阅读说明：本技术 含有水性涂料和粉末涂料的汽车车身涂层结构及制备方法 (Automobile body coating structure containing water-based paint and powder paint and preparation method thereof ) 是由 王文文 苏军 张丽桂 李庆华 殷坤 于 2021-06-25 设计创作，主要内容包括：本申请涉及车身涂装技术领域,特别涉及一种含有水性涂料和粉末涂料的汽车车身涂层结构及制备方法。本申请提供的含有水性涂料和粉末涂料的汽车车身涂层结构,由内至外依次包括：电泳涂层、中涂漆层、色漆层、珠光漆层和清漆层；其中,所述中涂漆层由水性中涂漆喷涂形成,所述色漆层由水性色漆喷涂形成,所述珠光漆层由水性珠光漆喷涂形成,所述清漆层由粉末涂料喷涂形成。本申请解决了相关技术中粉末涂料尚未实现整车涂装工业化应用的问题。(The application relates to the technical field of automobile body coating, in particular to an automobile body coating structure containing water-based paint and powder paint and a preparation method thereof. The application provides a car body coating structure who contains water based paint and powder coating, from interior to exterior includes in proper order: an electrophoretic coating layer, a middle paint coating layer, a colored paint coating layer, a pearl paint coating layer and a clear paint coating layer; the middle paint layer is formed by spraying water-based middle paint, the colored paint layer is formed by spraying water-based colored paint, the pearlescent paint layer is formed by spraying water-based pearlescent paint, and the clear paint layer is formed by spraying powder paint. The application solves the problem that the powder coating in the related technology is not applied to the industrial coating of the whole vehicle.)

1. An automobile body coating structure containing water paint and powder paint is characterized by sequentially comprising the following components from inside to outside: an electrophoretic coating layer (101), a middle paint layer (102), a colored paint layer (103), a pearl paint layer (104) and a clear paint layer (105); the middle paint layer (102) is formed by spraying water-based middle paint, the colored paint layer (103) is formed by spraying water-based colored paint, the pearl paint layer (104) is formed by spraying water-based pearl paint, and the clear paint layer (105) is formed by spraying powder paint.

2. The coating structure of an automobile body containing water paint and powder paint according to claim 1, characterized in that the color paint layer (103) is formed by one-stop spray coating, and the thickness of the formed film is 5-8 μm.

3. The coating structure of an automobile body containing water paint and powder paint according to claim 1, characterized in that the pearl paint layer (104) is formed by one-stop spraying and has a film thickness of 4-6 μm.

4. A method for producing an automotive body coating structure containing an aqueous coating material and a powder coating material according to any one of claims 1 to 3, characterized by comprising the steps of: the method comprises the following steps of sequentially carrying out pretreatment, electrophoresis drying, electrophoresis polishing, water washing intermediate coat paint spraying, water washing colored paint spraying, water washing pearlescent paint spraying, flash drying, powder coating spraying, finish paint drying and finishing off line on an automobile body.

5. The method for preparing the coating structure of the automobile body containing the water-based paint and the powder paint according to claim 4, wherein the flash drying temperature is 120-140 ℃, the flash drying time is 8-12 min, and the wind speed is 8-12 m/s.

6. The method for preparing the coating structure of the automobile body containing the water-based paint and the powder paint according to claim 4, wherein the temperature for drying the finish paint is 160-180 ℃ and the time is 20-30 min.

7. The method for preparing an automobile body coating structure containing the water-based paint and the powder paint according to claim 4, wherein the film forming thickness of the powder paint is 40-60 μm.

8. The method for preparing an automobile body coating structure containing the water-based paint and the powder paint according to claim 4, wherein the pretreatment mode is a film pretreatment, and the film pretreatment comprises the following steps:

(1) pre-washing: spraying industrial water at the temperature of 30-50 ℃ on the automobile body, wherein the spraying time is 20-30 s, and the spraying pressure is 0.05-0.15 MPa;

(2) pre-degreasing: spraying the automobile body with pre-degreasing bath solution for 30-60 s at a spraying pressure of 0.2-0.3 MPa at a temperature of 40-50 ℃ and a pH value of less than 12.5;

(3) degreasing: immersing the automobile body into degreasing bath liquid for 180-240 s, wherein the surface flow circulation pressure of the degreasing bath liquid is 0.08-0.12 MPa, the temperature of the degreasing bath liquid is 40-50 ℃, and the pH value of the degreasing bath liquid is less than 12;

(4) first water washing: immersing the automobile body into industrial water with the pH value less than or equal to 11.8 and the conductivity less than or equal to 3000 mu s/cm, wherein the immersion time is 120-150 s, and the spraying pressure during the immersion of the automobile body are both 0.1-0.18 MPa;

(5) and (3) second water washing: spraying industrial water with the pH value of less than or equal to 9.5 and the conductivity of less than or equal to 1000 mu s/cm on the automobile body, wherein the spraying time is 20-30 s, and the spraying pressure is 0.1-0.18 MPa;

(6) and (3) washing for the third time: immersing the automobile body into pure water with the pH value less than or equal to 8.9 and the conductivity less than or equal to 300 mu s/cm, wherein the immersion time is 120-150 s, and the spraying pressure during the immersion of the automobile body are both 0.1-0.18 MPa;

(7) silane treatment: immersing the automobile body into silane tank liquor with the pH value of 4.2-5.5 and the conductivity of less than 4000 mu s/cm, wherein the immersion time is 120-180 s, and the temperature of the silane tank liquor is 27-38 ℃;

(8) fourth water washing: spraying pure water with the pH value of 6-9 and the conductivity of less than or equal to 600 mu s/cm on the automobile body for 20-30 s, wherein the spraying pressure is 0.1-0.18 MPa;

(9) and (3) circulating pure water washing: immersing the automobile body into pure water with the pH value of 5.5-8 and the conductivity of less than or equal to 60 mu s/cm, wherein the immersion time is 120-150 s, and the spraying pressure during immersion and leaching of the automobile body is 0.1-0.18 MPa;

(10) fresh pure water washing: pure water with the conductivity less than or equal to 5 mu s/cm is adopted to spray the automobile body, the spraying time is 20-30 s, the spraying pressure is 0.1-0.18 MPa, the spraying flow is 50-80L/min, and the water dropping conductivity of the automobile body is less than or equal to 50 mu s/cm.

9. The method of claim 8, wherein the degreasing bath and the pre-degreasing bath are both alkaline surfactants.

10. The method of claim 8, wherein the silane bath solution comprises: the Zr content is 100-300 mg/L, the Cu content is 0.5-3 mg/L, the Si content is 25-55 mg/L, and the free fluorine content is 20-52 mg/L.

Technical Field

The application relates to the technical field of automobile body coating, in particular to an automobile body coating structure containing water-based paint and powder paint and a preparation method thereof.

Background

VOC emission is one of important indexes for measuring the environmental protection performance of automobile coating, and the existing mode for controlling the VOC emission mainly comprises the steps of selecting coating raw materials and changing a coating process. The paint for automobile painting is mainly solvent type paint and powder paint, and the powder paint is solid powdered synthetic resin paint comprising solid resin, pigment, stuffing, assistant, etc. and has the features of no solvent pollution, 100% filming and low power consumption. Therefore, applying the powder coating to automobile painting can solve the problem of VOC emission.

Due to the matching problem of the powder coating and the electrophoresis layer, the powder coating is only applied to automobile parts such as automobile hubs, frames and shock absorbers which are simple in color and low in coating process requirement at present, and industrial application is not realized in the field of finished automobile coating.

In view of the above, there is a need for an automotive body coating structure containing a powder coating that can be used widely.

Disclosure of Invention

The embodiment of the application provides an automobile body coating structure containing water-based paint and powder paint, and aims to solve the problem that the powder paint is not applied to the industrial coating of a whole automobile in the related art.

In a first aspect, the present application provides an automotive body coating structure comprising a water-based paint and a powder paint, which sequentially comprises from inside to outside: an electrophoretic coating layer, a middle paint coating layer, a colored paint coating layer, a pearl paint coating layer and a clear paint coating layer; the middle paint layer is formed by spraying water-based middle paint, the colored paint layer is formed by spraying water-based colored paint, the pearlescent paint layer is formed by spraying water-based pearlescent paint, and the clear paint layer is formed by spraying powder paint.

In some embodiments, the intermediate paint layer is formed by one-stop spraying, and the film thickness is 15-20 μm.

In some embodiments, the color paint layer is formed by one-stop spraying, and the film thickness is 5-8 μm.

In some embodiments, the pearlescent paint layer is formed by one-stop spray coating, and the thickness of the formed pearlescent paint layer is 4-6 μm.

In some embodiments, the spraying of the varnish layer comprises:

(1) cleaning a powder spraying room: the dust in the powder spraying room is cleaned, and the dust in each cubic foot of air is ensured to be as follows: the dust particle with the particle size of more than or equal to 5 mu m is not contained, and the number of the dust particles with the particle size range of 0.5 to 5 mu m is not more than 30000;

(2) setting the wind direction, the wind speed and the temperature and humidity of the powder spraying room: setting the wind direction of the powder spraying room to be vertical downward, setting the wind speed to be 0.3-0.5 m/s, setting the temperature to be 20-30 ℃ and setting the humidity to be 50-70%;

(3) spraying: conveying the automobile body to be treated into a powder spraying room, spraying powder coating on the surface of the automobile body under the condition that the electrostatic voltage is-70 to-60 kV, wherein the film forming mode is a one-stop spraying film forming mode, the film forming thickness is 40 to 60 mu m, the distance between spraying guns is 15 to 25cm, and the speed of the spraying guns is 400 to 600 mm/s.

In a second aspect, the present application also provides a method for preparing the coating structure of the automobile body containing the water-based paint and the powder paint, which comprises the following steps: the method comprises the following steps of sequentially carrying out pretreatment, electrophoresis drying, electrophoresis polishing, water washing intermediate coat paint spraying, water washing colored paint spraying, water washing pearlescent paint spraying, flash drying, powder coating spraying, finish paint drying and finishing off line on an automobile body.

In some embodiments, the pretreatment is performed by a phosphating pretreatment or a film pretreatment.

In some embodiments, the pre-phosphating treatment comprises the following processes:

(1) pre-washing: spraying industrial water at the temperature of 30-50 ℃ on the automobile body, wherein the spraying time is 20-30 s, and the spraying pressure is 0.05-0.15 MPa;

(2) pre-degreasing: spraying the automobile body with pre-degreasing bath solution for 30-60 s, wherein the spraying pressure is 0.2-0.3 MPa, the temperature of the pre-degreasing bath solution is 40-50 ℃, and the pH value of the pre-degreasing bath solution is 12-14;

(3) degreasing: immersing the automobile body into degreasing bath solution with the pH value of 12-14, wherein the immersion time is 180-240 s, the surface flow circulation pressure is 0.08-0.12 MPa, and the temperature of the degreasing bath solution is 40-50 ℃;

(4) first water washing: immersing the automobile body into industrial water for 120-150 s, wherein the spraying pressure during the immersion of the automobile body and the spraying pressure during the immersion of the automobile body are both 0.23-0.27 MPa;

(5) and (3) second water washing: spraying industrial water on the automobile body for 20-30 s at a spraying pressure of 0.23-0.31 MPa;

(6) surface conditioning: immersing the automobile body into surface conditioning bath solution with the pH value of 9.5-10.5, wherein the soaking time is 60-120 s, and the temperature of the surface conditioning bath solution is 25-35 ℃;

(7) phosphorization: immersing an automobile body into phosphating tank liquor with the ratio of total acid to free acid of 21-23, wherein the immersion time is 180-240 s, the surface flow spraying pressure of the phosphating tank liquor is 0.02-0.06 MPa, and the temperature of the phosphating tank liquor is 40-45 ℃; the phosphated automobile body needs to be ensured: the size of phosphorization crystal is less than or equal to 10 mu m, the zinc-iron phosphate content in the phosphorization film is more than or equal to 90 percent, and the weight of the phosphorization film on the surface of the cold-rolled steel plate is 2-3 g/m²The weight of the phosphating film on the surface of the galvanized steel sheet is 2-4 g/m²；

(8) And (3) washing for the third time: immersing the automobile body into industrial water for 120-150 s, wherein the spraying pressure during the immersion of the automobile body and the spraying pressure during the immersion of the automobile body are both 0.13-0.21 MPa;

(9) fourth water washing: spraying industrial water on the automobile body for 20-30 s at a spraying pressure of 0.13-0.17 MPa;

(10) and (3) circulating pure water washing: immersing the automobile body into pure water with the conductivity less than or equal to 20 mu s/cm, wherein the immersion time is 120-150 s, and the spraying pressure during the immersion of the automobile body and the spraying pressure during the leaching of the automobile body are both 0.13-0.31 MPa;

(11) fresh pure water washing: pure water with the conductivity less than or equal to 5 mu s/cm is adopted to spray the automobile body, the spraying time is 20-30 s, the spraying pressure is 0.15-0.25 MPa, the spraying flow is 70-130L/min, and the water dropping conductivity of the automobile body is less than or equal to 50 mu s/cm.

In some embodiments, both the pre-degreasing bath and the degreasing bath employ an alkaline surfactant.

In some embodiments, both the surface conditioning bath and the phosphating bath employ zinc-based phosphating solutions.

In some embodiments, the film pre-treatment comprises the following processes:

(1) pre-washing: spraying industrial water at the temperature of 30-50 ℃ on the automobile body, wherein the spraying time is 20-30 s, and the spraying pressure is 0.05-0.15 MPa;

(2) pre-degreasing: spraying the automobile body with pre-degreasing bath solution for 30-60 s at a spraying pressure of 0.2-0.3 MPa at a temperature of 40-50 ℃ and a pH value of less than 12.5;

(3) degreasing: immersing the automobile body into degreasing bath liquid for 180-240 s, wherein the surface flow circulation pressure of the degreasing bath liquid is 0.08-0.12 MPa, the temperature of the degreasing bath liquid is 40-50 ℃, and the pH value of the degreasing bath liquid is less than 12;

(4) first water washing: immersing the automobile body into industrial water with the pH value less than or equal to 11.8 and the conductivity less than or equal to 3000 mu s/cm, wherein the immersion time is 120-150 s, and the spraying pressure during the immersion of the automobile body are both 0.1-0.18 MPa;

(5) and (3) second water washing: spraying industrial water with the pH value of less than or equal to 9.5 and the conductivity of less than or equal to 1000 mu s/cm on the automobile body, wherein the spraying time is 20-30 s, and the spraying pressure is 0.1-0.18 MPa;

(6) and (3) washing for the third time: immersing the automobile body into pure water with the pH value of less than or equal to 8.9 and the conductivity of less than or equal to 300 mu s/cm, wherein the immersion time is 120-150 s, the spraying pressure during the immersion of the automobile body and the spraying pressure during the immersion of the automobile body are both 0.1-0.18 MPa, and the pure water replenishing flow is 30-70L/min;

(7) silane treatment: immersing the automobile body into silane tank liquid with the pH value of 4.2-5.5 and the conductivity of less than 4000 mu s/cm, wherein the soaking time is 120-180 s, the temperature of the silane tank liquid is 27-38 ℃, the stirring pressure in the silane tank liquid is 0.1-0.2 MPa, and the Zr content in the silane tank liquid is 100-300 mg/HL, Cu content is 0.5-3 mg/L, Si content is 25-55 mg/L, free fluorine content is 20-52 mg/L; the silane treated automobile body needs to guarantee: the weight of the silane film on the surface of the galvanized steel sheet is 70-180 mg/m²The weight of the silane film on the surface of the cold-rolled steel plate is 30-100 mg/m²；

(8) Fourth water washing: spraying pure water with the pH value of 6-9 and the conductivity of less than or equal to 600 mu s/cm on the automobile body for 20-30 s, wherein the spraying pressure is 0.1-0.18 MPa;

(9) and (3) circulating pure water washing: immersing the automobile body into pure water with the pH value of 5.5-8 and the conductivity of less than or equal to 60 mu s/cm, wherein the immersion time is 120-150 s, and the spraying pressure during immersion and leaching of the automobile body is 0.1-0.18 MPa;

(10) fresh pure water washing: pure water with the conductivity less than or equal to 5 mu s/cm is adopted to spray the automobile body, the spraying time is 20-30 s, the spraying pressure is 0.1-0.18 MPa, the spraying flow is 50-80L/min, and the water dropping conductivity of the automobile body is less than or equal to 50 mu s/cm.

In some embodiments, both the pre-degreasing bath and the degreasing bath employ an alkaline surfactant.

In some embodiments, electrophoresis comprises the following processes:

(1) electrophoresis: immersing an automobile body into an electrophoresis tank liquid with the pH value of 5.8-6.5, the conductivity of 1300-2200 mu s/cm, the throwing power of more than or equal to 60 percent and the solvent content of less than or equal to 2 percent, wherein the temperature of the electrophoresis tank liquid is 28-32 ℃, the solid content of the electrophoresis tank liquid is 19-22 percent, the ash content is 15-20 percent, the electrophoresis process adopts two-stage voltage step control, the first-stage voltage is 160-250V, the second-stage voltage is 200-300V, and the electrifying time of the electrophoresis process is more than or equal to 180 s;

(2) first ultrafiltration water washing: spraying the automobile body with the electrophoretic ultrafiltration water washing tank liquor for 20-30 s at a spraying pressure of 0.05-0.15 MPa;

(3) and (3) ultrafiltration washing for the second time: immersing an automobile body into the electrophoresis ultrafiltration washing tank liquor for 120-180 s, wherein the spraying pressure during the immersion of the automobile body and the leaching of the automobile body is 0.05-0.15 MPa, and the solid content of the electrophoresis ultrafiltration washing tank liquor is less than or equal to 2%;

(4) and (3) ultrafiltration washing for the third time: spraying the automobile body with the electrophoretic ultrafiltration water washing tank liquor for 20-30 s at a spraying pressure of 0.05-0.15 MPa;

(5) pure water washing is circulated for the first time: spraying pure water with the solid content of less than or equal to 0.5% on an automobile body for 20-30 s, wherein the spraying pressure is 0.05-0.12 MPa;

(6) and (3) circulating pure water for the second time: immersing the automobile body into pure water with the solid content of less than or equal to 0.5%, wherein the immersion time is 120-180 s, and the spraying pressure during the immersion of the automobile body and the leaching of the automobile body are both 0.05-0.12 MPa;

(7) fresh pure water washing: pure water is adopted to spray the automobile body, the spraying time is 20-30 s, the spraying pressure is 0.05-0.12 MPa, and the spraying flow is 70-130L/min.

In some embodiments, the temperature of the electrophoretic drying is 160-180 ℃ for 20-30 min.

In some embodiments, the hardness of the electrophoretic coating after electrophoretic drying is more than or equal to H, and the adhesive force of the electrophoretic coating measured by a Baige method is less than or equal to 0 level.

In some embodiments, the thickness of the electrophoretic coating satisfies: the thickness of the electrophoretic coating on the outer surface of the vehicle body is more than or equal to 15 microns, and the thickness of the electrophoretic coating on the inner cavity of the vehicle body is more than or equal to 10 microns.

In some embodiments, the process of aqueous intercoat spraying is: and (3) spraying the water-based primer surfacer on the surface of the automobile body by adopting an electrostatic rotary cup spray gun, wherein the film forming mode is a one-stop spraying film forming mode, and the film forming thickness is 15-20 mu m.

In some embodiments, the process of spraying the aqueous pigmented paint is: and (3) spraying the water-based colored paint on the surface of the automobile body by adopting an electrostatic rotary cup spray gun, wherein the film forming mode is a one-stop spraying film forming mode, and the film forming thickness is 5-8 mu m.

In some embodiments, the process of spraying the aqueous pearlescent paint is: and (3) spraying the water-based pearlescent paint on the surface of the automobile body by adopting an electrostatic rotary cup spray gun, wherein the film forming mode is a one-stop spraying film forming mode, and the film forming thickness is 4-6 microns.

In some embodiments, the powder coating spray coating process comprises:

(1) cleaning a powder spraying room: the dust in the powder spraying room is cleaned, and the dust in each cubic foot of air is ensured to be as follows: the dust particle with the particle size of more than or equal to 5 mu m is not contained, and the number of the dust particles with the particle size range of 0.5 to 5 mu m is not more than 30000;

(2) setting the wind direction, the wind speed and the temperature and humidity of the powder spraying room: setting the wind direction of the powder spraying room to be vertical downward, setting the wind speed to be 0.3-0.5 m/s, setting the temperature to be 20-30 ℃ and setting the humidity to be 50-70%;

(3) spraying: conveying the automobile body to be treated into a powder spraying room, spraying powder coating on the surface of the automobile body under the condition that the electrostatic voltage is-70 to-60 kV, wherein the film forming mode is a one-stop spraying film forming mode, the film forming thickness is 40 to 60 mu m, the distance between spraying guns is 15 to 25cm, and the speed of the spraying guns is 400 to 600 mm/s.

In some embodiments, the flash drying temperature is 120-140 ℃, the time is 8-12 min, and the wind speed is 8-12 m/s.

In some embodiments, the temperature for drying the finish paint is 160-180 ℃ and the time is 20-30 min.

In a third aspect, the present application further provides a method for coating by using the cooperation of three powder spraying rooms, specifically: spraying a main color (such as a color with a color scheduling ratio of more than or equal to 50%) by using the powder spraying room A, spraying an auxiliary color 1 by using the powder spraying room B, and spraying an auxiliary color 2 by using the powder spraying room C; when the main color needs to be sprayed in the production process, the automobile body is directly sent into a powder spraying room A for spraying; when colour 1 and supplementary colour 2 are assisted in the needs spraying, spout the room B by the powder and spout the room C and trade the colour spraying in turn by the powder, when the room B spraying of powder is assisted colour 1, the room C is spouted to the powder trades the colour and prepares the supplementary colour 2 of spraying, when the room C spraying is assisted colour 2 to the powder, the room B is spouted to the powder trades the colour and prepares the supplementary colour 3 of spraying, analogizes in proper order and accomplishes the spraying of all colours. The problem of low production efficiency of a coating production line caused by powder coating color changing waiting can be solved by using three parallel powder spraying rooms in a matched mode.

The beneficial effect that technical scheme that this application provided brought includes: the automobile body coating structure provided by the application uses the water washing coating and the powder coating in a matching way, the powder coating is applied to the whole automobile coating, the existing solvent type varnish is replaced, compared with the water-based 3C1B coating process, the VOC emission in finish coating is reduced by about 70%, and the control of the VOC emission is effectively realized; the preparation method provided by the application is simple in process and beneficial to industrial popularization and application.

Drawings

FIG. 1 is a schematic view of an automotive body coating structure containing a water-based paint and a powder paint provided in an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The embodiment of the application provides an automobile body coating structure containing water-based paint and powder paint, which can solve the problem that the powder paint is not applied to the industrial coating of a whole automobile in the related art.

Fig. 1 is a schematic view of an automotive body coating structure including an aqueous coating material and a powder coating material provided in an embodiment of the present application, and referring to fig. 1, the automotive body coating structure provided in an embodiment of the present application sequentially includes, from inside to outside: an electrophoretic coating layer 101, a middle paint layer 102, a colored paint layer 103, a pearl paint layer 104 and a clear paint layer 105; the intermediate paint layer 102 is formed by spraying water-based intermediate paint, the colored paint layer 103 is formed by spraying water-based colored paint, the pearl paint layer 104 is formed by spraying water-based pearl paint, and the clear paint layer 105 is formed by spraying powder paint.

The embodiment of the application also provides a preparation method of the automobile body coating structure, which comprises the following steps:

firstly, pretreatment:

the pretreatment mode is phosphating pretreatment or film pretreatment, and the phosphating pretreatment comprises the following processes:

(1) pre-washing: spraying industrial water at the temperature of 30-50 ℃ on the automobile body, wherein the spraying time is 20-30 s, and the spraying pressure is 0.05-0.15 MPa;

(2) pre-degreasing: spraying the automobile body with pre-degreasing bath solution for 30-60 s, wherein the spraying pressure is 0.2-0.3 MPa, the temperature of the pre-degreasing bath solution is 40-50 ℃, and the pH value of the pre-degreasing bath solution is 12-14; the pre-degreasing bath solution is an alkaline surfactant;

(3) degreasing: immersing the automobile body into degreasing bath solution with the pH value of 12-14, wherein the immersion time is 180-240 s, the surface flow circulation pressure is 0.08-0.12 MPa, and the temperature of the degreasing bath solution is 40-50 ℃; degreasing bath solution is alkaline surfactant;

(4) first water washing: immersing the automobile body into industrial water for 120-150 s, wherein the spraying pressure during the immersion of the automobile body and the spraying pressure during the immersion of the automobile body are both 0.23-0.27 MPa;

(5) and (3) second water washing: spraying industrial water on the automobile body for 20-30 s at a spraying pressure of 0.23-0.31 MPa;

(6) surface conditioning: immersing the automobile body into surface conditioning bath solution with the pH value of 9.5-10.5, wherein the soaking time is 60-120 s, and the temperature of the surface conditioning bath solution is 25-35 ℃; the surface conditioning bath solution is zinc phosphating solution;

(7) phosphorization: immersing an automobile body into phosphating tank liquor with the ratio of total acid to free acid of 21-23, wherein the immersion time is 180-240 s, the surface flow spraying pressure of the phosphating tank liquor is 0.02-0.06 MPa, and the temperature of the phosphating tank liquor is 40-45 ℃; the phosphated automobile body needs to be ensured: the size of phosphorization crystal is less than or equal to 10 mu m, the zinc-iron phosphate content in the phosphorization film is more than or equal to 90 percent, and the weight of the phosphorization film on the surface of the cold-rolled steel plate is 2-3 g/m²The weight of the phosphating film on the surface of the galvanized steel sheet is 2-4 g/m²(ii) a The phosphating tank solution is zinc phosphating solution;

(8) and (3) washing for the third time: immersing the automobile body into industrial water for 120-150 s, wherein the spraying pressure during the immersion of the automobile body and the spraying pressure during the immersion of the automobile body are both 0.13-0.21 MPa;

(9) fourth water washing: spraying industrial water on the automobile body for 20-30 s at a spraying pressure of 0.13-0.17 MPa;

(10) and (3) circulating pure water washing: immersing the automobile body into pure water with the conductivity less than or equal to 20 mu s/cm, wherein the immersion time is 120-150 s, and the spraying pressure during the immersion of the automobile body and the spraying pressure during the leaching of the automobile body are both 0.13-0.31 MPa;

(11) fresh pure water washing: spraying the automobile body with pure water with the conductivity of less than or equal to 5 mu s/cm for 20-30 s, spraying pressure of 0.15-0.25 MPa, spraying flow of 70-130L/min, and automobile body water drop conductivity of less than or equal to 50 mu s/cm;

the film pretreatment comprises the following processes:

(1) pre-washing: spraying industrial water at the temperature of 30-50 ℃ on the automobile body, wherein the spraying time is 20-30 s, and the spraying pressure is 0.05-0.15 MPa;

(2) pre-degreasing: spraying the automobile body with pre-degreasing bath solution for 30-60 s at a spraying pressure of 0.2-0.3 MPa at a temperature of 40-50 ℃ and a pH value of less than 12.5; the pre-degreasing bath solution selects an alkaline surfactant;

(3) degreasing: immersing the automobile body into degreasing bath liquid for 180-240 s, wherein the surface flow circulation pressure of the degreasing bath liquid is 0.08-0.12 MPa, the temperature of the degreasing bath liquid is 40-50 ℃, and the pH value of the degreasing bath liquid is less than 12; the degreasing bath solution selects an alkaline surfactant;

(4) first water washing: immersing the automobile body into industrial water with the pH value less than or equal to 11.8 and the conductivity less than or equal to 3000 mu s/cm, wherein the immersion time is 120-150 s, and the spraying pressure during the immersion of the automobile body are both 0.1-0.18 MPa;

(5) and (3) second water washing: spraying industrial water with the pH value of less than or equal to 9.5 and the conductivity of less than or equal to 1000 mu s/cm on the automobile body, wherein the spraying time is 20-30 s, and the spraying pressure is 0.1-0.18 MPa;

(6) and (3) washing for the third time: immersing the automobile body into pure water with the pH value of less than or equal to 8.9 and the conductivity of less than or equal to 300 mu s/cm, wherein the immersion time is 120-150 s, the spraying pressure during the immersion of the automobile body and the spraying pressure during the immersion of the automobile body are both 0.1-0.18 MPa, and the pure water replenishing flow is 30-70L/min;

(7) silane treatment: immersing the automobile body into silane tank liquid with the pH value of 4.2-5.5 and the conductivity of less than 4000 mu s/cm, wherein the immersion time is 120-180 s, the temperature of the silane tank liquid is 27-38 ℃, the stirring pressure in the silane tank liquid is 0.1-0.2 MPa, the Zr content in the silane tank liquid is 100-300 mg/L, Cu content, the Zr content in the silane tank liquid is 0.5-3 mg/L, Si content in the silane tank liquid is 25-55 mg/L, and the free fluorine content in the silane tank liquid is 25-55 mg/L20-52 mg/L; the silane treated automobile body needs to guarantee: the weight of the silane film on the surface of the galvanized steel sheet is 70-180 mg/m²The weight of the silane film on the surface of the cold-rolled steel plate is 30-100 mg/m²；

(8) Fourth water washing: spraying pure water with the pH value of 6-9 and the conductivity of less than or equal to 600 mu s/cm on the automobile body for 20-30 s, wherein the spraying pressure is 0.1-0.18 MPa;

(9) and (3) circulating pure water washing: immersing the automobile body into pure water with the pH value of 5.5-8 and the conductivity of less than or equal to 60 mu s/cm, wherein the immersion time is 120-150 s, and the spraying pressure during immersion and leaching of the automobile body is 0.1-0.18 MPa;

(10) fresh pure water washing: spraying the automobile body with pure water with the conductivity less than or equal to 5 mu s/cm for 20-30 s, spraying pressure of 0.1-0.18 MPa, spraying flow of 50-80L/min, and automobile body water drop conductivity less than or equal to 50 mu s/cm;

second, electrophoresis, specifically:

(1) electrophoresis: immersing an automobile body into an electrophoresis tank liquid with the pH value of 5.8-6.5, the conductivity of 1300-2200 mu s/cm, the throwing power of more than or equal to 60 percent and the solvent content of less than or equal to 2 percent, wherein the temperature of the electrophoresis tank liquid is 28-32 ℃, the solid content of the electrophoresis tank liquid is 19-22 percent, the ash content is 15-20 percent, the electrophoresis process adopts two-stage voltage step control, the first-stage voltage is 160-250V, the second-stage voltage is 200-300V, and the electrifying time of the electrophoresis process is more than or equal to 180 s;

(2) first ultrafiltration water washing: spraying the automobile body with the electrophoretic ultrafiltration water washing tank liquor for 20-30 s at a spraying pressure of 0.05-0.15 MPa;

(3) and (3) ultrafiltration washing for the second time: immersing an automobile body into the electrophoresis ultrafiltration washing tank liquor for 120-180 s, wherein the spraying pressure during the immersion of the automobile body and the leaching of the automobile body is 0.05-0.15 MPa, and the solid content of the electrophoresis ultrafiltration washing tank liquor is less than or equal to 2%;

(4) and (3) ultrafiltration washing for the third time: spraying the automobile body with the electrophoretic ultrafiltration water washing tank liquor for 20-30 s at a spraying pressure of 0.05-0.15 MPa;

(5) pure water washing is circulated for the first time: spraying pure water with the solid content of less than or equal to 0.5% on an automobile body for 20-30 s, wherein the spraying pressure is 0.05-0.12 MPa;

(6) and (3) circulating pure water for the second time: immersing the automobile body into pure water with the solid content of less than or equal to 0.5%, wherein the immersion time is 120-180 s, and the spraying pressure during the immersion of the automobile body and the leaching of the automobile body are both 0.05-0.12 MPa;

(7) fresh pure water washing: spraying the automobile body with pure water for 20-30 s, wherein the spraying pressure is 0.05-0.12 MPa, and the spraying flow is 70-130L/min;

thirdly, electrophoretic drying: baking the automobile body for 20-30 min at 160-180 ℃ to enable the electrophoretic coating to be dehydrated, then performing crosslinking reaction and curing, wherein after baking, the hardness of the electrophoretic coating is more than or equal to H, and the adhesive force of the electrophoretic coating measured by a Baige method is less than or equal to 0 level; the thickness of the electrophoretic coating satisfies: the thickness of the electrophoretic coating on the outer surface of the vehicle body is more than or equal to 15 microns, and the thickness of the electrophoretic coating on the inner cavity of the vehicle body is more than or equal to 10 microns;

fourthly, electrophoretic polishing: polishing the electrophoresis defects by using sand paper;

fifthly, water washing middle paint spraying: spraying water-based primer to the surface of the automobile body by using an electrostatic rotary cup spray gun, wherein the film forming mode is a one-stop spraying film forming mode, and the film forming thickness is 15-20 mu m;

sixthly, water washing colored paint spraying: after the spraying of the water-based intermediate coat is finished, 'wet-on-wet', spraying the water-based colored paint on the surface of the automobile body by using an electrostatic rotary cup spray gun, wherein the film forming mode is one-stop spraying film forming, and the film forming thickness is 5-8 mu m;

seventhly, water washing pearl varnish spraying: after the spraying of the water-based plain paint is finished, spraying the water-based pearlescent paint on the surface of the automobile body by using an electrostatic rotary cup spray gun, wherein the film forming mode is a one-stop spraying film forming mode, and the film forming thickness is 4-6 mu m;

eighthly, flash drying: baking the automobile body for 8-12 min at the temperature of 120-140 ℃ to carry out flash-drying dehydration, wherein the flash-drying air speed is 8-12 m/s;

ninth, powder coating spraying:

(1) cleaning a powder spraying room: the dust in the powder spraying room is cleaned, and the dust in each cubic foot of air is ensured to be as follows: the dust particle with the particle size of more than or equal to 5 mu m is not contained, and the number of the dust particles with the particle size range of 0.5 to 5 mu m is not more than 30000;

(2) setting the wind direction, the wind speed and the temperature and humidity of the powder spraying room: setting the wind direction of the powder spraying room to be vertical downward, setting the wind speed to be 0.3-0.5 m/s, setting the temperature to be 20-30 ℃ and setting the humidity to be 50-70%;

(3) spraying: conveying an automobile body to be treated into a powder spraying room, spraying powder coating on the surface of the automobile body under the condition that the electrostatic voltage is-70 to-60 kV, wherein the film forming mode is a one-stop spraying film forming mode, the film forming thickness is 40 to 60 mu m, the spraying gun distance is 15 to 25cm, and the spraying gun speed is 400 to 600 mm/s;

tenthly, drying finish paint: baking the automobile body for 20-30 min at the temperature of 160-180 ℃; the hardness of the dried paint film is more than or equal to HB, and the adhesive force of the paint film measured by a Baige method is less than or equal to 0 grade;

eleven, fine trimming and inserting the wire: and inspecting the vehicle body after the finish paint is dried, marking defects, and modifying the defects by adopting methods such as grinding, polishing and the like to prevent the defects of the paint film from flowing out.

The following will describe in detail the coating structure of an automobile body containing a water-based paint and a powder paint and the preparation method thereof provided by the present application with reference to examples.

Example 1:

example 1 of the present application provides a method for preparing an automotive body coating structure containing a water-based paint and a powder paint, comprising the steps of:

firstly, phosphating pretreatment:

(1) pre-washing: spraying industrial water at 45 ℃ on the automobile body for 25s at the spraying pressure of 0.1 MPa;

(2) pre-degreasing: spraying the automobile body with pre-degreasing bath solution for 50s at a spraying pressure of 0.25MPa at 45 deg.C and a pH of 14; the pre-degreasing bath solution is an alkaline surfactant;

(3) degreasing: immersing the automobile body into degreasing bath solution with the pH value of 13, wherein the immersion time is 200s, the surface flow circulation pressure is 0.1MPa, and the temperature of the degreasing bath solution is 45 ℃; degreasing bath solution is alkaline surfactant;

(4) first water washing: immersing the automobile body in industrial water for 130s, wherein the spraying pressure during the immersion of the automobile body and the spraying pressure during the immersion of the automobile body are both 0.25 MPa;

(5) and (3) second water washing: spraying industrial water to the automobile body for 25s under 0.28 MPa;

(6) surface conditioning: immersing the automobile body into surface adjustment tank liquid with the pH value of 10, wherein the immersion time is 100s, and the temperature of the surface adjustment tank liquid is 30 ℃; the surface conditioning bath solution is zinc phosphating solution;

(7) phosphorization: immersing an automobile body into phosphating tank liquor with the ratio of total acid to free acid of 22, wherein the immersion time is 200s, the surface flow spraying pressure of the phosphating tank liquor is 0.04MPa, and the temperature of the phosphating tank liquor is 42 ℃; the phosphated automobile body needs to be ensured: the size of phosphorization crystal is less than or equal to 10 mu m, the zinc-iron phosphate content in the phosphorization film is more than or equal to 90 percent, and the weight of the phosphorization film on the surface of the cold-rolled steel plate is 2-3 g/m²The weight of the phosphating film on the surface of the galvanized steel sheet is 2-4 g/m²(ii) a The phosphating tank solution is zinc phosphating solution;

(8) and (3) washing for the third time: immersing the automobile body in industrial water for 130s, wherein the spraying pressure during the immersion of the automobile body and the spraying pressure during the immersion of the automobile body are both 0.15 MPa;

(9) fourth water washing: spraying industrial water to the automobile body for 25s under 0.15 MPa;

(10) and (3) circulating pure water washing: immersing the automobile body into pure water with the conductivity less than or equal to 20 mu s/cm, wherein the immersion time is 130s, and the spraying pressure during the immersion of the automobile body are both 0.2 MPa;

(11) fresh pure water washing: spraying the automobile body with pure water with the conductivity less than or equal to 5 mus/cm for 25s, spraying pressure of 0.2MPa, spraying flow of 80L/min, and automobile body water dripping conductivity less than or equal to 50 mus/cm;

II, electrophoresis:

(1) electrophoresis: immersing an automobile body into an electrophoresis tank liquid with the pH value of 6, the conductivity of 1800 mu s/cm, the throwing power of more than or equal to 60 percent and the solvent content of less than or equal to 2 percent, wherein the temperature of the electrophoresis tank liquid is 30 ℃, the solid content and the ash content of the electrophoresis tank liquid are 20 percent and 18 percent, the electrophoresis process adopts two-stage voltage step control, the first-stage voltage is 200V, the second-stage voltage is 250V, and the electrifying time of the electrophoresis process is 200 s;

(2) first ultrafiltration water washing: spraying the automobile body with the electrophoretic ultrafiltration water washing tank liquor for 25s at a spraying pressure of 0.1 MPa;

(3) and (3) ultrafiltration washing for the second time: immersing the automobile body into the electrophoresis ultrafiltration washing tank liquor for 160s, wherein the spraying pressure during the immersion of the automobile body and the leaching of the automobile body are both 0.1MPa, and the solid content of the electrophoresis ultrafiltration washing tank liquor is less than or equal to 2%;

(4) and (3) ultrafiltration washing for the third time: spraying the automobile body with the electrophoretic ultrafiltration water washing tank liquor for 25s at a spraying pressure of 0.1 MPa;

(5) pure water washing is circulated for the first time: spraying pure water with the solid content of less than or equal to 0.5 percent on the automobile body for 25s at the spraying pressure of 0.08 MPa;

(6) and (3) circulating pure water for the second time: immersing the automobile body into pure water with the solid content of less than or equal to 0.5%, wherein the immersion time is 150s, and the spraying pressure during the immersion of the automobile body and the leaching of the automobile body are both 0.08 MPa;

(7) fresh pure water washing: spraying pure water on the automobile body for 25s, wherein the spraying pressure is 0.1MPa, and the spraying flow is 80L/min;

thirdly, electrophoretic drying: baking the automobile body for 25min at the temperature of 170 ℃ to ensure that the electrophoretic coating is dehydrated, then, has a crosslinking reaction and is cured, after baking, the hardness of the electrophoretic coating is more than or equal to H, and the adhesive force of the electrophoretic coating measured by a Baige method is less than or equal to 0 grade; the thickness of the electrophoretic coating satisfies: the thickness of the electrophoretic coating on the outer surface of the vehicle body is 20 microns, and the thickness of the electrophoretic coating in the inner cavity of the vehicle body is 12 microns;

fourthly, electrophoretic polishing: polishing the electrophoresis defects by using sand paper;

fifthly, water washing middle paint spraying: spraying water-based primer to the surface of the automobile body by using an electrostatic rotary cup spray gun, wherein the film forming mode is a one-stop spraying film forming mode, and the film forming thickness is 16 microns;

sixthly, water washing colored paint spraying: after the spraying of the water-based intermediate coat paint is finished, 'wet-on-wet', spraying the water-based colored paint on the surface of the automobile body by using an electrostatic rotary cup spray gun, wherein the film forming mode is one-stop spraying film forming, and the film forming thickness is 6 mu m;

seventhly, water washing pearl varnish spraying: after the spraying of the water-based plain paint is finished, 'wet-on-wet', spraying the water-based pearlescent paint on the surface of the automobile body by using an electrostatic rotary cup spray gun, wherein the film forming mode is one-stop spraying film forming, and the film forming thickness is 5 mu m;

eighthly, flash drying: baking the automobile body for 10min at the temperature of 130 ℃ to carry out flash-drying dehydration, wherein the flash-drying wind speed is 10 m/s;

ninth, powder coating spraying:

(1) cleaning a powder spraying room: the dust in the powder spraying room is cleaned, and the dust in each cubic foot of air is ensured to be as follows: the dust particle with the particle size of more than or equal to 5 mu m is not contained, and the number of the dust particles with the particle size range of 0.5 to 5 mu m is not more than 30000;

(2) setting the wind direction, the wind speed and the temperature and humidity of the powder spraying room: setting the wind direction of the powder spraying room to be vertical and downward, setting the wind speed to be 0.4m/s, setting the temperature to be 25 ℃ and setting the humidity to be 60 percent;

(3) spraying: conveying the automobile body to be processed into a powder spraying room, spraying powder coating on the surface of the automobile body under the condition that the electrostatic voltage is-65 kV, wherein the film forming mode is one-stop spraying film forming, the film forming thickness is 50 mu m, the spraying gun distance is 20cm, and the spraying gun speed is 500 mm/s;

tenthly, drying finish paint: baking the automobile body for 25min at the temperature of 170 ℃; the hardness of the dried paint film is more than or equal to HB, and the adhesive force of the paint film measured by a Baige method is less than or equal to 0 grade;

eleven, fine trimming and inserting the wire: and inspecting the vehicle body after the finish paint is dried, marking defects, and modifying the defects by adopting methods such as grinding, polishing and the like to prevent the defects of the paint film from flowing out.

Example 2:

example 2 of the present application provides a method for preparing an automotive body coating structure containing a water-based paint and a powder paint, comprising the steps of:

firstly, pretreatment of a film:

(1) pre-washing: spraying industrial water at 35 ℃ on the automobile body for 25s at the spraying pressure of 0.08 MPa;

(2) pre-degreasing: spraying the automobile body with pre-degreasing bath solution for 45s under 0.22MPa at 45 deg.C and pH value less than 12.5; the pre-degreasing bath solution selects an alkaline surfactant;

(3) degreasing: immersing the automobile body in degreasing bath liquid for 220s, wherein the surface flow circulation pressure of the degreasing bath liquid is 0.1MPa, the temperature of the degreasing bath liquid is 45 ℃, and the pH value of the degreasing bath liquid is less than 12; the degreasing bath solution selects an alkaline surfactant;

(4) first water washing: immersing the automobile body into industrial water with the pH value of 9 and the conductivity of 1800 mu s/cm, wherein the immersion time is 135s, and the spraying pressure during the immersion of the automobile body and the spraying pressure during the extraction of the automobile body are both 0.15 MPa;

(5) and (3) second water washing: spraying industrial water with pH value of 9 and conductivity of 800 μ s/cm for 25s under 0.12 MPa;

(6) and (3) washing for the third time: immersing an automobile body into pure water with the pH value of 8 and the conductivity of 200 mu s/cm, wherein the immersion time is 140s, the spraying pressure during the immersion of the automobile body and the spraying pressure during the leaching of the automobile body are both 0.15MPa, and the supplementing flow rate of the pure water is 50L/min;

(7) silane treatment: immersing an automobile body into silane tank liquid with the pH value of 5 and the conductivity of 3000 mu s/cm, wherein the immersion time is 150s, the temperature of the silane tank liquid is 35 ℃, the stirring pressure in the silane tank liquid is 0.12MPa, the Zr content in the silane tank liquid is 200mg/L, Cu content, the Zr content in the silane tank liquid is 2mg/L, Si content, and the free fluorine content in the silane tank liquid is 40 mg/L; the silane treated automobile body needs to guarantee: the weight of the silane film on the surface of the galvanized steel sheet is 70-180 mg/m²The weight of the silane film on the surface of the cold-rolled steel plate is 30-100 mg/m²；

(8) Fourth water washing: spraying pure water with the pH value of 8 and the conductivity of 500 mu s/cm on the automobile body for 25 minutes at the spraying pressure of 0.15 MPa;

(9) and (3) circulating pure water washing: immersing the automobile body into pure water with the pH value of 7 and the conductivity of 50 mu s/cm, wherein the immersion time is 130s, and the spraying pressure of the automobile body during immersion and leaching is 0.15 MPa;

(10) fresh pure water washing: spraying the automobile body with pure water with the conductivity of 4 mus/cm for 25s, spraying pressure of 0.15MPa, spraying flow of 60L/min, and automobile body water drop conductivity of less than or equal to 50 mus/cm;

II, electrophoresis:

(1) electrophoresis: immersing an automobile body into an electrophoresis tank liquid with the pH value of 6.0, the conductivity of 1800 mu s/cm, the throwing power of more than or equal to 60 percent and the solvent content of less than or equal to 2 percent, wherein the temperature of the electrophoresis tank liquid is 30 ℃, the solid content and the ash content of the electrophoresis tank liquid are 21 percent and 16 percent, the electrophoresis process adopts two-stage voltage step control, the first-stage voltage is 210V, the second-stage voltage is 255V, and the electrifying time of the electrophoresis process is 220 s;

(2) first ultrafiltration water washing: spraying the automobile body with the electrophoretic ultrafiltration water washing tank liquor for 25s at a spraying pressure of 0.1 MPa;

(3) and (3) ultrafiltration washing for the second time: immersing the automobile body into the electrophoresis ultrafiltration washing tank liquor for 150s, wherein the spraying pressure during the immersion of the automobile body and the leaching of the automobile body are both 0.1MPa, and the solid content of the electrophoresis ultrafiltration washing tank liquor is less than or equal to 2%;

(4) and (3) ultrafiltration washing for the third time: spraying the automobile body with the electrophoretic ultrafiltration water washing tank liquor for 25s at a spraying pressure of 0.1 MPa;

(5) pure water washing is circulated for the first time: spraying pure water with the solid content of less than or equal to 0.5 percent on the automobile body for 25s at the spraying pressure of 0.08 MPa;

(6) and (3) circulating pure water for the second time: immersing the automobile body into pure water with the solid content of less than or equal to 0.5%, wherein the immersion time is 150s, and the spraying pressure during the immersion of the automobile body and the leaching of the automobile body are both 0.09 MPa;

(7) fresh pure water washing: spraying pure water on the automobile body for 25s, wherein the spraying pressure is 0.08MPa, and the spraying flow is 80L/min;

thirdly, electrophoretic drying: baking the automobile body for 25min at 165 ℃ to dehydrate the electrophoretic coating, then performing crosslinking reaction and curing, wherein after baking, the hardness of the electrophoretic coating is more than or equal to H, and the adhesive force of the electrophoretic coating is measured by a Baige method to be less than or equal to 0 level; the thickness of the electrophoretic coating satisfies: the thickness of the electrophoretic coating on the outer surface of the vehicle body is 18 microns, and the thickness of the electrophoretic coating in the inner cavity of the vehicle body is 12 microns;

fourthly, electrophoretic polishing: polishing the electrophoresis defects by using sand paper;

fifthly, water washing middle paint spraying: spraying water-based primer to the surface of the automobile body by using an electrostatic rotary cup spray gun, wherein the film forming mode is a one-stop spraying film forming mode, and the film forming thickness is 16 microns;

sixthly, water washing colored paint spraying: after the spraying of the water-based intermediate coat paint is finished, 'wet-on-wet', spraying the water-based colored paint on the surface of the automobile body by using an electrostatic rotary cup spray gun, wherein the film forming mode is one-stop spraying film forming, and the film forming thickness is 7 mu m;

seventhly, water washing pearl varnish spraying: after the spraying of the water-based plain paint is finished, 'wet-on-wet', spraying the water-based pearlescent paint on the surface of the automobile body by using an electrostatic rotary cup spray gun, wherein the film forming mode is one-stop spraying film forming, and the film forming thickness is 5 mu m;

eighthly, flash drying: baking the automobile body for 10min at the temperature of 135 ℃ to carry out flash-drying dehydration, wherein the flash-drying wind speed is 9 m/s;

ninth, powder coating spraying:

(1) cleaning a powder spraying room: the dust in the powder spraying room is cleaned, and the dust in each cubic foot of air is ensured to be as follows: the dust particle with the particle size of more than or equal to 5 mu m is not contained, and the number of the dust particles with the particle size range of 0.5 to 5 mu m is not more than 30000;

(2) setting the wind direction, the wind speed and the temperature and humidity of the powder spraying room: setting the wind direction of the powder spraying room to be vertical and downward, setting the wind speed to be 0.4m/s, setting the temperature to be 28 ℃ and setting the humidity to be 65 percent;

(3) spraying: conveying the automobile body to be processed into a powder spraying room, spraying powder coating on the surface of the automobile body under the condition that the electrostatic voltage is-63 kV, wherein the film forming mode is one-stop spraying film forming, the film forming thickness is 55 mu m, the spraying gun distance is 18cm, and the spraying gun speed is 450 mm/s;

tenthly, drying finish paint: baking the automobile body for 25min at the temperature of 175 ℃; the hardness of the dried paint film is more than or equal to HB, and the adhesive force of the paint film measured by a Baige method is less than or equal to 0 grade;

eleven, fine trimming and inserting the wire: and inspecting the vehicle body after the finish paint is dried, marking defects, and modifying the defects by adopting methods such as grinding, polishing and the like to prevent the defects of the paint film from flowing out.

The performance of the finish paint film prepared in example 2 was tested and the results are shown in Table 1.

Table 1: example 2 Performance test results of the topcoat paint film

As can be seen from Table 2, the appearance, mechanical properties, resistance to humidity and heat, water resistance, resistance to chemical agents, resistance to thermal cycling and xenon lamp aging properties of the paint film prepared in example 2 all meet the technical requirements of passenger cars.

The water-based primer surfacer, the water-based pearlescent paint, the water-based colored paint and the powder coating used in the embodiment of the present application are not particularly limited, and the water-based primer surfacer, the water-based pearlescent paint, the water-based colored paint and the powder coating which are suitable for being sprayed on the automobile body in the prior art are all specific embodiments of the water-based primer surfacer, the water-based pearlescent paint, the water-based colored paint and the powder coating which correspond to the present application.

It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.