US20150064482A1

US20150064482A1 - Vehicle body and method for coating a vehicle body

Info

Publication number: US20150064482A1
Application number: US14/166,301
Authority: US
Inventors: Hua-Tzu Fan; Robert Bruce Tilove
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2013-08-27
Filing date: 2014-01-28
Publication date: 2015-03-05
Also published as: DE112014003935T5; WO2015030934A1; CN105492208B; CN105492208A

Abstract

A method can be used to coat a vehicle body. The method includes: (a) providing a metallic substrate; (b) applying a foundation coat over the metallic substrate; (c) applying a basecoat over the foundation coat; (d) applying a clearcoat over the basecoat; and (e) heating the metallic substrate, the foundation coat, the basecoat, and the clearcoat simultaneously in order to cure the foundation coat, the basecoat, and the clearcoat. The foundation coat is inherently UV stable and is configured to protect the vehicle body against corrosion, and bonds the metallic substrate to the basecoat and the clearcoat. A vehicle body includes a metallic substrate, a foundation coat bonded to the metallic substrate, a basecoat disposed over the foundation coat, and a clearcoat disposed over the basecoat.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/870,278, filed Aug. 27, 2013, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a vehicle body and a method for coating a vehicle body.

BACKGROUND

Vehicle bodies can be coated to provide, among other things, an aesthetically pleasing appearance. The coatings applied to a vehicle body can not only provide a desirable aesthetic appearance for the vehicle, but can also protect the vehicle body from the elements (e.g., rain).

SUMMARY

Automotive vehicle bodies may include a metallic substrate and are typically coated with five layers or coats, namely: (a) a phosphate coat; (b) an electro-deposition coat (i.e., e-coat); (c) a primer; (d) a basecoat; and (e) a clearcoat. The phosphate coat promotes adhesion between the paint layers (e.g., e-coat, primer, basecoat, and clearcoat) and the metallic substrate (e.g., steel or aluminum). As used herein, the terms “electro-deposition coat” and “e-coat” refer to a coating created using any suitable electro-deposition operation or process (i.e., an anti-corrosion electroplating bath). The e-coat provides corrosion protection. As used herein, the term “primer” means a coating capable of protecting the metallic substrate and the other coatings (e.g., phosphate coat, e-coat, basecoat, and clearcoat) against ultraviolet (UV) radiation from the sun. The primer therefore provides UV radiation resistance. In this disclosure, the term “basecoat” means a polymeric coating including a color pigment and can impart a color (e.g., red) to the vehicle body. The basecoat therefore provides color. As used herein, the term “clearcoat” refers to a polymeric coating that can provide gloss and protection to the vehicle body. The clearcoat therefore enhances the appearance of the vehicle body and can provide protection against scratches and the environment. It is useful, however, to minimize the number of coats in a vehicle body in order to minimize manufacturing costs. Specifically, it is useful to develop a method of coating a vehicle body that employs a single coat that provides adhesion promotion, corrosion protection, and UV radiation resistance, and thereby replaces the phosphate coat, e-coat, and possibly primer.
The present disclosure relates to a method for coating a vehicle body. The method includes the following steps: (a) providing a metallic substrate; (b) applying a foundation coat over the metallic substrate; (c) applying an optional primer coat over the foundation coat; (d) applying a basecoat over the foundation or the optional primer coat; (e) applying a clearcoat over the basecoat; and (f) heating the metallic substrate, the foundation coat, the optional primer coat, the basecoat, and the clearcoat simultaneously in order to cure the foundation coat, the basecoat, and the clearcoat. It may also be necessary to cure the foundation coat and the primer coat first with a cure oven before applying the basecoat and the clearcoat. Once cured, the foundation coat is configured to protect the vehicle body against corrosion, and bonds the metallic substrate to the basecoat and the clearcoat.
The present disclosure also relates to vehicle bodies. In an embodiment, the vehicle body includes a metallic substrate, a foundation coat bonded to the metallic substrate, a basecoat disposed over the foundation coat, and a clearcoat disposed over the basecoat. The foundation coat is disposed between the metallic substrate and the basecoat. The basecoat is disposed between the clearcoat and the foundation coat. The foundation coat is configured to protect the vehicle body against ultraviolet radiation and corrosion, and bonds the metallic substrate to the basecoat and the clearcoat.
In another embodiment, the method for coating a metallic substrate includes the following steps: (a) dipping the metallic substrate in a tank containing a solution including a foundation coat in order to apply the foundation coat over the metallic substrate; (b) applying a basecoat over the foundation coat; (c) applying a clearcoat over the basecoat; and (d) heating the metallic substrate, the foundation coat, the basecoat, and the clearcoat simultaneously in order to cure the foundation coat, the basecoat, and the clearcoat. The foundation coat is configured to be UV stable and to protect the metallic substrate against corrosion, and bonds the metallic substrate to the subsequent layers of paint. A material or coat can be inherently UV stable if the material or coat does not crack or disintegrate when attacked by ultraviolet radiation. In this method, the metallic substrate does not undergo an electro-deposition process, and a primer coat may be applied over the foundation coat if it is required to achieve certain quality requirement such as a smooth paint finish.
The above features and advantages, and other features and advantages, of the present invention are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the invention, as defined in the appended claims, when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a vehicle including a vehicle body;

FIG. 2 is a schematic illustration of the vehicle body shown FIG. 1, wherein the vehicle body includes a metallic substrate and coatings in accordance with an embodiment of the present disclosure;

FIG. 3 is a flowchart of a method for coating a vehicle body in accordance with an embodiment of the present disclosure;

FIG. 4 is a flowchart of a method for coating a vehicle body in accordance with another embodiment of the present disclosure; and

FIG. 5 is a schematic illustration of a vehicle body including a metallic substrate and coatings in accordance with another embodiment of the present disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the like numerals indicate corresponding parts throughout the several views, FIG. 1 schematically illustrates a vehicle 10 such as a car or a truck. In the depicted embodiment, the vehicle 10 includes a vehicle body 12 and wheels 13 operatively coupled to the vehicle body 12. A tire 15 is operatively coupled to each wheel 13. Although FIG. 1 illustrates a car, it is envisioned that the vehicle 10 may alternatively be a motorcycle or another kind of vehicle.
FIG. 2 schematically illustrates a portion of the vehicle body 12 in cross-sectional view. The vehicle body 12 includes a substrate or base material 14 wholly or partly made of a metallic material such as steel or aluminum. The substrate 14 is therefore referred to as a metallic substrate. Alternatively, the substrate 14 may be referred to as a workpiece. In addition to the metallic substrate 14, the vehicle body 12 includes a foundation coat 16 directly applied by using a dipping process over the metallic substrate 14. As used herein, the term “foundation coat” means a polymeric coating that is inherently UV stable and is capable of protecting the vehicle body 12 against corrosion, and helps bond the metallic substrate 14 to other coatings. The term “inherently UV stable” means that the material forming the foundation coat 16, by itself and without any UV stable additives, does not crack or disintegrate when attacked by ultraviolet radiation. As a non-limiting example, the foundation coat 16 can be rated UV-8. A material or coat rated UV-8 withstood 8000 hours of exposure to UV light before the elongation at break was reduced to 50% of the original value during testing in a Weather-OMeter. UV ratings (e.g., UV-X) are expressed as a multiple of 1000 hours of exposure until a chosen mechanical property (e.g., elongation at break or tensile strength) reaches 50% of the original value (i.e., the value of the mechanical property before the material was subjected to UV light.) As a non-limiting example, the UV rate of the foundation coat 16 may range between UV-5 and UV-10. As a non-limiting example, the foundation coat 16 can protect the vehicle body 12 against corrosion such the corrosion rate (as expressed in mils penetration per year (mpy)) ranges between the 0.9 and 10 mpy. For example, the corrosion rate (as expressed in mpy) may be 3 mpy.
The foundation coat 16 is chemically bonded to the metallic substrate 14. The term “chemically bonded” means that a chemical covalent or ionic bond couples the foundation coat 16 with the metallic substrate 14. The foundation coat 16 is therefore configured to establish a strong adhesion bond with the metallic substrate 14. As a non-limiting example, the bond energy of the chemical bond between the foundation coat 16 and the metallic substrate 14 may range between 600 and 800 kilojoule per mol (kJ/mol). As a non-limiting example, the bond energy of the chemical bond between the foundation coat 16 and the metallic substrate 14 may be 700 kJ/mol. It is contemplated that the foundation coat 16 may be one of the coatings sold by COVAL MOLECULAR COATINGS such as the coating sold under the trade name COVAL METAL COAT™. It has to be applied by a dip coating process in order to provide 100% coverage for both the interior and exterior surfaces of the metallic substrates 14 (vehicle bodies).
The vehicle body 12 further includes a basecoat 18 directly applied over the foundation coat 16. In this disclosure, the term “basecoat” means a polymeric coating including at least one color pigment. Accordingly, the basecoat 18 can impart a color (e.g., red) to the vehicle body 12. The color of the basecoat 18 is mainly a function of the pigments used. The foundation coat 16 is disposed between the metallic substrate 14 and the basecoat 18. The basecoat 18 may be wholly or partly made of acrylics, vinyls, polyurethanes, polycarbonates, polyesters, alkyds, polyepoxy, polysiloxanes, resins, and combinations thereof
Further, the vehicle body 12 includes a clearcoat 20 directly applied over the basecoat 18. As used herein, the term “clearcoat” refers to a polymeric coating that can provide gloss and protection to the vehicle body 12. The clearcoat 20 is therefore used to provide gloss and protection to the vehicle body 12. The basecoat 18 is disposed between the clearcoat 20 and the foundation coat 16. As a non-limiting example, the clearcoat 20 may include a polymer such as an acrylic based material. For example, the clearcoat 20 can be formulated based on the following: hydroxyl acrylic, polyester carbamate acrylic, polyester, epoxy, a blocked isocyanate system, or combinations thereof
FIG. 3 includes a flowchart illustrating a method 100 of coating the vehicle body 12. Specifically, in this method 100, the metallic substrate 14 of the vehicle body 12 is coated with different coatings. The method 100 begins at step 102 and includes at least three coats and one bake. As used herein, the term “bake” means a process in which at least one polymer coat is heated in an oven to cure that polymeric coat. Step 102 entails providing the metallic substrate 14, which may be a vehicle body-in-white (BIW). As used herein, the term “vehicle BIW” refers to the sheet metal components of the vehicle body that welded together including swing metals (e.g. doors, hood, and decklid), but without moving parts (e.g., wheels and tires), the motor, chassis sub-assemblies, or trim (e.g., glass, seats, upholstery, electronics, etc.) and before painting. The metallic substrate 14 (e.g., vehicle BIW) may be supplied using a conveyer. At this point, all the sealers and adhesives in the vehicle BIW are fully cured or gelled. The method 100 then continues to step 104.
Step 104 entails cleaning the metallic substrate 14 (e.g., vehicle BIW). At step 102, for example, the vehicle BIW may undergo a multi-stage cleaning process in order to remove contamination from the entire vehicle BIW. Water and cleaner may be sprayed on the vehicle BIW to clean it. After the metallic substrate 14 has been cleaned, the method 100 continues to step 106.
Step 106 entails applying the foundation coat 16 directly on the metallic substrate 14 (e.g., vehicle BIW). To do so, the metallic substrate 14 (e.g., vehicle BIW) may be dipped in a tank containing a solution including the foundation coat 16. It is contemplated that the vehicle BIW may be dipped into a tank containing the foundation coat 16 in order to apply the foundation coat 16 to all the interior and exterior surfaces of the vehicle BIW. This foundation coat 16 provides corrosion protection, UV resistance, and promotes adhesion between the coats (i.e., basecoat 18 and clearcoat 20) and the metallic substrate 14. At this stage, the foundation coat 16 is not cured. After applying the foundation coat 16 on the metallic substrate 14, the method 100 proceeds to step 108.
Step 108 entails applying the basecoat 18 directly over the foundation coat 16. The basecoat 18 can be applied over the foundation coat 16 before the foundation coat 16 is cured. To do so, the metallic substrate 14 (e.g., vehicle BIW) is moved into a basecoat spraying booth. While in the basecoat spraying booth, the basecoat 18 is sprayed over the foundation coat 16 that is already on the metallic substrate 14. At this stage, the basecoat 18 is not cured. Accordingly, the basecoat 18 is applied over the foundation coat 16 before the foundation coat 16 is cured. However, step 108 may further include heating the basecoat 18 after it has been applied over the foundation coat 16 using, for example, a heated flash oven. The method 100 then continues to step 110.
Step 110 entails applying the clearcoat 20 directly over the basecoat 18. The clearcoat 20 can be applied over the basecoat 18 before the basecoat 18 is cured. At step 110, the metallic substrate 14 (e.g., vehicle BIW) can be advanced to a clearcoat spraying booth. While in the clearcoat spraying booth, the clearcoat 20 is sprayed on the basecoat 18 that is already disposed over the foundation coat 16 and metallic substrate 14. At this stage, the clearcoat 20 is not cured. After applying the clearcoat 20 over the basecoat 18, the method 100 proceeds to step 112.
Step 112 entails heating the metallic substrate 14 (e.g., vehicle BIW), foundation coat 16, basecoat 18, and clearcoat 20 simultaneously in order to cure all the coats (i.e., foundation coat 16, basecoat 18, and clearcoat 20). A typical heating temperature may be 280 degrees Fahrenheit for 30 minutes. The foundation coat 16, basecoat 18, and clearcoat 20 may be collectively referred to as paint layers or coatings. It is envisioned that the entire vehicle body 12 (i.e., the metallic substrate 14, foundation coat 16, basecoat 18, and clearcoat 20) may be baked in an oven in order to cure all the coats. For example, the vehicle BIW can be positioned in an oven in order to cure the foundation coat 16, basecoat 18, and clearcoat 20 in one bake. As discussed above, the term “bake” means a process in which a polymer coat is heated in an oven to cure that polymeric coat. The vehicle body 12 is then removed from the oven, and the method 100 then continues to step 114.
Step 114 entails inspecting the vehicle body 12 to identify defects. For example, at step 114, the vehicle body 12 is subjected to a quality inspection. If the vehicle body 12 passes the quality inspection, the vehicle body 12 is sent to a general assembly area at step 116. At the general assembly area (see step 116), the vehicle body 12 is coupled to the other components of the vehicle 10. Conversely, if the vehicle body 12 fails the quality inspection because, for example, some defects are identified, the method 100 proceeds to step 118. At step 118, the identified defects are repaired. These repairs may be conducted in-line by re-routing the vehicle body 12 back to the basecoat spraying booth at step 108 as shown in FIG. 4. Alternatively, the repairs may be conducted offline after the quality inspection at step 114, and the vehicle body 12 is sent to the general assembly area after the defects have been repaired. In the method 100, the metallic substrate 14 does not undergo an electro-deposition (ELPO) operation or process (i.e., an anti-corrosion electroplating bath) in order to create an ELPO coat or layer, which may be made of an epoxy based material. In other words, the metallic substrate 14 (or any other part of the vehicle body 12) is not subjected to an ELPO operation. The ELPO coat may be referred to as an electro-deposition coat, an electrophoretic deposition (EPD) coat, or an e-coat. Accordingly, the vehicle body 12 does not include an electro-deposition coat. As used herein, an “electro-deposition coat” means a coating created using any suitable electro-deposition operation (i.e., an anti-corrosion electroplating bath).
FIG. 4 is a flowchart illustrating a method 200 of coating a vehicle body 212 (FIG. 5) in accordance with another embodiment of the present disclosure, and FIG. 5 shows a schematic illustration of a vehicle body 212 made using the method 200. The method 200 is identical to the method 100 described above but includes two additional steps (i.e., steps 202 and 204). In the interest of brevity, only steps 202 and 204 are described in detail below.
Step 202 entails applying a primer coat 214 (FIG. 5) directly over the foundation coat 16 after applying the foundation coat 16 to the metallic substrate 14 (e.g., vehicle BIW) at step 106. As used herein, the term “primer coat” means a coating capable of protecting the metallic substrate 14 and the other coats (i.e., foundation coat 16, basecoat 18, and clearcoat 20) against UV radiation exposure. At step 202, the metallic substrate 14 (e.g., vehicle BIW) is positioned in a primer spraying booth. While in the primer spraying booth, the primer coat 214 is sprayed directly over the foundation coat 16 that is already disposed on the metallic substrate 14. The method 200 then proceeds to step 204.
Step 204 entails heating the metallic substrate 14 (e.g., vehicle BIW) and the primer coat 214 in order to cure the primer coat 214 (FIG. 5). To do so, the metallic substrate 14 (e.g., vehicle BIW) and the primer coat 214 may be placed in an oven in order to bake the primer coat 214. After the primer coat 214 is cured, the method 200 proceeds to step 108, which entails applying the basecoat 18 directly over the primer coat 214. In the method 200, if an inline repair is conducted at step 118, the method 200 returns to step 202.
FIG. 5 schematically illustrates a portion of the vehicle body 212 in accordance with another embodiment of the present disclosure. The vehicle body 212 can be made using the method 200 described above and is substantially identical to the vehicle body 12 shown in FIG. 2. However, the vehicle body 212 includes the primer coat 214 in addition to the metallic substrate 14 and the coats described above with respect to FIG. 2 (i.e., foundation coat 16, basecoat 18, and clearcoat 20). The primer coat 214 is directly disposed over the foundation coat 16. In particular, the primer coat 214 is disposed between the foundation coat 16 and basecoat 18. The primer coat 214 may be needed in order to mask out surface imperfections on the metallic substrates of vehicle bodies and therefore improve the smoothness of the final paint finish. This coat may be needed in order to achieve a higher level of paint appearance quality for certain premium vehicles.
The detailed description and the drawings or figures are supportive and descriptive of the invention, but the scope of the invention is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed invention have been described in detail, various alternative designs and embodiments exist for practicing the invention defined in the appended claims.

Claims

1. A method for coating a vehicle body, the method comprising:

providing a metallic substrate;

applying a foundation coat on the metallic substrate;

applying a basecoat over the foundation coat;

applying a clearcoat over the basecoat; and

heating the metallic substrate, the foundation coat, the basecoat, and the clearcoat simultaneously in order to cure the foundation coat, the basecoat, and the clearcoat;

wherein the foundation coat is inherently ultraviolet (UV) stable and is configured to protect the metallic substrate against corrosion, and bonds the metallic substrate to the basecoat and the clearcoat.

2. The method of claim 1, wherein the metallic substrate is not subjected to an electro-deposition (ELPO) operation.

3. The method of claim 1, wherein the basecoat is applied over the foundation coat before the foundation coat is cured.

4. The method of claim 1, wherein the foundation coat is chemically bonded to the metallic substrate after heating the metallic substrate, the foundation coat, the basecoat, and the clearcoat.

5. The method of claim 1, wherein applying the foundation coat includes dipping the metallic substrate in a tank containing a solution including the foundation coat.

6. The method of claim 1, wherein the clearcoat is applied over the basecoat before the basecoat is cured.

7. The method of claim 1, wherein applying the basecoat includes spraying the basecoat over the foundation coat after the foundation coat has been applied on the metallic substrate.

8. The method of claim 1, wherein applying the clearcoat includes spraying the clearcoat over the basecoat after the basecoat has been applied over the foundation coat.

9. The method of claim 1, wherein heating the metallic substrate includes positioning the vehicle body in an oven after applying the foundation coat, the basecoat, and the clearcoat, and heating the vehicle body using the oven.

10. The method of claim 1, further comprising inspecting the vehicle body after heating the metallic substrate, the foundation coat, the basecoat, and the clearcoat.

11. The method of claim 1, further comprising applying a primer coat over the foundation coat before applying the basecoat.

12. The method of claim 1, further comprising heating the metallic substrate and the primer coat before applying the basecoat in order to cure the primer coat.

13. A vehicle body, comprising:

a metallic substrate;

a foundation coat bonded to the metallic substrate;

a basecoat disposed over the foundation coat, wherein the foundation coat is disposed between the metallic substrate and the basecoat;

a clearcoat disposed over the basecoat, wherein the basecoat is disposed between the clearcoat and the foundation coat; and

14. The vehicle body of claim 13, wherein the vehicle body does not include an electro-deposition coat.

15. The vehicle body of claim 13, further comprising a primer coat disposed over the foundation coat.

16. The vehicle body of claim 15, wherein the primer coat is disposed between the foundation coat and the basecoat.

17. The vehicle body of claim 13, wherein the basecoat includes a color pigment.

18. The vehicle body of claim 13, wherein the clearcoat comprises an acrylic based material.

19. A method for coating a metallic substrate, the method comprising:

dipping the metallic substrate in a tank containing a solution including a foundation coat in order to apply the foundation coat over the metallic substrate;

applying a basecoat over the foundation coat;

applying a clearcoat over the basecoat;

wherein the foundation coat is inherently ultraviolet (UV) stable and is configured to protect the metallic substrate against corrosion, and bonds the metallic substrate to the basecoat and the clearcoat; and

wherein the metallic substrate does not undergo an electro-deposition process.

20. The method of claim 19, further comprising applying a primer coat after applying the foundation coat but before applying the basecoat.