Challenge

Underbody Coating

OOswald Coutinho22 Aug 2022

Underbody Coating:

Underbody coation is an application where body is painted to form corrosion resistance so that it can be used for prolonged application. It also protects parts like internal body panels, frame rails and other inner cavities that are not physically accessible but are prone to corrosion.The treatment offers an long term solution for issues against rust and corrosion. Under coating helps i nprotecting the underbody from water, road debris, gravel and small pebbles.

Process of under coating:

1st : The body is washed and ungressed.

2nd: Then the body is dipped into ED bath where as per the plant capacity time for each dipping activity is decided.

3rd: The body is then removed from the bath at an particular angle to avaoid slag formation on the paint .

4th: It is then passed to heating chamber, where the color is left to dry.

5th: After that primer coating is done on the surace of the car to ensure life of the components.

6th: The car is then painted with particular coating which can be automatic or semiautomic depending on the type of industry.

Modern automotive coating process.

Pretreatment:

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.Pretreatments help primer to bond intometal.

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. In surface conditioner which creates nucleation sites for phosphate crystal growth. It increases the number of crystallization nuclei on the metal surface that enchance bonding mechanism for the subsequent phosphate sequence. Finally, the liquid dip phosphate ions, nitrate ions, zinc & hydrogen ions. The free acid etches the steel surface, causing hydrogen to be released while metal phosphate ions are precipitated onto the surface in a crystalline form.

2. ELETRODEPOSITION

In ED deposition the automobile is dipped into coating solution at certain angle according to the need, and with the help of electricity the part is coated.Beacuse of the charge process the body is coated in the best way where the charge in not able to 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 ED coating it enters into the hearting chambe of 160 degree celcius causes film curing to promote maximum performance properties.A common challenge in the cureent E-coating process is that of water spots that contaminate coated surfaces. If water spots are present, they have removed any sanding. Hence, it is necessary to use well-deionoised water& routinely monitor its conductivity. Alternatively, operators also add surfactants or ultrafiltrates to the water rinse zone to eliminate or manage water spots.

3.RUST-PROOF MATERIALS: SEALER/PVC

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.

It helps in increaing paint durability.

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 increases paint durability.

5. TOPCOAT

The final step in the body coating process is toapply the topcoat, which consists of two layers the basecoat & clearcoat.

Basecoat has primary coating pigments while clearcoat consists of final coating

Pros of under coating:

It helps in long lasting of car parts.Undercoating gives you an extra layer of protection against rust and corrosion, protecting your ca.

Cons: For already affected car i.r for a car which had already have rusted undercoating will not work well for it. i.e ndercoating 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.

Types of coating:

1. Rubberized Under body coating.

It preserves the underbody well, protecting it from scratches.

2.Wax Based Underbody Coating.

This – more or less – ephemeral undercoating will wear away in a few months’ time. On the upside, wax-based undercoating puts up a big fight against moisture. It is also the most affordable option.

3.Asphalt Based Automotive Undercoating

Best suited for lorries, trucks and large vehicles this provides a greater degree of protection compared to rubber-based coatings. However, asphalt-based coatings contain little amounts of rubber for sound-insulation purposes. The process of applying this coating is a bit time-consuming though.

Advantages of undercoating :

1.Fight against rust

2.Absorbs noise.-Since it is made of rubber it absorbs noise.

3.Reinforcement.

4. Prolonged life.

Underbody Coating

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Ship work like thisin your own course.

Talk to a career counsellor

Ship work like this
in your own course.