Metal surface anti-corrosion treatment method

Abstract

The invention belongs to the technical field of anti-corrosion treatment, and particularly relates to a metal surface anti-corrosion treatment method which comprises the following steps: (1) adding a metal workpiece, zinc powder, an impregnation accelerant and an anti-binding agent into a zinc impregnation furnace, pushing the zinc impregnation furnace into a combustion engine, rotating a furnace body, starting heating, starting timing when the zinc impregnation furnace reaches a set temperature, stopping heating after a certain time, and stopping heating after the set temperature is reached; opening a combustion engine door, and stopping rotation after the furnace body rotates for a certain time; (2) discharging after the zinc impregnation furnace is cooled to 100 DEG C or below, separating the metal workpiece from other furnace charges by adopting a vibration separation sieve, and washing and drying the separated metal workpiece; (3) the surface of the metal workpiece is coated with raw materials of the zinc-chromium coating, and then curing treatment is conducted; and (4) the surface of the metal workpiece is coated with the sealing paint, then drying treatment is conducted, and the metal workpiece is obtained. According to the anti-corrosion treatment method, ultra-long salt mist resistance and damp and hot duration of the metal surface are achieved, and the designed anti-corrosion requirement for coping with seaborne harsh conditions is met.

Description

Technical Field

[0001] The invention belongs to the technical field of anti-corrosion treatment, and in particular relates to a metal surface anti-corrosion treatment method. Background Art

[0002] Metal corrosion is a common problem in human production and life. In some harsh environments such as offshore ships, offshore wind power, cross-sea highway bridges, etc., metal matrix corrosion can cause serious consequences and impacts. The main purpose of metal surface treatment is to prevent corrosion or slow down the corrosion rate of metals.

[0003] Common anti-corrosion treatments for metal surfaces include blackening, bluing, phosphating, electrogalvanizing, electrochromizing, hot-dip galvanizing, etc. In testing, the duration of salt spray and wet heat test is often used as a standard to evaluate the corrosion resistance of metal surfaces. The longer the time, the stronger the corrosion resistance. The salt spray and wet heat test time for blackening, bluing and phosphating is between 5-50 hours, the salt spray and wet heat test time for metal electrogalvanizing and electrochromizing is between 20-200 hours, and the salt spray and wet heat test time for hot-dip galvanizing is between 100-600 hours. None of them can meet the ultra-long salt spray and wet heat test time required for metal surfaces under the harsh conditions at sea. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for anti-corrosion treatment of metal surfaces, which creatively integrates and utilizes three anti-corrosion technologies: zinc infiltration, zinc-chromium coating and sealing layer. The three technologies work synergistically to achieve ultra-long salt spray and wet heat test time for the metal surface, thereby meeting the design anti-corrosion requirements that can cope with harsh offshore conditions.

[0005] Specifically, the present invention provides the following technical solutions:

[0006] A method for anti-corrosion treatment of metal surface comprises the following steps:

[0007] (1) Sherardizing treatment: Add metal workpieces, zinc powder, catalytic agent and anti-adhesive agent into the sherardizing furnace, push the sherardizing furnace into the burner, rotate the furnace body and start heating. When the sherardizing furnace reaches the set temperature, start timing, stop heating after a certain period of time, open the burner door, and let the furnace body continue to rotate for a certain period of time before stopping;

[0008] (2) Vibration screening and cleaning: After the zincizing furnace is cooled to below 100°C, the material is discharged and the metal workpieces are separated from other furnace materials using a vibrating separation screen. The separated metal workpieces are washed and dried;

[0009] (3) preparing the zinc-chromium coating: coating the raw material of the zinc-chromium coating on the surface of the metal workpiece, and then performing a curing treatment;

[0010] (4) Preparation of a sealing paint layer: Apply the sealing paint on the surface of the metal workpiece and then dry it.

[0011] Preferably, before the sherardizing treatment, the surface of the metal workpiece is first subjected to degreasing, decontamination and roughening treatment. The degreasing and decontamination methods may be carbonization degreasing, ultrasonic degreasing and washing degreasing, etc.; the roughening treatment methods may be sandblasting, shot blasting, etc., the main purpose of which is to improve the adhesion of the workpiece surface. In addition, sandblasting and shot blasting can also remove residual oil, rust and oxide film on the workpiece surface, improve the mechanical properties of the workpiece surface, and make the workpiece more beautiful.

[0012] Preferably, in step (1), based on the mass of each ton of metal workpiece, the amount of the zinc powder is 18-25 kg, the amount of the catalyst is 19-21 kg, and the amount of the anti-adhesive agent is 140-160 kg;

[0013] The penetration catalyst is selected from at least one of ammonium chloride and zinc chloride;

[0014] The anti-adhesive agent is quartz sand.

[0015] Preferably, in step (1), when the zincizing furnace reaches 480-510°C, the timing is started, and the heating is stopped after 210-270 minutes. The burner door is opened, and the furnace body is allowed to continue rotating for 150-180 minutes before stopping the rotation. In the existing process, after the heating is stopped, the furnace body does not rotate, and is directly cooled to below 100°C with the furnace before being taken out of the furnace. The present invention has found that after the rotation is stopped, the temperature in the center of the furnace is still high, and the heat cannot be quickly dissipated, resulting in the internal workpieces being easily burnt yellow and brittle, which seriously affects the appearance and adhesion of the infiltration layer. After the heating is stopped, the present invention allows the furnace body to continue to rotate for 150-180 minutes, so that the residual zinc powder continues to diffuse to the metal surface under the action of residual heat, while accelerating the heat dissipation and shortening the cooling time, thereby overcoming the disadvantages of the prior art.

[0016] Preferably, in step (2), the surface of the separated metal workpiece is treated with a shot blasting machine or a sand blasting machine for 15-25 seconds, and then washed and dried. After the vibration separation and screening, the existing process is to directly wash and dry the zinc-chromium coating, but zinc infiltration is prone to produce zinc slag and tumors, and the surface is uneven, which affects the appearance, and washing cannot be completely removed. The present invention is to put the zinc-infiltrated metal workpiece into a shot blasting machine or a sand blasting machine for back-throwing to remove the zinc slag tumor that is difficult to wash off with water on the surface. The back-throwing time must also be mastered. If the time is too short, the zinc slag tumor cannot be thrown away, and if the time is too long, the surface zinc layer that has been zinc infiltrated is easily destroyed. After repeated experiments and studies, it is determined that it is more appropriate within a time of 15-25 seconds, and generally 20 seconds is taken.

[0017] Preferably, in step (3), the zinc-chromium coating material is coated on the surface of the metal workpiece by spraying or dipping. Different zinc-chromium coating methods are required for workpieces of different sizes. Generally, dipping is used for smaller workpieces, and spraying is used for larger workpieces.

[0018] Preferably, in step (3), when the zinc-chromium coating material is coated on the surface of the metal workpiece by dipping, the process further comprises the following steps: firstly drying the metal workpiece after dipping with a centrifugal dryer, and then performing the curing treatment. The workpiece after dipping is fully spun off with a centrifugal dryer, so that the coating liquid accumulated on the surface of the workpiece can be fully and evenly covered, thereby avoiding accumulation of liquid, hanging liquid, bubbles, missing coating, etc.

[0019] Preferably, in step (3), the curing treatment is carried out at a temperature of 300 to 360° C. and for a time of 30 to 50 minutes.

[0020] Preferably, step (3) is repeated 1 to 3 times before step (4) is performed. According to the actual anti-corrosion technology requirements, step (3) can be repeated 1 to 3 times, that is, the zinc-chromium coating can be subjected to "two coatings and two bakings" or "three coatings and three bakings" or "four coatings and four bakings". Increasing the thickness of the zinc-chromium coating can effectively extend the salt spray resistance and wet heat test time.

[0021] Preferably, in step (4), the sealing paint is applied to the surface of the metal workpiece by spraying or dipping.

[0022] Preferably, in step (4), when the sealing varnish is applied to the surface of the metal workpiece by dipping, the step further includes the following steps: firstly drying the metal workpiece after dipping by using a centrifugal dryer (the purpose is to remove excess sealing varnish on the surface of the workpiece), and then performing the drying treatment.

[0023] In step (4), the drying process can be carried out by naturally drying in the air for about 2-3 hours. If the time needs to be shortened, the workpiece can also be placed on a mesh belt for high-temperature drying. The mesh belt hot air temperature is set at 70-100°C and the drying time is 20 to 30 minutes.

[0024] Beneficial effects achieved by the present invention:

[0025] (1) The metal surface anti-corrosion treatment method provided by the present invention combines the advantages of zinc diffusion, zinc-chromium coating, and sealing layer surface treatment technology and integrates the three surface treatment processes. The synergistic effect of the three greatly improves the corrosion resistance of the workpiece, making the workpiece resistant to salt spray and wet heat performance up to 4000 hours;

[0026] (2) The metal surface anti-corrosion treatment method provided by the present invention has a metal workpiece with strong corrosion resistance, high surface hardness and strong wear resistance of the anti-corrosion coating, and a more beautiful appearance, and has wide applicability;

[0027] (3) The metal surface anticorrosion treatment method provided by the present invention has high material utilization rate, low environmental pollution degree, and reduced production cost;

[0028] (4) The metal surface anti-corrosion treatment method provided by the present invention has relatively simple process steps, strong operability, and is easy to use, thereby improving production efficiency. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention is described clearly and completely below. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product instructions are used.

[0030] In the following examples, information on the reagents and devices used is shown in Table 1.

[0031] Table 1 Information of reagents used in the examples

[0032] Reagents model factory Penetration accelerator Ammonium chloride Qingdao Longshitai Environmental Protection Technology Co., Ltd. Anti-adhesive Quartz sand Qingdao Longshitai Environmental Protection Technology Co., Ltd. BY-380A MX6800A Changzhou Meixin Machinery Technology Co., Ltd. BY-380B MX6800B Changzhou Meixin Machinery Technology Co., Ltd. BY-380C MX6800C Changzhou Meixin Machinery Technology Co., Ltd. Sealing paint MX7800 Changzhou Meixin Machinery Technology Co., Ltd. Shearing furnace SX25-11-BQL Luoyang Xinyida Industrial Equipment Co., Ltd. Vibrating separation screen KZG / Q-25-11 Luoyang Xinyida Industrial Equipment Co., Ltd. Centrifugal dryer KZG / B-650 Luoyang Xinyida Industrial Equipment Co., Ltd.

[0033] Example 1

[0034] Example 1 provides a method for anti-corrosion treatment of metal surface. The metal workpiece to be treated is an M20*50 bolt. The specific steps are as follows:

[0035] (1) Surface pretreatment: ultrasonically degrease the bolts, and then roughen the bolt surface by sandblasting to increase surface adhesion;

[0036] (2) Zinc treatment: 7.5 kg zinc powder, 6 kg catalyst and 45 kg anti-adhesive agent were mixed evenly, and then put into the electro-zinc furnace together with 300 kg bolts. The electro-zinc furnace was pushed into the burner, and the furnace body was rotated at a speed of 3 r / min and started to heat. When the electro-zinc furnace reached 500 ° C, the timing was started, and the heating was stopped after keeping the temperature at this temperature for 240 minutes. The burner door was opened, and the furnace body was allowed to continue to rotate for 160 minutes before stopping.

[0037] (3) Vibration screening and cleaning: After the electro-zincification furnace is cooled to below 100°C, the furnace cover is opened. At this time, the bolts are buried in the anti-adhesive agent in the furnace. The entire charge is poured into the vibration separation screen and the bolts are separated from other charge by vibration separation (speed of 100 r / min, amplitude of 10 mm);

[0038] In addition to some zinc ash remaining on the surface of the bolt after separation, there are also zinc slag tumors, so the bolt is first put into the sandblasting machine for back-blasting for 20 seconds, and then cleaned and dried with water;

[0039] (4) The ratio and preparation method of zinc-chromium coating raw materials are as follows:

[0040] 1) Preparation ratio: BY-380A (referred to as Agent) 2kg, BY-380B (referred to as Bgent) 3kg, BY-380C (referred to as Cgent) 12kg;

[0041] 2) Reagent preparation method: ① Before preparation, first use a water bath to keep the temperature of the weighed A and B agents at 25±2℃, then use a variable frequency mixer to fully stir A agent to make the metal slurry completely dispersed and evenly distributed, then reduce the speed to 60 rpm and wait for the addition of B agent; ② Slowly add B agent into the A agent barrel that is being stirred. At this time, the temperature in the barrel will slowly rise. When the temperature reaches 35℃, start the refrigeration device to keep the temperature at around 35℃ and stir; ③ After adding B agent, the mixer stirs continuously and rapidly for 1-2 hours, then add C agent and continue stirring for 12 hours to obtain the zinc-chromium coating raw material; ④ After stirring, when the zinc-chromium coating raw material is poured into the dipping tank, it must be filtered with a 100-mesh stainless steel filter; ⑤ The on-site dipping tank must be equipped with a temperature control device to keep the coating liquid temperature at 22±2℃ (if the temperature is too high, the coating liquid is prone to aging and affects the viscosity), and the coating liquid must be kept circulating to maintain uniform dispersion and prevent precipitation.

[0042] (5) preparing a zinc-chromium coating: immersing the bolt workpiece obtained in step (3) into a dipping tank containing a zinc-chromium coating raw material for dipping, then placing the dipped bolt workpiece into a centrifugal dryer to fully remove excess coating liquid from the workpiece surface (the speed of removal is 600 r / min, and the time is about 40 s), and finally placing the dried bolt workpiece on a mesh belt for curing treatment to obtain a bolt workpiece with a zinc-chromium coating thickness of 10-20 μm, wherein the mesh belt transmission speed is 0.25 m / min, the mesh belt hot air temperature is 340° C., and the curing time is 40 min;

[0043] Four coatings and four bakings: After the curing is completed, the above-mentioned step of "preparing the zinc-chromium coating" is repeated after the workpiece is cooled to below 60°C. After repeating it three times in a row, step (6) is performed, i.e., the workpiece is subjected to "four coatings and four bakings" to enhance the thickness of the surface zinc-chromium coating;

[0044] (6) Preparation of sealing paint layer: After the bolt workpiece is cooled to room temperature, it is immersed in a dipping tank containing sealing paint for dipping, and then the bolt workpiece after dipping is placed in a centrifugal spin dryer to fully spin off the excess sealing paint on the workpiece surface (the spinning speed is 800 r / min, and the time is about 60 s). Finally, the bolt workpiece after spinning is dried to obtain a bolt workpiece with a sealing paint thickness of 10-20 μm, wherein the mesh belt transmission speed is 0.5 m / min, the mesh belt hot air temperature is 80° C., and the drying time is 25 min.

[0045] The metal workpiece after the anti-corrosion treatment of Example 1 is subjected to a moisture and heat resistance test according to GB / T1740, and the test duration can reach 4000 hours. The neutral salt spray resistance test is subjected to a neutral salt spray resistance test according to GB / T1771, and the test duration can reach 3600 hours.

[0046] Although the present invention has been described in detail above by general description, specific implementation methods and experiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for anticorrosion treatment of metal surface, characterized in that: The following steps are involved: (1) Sherardizing treatment: Add metal workpieces, zinc powder, catalytic agent and anti-adhesive agent into the sherardizing furnace, push the sherardizing furnace into the burner, rotate the furnace body and start heating. When the sherardizing furnace reaches the set temperature, start timing, stop heating after a certain period of time, open the burner door, and let the furnace body continue to rotate for a certain period of time before stopping; (2) Vibration screening and cleaning: After the zincizing furnace is cooled to below 100°C, the material is discharged and the metal workpieces are separated from other furnace materials using a vibrating separation screen. The separated metal workpieces are washed and dried; (3) preparing the zinc-chromium coating: coating the raw material of the zinc-chromium coating on the surface of the metal workpiece, and then performing a curing treatment; (4) Preparation of a sealing paint layer: Apply the sealing paint on the surface of the metal workpiece and then dry it.

2. A method for anticorrosion treatment of metal surface according to claim 1, characterized in that: Before the sherardizing treatment, the surface of the metal workpiece is first degreased, decontaminated and roughened.

3. A metal surface anticorrosion treatment method according to claim 1 or 2, characterized in that: In step (1), based on the mass of the metal workpiece per ton, the amount of the zinc powder is 18-25 kg, the amount of the catalyst is 19-21 kg, and the amount of the anti-adhesive agent is 140-160 kg; The penetration catalyst is selected from at least one of ammonium chloride and zinc chloride; The anti-adhesive agent is quartz sand.

4. A metal surface anticorrosion treatment method according to claim 1 or 2, characterized in that: In step (1), when the sherardizing furnace reaches 480-510° C., the timing is started, and the heating is stopped after 210-270 minutes. The burner door is opened, and the furnace body is allowed to continue rotating for 150-180 minutes before stopping.

5. A metal surface anticorrosion treatment method according to claim 1 or 2, characterized in that: In step (2), the surface of the separated metal workpiece is first treated with a shot blasting machine or a sand blasting machine for 15-25 seconds, and then washed and dried.

6. A metal surface anticorrosion treatment method according to claim 1 or 2, characterized in that: In step (3), when the raw material of the zinc-chromium coating is coated on the surface of the metal workpiece by dipping, the following steps are also included: the metal workpiece after dipping is first dried by a centrifugal dryer, and then the curing treatment is performed.

7. A metal surface anticorrosion treatment method according to claim 1 or 2, characterized in that: After the step (3) is repeated 1 to 3 times, the step (4) is performed.

8. A metal surface anticorrosion treatment method according to claim 1 or 2, characterized in that: In step (4), when the sealing paint is applied to the surface of the metal workpiece by dipping, the method further includes the following steps: firstly drying the metal workpiece after dipping by a centrifugal dryer, and then performing the drying treatment.