Japanese nano-film coating keeps motorcycles shiny

Japan’s Yamaha Motor has developed a nano-film coating technology that makes motorcycle exhaust pipes more heat- and corrosion-resistant, so as to help prevent discoloration and rust. The versatile technology is expected to find a variety of other uses, such as in making kitchenware and automotive parts.

Motorcycle exhaust pipes generally consist of a set of polished, chromed stainless pipes. They are mainly responsible for reducing noise, purifying exhaust gases and controlling engine output.

Since these pipes discolor and rust after a year or so, demand was growing for an exhaust pipe that can prevent such changes. Yamaha Motor’s manufacturing technology center took on the challenge around 2002.

But the task proved difficult. The team, led by Naohisa Takahashi, manager of material analysis group,materials division, discovered that a common heat- and corrosion-resistant coating technology is not a viable option because exhaust pipes are constantly exposed to high-temperature exhaust gases running through them.

Then, the team decided to focus on surface treatment and started to develop relevant technologies around 2005.

One challenge was the choice of material. Stainless or chromed pipes — the usual metallic exhaust pipes — do not rust easily. But if they are heated to 400 C or higher for a long period of time, they oxidize and discolor. One solution was to cover the pipes to hide discoloration, or to use multi-layer exhaust pipes to release heat more efficiently. But that would increase the overall weight.

The team also worked intensively on developing a new coating technology. They placed major components in a processing oven and created plasma in a vacuum to make it easier for silicon, oxygen and nitrogen ions to bond.

After much trial and error, they found the right balance of these molecules to make a highly heat- and corrosion-resistant ultra-thin film that is only 20 to 150 nanometers, or roughly one ten-thousandth of a millimeter, in thickness.

The technology reduced the weight of exhaust pipes by about 20%. Also, by adjusting the thickness and the oxygen-nitrogen ratio, the refraction of light can be controlled to make the film transparent and colorless, or emit various colors.

The technology, dubbed “SixONy,” was registered as a trademark last year. Yamaha Motor applied it to exhaust pipes used in the FZ1 motorcycle, which debuted in 2007, and the YZF-R1, introduced in 2008. The long-selling SR400 model began featuring the film in 2010, becoming lighter because the triple-layer exhaust pipe previously used was replaced by a double-layer one. The change also helped prevent discolouration.

Last September, Yamaha Motor teamed up with a kitchenware maker to develop a golden cocktail shaker. The company is eager to find a variety of other applications for its nano-film technology.

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