The Hindu Business Line : Where BMWs powder their noses

At Dingolfing, some 100 km east of Munich, is the BMW plant that gives the luxury sports cars the one-of-a-kind powder clear coat that gives the unique glossy finish.

THE BMW 7-SERIES import... Gleaming under the Chennai sun. — S. Muralidhar

BMW's massive manufacturing facility at Dingolfing, some 100 km east of Munich, is unique for many reasons. It is one of the largest luxury vehicle assembly plants in the world and this one facility rolls out about three lakh Beemers annually. The Dingolfing plant is also famous for being the facility where the body-in-white of the Rolls-Royce Phantom is hand built. But the what the plant is really famous for is the state-of-the-art paint and finish shop.

The one-of-a-kind powder clear coat process is what gives the BMW luxury sports car the unique glossy finish. BMW India's plant near Chennai will assemble the 3-Series sedans and later this year also the 5-Series. The body panels for these cars will come pre-painted and finished from the Dingolfing plant.

But what is powder clear coat?

The quality of the paint job in luxury cars has a trademark classiness about them. How do they manage to retain their gleaming paint finish even after a long journey? The gloss and depth of the paint finish lasts much longer than the average polished, waxed finish that local car dealer can manage.

Several coats

The body panels of most modern day cars get three-four layers, or coats, of different materials to achieve the final reflective finish. These will include the base coat, the anti-rust treatment, if any, the primary pigment paint and the clear coat. The secret to the lustre is the clear coat that automobile companies spray on to the vehicle's exterior panels.

This coat of clear paint (lacquer or polymer) creates a transparent, protective layer over the car's primary coloured paint. The clear coat acts like a shell or a shield wrapped over the car's painted panels, protecting them from damage due to prolonged exposure to the sun's ultra-violet (UV) rays and other harmful contaminants such as bird droppings and acid rain. Depending on the strength and quality of the clear coat, it also protects the car's body from minor nicks and scratches.

There are broadly two types of clear coats — the solvent-based and the powder-based. The more commonly used solvent-based clear coats use a material that is colourless. This clear liquid is sprayed on and the car's panels are air-dried to get a final clear finish.

On the other hand, a powder clear coat, as the name suggests, is a clear finish achieved by spraying on a type of powder polymer that melts to bond and form the clear coat on the car's painted surface (instead of the solvent-based liquid clear paint). Powder clear coats are becoming increasingly popular for three reasons. They are more environmentally-friendly (than solvent coats), wastage is dramatically lower, and offer a much better, longer lasting finish.

Luxury car manufacturers, whose customers seek exclusivity and are willing to pay for it, have been working with powder clear coats to both achieve unique finish quality for their vehicles and also to meet the their own corporate, environment responsibility goals.

Automobile manufacturers often work in close cooperation with paint and chemical companies to develop their own concoction of applications and materials that will deliver a unique finish to the vehicles. In the case of the powder clear coat, the result is specialty chemicals and proprietary, patented processes that enable carmakers like BMW offer a one-of-a-kind clear coat finish.

Powder clear coat process

The process of giving painted car bodies a powder clear coat finish starts with the spraying of specially developed white polymer flakes or powder on to the car's painted body in a climate-controlled booth. As the spray of powder clear coat is done on an earthed car body, the electro-statically charged particles cling on to the car's panels forming an even layered coat. Then the car's body with the white powder coat is literally baked in an oven, where the high heat melts the special polymer and makes it cling on to the body panels forming the clear coat of even thickness.

The process ensures that there is no excess collection of the polymer in one spot and also eliminates the possibility of drip lines forming on the body.

As no solvent is used, no harmful chemical fumes are released in the powder coat process. So, there is no need to dispose the solvent fumes and automatically make the powder clear coat process more environment-friendly. Air from the baking oven can be recycled and the small amount of powder clear coat that falls off the car's panels during the spraying process can be cleaned and recycled.

What is more, this powder clear coat process is much more consistent, does not lead to the formation of weak spots or air bubbles in the finish and offers much better scratch resistance than solvent-based clear coats.

However, even as the process seems to indicate, powder clear coats are expensive to apply and also to maintain when you have to fix a scratch or dent in the after market.

For now, only the luxury end of the car mart gets to flaunt the exclusive, expensive `bling' that powder clear coats bring to the world of cars.

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