Underbody Coating
Under Body Coating (UBC): What:
Under body coating is a type of automotive coatings like paint, primer protective coatings, etc. Often neglected UBC plays a vital role in service life of a Car. It is mandatory to have a standardised amount of UBC for homologation in markets around the world with variations in the layer thickness and positioning of these coatings. As the bottom or underbody of a car is not visible easily it used to be neglected in terms of aesthetics by manufacturers to save money in older days. Over the development in the last couple of decades manufacturers have established that a small investment in UBC can improve the service life of a vehicle by a significant amount.
Under Body coating is done by Airless spraying with help of robots or humans in some cases. The materials used include PVC (Poly Vinyl Chloride), acryl/Urethane sealants, Teflon, Rubber based compounds etc. The thickness of this coating may vary from 0.1 to 10mm as per the model, market, manufacturer.For example, in a competitive price market like India the coatings are provided conservatively for budget models usually just enough to get through regulations,whereas premium class models where comfort is priority over budget no such limitations are practiced.
Where:
As the name suggests UBC is applied on the outside of the floor panels, bottom of the trunk/boot. Shaft/Exhaust pipe tunnels, and inside of the wheel arches. Due to sealing properties UBC is also applied on gaps, naked welds, and any other openings on the underbody of the
car.
When:
UBC is applied in the later stages of the pre-treatment process. After cleaning the welded BIW through a number of baths, and electrodeposition the BIW is passed through baking and the UBC is applied. These layers are then dried off to ensure adhesion to the body and then the painting procedure is started.
Why:UBC provides the vehicle protection from:
1.Stone chipping: As the underbody of the vehicle is the nearest to the road surface it is frequently bombarded by small stones and debris during the running of the vehicle. The wheel arches are particularly tortured due to the centrifugal action by wheels and tyres.UBC layers provide absorption of such impacts and the body surface remains undamaged.
2.Rusting: Due to regular contact with saline air/ water in coastal areas, the underbody of car are susceptible to rusting. After repairing of the underbody due to accidental damage or rusting the welds and repairs are prone to rusting. The UBC layers act as a wall and prevent the direct contact between such rusting agents and the car body. Aftermarket brands like 3M provide compact UBC solutions like Cans which can be sprayed to apply without any pre or post treatment involved.
3.Dampening: The rubber like damping property of UBC layers help reducing the outer noises such as Exhaust noise, road noise, chipping noises etc. This makes the ride more comfortable and reduces the fatigue for the occupants. Any sort of vibrations produced by the tyres due to changing road conditions / surfaces or any other unpleasant excitations die down before reaching the cabin.
4.Other foreign elements: As the UBC layers seals the cockpit from the outside, nothing passes through the floor of the vehicle. This includes protection from high water during floods, corrosive Anti-freeze agents and salts, any terrain specific elements like snow, sand, etc.
This is the prosses of car coating.