Patent Publication Number: US-2015064482-A1

Title: Vehicle body and method for coating a vehicle body

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.