UNDER-BODY COATING

Underside of vehicles serves as an intermediate between metal components of a vehicle and outer environment. Underbody of vehicles is prone to damages due to harsh environmental conditions. Coatings are applied to the underside of vehicles to protect them against factors such as corrosion, chemicals, moisture, water damage, and chipping of the underbody. Automotive underbody coatings offer a protective layer to vehicles’ underside.

Most of these coatings provide chemical and corrosion resistance, along with several other properties based on different product formulations. Protection of underbody and wheel arches against chip damage is achieved by applying automotive underbody coatings, which protect the metal from debris of gravel, stones, salts, etc. tossed by the road.

Coating process of a vehicle body (automotive coating process) comprises minimum five layers of paint, while the underbody coating process comprises the first two layers in the overall coating process. These two layers provide durable protection against corrosion; however, damage over time requires renewal of these coatings. Automotive aftermarket service providers often provide these services during scheduled vehicle maintenance.

Automotive underbody coatings also offer protection against humidity, moisture, and wet conditions that can seep through the undercarriage of a vehicle through joints or cracks in the paintwork; and cause corrosion.

Elasticity of polymers used in automotive underbody coatings allows for low noise when struck by road debris compared to that with uncoated underbody. As a result, vibrations of vehicles are dampened and kept to a minimum.

Automotive coating process

• 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 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.

Different types of underbody coating are: -

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

Pros of Underboady coating

1. 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.

2. 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.

3. 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.

4. 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.

Cons of Underboady coating

• Undercoating will not help you if corrosion already exists and the corrosion needs to be removed first before it can be applied, which can be expensive for you.
• It must be reapplied every 3 to 5 years for the best results
• It adds weight to the vehicle.
• can only be aplied on new vehicles.