Development of New Coloring Method using Air Oxidation for Silencer Body in Titanium

The silencer body is required to a function of noise reduction, design component and lightweight. Recently use of titanium is getting popular for mass production exhaust parts of a motorcycle. And the titanium is required to be colored for the sophisticated appearance. Although titanium can be commonly colored by anodizing, the anodic oxide film shows discoloration at elevated temperature and to the direct rays of the sun.

Yamaha has developed a new air oxidation method by which an impressive blue colored surface can be obtained. At first coating of ceramics and the glass is performed on the surface of silencer body. Then it is put into the air oxidation process and the surface color turns to blue. The color does not show any discoloration either at high temperature or under strong sunrays.

In this study the manufacturing procedure will be described and relationship between the structure of oxide film and manufacturing parameters will be discussed based on the investigation result of Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM), Electron Probe Microanalysis (EPMA), and Auger Electron Spectroscopy (AES)analysis.

The silencer body colored by this new procedure has been successively applied to the super sports motorcycle since March 2000.