Underbody Coating

INTRODUCTION :

A Car Body is made up of several Metals such as Iron, Steel, Aluminum, Copper, etc.
Rusting is the common term for the corrosion of iron and its alloys. Corrosion is the reaction of Iron and Oxygen, as may present in Water or Air Moisture. Any Iron material when exposed to both oxygen and water is bound to rust, unless a preventive coating is applied to it.

UNDERBODY COATING :

A car’s underbody is exposed to the most wear and tear caused by muddy water, stones, and other obstacles on the road. Because it’s not in plain sight, we often do not see the damage. Underbody Coating or Treatment offers a long-term solution for issues related to corrosion and rust.

MODERN COATING PROCESS :

Modern automotive coating consists of five steps:

• Pre-treatment: removes and cleans excess metal and forms an appropriate surface structure enabling bonding of a corrosion protection layer.
• electrodeposition (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 clear coat are applied; they provide surface properties that are sought after, including color, appearance, gloss, smoothness, and weather resistance.

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 the outer area of the back wheel well.

Primer:

The fourth coating step is the application of a primer surface or simple primer. It can be water-borne, solvent-borne, or 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 base coat and the clear coat. The basecoat contains the primary coloring pigment and the clear coat provides a protective coating against environmental effects, corrosion, and UV light degradation promoting unmatched color retention and providing a smooth unblemished even finish.

Types:
1. Rubberized Undercoating
Rubberized vehicle undercoating is easy to apply and offers good cushioning as well as protection from dust, moisture, and dents. Which is generally the best option for protecting the vehicle’s underbody, as it provides the simplest and best protective measures against rust and moisture.

2. Polyurethane Undercoating
The other option for undercoating the vehicle is to use a polyurethane based sealant. This type of vehicle undercoating is a little bit quicker and easier to apply.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.

3. Wax or Paraffin-Based Undercoatings
A paraffin-based undercoating will be the cheapest and quickest option available with which to protect the undercarriage of the 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.

4. Asphalt-Based Undercoating
For standard vehicles, any of the above mentioned 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. This type of undercoating also needs more cure time than the other three, and is not paintable, making it best to use only for underbodies.

Some benefits of underbody coating:

Rust Prevention
Ideally, any additional underbody coating should be applied when the car is brand new and clean. Car manufacturers use thick paints and sealants for the underbody, but adding an underbody coat, especially in coastal cities is useful. Salt water tends to corrode cars really badly.
On bad roads, flying stones and pebbles can chip off the original underbody coating and leave the metal exposed. Using underbody coating offer extra protection.

Sound insulation
The thicker underbody coatings used on cars also act as effective sound dampeners. They can reduce road noise and tire noise and make the cabin seem quieter due to the sound-absorptive nature of rubberized paints.

Easy maintenance
A uniform black underbody coating gives a car a clean look. It also makes the car easier to maintain by just hosing the underside down. You can be confident that slush build-up won’t lead to rusting easily. Most underbody coats these days come with a five year warranty, which is the lifetime of such a coating.

Some of the downsides to underbody coating:
High cost
The cost of underbody coating has come down but is still expensive. This is because underbody coating offered by a car dealer is one way in which they make money off the customer.

Risk of damage during application
Care must be taken while applying underbody coating. This thick rubberized paint if not applied properly, can get into moving mechanical parts and cause premature failure – such as into the U-joint or CV joints in a car's propeller shaft or drive shafts. They can also hinder smooth movement of suspension components if applied incorrectly. And there’s also the risk of overspray on to the car’s paint finish on the lower edges of the car.

Below you could see the Pictures of with and Without Underbody coating images for better understanding.

Without Underbody Coating

With Underbody Coating