Underbody Coating

Challenge: Under body coating

We all know that most of the parts of cars are made of metal and plastic. The sheet metal parts used in car manufacturing are corosive and they are coated with anti corosive chemicals and paints or will undergo plating to prevent rusting. So when a new car rolls out of the manufacturing unit they will be fully protected against rust. As years pass on these preventive coats and plating which will be exposed to waters and other chemical liquids in turn will loose its protective ability. So all new cars after a span of 2 to 3 years have to be re coated against corrosion.

The under body is the area at bottom of cars around the tyre area and bottom of passenger seating area. These area are directly exposed to the liquids on the roads for example water, drain water, chemical or acid water flowing on the roads which will spill on these area by rotating tyre. So the under body area of car requires extra care and frequent protection. As the car is moving on the road the water and other chemicals flowing on the roads is spilled on the under body area by the tyres. So the under body is more exposed to all sort of extreme conditions and are porne to rusting. Secondly these chemicals and water on the road mixed in mud on the roads will stick to the under body and above tyre areas. This is major issue or challenge for the car manufactures for better rust prevention. For the car users it is better for regular wash to remove these sticky materials from car underbody areas to have long, good healthy metal structures of car.

Purpose:

As mentioned the above the metal structure and sheet metal parts are prone to rust. So car manufactures have come up in giving maximum life against rust by means of the body-BIW giving multple coating and treatments.

The BIW is first dipped in cleaning liquid and then is immersed in a coating and finally is painted. The under body is coated by anti rust coating a standard coating used by OEM. Silencers are normally zinc plated and this is exposed to high temperatures and coating will not withstand high temperatures.

Normally the OEM under body coating will last for 2-3years. Once the coating ability to prevent rust is gone, we find under body with rust patches. Now when the cars are given for routine servicing, the mechanic will suggest about under body coating. If the rust are not prevented in the intial stages the damage is that the particular portion of metal be damaged. Rust is nothing but oxidation of ferrous (iron) and this is a chemical reaction. This chemical reaction is irreversable. They can only be prevented. The strong metal once is oxidised or rusted will be brittle and will easily collapse under small external force. The metal will break into pieces or powder if rusted. So prevention is the only solution.

There are different grades and types of under body coating now available in the market (After market solutions).

Some of the Underbody coatings in market are as below

Rubberized Coating, Wax based coating, Asphalt (Tar) based coating, Polyurethane coating. All these are Spray painting . First the rusty area is cleaned by emery sheets and polished for removing rusts and then the spray coating is applied by spray. These spray only prevent from the metal exposed directly to atmosphere and by doing so they help in preventing rust of the metal parts.

Note if the intial rust is not removed and only spray coating applied, then the rust will immediately appear and the coating will have no benefit. Full care to be taken to remove all rust before coating to avail full benefit of anti rust coating.

The under body is part of full car. This cannot be seperated for any sort of treatment during the servicing of car at the mechanic shop. So the car is completely washed, dried, cleaned and preparation is made to spray paint the coating in the assembled condition. The silencer is another part in the underbody area. The silencer is sprayed coated with zinc anti rust coating as this exposed to higher temperatures and other normal coating will not withstand high temperatures.

Pro's and Con's

Each car manufacture has different thicknes of coating in OEM. This really is important consideration as good coating or higher thickness coating in OEM will last more than 3 years for next action of coating.

Finally the conclusion is all cars after 2-3years in use is good to have underbody coating for prevention of rust in this area. Not doing so will surely result in rust and once the rust is developed even anti rust coating will not reverse the damage done. So coating to under body area has only advantages and no disadvantages. Even after three years if there is no rust still going for a coating will hot harm the metal bodies of car in any way but will give extra protection against rust. This in my conclusion is that the cost of coating is small against the investment made in purchasing the car and also our responsibility to maintain the condition of the car.

The disadvantages can only be the cost for regurlar expenditure in coating.

below the photos of comparision.

Before coating rust is about start

This is photo of a fully coated underbody area.