[EnricoBrun]

Can anyone give an explanation of why certain exhaust manifolds slowly become all golden shades like mine and certain others remain with the original chrome tone in the area under the bike? depends on what ? my motorbike is new, it has 5000km.
Thx

 

[Tim 2154]

I’m really only guessing but I think it’s most likely to be related to time spent stationary and in heavy traffic. Obviously environmental conditions will effect how quickly that change would happen.

 

[if0rg0t2remember]

It is simple heat. That is why there is the most color change right up by the cylinder heads and right in front of the catalytic converter. All metals will change color slightly with heat, and the higher the heat the deeper the color change. In this case the gold hues are where it got only slightly warm, the purple a little hotter and blue is the hottest area.

 

[gene_apodaca]

Kewl. Metallurgy. I love learning new things.

 

[EnricoBrun]

Of course, I perfectly understand that this phenomenon of alteration of the color tone is basically due to the heat.. but my question was: why to me yes and not to many users with many more kilometers travelled?!?

 

[Uncle Kebo]

Keep in mind, its also a badge of honor.

 

[EnricoBrun]

example: three different r ninet with different km each and mine has a golden exhaust ... mystery

 

[Lelc2]

I don´t know why others are not the same. Probably less kilometers? Not hotter conditions? Image light effect of picture? Clean/brush pipes?

I only know all boxer I have seen have the same blue-purple-orange colors if they are chrome plated finished. If pipes are not chrome plated (only steel) they will get worse a bit rusted and dirty etc.

I only get worried about colour if both are not the same. If each cylinder is different colour probably is not working properly.

Here you can see. From purple (hottest part), blue and orange.

 

[Vectorbug]

When you take a torch to a material like wood and burn it, it turns black and peels like a dry lake bed. If you don't go so far as to turn it to a black charred surface, you have a bit of a spectrum of color change. It darkens, turns brown, and then eventually turns black. It turns black because it's reflecting less light (or absorbing more). The same way a sound damping material absorbs certain wavelengths of air pressure movement, which we refer to as sound.

This is essentially what is happening to the chrome surface of the exhaust pipe, but at a microscopic level. It doesn't "dye" the surface, as much as it creates microscopic canyons and texture that traps longer wavelengths of light, which allows shorter wavelengths to bounce off. Longer wavelengths of light are more red, shorter and more blue (redshift / blueshift). The gold color is pre-blue, it'll eventually turn blue. It's a sign that hot air is bombarding the "kink" in the exhaust pipe as seen below, which causes more friction, slows down because the particles have to wait for the faster moving particles next to it, and as we all know, friction causes heat.

This is essentially how anodizing titanium works with electricity (aluminum anodizing is actually a dye). You're corroding the surface with electrolyte and a charge to create microscopic texture that traps certain wavelengths of light, filtering them out, and allowing other wavelengths to bounce off and be detected the electromagnetic sensing components in your cranium (your eyeballs).

Light and color doesn't actually exist, your eyes detect certain frequencies of electromagnetic energy waves and particles and your brain converts these pulses and frequencies into color and "brightness".

You can remove the color by polishing the surface and smoothing it out so it reflects a more consistent wavelength of electromagnetic energy (light).

 

[if0rg0t2remember]

three different r ninet with different km each and mine has a golden exhaust ... mystery

It absolutely isn't just yours with exhaust that has color changes. Mine has very similar coloration.

Exhaust heat is going to be a factor of many things including the ambient temperature, how hard and how long your rides are etc. It isn't something to worry about or obsess over really unless the color changes bother you.

 

[EnricoBrun]

It absolutely isn't just yours with exhaust that has color changes. Mine has very similar coloration.

Exhaust heat is going to be a factor of many things including the ambient temperature, how hard and how long your rides are etc. It isn't something to worry about or obsess over really unless the color changes bother you.

I'm not worried, I was just wondering why the ninet that have much more kilometers than mine keep a nice chrome over time!

 

[TimC]

I wonder if the amount of time spent idling has anything to do with the coloring of the pipes under the engine. Heat must build up there more for folks who frequently sit in (or slowly lane split through) traffic, so maybe that's a factor.

I think it's also possible it could vary according to the quality of the chrome being applied during the plating process. Or maybe the plating was applied too thinly that batch and those pipes are more susceptible to discoloration than most.

I was bothered a little at first by my R9T's header pipes becoming discolored, but now I hardly notice it. It would take more work to polish them back to silver than it's worth to me.

Also, reading the post above from @Vectorbug was very educational!