Forgive me! My semantics get in my way at times. The blue/black on the steel pins is actually a type of magnetite, created by heat(and oxygen), during the manufacture of the tube(as previously mentioned). That's a very thin, stable and anti-corrosive layer. A thickness of about .072 micron results in light refraction(per Michael Faraday's observed, "Temper Colors") and the blue appearance. It actually protects the steel from the nefarious, unstable corrosion/oxidation we call, "rust."
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- 9 posts total
- 9 posts total