Underbody Coating

UNDERBODY COATING

• In Indian road conditions, a car's 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.
• No matter the climate, the
  the underbelly of every vehicle needs
  proper care and protection.
  Undercoating helps protect your
  vehicle against rust and corrosion.
• Seals on the underbelly parts have
  gotten a lot tighter and more
  effective at keeping out dust and
  moisture, but there are other
  factors to consider.
  
  
• Poor roads, rocks getting thrown
  from the tires and denting the
  metal, and corrosion from road salt
  in the winter all play a huge part in
  the damage or decay of a vehicle's
  underbelly.
• Used vehicles especially will need a
  little underbelly protection, while it's
  already been exposed to
  contaminants and rust, applying
  undercoating will prevent further
  damage.
  

Modern Automotive Coating Processes:

The modern automotive coating method
consists of five Steps.

1. Pre-treatment: removes and
   cleans excess metal and forms an
   appropriate surface structure
   enabling bonding of a corrosion
   protection layer.

2. Electrodeposition (ED) of the anti-

   corrosion or rust prevention layer.

3. A sealer like Poly Vinyl Chloride
   (PVC) is applied for anti-corrosion,
   elimination of water leaks, and
   minimization of chipping and
   vibrational noise.
4. 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.

5. Finally, the topcoats that include basecoat and clearcoat are applied; they provide surface
   properties that are sought after,
   including color, appearance,
   gloss, smoothness, and weather
   resistance.

The areas of an automobile
depicted and where these five steps of
coating and other additional coatings
are used were shown in the below image.

1. Pre-treatment:

• When the automobile body sheet
  metal components are welded
  together, the resulting structure is
  referred to as the body-in-white
  (BIW). The first sequence in
  preparing the BIW for subsequent
  the coating is pretreatment.
• 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 process is done on pre-
  treatment was shown below
  image.

2.Electrodeposition (ED):

• 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.

3. Rust-Proof Materials: Sealer/PVC

• The third step is underbody coating
  (UBC) and seam sealing using PVC
  (Polyvinyl Chloride) 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;
  application of the sealant is
  accomplished either manually or
  with robots and prevents air and
  water ingress and inhibits rust
  formation.

4. Primer:

• The fourth coating step is the
  application of a primer surfacer or
  simply primer.
• It can be water-borne, solvent-
  borne, or a powder.
• The main reason for the primer
  the application was to improve
  weather resistance, appearance,
  and chipping resistance.
• The primer fills and smooths minor
  imperfections and scratches that
  may be created during prior steps
  and by the intermediate sanding or
  grinding used to remove small
  imperfections.

5. TopCoat:

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

Types of UnderCoating:

Rubberized Undercoating:

• Rubberized undercoating is easy to
  apply, and generally offers the best
  protective coating for your car's
  undercarriage.
• It cushions surfaces against
  moisture, rust, dings, and dents.
• Rubberized undercoating is safe to
  use on quarter panels and wheel
  wells and dries with a soft rubbery
  finish.

Asphalt-based Undercoating:

• Asphalt-based undercoating offers
  a higher level of protection suitable
  for large trucks, recreational
  vehicles, and heavy machinery.
• It’s formulated with some bits of
  rubberized material to aid in noise
  reduction.
• It offers extra protection against
  chips and moisture but is not
  paintable and, therefore, only
  suitable for undercarriages.

Polyurethane Coating:

• Polyurethane coating is easy to
  apply and works by sealing up
  cracks and seams.
• The compound displaces salt and
  moisture and protects the
  unoxidized metal from rust.
• It’s often sold in canisters that are
  ready to preload into an
  application gun.
• It, however, requires some surface
  prep work before application, like
  degreasing, and applying an
  etching primer to the bare metal.

Wax or Paraffin-based Undercoating:

• Wax or paraffin-based
  undercoating sprays are the
  cheapest and quickest options
  available.
• However, their results don’t last
  long, and you may have to apply a
  fresh coat after only a few months.
• In addition, the wax isn’t very
  the adhesive on a metal surface.
• Its main advantage is that it seeps
  quickly into cracks and seams, and
  offers moderate protective
  properties against moisture.

Before Treatment & After treatments images:

Advantages:

1. It extends the life span of the car
2. No more loud road noise.
3. It provides an extra layer of protection
   from rust and corrosion.
4. Heat Insulation: It insulates the
   interior of the car from extreme
   temperatures from beneath the
   vehicle providing a comfortable
   cabin experience.

5. Anti-chipping property: If any stone hits the coating it does not get chipped away hence protecting the
   underbody from exposure to water.

Disadvantages:

1. It won't do anything about the
   corrosion which is already
   present(Major damages).
   
2. It adds weight to the vehicle, results
   reduce fuel economy (Research
   done that there is a reduction of
   mileage of 1.6 km for every 3 to 4
   liters of fuel).
3. Risk of damage during the application,
   an improper coat to the body may
   cause extra damage to the car.
4. The cost will be high for the aged
   vehicles, from the 6th year it starts
   rusting (the term may be varied
   depend upon the weather condition
   of that area).