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.

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.

MODERN AUTOMOTIVE COATING PROCESSES

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

• Pretreatment: removes and cleans excess metal and forms an appropriate surface structure enabling bonding of a corrosion protection layer.
• The next step is electro deposition (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 clearcoat are applied; they provide surface properties that are sought after, including color, appearance, gloss, smoothness, and weather resistance.

Coating on specific areas

1) PRETREATMENT

The first sequence in preparing the BIW for subsequent coating is pretreatment sees Figure. Pretreatment 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. Pretreament helps the primer to bond onto the metal.

Pretreatment sequences for the body-in-white

2) ELETRODEPOSITION

E-coating involves dipping automobile bodies into the coating solution and passing an electric current through the body and 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. The ED paint is promoted to bond with the metal substrate, and a uniform coating thickness is produced. The result is an insoluble, deposited layer with a very high solids content and firm adherence to the pretreated body.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.

Electrocoating process.

3) RUST-PROOF 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. . Recently, PVC and acryl/urethane sealants have also been used in the underbody areas, a process called the Dampening Coat (DC), to impart noise-proofing and vibration-deadening. The noise and vibration are transferred from the engine, drive train, suspension system, road noise of the tires, and flowing air, and the underbody sealants reduce noise transfer into the passenger compartment of the automobile. 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.

Underbody coating

4) PRIMER

The fourth coating step is the primer. It can be water-borne, solvent-borne, or a powder. The primer fills & smoothest 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 increases paint durability.

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 clear coat. 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 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 non- removable 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 clarcoat surface.

DIFFERENT TYPES OF UNDRCOATING

1. Wax or Paraffin-based Undercoating

it is the preferred undercarriage coating for cars often driven on highways and normal roads. Sometimes referred to as wax-based undercoating, it provides sufficient guard for cars in fairly moist regions.

Advantages:

• Readily flows into seams to guarantee any exposed and prone surfaces are protected
• The most inexpensive undercoating option
• Conveniently available in spray guy canisters or aerosol cans

disadvantages

• Wears off quicker in comparison to other types
• Unlike the rubberized type, it does not really dry
• Needs to be stripped and reapplied at least once a year as soon as signs of wear and tear start to show

2. Rubberized Undercoating

Ideal for cars driven in rough terrain, as its name suggests, this undercarriage coating involves applying a rubber agent to the underbelly to protect and cushion it against dents, dust, and moisture.It can also be applied around wheel wells and quarter panels. Considered the best option for standard vehicles when it comes to the different types of undercoating.

Advantages:

• Safe and Easy to apply
• Quickly applied with no fuss
• Undercoat can be painted for a neat finish
• Provides satisfactory protection
• Truly dries to a soft rubbery finish that prevents further rust, damage, or moisture seepage

3. Polyurethane Undercoating

Uses a polyurethane-based sealant that comes in canisters ready to be loaded into a spray gun and sprayed to guard the undercarriage of your vehicle.The polyurethane used in this product is a high-quality and durable material that is perfect for any weather condition. It is ideal for standard vehicles.

Advantages:

• It has a long lifespan and is resistant to wear and tear
• Easily and quickly applicable
• Trickles into cracks and rusty spots already present on the underbelly of your car and fills them, hence protecting the underlying metal
• Quick and simple to remove, as it sands easily
• Can be painted over

disadvantages

• For better adherence, needs undercarriage preparation before application
• Requires time-consuming etching with primer to bare metals

4. Asphalt-Based Undercoating

Unlike the rubberized, wax/paraffin-based, and Polyutherane undercoatings, this type is made of asphalt and generally also contains some rubberized material that sets up firmly and helps soften noise from the engine. It reportedly has the most damage-resistant properties. Although asphalt-based undercoating is ideal for trucks, military, and all-terrain vehicles, it will also help protect your car, truck, motorcycle, and heavy machinery from the elements.It last long and is best for endurance vehicles that have to undergo heavy road use.When it comes to large trucks, heavy machinery, military, and all-terrain vehicles, asphalt-based undercoating provides added durability against rocks, chips, and moisture.

Advantages:

• Formulated to protect from dirt, rust, and corrosion, it normally has a shelf life of up to two years.
• Provides extra durability as it is the strongest and thickest undercoating available.

Disadvantages

• It takes time to harden and so requires more cure time than the other three types
• Unlike the other three, it is also, not paintable as such, not very aesthetically suitable for standard vehicles
• For best used only for the undercarriages of utility vehicles and trucks

5. Water-based Undercoating

Water-based undercoating is a protective layer that helps your car stay protected from harsh weather conditions. It is made from an advanced polymer that is non-toxic and environmentally friendly. The product can be applied to any surface, including metal, plastic, rubber, and glass. It will keep your car protected from rust, salt, and moisture. This undercoating provides a protective barrier that lasts for only a year-depending on where you drive your car.

Advantages:

• Thin-set, it takes a short time to dry

Disadvantages:

• It requires frequent repetition as it’s not very durable
• It cannot repel ice and water like petroleum-based undercoating

6. Petroleum-Based Undercoating

Petroleum-based undercoating is a heavy, viscous oil-based liquid product that provides an effective barrier against moisture and corrosion.

The liquid dries and hardens to provide tough, durable, and long-lasting protection against moisture and corrosion. This product is typically applied to the undercarriage of automobiles, trucks, and other vehicles

Advantages:

• Has greater deflective abilities for road salts and grime
• Repels ice and water because of its petroleum base

Disadvantages:

• Requires annual replacement

ADVANTAGES OF UNDERBODY COATING

• Fights Rust

it plays an important role in preventing rust and other corrosion issue . Underbody coating can come in handy especially in coastal region 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. When an undercoating is properly applied to a vehicle, then you’ll be providing the underbelly with a layer of protection against rust and corrosion.

• Absorbs Noise

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 the 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 the vehicle. There would be fewer dents, dings and scratches on the undercarriage.