Underbody Coating

Automotive Underbody Coatings

Underside of vehicles serves as an intermediate between metal components of a vehicle and outer environment. Underbody of vehicles is prone to damages due to harsh environmental conditions. Coatings are applied to the underside of vehicles to protect them against factors such as corrosion, chemicals, moisture, water damage, and chipping of the underbody. Automotive underbody coatings offer a protective layer to vehicles’ underside.

Most of these coatings provide chemical and corrosion resistance, along with several other properties based on different product formulations. Protection of underbody and wheel arches against chip damage is achieved by applying automotive underbody coatings, which protect the metal from debris of gravel, stones, salts, etc. tossed by the road.

Coating process of a vehicle body (automotive coating process) comprises minimum five layers of paint, while the underbody coating process comprises the first two layers in the overall coating process. These two layers provide durable protection against corrosion; however, damage over time requires renewal of these coatings. Automotive aftermarket service providers often provide these services during scheduled vehicle maintenance.

Automotive underbody coatings also offer protection against humidity, moisture, and wet conditions that can seep through the undercarriage of a vehicle through joints or cracks in the paintwork; and cause corrosion.

Elasticity of polymers used in automotive underbody coatings allows for low noise when struck by road debris compared to that with uncoated underbody. As a result, vibrations of vehicles are dampened and kept to a minimum.

PURPOSE OF UNDERBODY COATING

• Prevent from stone chip

There are thousands of pieces of stones on the road, and they are constantly hitting your car on the under body, wheel arches, sills and the trunk lower part while driving on the road. In some cases, the under body might be scratched by uneven road. As such the thin corrosion protection coating on the metal sheet will be destroyed and leave the bare metal exposed to the air, which will soon come to corrosion when contact with the moisture in the air. If not promptly getting anti-rust treatment, then the rust will soon spread to large areas. Under body coating or the anti-stone chip coating is a thick elastic layer which could not be easily damaged by stone chipping or scratch, therefore could basically protect the metal sheet of the under body.

• Prevents Paint Chipping

Running on the highway or while pacing through a city road, you will often encounter sharp gravel or any other unattended object hitting the belly of your car with high momentum. This scrapes and chips off the metal from down below. A thick layer of Underbody Coating definitely comes to aid and minimises the effects of such contacts on the body.

• Protects Against Rust & Corrosion

The primary objective of getting underbody coating done is preventing metal components that are exposed on the bottom side of the car to damage from corrosion. You can shut out the Adverse effects of corrosion on your car by simply applying a rubberised anti-rust coating all over the belly of your car.

• External influence

External environment, such as the baking from the hot road in summer, the road’s anti-frozen gent in winter, raining water and the salty water in the atmosphere, will attach the under body of a car. Particular in coast areas, the wind from the sea will bring more salt to the air, which will accelerate the corrosion and reduce the service life of a car. While the under body is covered by the thick and tight layers, it would act as a strong barrier to prevent these external substances attaching the metal sheet.

• Protects Vital Components

Underneath a car is somewhere a lot of indispensable parts of a car are left exposed like the Engine, silencer, etc. One simply can’t afford to let these parts go bad due to rusting and hence in order to save yourself from a hefty repair bill, a considerably less expensive Anti-Rust Coating is a must.

• Reduces NVH (Noise Vibrations Harshness) Levels

Our country is filled with roads having uneven patches and potholes and while we manoeuvre our cars through such sections, the unpaved crumbs, and pebbles hit the car from underneath or get stuck in the wheel wells. The underbody coating’s consistency is so thick that the layer it creates absorbs all the unpleasant noises and vibrations and marginally improves the driving experience.

Automotive coating process

• Pre-treatment:

The first step in preparing BIW for subsequent coating is the pre-treatment process. Pre-treatment consists of cleaning the body surface to remove remaining oils from the stamping process and welding residues through three primary liquid dip processes of degreasing, conditioning and phosphating. The degreasing solution is composed of alkaline salts and surfactants and can include caustic soda, tri-sodium phosphate, and sodium carbonate. The surfactants are types of detergents for emulsifying oils and lubricants on the BIW.

• Electrodeposition (ED):

The metal underbody and frames of automobiles are coated to prevent corrosion, whereas other areas like the roof are not rust-proofed. When not coated to prevent corrosion, the structural metals (or other materials) are primed before applying additional coatings. The ED processes are modified as per the BIW material property. This ED coating provides rust and corrosion protection.

• Rust-proof materials: Sealer/PVC

The third step is underbody coating (UBC) and seam sealing using PVC and urethane. The sealant is applied around and inside the doors, hood, trunk, and front dash and onto the exterior and interior of metal joints and outer area of the back wheel well.

• Primer:

The fourth coating step is the application of a primer surface or simply primer. It can be water-borne, solvent-borne or a powder. These primers are used to improve adhesion between the E-coat and topcoat, provide chipping protection, enhance paint appearance and also be environmentally compatible with emission regulations.

• Top-coat:

The final step in the body coating process is to apply the topcoat, which consists of two layers—the basecoat and clear coat. The basecoat contains the primary colouring pigment and the clear coat provides a protective coating against environmental effects, corrosion, and UV light degradation promotes unmatched colour retention and provides a smooth unblemished even finish.

Types of Undercoating

Having undercoating professionally applied to your vehicle can be expensive, but fortunately, if your budget is tight, you can do it yourself for a fraction of the price. Here are some of the various types of undercoating available.

Rubberized Undercoating

Rubberized vehicle undercoating is easy to apply and offers sound-cushioning as well as protection from dust, moisture, and dings or dents.

In addition to your undercarriage, rubberized undercoating is also safe to use on wheel wells and quarter panels, and dries to a soft rubbery finish that prevents further rust, damage, or moisture seeps. The coating can be painted over and, if necessary for bodywork, can be easily removed with an undercoating removal spray.

Overall, rubberized coating is generally the best option for protecting your vehicle's undercarriage, as it provides the simplest and best protective measures against rust and moisture.

Polyurethane Undercoating

The other option for undercoating your vehicle is to use a polyurethane-based sealant. This type of vehicle undercoating is a little bit quicker and easier to apply.

Oftentimes, polyurethane undercoating will come in canisters ready to preload into an application gun. This type of sealant works by seeping into all cracks and seams, displacing salt and moisture and oozing around rusty areas to bond with and protect unoxidized metal. It also sands quickly in case you'll need to perform bodywork and can be painted over.

On the flipside, this type of car undercoating generally requires a little bit more surface prep work before applying -- sanding and applying an etching primer to bare metals before using are generally recommended.

Wax or Paraffin-Based Undercoatings

A paraffin-based undercoating will be the cheapest and quickest option available with which to protect the undercarriage of your vehicle. However, keep in mind that it will wear off quicker than other types of undercoating and will need to be stripped and reapplied at least once every year.

Wax-based undercoatings never truly harden. During application, they drip or flow into seams and cracks to provide protective properties. They are usually available in a spray gun canister or in an aerosol can and offer at least a base protection in moderately humid climates.

Asphalt-Based Undercoating

For standard vehicles, any of the aforementioned types of undercoating will provide sufficient protection. For large trucks and heavy machinery, asphalt-based undercoating provides a bit of extra durability against rocks, chips, and moisture.

Asphalt-based undercoating generally contains a little bit of rubberized material that sets up firmly and also helps soften noise. Generally sold in five gallon containers, this type of undercoating also needs more cure time than the other three, and is NOT paintable, making it best to use only for undercarriages.

Advantages of Underboady coating

• Undercoating gives an extra layer of protection against rust and corrosion, protecting your car.
• Undercoating will eventually wear out, but you can get years of protection from it. Even vehicles in warmer climates gain protection as debris is repelled and kept away from eating at the vehicle.
• It can be self-applied.
• It minimizes the sound from underneath the car.
• It insulates the interior of the car from the extreme temperature from beneath the vehicle.
• The coating does not chip away when hit by stones

Disadvantages of Underboady coating

• Undercoating will not help you if corrosion already exists and the corrosion needs to be removed first before it can be applied, which can be expensive for you.
• It must be reapplied every 3 to 5 years for the best results
• It adds weight to the vehicle.

APPLICATION PROCEDURE OF UNDERBODY COATING

1. Lift up the vehicle, take off the wheel and plastic wheel covering.
2. Thoroughly clean the under body of the vehicle by high pressure water.
3. Blasting with compressed air could accelerate the drying.
4. Mask off the adjacent areas and parts with paper where not allowed to spray, such as exhausting pipe, brake system, engine, paint surface and etc.
5. Shake the can approx. 40 times before use, connect the can with spray gun.
6. Spray at room temperature and from a distance of approx. 25 cm in an X motion to build up a continuous coat. Do not spray on parts of the brake, engine or exhaust system.
7. Apply this product until the desired layer thickness is reached. If a thick layer is required, let layers dry in between.
8. After each use, clean the spray by flushing with suitable solvent.
9. After tough free, remove all the mask paper, re-install all the parts.
10. In case the under-body coating is sprayed to unwanted areas, clean it before drying.