and ammonium chloride is 130 g / L respectively; the flux temperature is 75°C, and the flux time is 3 minutes.

[0080] The steel after the assisted plating is dried and then sent to the zinc bath, which contains zinc-aluminum-magnesium solution with an aluminum content of 16.0 wt.% and a magnesium content of 3.0 wt.%.

[0081] The zinc liquid tank is also equipped with a rotating gear device, which consists of a sinking roller and a rotating gear fixedly installed on the sinking roller. The rotating gear device presses the steel that falls into the zinc-aluminum-magnesium liquid into the zinc-aluminum-magnesium liquid, so that the steel and the zinc-aluminum-magnesium liquid are fully in contact and reacted. When the steel is separated from the zinc-aluminum-magnesium liquid through the rotating gear device and the zinc-aluminum-magnesium liquid refluxes for a short time, the plated steel is shifted to the right water-cooling tank for water cooling via the fork device installed on the right. The fork device consists of a shift shaft and a shift gear fixedly installed on the shift shaft. The shift gear and the rotating gear are staggered and arranged at intervals. The fork device is fixed to the wall panel through the shift shaft.

[0082] When the steel is taken out of the water cooling tank, visual inspection shows that the galvanized layer on the surface of the steel has obvious large-scale non-galvanizing phenomenon, and the coating cannot effectively achieve the purpose of corrosion protection.

[0083] Comparative Example 2

[0084] A method for improving the corrosion resistance of steel, comprising the following steps: pickling - rinsing - flux plating - drying - hot-dip plating - passivation - drying - packaging;

[0085] The flux solution is composed of zinc chloride and ammonium chloride, the solvent is water, and the pH value is 3.5; the total mass of zinc chloride and ammonium chloride is 260 g / L, and the mass content of zinc chloride and ammonium chloride is 130 g / L respectively; the flux temperature is 75°C, and the flux time is 3 minutes.

[0086] After the galvanizing process, the steel is dried and then sent to the zinc bath, which contains pure zinc liquid.

[0087] The zinc liquid tank is also equipped with a rotating gear device, which consists of a sinking roller and a rotating gear fixedly installed on the sinking roller. The rotating gear device presses the steel that falls into the pure zinc liquid into the pure zinc liquid, so that the steel and the pure zinc liquid are fully in contact and react. When the steel is separated from the pure zinc liquid through the rotating gear device, the pure zinc liquid refluxes for a short time, and then the plated steel is shifted to the right water cooling tank for water cooling through the fork device installed on the right. The fork device consists of a shift shaft and a shift gear fixedly installed on the shift shaft. The shift gear and the rotating gear are staggered and arranged at intervals. The fork device is fixed to the wall panel through the shift shaft.

[0088] The steel was taken out of the water cooling tank, and visual inspection showed that the zinc coating on the surface of the steel had obvious large-area non-plating phenomenon; the neutral salt spray resistance of the zinc coating was tested using the "GBT 10125-2012 Artificial Atmosphere Corrosion Test Salt Spray Test" method, and the results showed that its neutral salt spray resistance was 200h.

[0089] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for improving the corrosion resistance of steel, comprising the following steps: pickling - rinsing - drying - reduction - hot dip plating - passivation - drying - packaging; characterized in that: Replacing the fluxing process in the hot-dip plating process with a thermal reduction process; The thermal reduction process uses hydrogen with a volume content of 3-25% for thermal reduction.

2. The method for improving the corrosion resistance of steel according to claim 1, characterized in that: The thermal reduction process uses a mixed gas of nitrogen and hydrogen for thermal reduction, and the volume content of the hydrogen is 3-25%.

3. The method for improving the corrosion resistance of steel according to claim 1, characterized in that: The temperature of the thermal reduction is 100-900°C.

4. The method for improving the corrosion resistance of steel according to claim 1, characterized in that: The hot-dip plating process uses zinc liquid for hot-dip plating.

5. The method for improving the corrosion resistance of steel according to claim 4, characterized in that: The zinc liquid is selected from aluminum-zinc-silicon liquid or zinc-aluminum-magnesium liquid.

6. The method for improving the corrosion resistance of steel according to claim 5, characterized in that: The aluminum content of the aluminum-zinc-silicon liquid is 0.01-55.0 wt.%, and the silicon content is 0.02-0.3 wt.%. The aluminum content of the zinc-aluminum-magnesium liquid is 0.01-55.0 wt.%, and the magnesium content is 0.01-3.0 wt.%.

7. The method for improving the corrosion resistance of steel according to claim 1, characterized in that: The equipment used in the reduction process includes an atmosphere box (1) and a conveying mechanism (4); The top of the atmosphere box (1) is provided with a plurality of nitrogen-hydrogen mixed gas inlet ports (5); The atmosphere box (1) is provided with a steel material inlet and a steel material outlet; The conveying mechanism (4) is fixed on the bottom of the atmosphere box (1).

8. The method for improving the corrosion resistance of steel according to claim 7, characterized in that: The number of the nitrogen-hydrogen mixed gas input ports (5) is 6-10.

9. The method for improving the corrosion resistance of steel according to claim 7, characterized in that: The steel material inlet and the steel material outlet are both flat slits; the slit height of the steel material inlet is adjusted by an inlet baffle (13); and the slit height of the steel material outlet is adjusted by an outlet baffle (14).

10. The method for improving the corrosion resistance of steel according to claim 7, characterized in that: The length of the slit passage at the steel outlet is 5-10 meters; 6-10 nitrogen filling inlets are evenly distributed at the steel outlet to control the hydrogen content at the steel outlet to be below 4%.

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