Underbody Coating

Challenge:

Under-Body 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.In Indian road conditions, a cars underbody is most prone to corrosion. 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.

Under-Body coating process:

1. Pre-treatment:

The first sequence in preparing the BIW for subsequent coating is pretreatment sees Fig. Preatrament 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 staming process & welding residues through three primary liquid dip processes of degreasing, conditioning, & phosphating. Pretreament helps the primer to bond onto the metal. A phosphate treatment applies an inert layer of metal phosphate, providing resistance to corrosion spread. The
degreasing solution is composed of alkaline salts & surfactants & can include caustic soda, sodium carbonate. The surfactants are types of detergents for emulsifying oils & lubricants on the BIW.

2. 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 chargednature 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.

3. Rust-Proof materials: Sealer/PVC

The third step is underbody coating & seam sealing using PVC. Fig. 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 rar areas of the body are coated with a relatively dull black pigment called a blackout coating.

4. 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.

5. 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 non-removable 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.

Under-Body coating types:

1. Rubberized Underbody Coating:

This is widely considered to be the best underbody coating for your car. It protects the underbody from scratches and keeps it properly. It’s also not difficult to apply this to the undercarriage. This can be done at the authorized service center or by the local repair shop at a reasonable price. Rubberized coating is ideal if you want to keep the road noise to a minimum and rust and corrosion away.

2. Wax based under-body coating:

This transitory undercoating will, on the whole, fade away after a few months. On the plus side, wax-based undercoating is resistant to dampness. It is also the most cost-effective alternative.

3. Asphalt based automoive undercoating:

Suitable for lorries, trucks, and other heavy vehicles. In comparison to rubber-based coatings, this gives a higher level of protection. Asphalt-based coatings, on the other hand, incorporate a small quantity of rubber for sound insulation. The application of this coating, however, takes some time.

4. Polyurethane Underbody Coating:

This covering seals breaks and fractures in the vehicle’s underbody. It provides strong corrosion resistance and also binds to the metal. Unlike an asphalt-based coating, the polyurethane coating may be painted over.

Advantages of Under-body coating:

1. Fights Rust:

It has a crucial function in preventing corrosion. Underbody coating is particularly useful if you live near the sea, where there is excessive humidity and rust is a common occurrence. If you live somewhere where it snows in the winter, you should seriously consider undercoating. During the monsoon season, cars are at high risk of getting corrosion. If you want to extend your car’s life you should get an underbody coating.

2. Absorb noise:

Very strong undercoating, realize it or not, can attenuate noises that enter the cabin. The undercoating, which is frequently made of rubber, absorbs part of the rackets. The car’s occupants could avoid the road sounds — at least to some extent. So if you want a quite ride and pleasant experience it is always a good idea to consider getting an underbody coating.

3. Reinforcement:

If your automobile already has an underbody covering, applying another one on top of it will not harm it. It will provide further protection for the underbody from water, road debris, gravel, and tiny stones. The factory coat would also have a lower risk of flaking away.

4. Prolong car's life:

A good undercoat protects not just the underbody from corrosion, but also the engine and gearbox! Less corrosion combined with slower wear and tear can extend the life of your car by many years. On the undercarriage, there would be fewer dents, dings, and scratches to worry about.

Conclusion:

Automotive coatings confront an almost limitless variety of environments & environmental assaults. Targeting customers, expectations, together with maximizing efficiencies & meeting environmental regulations with new processes, has brought automotive coating to a level not imagined 100 years ago. The appearance of the surface significantly affects a customer’s perception of product quality. Additionally, customer expectations for the attributes given by the appearance of coatings continue to increase as manufactures compete to provide surfaces that offer enhanced surface characteristics.

Thanks & Regards,

Harshal Patil.