UNDERBODY COATING

UNDERBODY COATING:

        Underbody coatings are those which are used to prevent car bodies against rust & corrosion. This underbody coating helps in protection from dust and moisture also some other factors such as poor road conditions, rocks getting thrown from tires and denting the metal and salt from water during monsoon which plays an important role in damaging the underbelly of a car.Underbody coating is usually a dense cladding (often based on rubber) applied uniformly to the undercarriage of the automobile. It is normally sprayed or painted on when the car is just out of the dealership and is clean. But even if you are getting the undercoating applied after a couple of years, it’s fine too. This is because it can prevent further damage to the undercarriage.

The main purpose of undercoating is to check rust especially in the body components like frame rails along with other exposed metal parts. Underbody coating can also reduce wear and tear. Getting a fresh coat can cost you up to ₹6,000.

                                                 

Modern automotive coating process:

The modern automotive coating consists of five steps:

• Pre-treatment: removes and cleans excess metal and forms an appropriate surface structure enabling bonding of a corrosion protection layer.
• The next step is electrodeposition (ED) of the anti-corrosion or rust prevention layer.
• A sealer like Poly Vinyl Chloride (PVC) is applied for anti-corrosion, elimination of water leaks, and minimization of chipping and vibrational noise.
• A primer is then applied to promote adhesion between the surface and the basecoat; it also imparts a smoother surface for subsequent layers and has anti-chipping properties.
• Finally, the topcoats that include a basecoat and clear coat are applied; they provide surface properties that are sought after, including colour, appearance, gloss, smoothness, and weather resistance.

Pre-treatment:

        The first step in preparing BIW for subsequent coating is the pre-treatment process. Pre-treatment consists of cleaning the body surface to remove remaining oils from the stamping process and welding residues through three primary liquid dip processes of degreasing, conditioning and phosphating. The degreasing solution is composed of alkaline salts and surfactants and can include caustic soda, tri-sodium phosphate, and sodium carbonate. The surfactants are types of detergents for emulsifying oils and lubricants on the BIW.

Electrodeposition (ED):

        The metal underbody and frames of automobiles are coated to prevent corrosion, whereas other areas like the roof are not rust-proofed. When not coated to prevent corrosion, the structural metals (or other materials) are primed before applying additional coatings. The ED processes are modified as per the BIW material property. This ED coating provides rust and corrosion protection.

                                                               

Rust-proof materials: Sealer/PVC

        The third step is underbody coating (UBC) and seam sealing using PVC and urethane. The sealant is applied around and inside the doors, hood, trunk, and front dash and onto the exterior and interior of metal joints and outer area of the back wheel well.

                                                                                        

Primer:

        The fourth coating step is the application of a primer surface or simply primer. It can be water-borne, solvent-borne or a powder. These primers are used to improve adhesion between the E-coat and topcoat, provide chipping protection, enhance paint appearance and also be environmentally compatible with emission regulations.

                                                    

Top-coat:

        The final step in the body coating process is to apply the topcoat, which consists of two layers—the basecoat and clear coat. The basecoat contains the primary colouring pigment and the clear coat provides a protective coating against environmental effects, corrosion, and UV light degradation promotes unmatched colour retention and provides a smooth unblemished even finish.

Types of Underbody coating:

Now let us look at the various kinds of automotive underbody coating you can go for, for your vehicle.

1. Rubberized Underbody Coating
   

   This is generally thought of as the best underbody coating for your car. It preserves the underbody well, protecting it from scratches. Applying this to the undercarriage is not much of a hassle either.

2. Wax Based Underbody Coating
   

   This – more or less – ephemeral undercoating will wear away in a few months’ time. On the upside, wax-based undercoating puts up a big fight against moisture. It is also the most affordable option out there.

3. Asphalt Based Automotive Undercoating
   

   Best suited for lorries, trucks and large vehicles this provides a greater degree of protection compared to rubber-based coatings. However, asphalt-based coatings contain little amounts of rubber for sound-insulation purposes. The process of applying this coating is a bit time-consuming though.

4. Polyurethane Underbody Coating

   This coating closes up splits and fractures on the underbody of the vehicle. It offers up good protection against corrosion and also bonds with the metal. Unlike in the case of asphalt-based coating, you can paint over the polyurethane coating.

   Advantages of Underbody coating

   Now we will tell you why you should consider investing in a vehicle underbody coating.

   • Fights Rust
     

     It plays an important role in keeping corrosion at bay. Underbody coating can come in handy especially if you live near the sea, where there is too much humidity, and rusting is just one of those everyday things. You should also seriously consider undercoating if you reside in a place where it snows in winter.

   • Absorbs Noise

     Believe it or not, very thick undercoating can soften the noises that reach the cabin. Since the undercoating is often made up of rubber it absorbs some of the rackets. The occupants of the car could spare themselves of the road noises – at least up to a certain extend.

   • Reinforcement
     

     If your car comes with stock underbody coating, using another coating on top of it, is not going to hurt. It will offer additional reinforcement, protecting the underbody from water, road debris, gravel and small pebbles. There would also be a lesser chance for the factory coat to flake away.

   • Prolong Car’s Life
     

     Good undercoating not only defends the underbody from corrosion but also protects the engine and transmission as well! Less rusting coupled with slower wear and tear can surely add years to the lifespan of your vehicle. There would be fewer dents, dings and scratches on the undercarriage for you to fret about.

     Disadvantages of Underbody coating

     • It won’t do anything about the corrosion which is already present.
       For an undercoating to be effective, it must be in place before the underbelly of your car begins to rust. If you apply it over corrosion, you won’t be making an improvement.
     • It works best on new cars.
       If you’ve purchased a used vehicle, then the cost of preparing the underbelly for an undercoating might be more than the value of the car. You must remove all the residue from the bottom before it can be applied.

      

     • Most vehicles make it five years before corrosion begins to show.
       For vehicle owners who purchase something new every 3 to 5 years, then rustproofing may not be a good use of your cash.

      

     • A third-party undercoating service might void your vehicle’s warranty.
       Some new cars no longer need the undercoating service provided because the structure of the vehicle has it built-in already. If you hire a third-party provider to apply an undercoating, you could void the corrosion-perforation warranty that is factory-provided. Most vehicles today that leave the factory floor are all provided with included rust-proofing.

                     Underbody Coating Process Images: