Underbody Coating

AUTOMOTIVE COATING PROCESSES:

Modern automotive coating methods consist of five main steps. They include the following:

• PRETREATMENT
• ELECTRODEPOSITION
• RUST-PROOF MATERIALS: SEALER/PVC
• PRIMER
• TOPCOAT

1.PRETREATMENT:

• The first sequence in preparing the BIW for subsequent coating is pre-treatment removing & clean excess metal & forms an appropriate surface structure enabling bonding of a corrosion protection layer. It consists of cleaning the body surface to remove remaining oils from the steaming process & welding residues through three primary liquid dip processes of degreasing, conditioning, & phosphating.
• The degreasing solution is composed of alkaline salts & surfactants & can include caustic soda, sodium carbonate. The surfactants are types of detergents for emulsifying oils & lubricants on the BIW.
• Finally, the liquid dip phosphate ions, nitrate ions, zinc & hydrogen ions.
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2.ELECTRODEPOSITION:

• E-coating involves dipping automobile bodies into the coating solution & passing an electric current through the body & the liquid ELETRODEPOSITION paint solution. Because of the charged nature of this coating process, the ED paint penetrates places a spray would not reach

• The oven temperature & heating time primarily enhanced chip resistance & film adhesion to the body.
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3. RUST-PROOF MATERIALS:

• During this third step, it is also typical to apply a soft tip primer coat that improves the chipping resistance. This layer is applied to the front edge of the hood, which is an area prone to chipping shock, using a high elastic resin that resides between the ED & primer coats.
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4.PRIMER:

• The fourth coating step is the primer. It can be water-borne, solvent-borne, or powder. The primer fills & smoothed minor imperfections & scratches that may be created during prior steps & by the intermediate sanding or grinding used to remove small imperfections.

• Primer coating operations in an automobile assembly plant are usually implemented in three stages: Interior coating, Exterior coating, & then cutting in an oven.
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5.TOPCOAT:

• The final step in the body coating process is to apply the top coat, which consists of two layers the basecoat & clearcoat.
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• Basecoat: It contains the primary coloring pigments. As part of the topcoat, the basecoat is the third layer added to the car after the primer & before the clearcoat.

• Clearcoat:

  The final coating on an automobile surface is the clear coat.

  it provides durability, environmental etch, & scratch resistance to the overall coating.

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