Underbody Coating

UNDERBODY COATINGS:

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.

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.

DIFFERENT TYPES OF UNDERBODY COATING:

Underbody coatings are categorised into various types based on the type of material used and also the cost of the material.

Rubberized underbody coating:

These coatings are easy to apply and offer sound-cushioning as well as protection from dust, moisture and dents. The coatings are safe even to use on wheel wells and quarter panels and when it is dried forms a soft rubbery finish that prevents further rust and moisture seep.

Polyurethane underbody coating:

This type of undercoating is a lit a bit quicker and easy to apply. This type of undercoating often comes in a canister ready to preload into application gun. This type of undercoating always requires surface preparations before applying.

Wax or paraffin-based underbody coating:

Wax or paraffin-based undercoating will be the cheapest and quickest option available in the market. But these coatings last only for one year of duration.

Asphalt-based underbody coating:

The above-mentioned undercoating is mainly used for light commercial vehicles. For vehicles such as trucks, buses, vans etc. asphalt-based undercoating is used for sufficient protection against rock chips and moisture. These asphalt-based undercoatings have a little bit of rubberised material that set up firmly and also helps in reduction in noise.

Overall benefits of underbody coating:

Minimizes sound: It minimizes the sound from underneath the car.

Heat insulation: It insulates the interior of the car from the extreme temperature from beneath the vehicle.

Anti-chipping property: The coating does not chip away when hit by stone