Underbody Coating

UNDERBODY COATING –

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.

Underbody coating provides long term protection from corrosion to car's underbody. It also protects parts like internal body panels, frame rails and other inner cavities that are not physically accessible but are prone to corrosion.

TYPES OF UNDERCOATING –

• 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.

• 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.
• 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.

• 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.

PROCESS OF UNDERCOATING

The current trends in automotive coating process are motivated by lowering manufacturing costs, delivering customer satisfaction via aesthetic features and corrosion protection, and mitigating environmental concerns.

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

• Pre-treatment
• Electrodeposition
• Rust Roof Material
• Primer
• Topcoat

• Pre-treatment - The first sequence in preparing the BIW for subsequent coating is pre-treatment. Pre-treatment removes & 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 stamping process & welding residues through three primary liquid dip processes of degreasing, conditioning, & phosphating. Pre-treatment helps the primer to bond onto the metal.

• Electrodeposition - E-coating involves dipping automobile bodies into the coating solution & passing an electric current through the body & the liquid ED paint solution. Because of the charged nature of this coating process, the ED paint penetrates into places a spray would not reach. During operation, a mixture of resin, binder, & a paste containing the pigments is fed into the ED tank. The automobile body is lowered into the tank, & an electric current applied; the solution in the tank consists of 80-90% deionised water & 10-20% paint solids. The resin is the backbone of the final paint film & provides corrosion protection, durability, & toughness. Pigments are used to provide colour & gloss. After E-coat, the automobile body enters a bake oven, in which heating & keeping at a temperature of 160_C for 10 min causes film curing to promote maximum performance properties.

• Rust Roof Materials: Sealer/PVC - The third step is underbody coating & seam sealing using PVC. Figure displays the lower door sections & rocker panel locations where PVC or urethanes are applied as an anti-chipping protection, & shows the cross section of this layer with respect to the other coatings on the body parts.

• Topcoat - The final step in the body coating process is to apply the topcoat, which consists of two layers the basecoat & clearcoat.

Basecoat: It contains the primary colouring pigments. As part of the topcoat, the basecoat is third layer added to the car after the primer & before the clearcoat. It imparts the automobiles colour; roughly 40,000 base coat colours are known today, & approximately 1000 new colours are added to this list each year. Three different types of basecoats are used for automobiles, including solvent-borne medium solids (MS), solvent-borne high solids (HS), & water-borne.

Clearcoat: The final coating on an automobile surface is the clearcoat; it provides durability, environmental etch, & scratch resistance to the overall coating. It protects against damage such as fading that is caused by UV rays from the sun & imparts a gloss & depth that otherwise are not as vivid. The clearcoat also makes repairs & maintenance easier. Environmental etch is an appearance issue associated with the formation of permanent water spots or nonremovable marks from bird droppings, tree resin, or other chemicals after contact with an automobiles surface. The physical damage resulting from etching is associated with a localized loss of material & deformation or pitting of the clearcoat surface.

PURPOSE -

• 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.

• Heat Insulation -It insulates the interior of the car from extreme temperatures from beneath the vehicle providing a comfortable cabin experience.

ADVANTAGES

1. Undercoating gives extra layer of protection against rust, corrosion and water.
2. It can be self-applied.
3. It minimizes sound underneath the car.
4. It insulates the car from extreme temperature.
5. The coating doesn’t chip away when hit by stone.

DISADVANTEGES

1. It must be reapplied every 3-5 years for the best results.
2. It adds weight to car.