Underbody Coating
UNDERBODY COATING:
Underbody coatings are the protective coating used to protect the vehicles chassis from the external environment to ensure the integrity and safety of cars. The use of underbodycoating plays a very important rile in the service life of the vehicle. In general it is required to spray such a protective coating in the manufacture vehicle for fullfilment of life price ad life span.
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.
Cars today are manufactured with corrosion protection, which makes this added treatment unnecessary, though it is profitable for car dealerships. Consumer Reports recommends that car buyers skip the undercoating and several other pricey add-ons, including VIN etching, fabric protection, and extended warranties.
TYPES OF UNDERBODY COATING:
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.
PROCEDURE OF UNDERBODY COATNG:
Under body coating consist of the following steps:
Pre treatment
Electrodeposition
Rustproof material
Primer
Topcoat
PRETREATMENT:
The first step in preparing the BIW for subsequent coating is pretreatment. Pretreatment removes & clean excess metal & forms an appropriate surface structure enabling bonding of a corrosion protrction layer. It consists of cleaning the boady surface to remove remining oils from the staming process & welding residues through three primary liquid dip processes od degreasing, conditioning, & phosphate treatment helps the primer to bond oto the metal. A phosphate treatment applies an inter layer of metal phosphate, providing resistace to corrosion spread. The degreasing solution is composed of alkine salts & surfactants & can include caustic soda, sodium carbonate. The surfactants are types of detergents for emulsifying oils & lubrication on the BIW.
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 color & 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. The oven temperature & heating time primarily enchance chip resistance & film adhesion to the body; corrosion protected is affected less by these conditions. Because surface roughness influences the smoothness & brilliance of the topcoat, some sanding of the surface is usually performed to remove or eliminate defects before the body enters the next application step.
REST PROOF MATERIAL:
The third step is underbody coating & seam sealing using PVC. Fig.4 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.
During this third step, it is also typical to apply a soft tip primer coat that improves the chipping resistance. This layer is applied to the front edge of the hood , which is an area prone to chipping shock, using a high elastic resin that resides between the ED & primer coats. Also, during the third step, the radiator supports, wheel housing, & under rear areas of the body are coated with a relatively dull black pigment called a blackout coating.
PRIMER:
The fourth coating step is the primer. It can be water-borne, solvent-borne, or a powder. The primer fills & smoothes minor imperfections & scratches that may be created during prior steps & by the intermediate sanding or grinding used to remove small imperfections. It also provides additional protection against corrosion & maximizes adhesion between it & the E-coat & basecoat; thereby, the primer incrases paint durability.
Primer coating operations in an automobile assembly plant are usually implemented in three stages: Interior coating, Exterior coating, & then cutting in an oven. Manual spray painting is used for the interior coating of the doors, engine compartment, & luggage or trunk space. Some of the areas are not sprayed with basecoat. It is important that are primer color matches the basecoat to be able to impart uniform coating appearances between interior & exterior coats.
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 coloring pigments. As part of the topcoat, the basecoat is third layr added to the car after the primer & before the clearcoat. It imparts the automobiles color; roughly 40,000 base coat color are known today , & approximately 1000 new colors 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 clearcoa; 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 etchi=ng is associated with a localized loss of material & deformation or pitting of the clarcoat surface.
Advantages of Undercoating
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.
PROS:
It provides a extra layer of protection against rust and corrosion.
It will extend the life of vehicle.
It can be applied to damaged areas.
It can be self applied.
It minimize the sound from undernearth the car.
The coating doesnot chip away when hit by stones.
CONS:
It won't do anything about the corrosion which is already present.
It adds weight to the vehicles.
It works best on ew car.
An under coating is not impervious to damgage.
It must be reapplied every 3 to 5 years for best result.
The underbody coting is expensive.