Developments In Magnesium Can corrosion be stopped?
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Photographer : Gordon Cameron
I stared at a strange brightness on the point of the lathe tool as I machined a brake-disc carrier. Then, I understood. Cutting friction had ignited magnesium chips. Brilliant, white light flared. White smoke billowed to the ceiling and then died away as the fuel was exhausted. I hardly had time to think, “Pooh-bah, I’ve burned my shop down!”
Magnesium is that compromised metal whose lightness is so attractive (much cheaper than similarly light beryllium!) but whose softness, ease of catching fire and rapid corrosion have made engineers think twice. In 1972, when the late mag-wheel pioneer, Elliott Morris, asked his friend at Lockheed why magnesium wheels were no longer used on aircraft, the reply was, “We don’t use that damn metal anymore. Now, we have engines that’ll lift anything!” In the 1930s, Velocette’s racing manager, Harold Willis, called magnesium “trouble metal.”
A good many racing motorcycles have had lightweight magnesium case covers (today, on factory prototypes, they are carbon fiber). The cam-chain covers on AJS 7Rs and Matchless G-50s were painted a distinctive gold color, and factory Kawasaki H2-R 750s had primary-gear covers protected from corrosion by the Dow-19 chemical process, which produced a gold color. That color, and a competing matte brown found on the mag carbs of Yamaha factory 0W-31 750s, shouted, “Secret factory stuff